Electric fields measured by ISEE-1 within and near the neutral sheet during quiet and active times

NASA Technical Reports Server (NTRS)

Cattell, C. A.; Mozer, F. S.

1982-01-01

An understanding of the physical processes occurring in the magnetotail and plasmasheet during different interplanetary magnetic field orientations and differing levels of ground magnetic activity is crucial for the development of a theory of energy transfer from the solar wind to the particles which produce auroral arcs. In the present investigation, the first observations of electric fields during neutral sheet crossings are presented, taking into account the statistical correlations of the interplanetary magnetic field direction and ground activity with the character of the electric field. The electric field data used in the study were obtained from a double probe experiment on the ISEE-1 satellite. The observations suggest that turbulent electric and magnetic fields are intimately related to plasma acceleration in the neutral sheet and to the processes which create auroral particles.

Hy-wire and fast electric field change measurements near an isolated thunderstorm, appendix C

NASA Technical Reports Server (NTRS)

Holzworth, R. H.; Levine, D. M.

1983-01-01

Electric field measurements near an isolated thunderstorm at 6.4 km distance are presented from both a tethered balloon experiment called Hy-wire and also from ground based fast and slow electric field change systems. Simultaneous measurements were made of the electric fields during several lightning flashes at the beginning of the storm which the data clearly indicate were cloud-to-ground flashes. In addition to providing a comparison between the Hy-wire technique for measuring electric fields and more traditional methods, these data are interesting because the lightning flashes occurred prior to changes in the dc electric field, although Hy-wire measured changes in the dc field of up to 750 V/m in the direction opposite to the fair weather field a short time later. Also, the dc electric field was observed to decay back to its preflash value after each flash. The data suggest that Hy-wire was at the field reversal distance from this storm and suggest the charge realignment was taking place in the cloud with a time constant on the order of 20 seconds.

Bursting the Taylor cone bubble

NASA Astrophysics Data System (ADS)

Pan, Zhao; Truscott, Tadd

2014-11-01

A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

Demonstration of motion control of ZrO2 microparticles in uniform/non-uniform electric field

NASA Astrophysics Data System (ADS)

Onishi, Genki; Trung, Ngo Nguyen Chi; Matsutani, Naoto; Nakayama, Tadachika; Suzuki, Tsuneo; Suematsu, Hisayuki; Niihara, Koichi

2018-02-01

This study aims to elucidate the mechanism that drives dielectric microparticles under an electric field. The driving of microstructures is affected by various electrical phenomena occurring at the same time such as surface potential, polarization, and electrostatic force. It makes the clarification of the driving mechanism challenging. A simple experimental system was used to observe the behavior of spherical ZrO2 microparticles in a nonaqueous solution under an electric field. The results suggest that the mechanism that drives the ZrO2 microparticles under an electric field involved the combination of an electric image force, a gradient force, and the contact charging phenomenon. A method is proposed to control the motion of micro- and nanostructures in further study and applications.

AC Electric-Field-Induced Fluid Flow in Microelectrodes.

PubMed

Ramos; Morgan; Green; Castellanos

1999-09-15

During the AC electrokinetic manipulation of particles in suspension on microelectrode structures, strong frequency-dependent fluid flow is observed. The fluid movement is predominant at frequencies below the reciprocal charge relaxation time, with a reproducible pattern occurring close to and across the electrode surface. This paper reports measurements of the fluid velocity as a function of frequency and position across the electrode. Evidence is presented indicating that the flow occurs due to electroosmotic stress arising from the interaction of the electric field and the electrical double layer on the electrodes. The electrode polarization plays a significant role in controlling the frequency dependence of the flow. Copyright 1999 Academic Press.

Effects of electric and magnetic fields on the electronic properties of zigzag carbon and boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh; Ahmadi, Eghbal

2012-04-01

We have investigated the electronic properties of zigzag CNTs and BNNTs under the external transverse electric field and axial magnetic field, using tight binding approximation. It was found that after switching on the electric and magnetic fields, the band modification such as distortion of the degeneracy, change in energy dispersion, subband spacing and band gap size reduction occurs. The band gap of zigzag BNNTs decreases linearly with increasing the electric field strength but the band gap variation for CNTs increases first and later decreases (Metallic) or first hold constant and then decreases (semiconductor). For type (II) CNTs, at a weak magnetic field, by increasing the electric field strength, the band gap remains constant first and then decreases and in a stronger magnetic field the band gap reduction becomes parabolic. For type (III) CNTs, in any magnetic field, the band gap increases slowly until reaches a maximum value and then decreases linearly. Unlike to CNTs, the magnetic field has less effects on the BNNTs band gap variation.

Electro- and Magneto-Modulated Ion Transport through Graphene Oxide Membranes

PubMed Central

Sun, Pengzhan; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Zhu, Hongwei

2014-01-01

The control of ion trans-membrane transport through graphene oxide (GO) membranes is achieved by electric and magnetic fields. Electric field can either increase or decrease the ion transport through GO membranes depending on its direction, and magnetic field can enhance the ion penetration monotonically. When electric field is applied across GO membrane, excellent control of ion fluidic flows can be done. With the magnetic field, the effective anchoring of ions is demonstrated but the modulation of the ion flowing directions does not occur. The mechanism of the electro- and magneto-modulated ion trans-membrane transport is investigated, indicating that the electric fields dominate the ion migration process while the magnetic fields tune the structure of nanocapillaries within GO membranes. Results also show that the ion selectivity of GO membranes can be tuned with the electric fields while the transport of ions can be enhanced synchronously with the magnetic fields. These excellent properties make GO membranes promising in areas such as field-induced mass transport control and membrane separation. PMID:25347969

Particle-in-Cell Simulations of the Twisted Magnetospheres of Magnetars. I.

NASA Astrophysics Data System (ADS)

Chen, Alexander Y.; Beloborodov, Andrei M.

2017-08-01

The magnetospheres of magnetars are believed to be filled with electron-positron plasma generated by electric discharge. We present a first numerical experiment demonstrating this process in an axisymmetric magnetosphere with a simple threshold prescription for pair creation, which is applicable to the inner magnetosphere with an ultrastrong field. The {e}+/- discharge occurs in response to the twisting of the closed magnetic field lines by a shear deformation of the magnetar surface, which launches electric currents into the magnetosphere. The simulation shows the formation of an electric “gap” with an unscreened electric field ({\\boldsymbol{E}}\\cdot {\\boldsymbol{B}}\

Reconnection in Three Dimensions

NASA Technical Reports Server (NTRS)

Hesse, Michael

1999-01-01

Analyzing the qualitative three-dimensional magnetic structure of a plasmoid, we were led to reconsider the concept of magnetic reconnection from a general point of view. The properties of relatively simple magnetic field models provide a strong preference for one of two definitions of magnetic reconnection that exist in the literature. Any concept of magnetic reconnection defined in terms of magnetic topology seems naturally restricted to cases where the magnetic field vanishes somewhere in the nonideal (diffusion) region. The main part of this paper is concerned with magnetic reconnection in nonvanishing magnetic fields (finite-B reconnection), which has attracted less attention in the past. We show that the electric field component parallel to the magnetic field plays a crucial physical role in finite-B reconnection, and we present two theorems involving the former. The first states a necessary and sufficient condition on the parallel electric field for global reconnection to occur. Here the term "global" means the generic case where the breakdown of magnetic connection occurs for plasma elements that stay outside the nonideal region. The second theorem relates the change of magnetic helicity to the parallel electric field for cases where the electric field vanishes at large distances. That these results provide new insight into three-dimensional reconnection processes is illustrated in terms of the plasmoid configuration, which was our starting point.

Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics

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

Qi, Y.; Liu, S.; Lindenberg, A. M.

There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate (≈ 10 11 K/s) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in PbTiO 3 occurring on few picosecond time scales. Here, we explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on amore » ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of PbTiO 3 and BaTiO 3. Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.« less

Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics

DOE PAGES

Qi, Y.; Liu, S.; Lindenberg, A. M.; ...

2018-01-30

There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate (≈ 10 11 K/s) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in PbTiO 3 occurring on few picosecond time scales. Here, we explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on amore » ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of PbTiO 3 and BaTiO 3. Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.« less

Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics

NASA Astrophysics Data System (ADS)

Qi, Y.; Liu, S.; Lindenberg, A. M.; Rappe, A. M.

2018-01-01

There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate (≈1011 K /s ) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in PbTiO3 occurring on few picosecond time scales. We explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on a ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of PbTiO3 and BaTiO3 . Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.

The role of the large scale convection electric field in erosion of the plasmasphere during moderate and strong storms

NASA Astrophysics Data System (ADS)

Thaller, S. A.; Wygant, J. R.; Cattell, C. A.; Breneman, A. W.; Bonnell, J. W.; Kletzing, C.; De Pascuale, S.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.

2015-12-01

The Van Allen Probes offer the first opportunity to investigate the response of the plasmasphere to the enhancement and penetration of the large scale duskward convection electric field in different magnetic local time (MLT) sectors. Using electric field measurements and estimates of the cold plasma density from the Van Allen Probes' Electric Fields and Waves (EFW) instrument, we study erosion of the plasmasphere during moderate and strong geomagnetic storms. We present the electric field and density data both on an orbit by orbit basis and synoptically, showing the behavior of the convection electric field and plasmasphere over a period of months. The data indicate that the large scale duskward electric field penetrates deep (L shell < 3) into the inner magnetosphere on both the dusk and dawn sides, but that the plasmasphere response on the dusk and dawn sides differ. In particular, significant (~2 orders of magnitude) decreases in the cold plasma density occur on the dawn side within hours of the onset of enhanced duskward electric field. In contrast, on the dusk side, the plasmapause is located at higher L shell than it is on the dawn side. In some cases, in the post-noon sector, cold plasma density enhancements accompany duskward electric field enhancements for the first orbit after the electric field enchantment, consistent with a duskside, sunward flowing, drainage plume.

Electrorotation of novel electroactive polymer composites in uniform DC and AC electric fields

NASA Astrophysics Data System (ADS)

Zrinyi, Miklós; Nakano, Masami; Tsujita, Teppei

2012-06-01

Novel electroactive polymer composites have been developed that could spin in uniform DC and AC electric fields. The angular displacement as well as rotation of polymer disks around an axis that is perpendicular to the direction of the applied electric field was studied. It was found that the dynamics of the polymer rotor is very complex. Depending on the strength of the static DC field, three regimes have been observed: no rotation occurs below a critical threshold field intensity, oscillatory motion takes place just above this value and continuous rotation can be observed above the critical threshold field intensity. It was also found that low frequency AC fields could also induce angular deformation.

Relationships between Electrical and Radar Characteristics of Thunderstorms Observed During ACES

NASA Technical Reports Server (NTRS)

Buechler, Dennis E.; Mach, Douglas M.; Blakeslee, Richard J.

2003-01-01

The Altus Cumulus Electrification Study (ACES) took place near Key West, Florida during August 2002. A high altitude, remotely piloted aircraft obtained optical pulse and electric field data over a number of thunderstorms during the study period. Measurements of the vertical electric field and cross sections of radar reflectivity along the flight track are shown for 2 overpasses of a thunderstorm that occurred on 10 August 2002.

Direct measurement of the protein response to an electrostatic perturbation that mimics the catalytic cycle in ketosteroid isomerase.

PubMed

Jha, Santosh Kumar; Ji, Minbiao; Gaffney, Kelly J; Boxer, Steven G

2011-10-04

Understanding how electric fields and their fluctuations in the active site of enzymes affect efficient catalysis represents a critical objective of biochemical research. We have directly measured the dynamics of the electric field in the active site of a highly proficient enzyme, Δ(5)-3-ketosteroid isomerase (KSI), in response to a sudden electrostatic perturbation that simulates the charge displacement that occurs along the KSI catalytic reaction coordinate. Photoexcitation of a fluorescent analog (coumarin 183) of the reaction intermediate mimics the change in charge distribution that occurs between the reactant and intermediate state in the steroid substrate of KSI. We measured the electrostatic response and angular dynamics of four probe dipoles in the enzyme active site by monitoring the time-resolved changes in the vibrational absorbance (IR) spectrum of a spectator thiocyanate moiety (a quantitative sensor of changes in electric field) placed at four different locations in and around the active site, using polarization-dependent transient vibrational Stark spectroscopy. The four different dipoles in the active site remain immobile and do not align to the changes in the substrate electric field. These results indicate that the active site of KSI is preorganized with respect to functionally relevant changes in electric fields.

Direct measurement of the protein response to an electrostatic perturbation that mimics the catalytic cycle in ketosteroid isomerase

PubMed Central

Jha, Santosh Kumar; Ji, Minbiao; Gaffney, Kelly J.; Boxer, Steven G.

2011-01-01

Understanding how electric fields and their fluctuations in the active site of enzymes affect efficient catalysis represents a critical objective of biochemical research. We have directly measured the dynamics of the electric field in the active site of a highly proficient enzyme, Δ5-3-ketosteroid isomerase (KSI), in response to a sudden electrostatic perturbation that simulates the charge displacement that occurs along the KSI catalytic reaction coordinate. Photoexcitation of a fluorescent analog (coumarin 183) of the reaction intermediate mimics the change in charge distribution that occurs between the reactant and intermediate state in the steroid substrate of KSI. We measured the electrostatic response and angular dynamics of four probe dipoles in the enzyme active site by monitoring the time-resolved changes in the vibrational absorbance (IR) spectrum of a spectator thiocyanate moiety (a quantitative sensor of changes in electric field) placed at four different locations in and around the active site, using polarization-dependent transient vibrational Stark spectroscopy. The four different dipoles in the active site remain immobile and do not align to the changes in the substrate electric field. These results indicate that the active site of KSI is preorganized with respect to functionally relevant changes in electric fields. PMID:21949360

Electric-field-driven phase transition in vanadium dioxide

NASA Astrophysics Data System (ADS)

Wu, B.; Zimmers, A.; Aubin, H.; Ghosh, R.; Liu, Y.; Lopez, R.

2011-12-01

We report on local probe measurements of current-voltage and electrostatic force-voltage characteristics of electric-field-induced insulator to metal transition in VO2 thin film. In conducting AFM mode, switching from the insulating to metallic state occurs for electric-field threshold E˜6.5×107Vm-1 at 300K. Upon lifting the tip above the sample surface, we find that the transition can also be observed through a change in electrostatic force and in tunneling current. In this noncontact regime, the transition is characterized by random telegraphic noise. These results show that electric field alone is sufficient to induce the transition; however, the electronic current provides a positive feedback effect that amplifies the phenomena.

Mars Atmospheric Chemistry in Electrified Dust Devils and Storms

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Delory, G. T.; Atreya, S. K.; Wong, A.-S.; Renno, N. O.; Sentmann, D. D.; Marshall, J. G.; Cummer, S. A.; Rafkin, S.; Catling, D.

2005-01-01

Laboratory studies, simulations and desert field tests all indicate that aeolian mixing dust can generate electricity via contact electrification or "triboelectricity". In convective structures like dust devils or storms, grain stratification (or charge separation) occurs giving rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies [1] indicate that this storm electric field on Mars can approach atmospheric breakdown field strength of 20 kV/m. In terrestrial dust devils, coherent dipolar electric fields exceeding 20 kV/m have been measured directly via electric field instrumentation. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via the electric field to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with ambient electric field, with substantial production of dissociative products when fields approach breakdown levels of 20-30 kV/m.

Field distribution and DNA transport in solid tumors during electric field-mediated gene delivery.

PubMed

Henshaw, Joshua W; Yuan, Fan

2008-02-01

Gene therapy has a great potential in cancer treatment. However, the efficacy of cancer gene therapy is currently limited by the lack of a safe and efficient means to deliver therapeutic genes into the nucleus of tumor cells. One method under investigation for improving local gene delivery is based on the use of pulsed electric field. Despite repeated demonstration of its effectiveness in vivo, the underlying mechanisms behind electric field-mediated gene delivery remain largely unknown. Without a thorough understanding of these mechanisms, it will be difficult to further advance the gene delivery. In this review, the electric field-mediated gene delivery in solid tumors will be examined by following individual transport processes that must occur in vivo for a successful gene transfer. The topics of examination include: (i) major barriers for gene delivery in the body, (ii) distribution of electric fields at both cell and tissue levels during the application of external fields, and (iii) electric field-induced transport of genes across each of the barriers. Through this approach, the review summarizes what is known about the mechanisms behind electric field-mediated gene delivery and what require further investigations in future studies.

Communication: Polarizable polymer chain under external electric field in a dilute polymer solution.

PubMed

Budkov, Yu A; Kolesnikov, A L; Kiselev, M G

2015-11-28

We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such "field-induced" globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification.

THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: II. EFFECTIVE DIELECTRIC CONSTANT AND LOCAL FIELD ENHANCEMENT

EPA Science Inventory

Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

Magnetic ordering-induced multiferroic behavior in [CH 3NH 3][Co(HCOO) 3] metal-organic framework.

DOE PAGES

Gomez-Aguirre, Lilian Claudia; Zapf, Vivien S.; Pato-Doldan, Breogan; ...

2015-12-30

Here, we present the first example of magnetic ordering-induced multiferroic behavior in a metal–organic framework magnet. This compound is [CH 3NH 3][Co(HCOO) 3] with a perovskite-like structure. The A-site [CH 3NH 3] + cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii–Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is appliedmore » along this [101]: a spin rearrangement occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.« less

A novel approach for in vitro studies applying electrical fields to cell cultures by transformer-like coupling.

PubMed

Hess, R; Neubert, H; Seifert, A; Bierbaum, S; Hart, D A; Scharnweber, D

2012-12-01

The purpose of this study was to develop a new apparatus for in vitro studies applying low frequency electrical fields to cells without interfering side effects like biochemical reactions or magnetic fields which occur in currently available systems. We developed a non-invasive method by means of the principle of transformer-like coupling where the magnetic field is concentrated in a toroid and, therefore, does not affect the cell culture. Next to an extensive characterization of the electrical field parameters, initial cell culture studies have focused on examining the response of bone marrow-derived human mesenchymal stem cells (MSCs) to pulsed electrical fields. While no significant differences in the proliferation of human MSCs could be detected, significant increases in ALP activity as well as in gene expression of other osteogenic markers were observed. The results indicate that transformer-like coupled electrical fields can be used to influence osteogenic differentiation of human MSCs in vitro and can pose a useful tool in understanding the influence of electrical fields on the cellular and molecular level.

Electrical switching in cadmium boracite single crystals

NASA Technical Reports Server (NTRS)

Takahashi, T.; Yamada, O.

1981-01-01

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

The source of the electric field in the nightside magnetosphere

NASA Technical Reports Server (NTRS)

Stern, D. P.

1975-01-01

In the open magnetosphere model magnetic field lines from the polar caps connect to the interplanetary magnetic field and conduct an electric field from interplanetary space to the polar ionosphere. By examining the magnetic flux involved it is concluded that only slightly more than half of the magnetic flux in the polar caps belongs to open field lines and that such field lines enter or leave the magnetosphere through narrow elongated windows stretching the tail. These window regions are identified with the tail's boundary region and shift their position with changes in the interplanetary magnetic field, in particular when a change of interplanetary magnetic sector occurs. The circuit providing electric current in the magnetopause and the plasma sheet is extended across those windows; thus energy is drained from the interplanetary electric field and an electric potential drop is produced across the plasma sheet. The polar cap receives its electric field from interplanetary space on the day side from open magnetic field lines and on the night side from closed field lines leading to the plasma sheet. The theory described provides improved understanding of magnetic flux bookkeeping, of the origin of Birkeland currents, and of the boundary layer of the geomagnetic tail.

Growth rate and mitotic index analysis of Vicia faba L. roots exposed to 60-Hz electric fields.

PubMed

Inoue, M; Miller, M W; Cox, C; Carstesen, E L

1985-01-01

Growth, mitotic index, and growth rate recovery were determined for Vicia faba L. roots exposed to 60-Hz electric fields of 200, 290, and 360 V/m in an aqueous inorganic nutrient medium (conductivity 0.07-0.09 S/m). Root growth rate decreased in proportion to the increasing strength; the electric field threshold for a growth rate effect was about 230 V/m. The induced transmembrane potential at the threshold exposure was about 4-7 mV. The mitotic index was not affected by an electric field exposure sufficient to reduce root growth rate to about 35% of control. Root growth rate recovery from 31-96% of control occurred in 4 days after cessation of the 360 V/m exposure. The results support the postulate that the site of action of the applied electric fields is the cell membrane.

Turbulence-induced anomalous electron diffusion in the plume of the VASIMR VX-200

NASA Astrophysics Data System (ADS)

Olsen, Christopher; Ballenger, Maxwell; Squire, Jared; Longmier, Benjamin; Carter, Mark; Glover, Tim

2012-10-01

The separation of electrons from magnetic nozzles is critical to the function of the VASIMR engine and is of general importance to the field of electric propulsion. Separation of electrons by means of anomalous cross field diffusion is considered. Plume measurements using spectral analysis of custom high frequency probes characterizes the nature of oscillating electric fields in the expanding magnetic nozzle. The oscillating electric field results in frequency dependent density variations that can lead to anomalously high transport in the absence of collisions mimicking collisional transport. The spatial structure of the fluctuating fields is consistent with turbulence caused by separation of energetic (> 100 eV) non-magnetized ions and low energy magnetized electrons via the modified two-stream instability (MTSI) and generalized lower hybrid drift instability (GLHDI). Electric fields as high as 300 V/m are observed at frequencies up to an order of magnitude above the lower hybrid frequency. The electric field fluctuations dissipate with increasing axial distance consistent with changes in ion flux streamlines as plasma detachment occurs.

In situ study of electric field controlled ion transport in the Fe/BaTiO3 interface

NASA Astrophysics Data System (ADS)

Merkel, D. G.; Bessas, D.; Bazsó, G.; Jafari, A.; Rüffer, R.; Chumakov, A. I.; Khanh, N. Q.; Sajti, Sz; Celse, J.-P.; Nagy, D. L.

2018-01-01

Electric field controlled ion transport and interface formation of iron thin films on a BaTiO3 substrate have been investigated by in situ nuclear resonance scattering and x-ray reflectometry techniques. At early stage of deposition, an iron-II oxide interface layer was observed. The hyperfine parameters of the interface layer were found insensitive to the evaporated layer thickness. When an electric field was applied during growth, a 10 Å increase of the nonmagnetic/magnetic thickness threshold and an extended magnetic transition region was measured compared to the case where no field was applied. The interface layer was found stable under this threshold when further evaporation occurred, contrary to the magnetic layer where the magnitude and orientation of the hyperfine magnetic field vary continuously. The obtained results of the growth mechanism and of the electric field effect of the Fe/BTO system will allow the design of novel applications by creating custom oxide/metallic nanopatterns using laterally inhomogeneous electric fields during sample preparation.

Interaction of biological systems with static and ELF electric and magnetic fields

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

Anderson, L.E.; Kelman, B.J.; Weigel, R.J.

1987-01-01

Although background levels of atmospheric electric and geomagnetic field levels are extremely low, over the past several decades, human beings and other life forms on this planet have been subjected to a dramatically changing electromagnetic milieu. An exponential increase in exposure to electromagnetic fields has occurred, largely because of such technological advances as the growth of electrical power generation and transmission systems, the increased use of wireless communications, and the use of radar. In addition, electromagnetic field generating devices have proliferated in industrial plants, office buildings, homes, public transportation systems, and elsewhere. Although significant increases have occurred in electromagnetic fieldmore » strenghths spanning all frequency ranges, this symposium addresses only the impact of these fields at static and extremely low frequencies (ELF), primarily 50 and 60 Hz. This volume contains the proceedings of the symposium entitled /open quotes/Interaction of biological systems with static and ELF electric and magnetic fields/close quotes/. The purpose of the symposium was to provide a forum for discussions of all aspects of research on the interaction of static and ELF electromagnetic fields with biological systems. These systems include simple biophysical models, cell and organ preparations, whole animals, and man. Dosimetry, exposure system design, and artifacts in ELF bioeffects research were also addressed, along with current investigations that examine fundamental mechanisms of interactions between the fields and biological processes. Papers are indexed separately.« less

Effect of multilayer structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide.

PubMed

Chen, Xianping; Tan, Chunjian; Yang, Qun; Meng, Ruishen; Liang, Qiuhua; Jiang, Junke; Sun, Xiang; Yang, D Q; Ren, Tianling

2016-06-28

Development of nanoelectronics requires two-dimensional (2D) systems with both direct-bandgap and tunable electronic properties as they act in response to the external electric field (E-field). Here, we present a detailed theoretical investigation to predict the effect of atomic structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide (BP). We demonstrate that the splitting of bands and bandgap of BP depends on the number of layers and the stacking order. The values for the bandgap show a monotonically decreasing relationship with increasing layer number. We also show that AB-stacking BP has a direct-bandgap, while ABA-stacking BP has an indirect-bandgap when the number of layers n > 2. In addition, for a bilayer and a trilayer, the bandgap increases (decreases) as the electric field increases along the positive direction of the external electric field (E-field) (negative direction). In the case of four-layer BP, the bandgap exhibits a nonlinearly decreasing behavior as the increase in the electric field is independent of the electric field direction. The tunable mechanism of the bandgap can be attributed to a giant Stark effect. Interestingly, the investigation also shows that a semiconductor-to-metal transition may occur for the four-layer case or more layers beyond the critical electric field. Our findings may inspire more efforts in fabricating new nanoelectronics devices based on few-layer BP.

Deep-subwavelength imaging of both electric and magnetic localized optical fields by plasmonic campanile nanoantenna

DOE PAGES

Caselli, Niccolò; La China, Federico; Bao, Wei; ...

2015-06-05

Tailoring the electromagnetic field at the nanoscale has led to artificial materials exhibiting fascinating optical properties unavailable in naturally occurring substances. Besides having fundamental implications for classical and quantum optics, nanoscale metamaterials provide a platform for developing disruptive novel technologies, in which a combination of both the electric and magnetic radiation field components at optical frequencies is relevant to engineer the light-matter interaction. Thus, an experimental investigation of the spatial distribution of the photonic states at the nanoscale for both field components is of crucial importance. Here we experimentally demonstrate a concomitant deep-subwavelength near-field imaging of the electric and magneticmore » intensities of the optical modes localized in a photonic crystal nanocavity. We take advantage of the “campanile tip”, a plasmonic near-field probe that efficiently combines broadband field enhancement with strong far-field to near-field coupling. In conclusion, by exploiting the electric and magnetic polarizability components of the campanile tip along with the perturbation imaging method, we are able to map in a single measurement both the electric and magnetic localized near-field distributions.« less

Field-aligned particle currents near an auroral arc.

NASA Technical Reports Server (NTRS)

Choy, L. W.; Arnoldy, R. L.; Potter, W.; Kintner, P.; Cahill, L. J., Jr.

1971-01-01

A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970. The purpose of this flight was to obtain evidence of the low-energy electrons and protons that constitute a field-aligned sheet current, and also to obtain the magnetic signature of such a current and the electric field in and near the auroral-arc electric current system. Particular attention was given to a sudden increase in the field-aligned current associated with a prior sudden increase in the electric field and a sudden change in the magnetic field, all occurring near the edge of a visual auroral arc. Data obtained are discussed and analyzed; they present an important contribution to the problem of mapping of atmospheric auroral phenomena to the magnetospheric equatorial plane.

An Analysis of Teachers' Concept Confusion Concerning Electric and Magnetic Fields

ERIC Educational Resources Information Center

Hekkenberg, Ans; Lemmer, Miriam; Dekkers, Peter

2015-01-01

In an exploratory study, 36 South African physical science teachers' understanding of basic concepts concerning electric and magnetic fields was studied from a perspective of possible concept confusion. Concept confusion is said to occur when features of one concept are incorrectly attributed to a different concept, in the case of this study to…

Magnetic and Electric Transverse Spin Density of Spatially Confined Light

NASA Astrophysics Data System (ADS)

Neugebauer, Martin; Eismann, Jörg S.; Bauer, Thomas; Banzer, Peter

2018-04-01

When a beam of light is laterally confined, its field distribution can exhibit points where the local magnetic and electric field vectors spin in a plane containing the propagation direction of the electromagnetic wave. The phenomenon indicates the presence of a nonzero transverse spin density. Here, we experimentally investigate this transverse spin density of both magnetic and electric fields, occurring in highly confined structured fields of light. Our scheme relies on the utilization of a high-refractive-index nanoparticle as a local field probe, exhibiting magnetic and electric dipole resonances in the visible spectral range. Because of the directional emission of dipole moments that spin around an axis parallel to a nearby dielectric interface, such a probe particle is capable of locally sensing the magnetic and electric transverse spin density of a tightly focused beam impinging under normal incidence with respect to said interface. We exploit the achieved experimental results to emphasize the difference between magnetic and electric transverse spin densities.

Characteristics of Currents and Electric Fields Associated with the Initial Stage of Upward Lightning

NASA Astrophysics Data System (ADS)

Watanabe, N.; Nag, A.; Diendorfer, G.; Pichler, H.; Schulz, W.

2017-12-01

There is increasing interest in understanding processes associated with the initiation of upward lightning from tall structures. Characterization of such processes is essential for the development of appropriate models. We examine current and electric field waveforms for 15 negative upward flashes occurring in 2007-2009 initiated from the Gaisberg Tower located in Salzburg, Austria. Current was measured at the top of the tower using a 0.25 mΩ shunt. Electric field was measured simultaneously at close (170 m from the tower) and far (79 km from the tower in 2007 and 109 km in 2008-2009) distances. The initial stage (IS) of these flashes comprised of relatively slowly varying "background" current (having durations ranging from 132 to 692 ms), with faster, more impulsive current variations (pulses having durations ranging from 4.7 µs to 22.9 ms) overlaid on this background current. In five of the 15 (33%) flashes, this IS background current was negative while in the other ten (67%) flashes, the current was bipolar (changing between negative and positive values). 150 current pulses occurred during the IS of these 15 flashes, of which 28 (19%) were positive bipolar (positive initial polarity with a negative opposite polarity overshoot), 5 (3.3%) were positive unipolar (positive initial polarity with no opposite polarity overshoot), and 117 (78%) were negative unipolar. No negative bipolar pulses were found. The median peak current and risetime for the 28 bipolar pulses were 0.74 kA and 2.8 µs, respectively, and those for the 122 unipolar pulses were 0.87 kA and 70 µs, respectively. Generally speaking, majority of the pulses occurring at the beginning of the initial stage were lower-amplitude positive bipolar, while higher-amplitude unipolar pulses were more likely to occur at later times. These 150 IS current pulses produced 133 detectable electric field change signatures at the near station and 59 at the far station (all recorded at 79 km in 12 flashes occurring in 2007). We will examine in detail the characteristics of these electric field pulses in order to gain insights into the mechanisms of the underlying processes.

Statistical analysis of electric field parameters for negative lightning in Malaysia

NASA Astrophysics Data System (ADS)

Wooi, Chin-Leong; Abdul-Malek, Zulkurnain; Ahmad, Noor-Azlinda; El Gayar, Ali I.

2016-08-01

This paper presents a comparative study on the electric field and its derivative parameters of negative lightning in Malaysia and other regions. This study is the first in Malaysia where the parameters of negative electric field and its derivative are thoroughly analyzed. 104 negative lightning flashes containing 277 negative return strokes occurring within 10-100 km from the measuring station and recorded during monsoon period in the state of Johor, Malaysia had been analyzed. It was found that 73% of the recorded flashes are multiple strokes with an average multiplicity of 2.6 strokes per flash. For first return strokes, the arithmetic mean (AM) of initial peak electric field and the AM of initial peak electric field derivative are 21.8 V/m and 11.3 V/m/μs, respectively. The initial peaks of electric field and its derivative for first return strokes are larger than those for the subsequent return strokes. Comparison of overall results with those obtained earlier in Sri Lanka, Germany, Sweden, Japan, Florida indicates that several electric field and its derivative parameters are affected by propagation media and geographical region. Similarity of results with other countries having the same climatic condition is also observed.

Electric field strength determination in filamentary DBDs by CARS-based four-wave mixing

NASA Astrophysics Data System (ADS)

Boehm, Patrick; Kettlitz, Manfred; Brandenburg, Ronny; Hoeft, Hans; Czarnetzki, Uwe

2016-09-01

The electric field strength is a basic parameter of non-thermal plasmas. Therefore, a profound knowledge of the electric field distribution is crucial. In this contribution a four wave mixing technique based on Coherent Anti-Stokes Raman spectroscopy (CARS) is used to measure electric field strengths in filamentary dielectric barrier discharges (DBDs). The discharges are operated with a pulsed voltage in nitrogen at atmospheric pressure. Small amounts hydrogen (10 vol%) are admixed as tracer gas to evaluate the electric field strength in the 1 mm discharge gap. Absolute values of the electric field strength are determined by calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. Alteration of the electric field strength has been observed during the internal polarity reversal and the breakdown process. In this case the major advantage over emission based methods is that this technique can be used independently from emission, e.g. in the pre-phase and in between two consecutive, opposite discharge pulses where no emission occurs at all. This work was supported by the Deutsche Forschungsgemeinschaft, Forschergruppe FOR 1123 and Sonderforschungsbereich TRR 24 ``Fundamentals of complex plasmas''.

Liquid Dielectrics in an Inhomogeneous Pulsed Electric Field

NASA Astrophysics Data System (ADS)

Shneider, M. N.; Pekker, M.

2016-08-01

This book comprehensively describes the phenomena that occur in liquid dielectrics under the influence of an inhomogeneous pulsed electric field. Written by leading experts in the field, it is the first of its kind to address numerous potential applications such as the technology of high-voltage insulation in pulsed inhomogeneous fields, and applications related to cavitation development in liquid dielectrics, plasma treatment of different materials and plasma medicine dealing with living cells. Liquid Dielectrics in an Inhomogeneous Pulsed Electric Field is intended for a broad audience, from students to engineers and scientists, who are interested in current research questions in electrodynamics and hydrodynamics of liquid dielectrics. Part of the IOP Plasma Physics Series

A study of the electric field in an open magnetospheric model

NASA Technical Reports Server (NTRS)

Stern, D. P.

1972-01-01

The qualitative properties of an open magnetosphere and its electric field are examined and compared to a simple model of a dipole in a constant field and to actual observations. Many of these properties are found to depend on the separatrix, a curve connecting neutral points and separating different field-line regimes. In the simple model, the electric field in the central polar cap tends to point from dawn to dusk for a wide choice of external fields. Near the boundary of the polar cap electric equipotentials curve and become crescent-shaped, which may explain the correlation of polar magnetic variations with the azimuthal component of the interplanetary magnetic field, reported by Svalgaard. Modifications expected to occur in the actual magnetosphere are also investigated: in particular, it appears that bending of equipotentials may be reduced by cross-field flow during the merging of field lines and that open field lines connected to the polar caps emerge from a long and narrow slot extending along the tail.

Electric field measurements in nanosecond pulse discharges in air over liquid water surface

NASA Astrophysics Data System (ADS)

Simeni Simeni, Marien; Baratte, Edmond; Zhang, Cheng; Frederickson, Kraig; Adamovich, Igor V.

2018-01-01

Electric field in nanosecond pulse discharges in ambient air is measured by picosecond four-wave mixing, with absolute calibration by a known electrostatic field. The measurements are done in two geometries, (a) the discharge between two parallel cylinder electrodes placed inside quartz tubes, and (b) the discharge between a razor edge electrode and distilled water surface. In the first case, breakdown field exceeds DC breakdown threshold by approximately a factor of four, 140 ± 10 kV cm-1. In the second case, electric field is measured for both positive and negative pulse polarities, with pulse durations of ˜10 ns and ˜100 ns, respectively. In the short duration, positive polarity pulse, breakdown occurs at 85 kV cm-1, after which the electric field decreases over several ns due to charge separation in the plasma, with no field reversal detected when the applied voltage is reduced. In a long duration, negative polarity pulse, breakdown occurs at a lower electric field, 30 kV cm-1, after which the field decays over several tens of ns and reverses direction when the applied voltage is reduced at the end of the pulse. For both pulse polarities, electric field after the pulse decays on a microsecond time scale, due to residual surface charge neutralization by transport of opposite polarity charges from the plasma. Measurements 1 mm away from the discharge center plane, ˜100 μm from the water surface, show that during the voltage rise, horizontal field component (Ex ) lags in time behind the vertical component (Ey ). After breakdown, Ey is reduced to near zero and reverses direction. Further away from the water surface (≈0.9 mm), Ex is much higher compared to Ey during the entire voltage pulse. The results provide insight into air plasma kinetics and charge transport processes near plasma-liquid interface, over a wide range of time scales.

Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere.

PubMed

Marklund, G T; Ivchenko, N; Karlsson, T; Fazakerley, A; Dunlop, M; Lindqvist, P A; Buchert, S; Owen, C; Taylor, M; Vaivalds, A; Carter, P; André, M; Balogh, A

2001-12-13

The bright night-time aurorae that are visible to the unaided eye are caused by electrons accelerated towards Earth by an upward-pointing electric field. On adjacent geomagnetic field lines the reverse process occurs: a downward-pointing electric field accelerates electrons away from Earth. Such magnetic-field-aligned electric fields in the collisionless plasma above the auroral ionosphere have been predicted, but how they could be maintained is still a matter for debate. The spatial and temporal behaviour of the electric fields-a knowledge of which is crucial to an understanding of their nature-cannot be resolved uniquely by single satellite measurements. Here we report on the first observations by a formation of identically instrumented satellites crossing a beam of upward-accelerated electrons. The structure of the electric potential accelerating the beam grew in magnitude and width for about 200 s, accompanied by a widening of the downward-current sheet, with the total current remaining constant. The 200-s timescale suggests that the evacuation of the electrons from the ionosphere contributes to the formation of the downward-pointing magnetic-field-aligned electric fields. This evolution implies a growing load in the downward leg of the current circuit, which may affect the visible discrete aurorae.

Recovery curves of the surface electric field after lightning discharges occurring between the positive charge pocket and negative charge centre in a thundercloud

NASA Astrophysics Data System (ADS)

Pawar, S. D.; Kamra, A. K.

2002-12-01

Surface observations of the electric field recovery curves of the lightning discharges occurring between the positive charge pocket and negative main charge centre in an overhead thundercloud are reported. Such recovery curves are observed to have an additional step of very slow field-change observed at an after-discharge value of electric field equal to 5-6 kV m-1. The behavior of recovery curves is explained in terms of the coronae charge and the relative efficiencies of the charge generating processes responsible for growth of positive charge pocket and main negative charge centre in the thundercloud. The charging currents responsible for the growth of charge in positive charge pockets is computed to be 2-4 times larger than that for the growth of the main negative charge. However, the charge destroyed in such a discharge is found to be comparable to that in a discharge between the main charge centres of the thundercloud.

Direct Visualization of Planar Assembly of Plasmonic Nanoparticles Adjacent to Electrodes in Oscillatory Electric Fields.

PubMed

Ferrick, Adam; Wang, Mei; Woehl, Taylor J

2018-05-29

Electric field-directed assembly of colloidal nanoparticles (NPs) has been widely adopted for fabricating functional thin films and nanostructured surfaces. While first-order electrokinetic effects on NPs are well-understood in terms of classical models, effects of second-order electrokinetics that involve induced surface charge are still poorly understood. Induced charge electroosmotic phenomena, such as electrohydrodynamic (EHD) flow, have long been implicated in electric field-directed NP assembly with little experimental basis. Here, we use in situ dark-field optical microscopy and plasmonic NPs to directly observe the dynamics of planar assembly of colloidal NPs adjacent to a planar electrode in low-frequency (<1 kHz) oscillatory electric fields. We exploit the change in plasmonic NP color resulting from interparticle plasmonic coupling to visualize the assembly dynamics and assembly structure of silver NPs. Planar assembly of NPs is unexpected because of strong electrostatic repulsion between NPs and indicates that there are strong attractive interparticle forces oriented perpendicular to the electric field direction. A parametric investigation of the voltage- and frequency-dependent phase behavior reveals that planar NP assembly occurs over a narrow frequency range below which irreversible ballistic deposition occurs. Two key experimental observations are consistent with EHD flow-induced NP assembly: (1) NPs remain mobile during assembly and (2) electron microscopy observations reveal randomly close-packed planar assemblies, consistent with strong interparticle attraction. We interpret planar assembly in terms of EHD fluid flow and develop a scaling model that qualitatively agrees with the measured phase regions. Our results are the first direct in situ observations of EHD flow-induced NP assembly and shed light on long-standing unresolved questions concerning the formation of NP superlattices during electric field-induced NP deposition.

Response of ionospheric electric fields at mid-low latitudes during sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2015-06-01

Using in situ observations from the Republic of China Satellite-1 spacecraft, we investigated the time response and local time dependence of the ionospheric electric field at mid-low latitudes associated with geomagnetic sudden commencements (SCs) that occurred from 1999 to 2004. We found that the ionospheric electric field variation associated with SCs instantaneously responds to the preliminary impulse (PI) signature on the ground regardless of spacecraft local time. Our statistical analysis also supports the global instant transmission of electric field from the polar region. In contrast, the peak time detected in the ionospheric electric field is earlier than that of the equatorial geomagnetic field (~20 s before in the PI phase). Based on the ground-ionosphere waveguide model, this time lag can be attributed to the latitudinal difference of ionospheric conductivity. However, the local time distribution of the initial excursion of ionospheric electric field shows that dusk-to-dawn ionospheric electric fields develop during the PI phase. Moreover, the westward electric field in the ionosphere, which produces the preliminary reverse impulse of the geomagnetic field on the dayside feature, appears at 18-22 h LT where the ionospheric conductivity beyond the duskside terminator (18 h LT) is lower than on the dayside. The result of a magnetohydrodynamic simulation for an ideal SC shows that the electric potential distribution is asymmetric with respect to the noon-midnight meridian. This produces the local time distribution of ionospheric electric fields similar to the observed result, which can be explained by the divergence of the Hall current under nonuniform ionospheric conductivity.

Near field of an oscillating electric dipole and cross-polarization of a collimated beam of light: Two sides of the same coin

NASA Astrophysics Data System (ADS)

Aiello, Andrea; Ornigotti, Marco

2014-09-01

We address the question of whether there exists a hidden relationship between the near-field distribution generated by an oscillating electric dipole and the so-called cross-polarization of a collimated beam of light. We find that the answer is affirmative by showing that the complex field distributions occurring in both cases have a common physical origin: the requirement that the electromagnetic fields must be transverse.

Electricity and colloidal stability: how charge distribution in the tissue can affects wound healing.

PubMed

Farber, Paulo Luiz; Hochman, Bernardo; Furtado, Fabianne; Ferreira, Lydia Masako

2014-02-01

The role of endogenous electric fields in wound healing is still not fully understood. Electric fields are of fundamental importance in various biological processes, ranging from embryonic development to disease progression, as described by many investigators in the last century. This hypothesis brings together some relevant literature on the importance of electric fields in physiology and pathology, the theory of biologically closed electric circuits, skin battery (a phenomenon that occurs after skin injury and seems to be involved in tissue repair), the relationship between electric charge and interstitial exclusion, and how skin tissues can be regarded as colloidal systems. The importance of electric charges, as established in the early works on the subject and the relevance of zeta potential and colloid stability are also analyzed, and together bring a new light for the physics involved in the wound repair of all the body tissues. Copyright © 2013 Elsevier Ltd. All rights reserved.

Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

NASA Technical Reports Server (NTRS)

Mazuruk, K.; Volz, M. P.

1996-01-01

A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

Nongyrotropic Electrons in Guide Field Reconnection

NASA Technical Reports Server (NTRS)

Wendel, D. E.; Hesse, M.; Bessho, N.; Adrian, M. L.; Kuznetsova, M.

2016-01-01

We apply a scalar measure of nongyrotropy to the electron pressure tensor in a 2D particle-in-cell simulation of guide field reconnection and assess the corresponding electron distributions and the forces that account for the nongyrotropy. The scalar measure reveals that the nongyrotropy lies in bands that straddle the electron diffusion region and the separatrices, in the same regions where there are parallel electric fields. Analysis of electron distributions and fields shows that the nongyrotropy along the inflow and outflow separatrices emerges as a result of multiple populations of electrons influenced differently by large and small-scale parallel electric fields and by gradients in the electric field. The relevant parallel electric fields include large-scale potential ramps emanating from the x-line and sub-ion inertial scale bipolar electron holes. Gradients in the perpendicular electric field modify electrons differently depending on their phase, thus producing nongyrotropy. Magnetic flux violation occurs along portions of the separatrices that coincide with the parallel electric fields. An inductive electric field in the electron EB drift frame thus develops, which has the effect of enhancing nongyrotropies already produced by other mechanisms and under certain conditions producing their own nongyrotropy. Particle tracing of electrons from nongyrotropic populations along the inflows and outflows shows that the striated structure of nongyrotropy corresponds to electrons arriving from different source regions. We also show that the relevant parallel electric fields receive important contributions not only from the nongyrotropic portion of the electron pressure tensor but from electron spatial and temporal inertial terms as well.

Long-wave analysis and control of the viscous Rayleigh-Taylor instability with electric fields

NASA Astrophysics Data System (ADS)

Cimpeanu, Radu; Anderson, Thomas; Petropoulos, Peter; Papageorgiou, Demetrios

2016-11-01

We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a solid surface in the presence of a horizontally acting electric field. The competition between gravity, surface tension and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semi-spectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations and assess the accuracy of the obtained solutions when varying the electric field strength from zero up to the point when complete stabilization at the target finite wavelengths occurs. We employ DNS to examine the limitations of the asymptotically derived behavior in the context of increasing liquid film heights, with agreement found to be excellent even beyond the target lengthscales. Regimes in which the thin film assumption is no longer valid and droplet pinch-off occurs are then analyzed. Finally, the asymptotic and computational approaches are used in conjunction to identify efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.

Transverse conductivity of a relativistic plasma in oblique electric and magnetic fields

NASA Technical Reports Server (NTRS)

Melia, Fulvio; Fatuzzo, Marco

1991-01-01

Resistive tearing in a primary candidate for flares occurring in stressed magnetic fields. Its possible application to the strongly magnetized environments (Hz about 10 to the 12th G) near the surface of neutron stars, particularly as a mechanism for generating the plasma heating and particle acceleration leading to gamma-ray bursts, has motivated a quantum treatment of this process, which requires knowledge of the electrical conductivity sigma of a relativistic gas in a new domain (i.e., that of a low-density n/e/) plasma in oblique electric and magnetic fields. This paper discusses the mathematical formalism for calculating sigma and present numerical results for a wide range of parameter values. The results indicate that sigma depends very strongly on both the applied electric and magnetic fields.

Ionic components of electric current at rat corneal wounds.

PubMed

Vieira, Ana Carolina; Reid, Brian; Cao, Lin; Mannis, Mark J; Schwab, Ivan R; Zhao, Min

2011-02-25

Endogenous electric fields and currents occur naturally at wounds and are a strong signal guiding cell migration into the wound to promote healing. Many cells involved in wound healing respond to small physiological electric fields in vitro. It has long been assumed that wound electric fields are produced by passive ion leakage from damaged tissue. Could these fields be actively maintained and regulated as an active wound response? What are the molecular, ionic and cellular mechanisms underlying the wound electric currents? Using rat cornea wounds as a model, we measured the dynamic timecourses of individual ion fluxes with ion-selective probes. We also examined chloride channel expression before and after wounding. After wounding, Ca(2+) efflux increased steadily whereas K(+) showed an initial large efflux which rapidly decreased. Surprisingly, Na(+) flux at wounds was inward. A most significant observation was a persistent large influx of Cl(-), which had a time course similar to the net wound electric currents we have measured previously. Fixation of the tissues abolished ion fluxes. Pharmacological agents which stimulate ion transport significantly increased flux of Cl(-), Na(+) and K(+). Injury to the cornea caused significant changes in distribution and expression of Cl(-) channel CLC2. These data suggest that the outward electric currents occurring naturally at corneal wounds are carried mainly by a large influx of chloride ions, and in part by effluxes of calcium and potassium ions. Ca(2+) and Cl(-) fluxes appear to be mainly actively regulated, while K(+) flux appears to be largely due to leakage. The dynamic changes of electric currents and specific ion fluxes after wounding suggest that electrical signaling is an active response to injury and offers potential novel approaches to modulate wound healing, for example eye-drops targeting ion transport to aid in the challenging management of non-healing corneal ulcers.

Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface

NASA Astrophysics Data System (ADS)

Homin, Taras; Korsun, Anatolii

High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the φc varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut’s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects. These effects need to be studied, and appropriate remedies are to be developed. References 1. Mikatarian, R., et al., «Electrical Charging of the International Space Station», AIAA Paper No. 2003-1079, 41th. Aerospace Sciences Meeting and Exhibit, January 2003. 2. A.G. Korsun, «Electric discharge processes intensification mechanisms on International Space Station surface». Astronautics and rocket production, 1, 2011 (in Russian).

Nanoscale electron manipulation in metals with intense THz electric fields

NASA Astrophysics Data System (ADS)

Takeda, Jun; Yoshioka, Katsumasa; Minami, Yasuo; Katayama, Ikufumi

2018-03-01

Improved control over the electromagnetic properties of metals on a nanoscale is crucial for the development of next-generation nanoelectronics and plasmonic devices. Harnessing the terahertz (THz)-electric-field-induced nonlinearity for the motion of electrons is a promising method of manipulating the local electromagnetic properties of metals, while avoiding undesirable thermal effects and electronic transitions. In this review, we demonstrate the manipulation of electron delocalization in ultrathin gold (Au) films with nanostructures, by intense THz electric-field transients. On increasing the electric-field strength of the THz pulses, the transmittance in the THz-frequency region abruptly decreases around the percolation threshold. The observed THz-electric-field-induced nonlinearity is analysed, based on the Drude-Smith model. The results suggest that ultrafast electron delocalization occurs by electron tunnelling across the narrow insulating bridge between the Au nanostructures, without material breakdown. In order to quantitatively discuss the tunnelling process, we perform scanning tunnelling microscopy with carrier-envelope phase (CEP)-controlled single-cycle THz electric fields. By applying CEP-controlled THz electric fields to the 1 nm nanogap between a metal nanotip and graphite sample, many electrons could be coherently driven through the quantum tunnelling process, either from the nanotip to the sample or vice versa. The presented concept, namely, electron tunnelling mediated by CEP-controlled single-cycle THz electric fields, can facilitate the development of nanoscale electron manipulation, applicable to next-generation ultrafast nanoelectronics and plasmonic devices.

Phase-field model of insulator-to-metal transition in VO2 under an electric field

NASA Astrophysics Data System (ADS)

Shi, Yin; Chen, Long-Qing

2018-05-01

The roles of an electric field and electronic doping in insulator-to-metal transitions are still not well understood. Here we formulated a phase-field model of insulator-to-metal transitions by taking into account both structural and electronic instabilities as well as free electrons and holes in VO2, a strongly correlated transition-metal oxide. Our phase-field simulations demonstrate that in a VO2 slab under a uniform electric field, an abrupt universal resistive transition occurs inside the supercooling region, in sharp contrast to the conventional Landau-Zener smooth electric breakdown. We also show that hole doping may decouple the structural and electronic phase transitions in VO2, leading to a metastable metallic monoclinic phase which could be stabilized through a geometrical confinement and the size effect. This work provides a general mesoscale thermodynamic framework for understanding the influences of electric field, electronic doping, and stress and strain on insulator-to-metal transitions and the corresponding mesoscale domain structure evolution in VO2 and related strongly correlated systems.

Electro-optic Lightning Detector

NASA Technical Reports Server (NTRS)

Koshak, William J.; Solakiewicz, Richard J.

1996-01-01

The design, alignment, calibration, and field deployment of a solid-state lightning detector is described. The primary sensing component of the detector is a potassium dihydrogen phosphate (KDP) electro-optic crystal that is attached in series to a flat plate aluminum antenna; the antenna is exposed to the ambient thundercloud electric field. A semiconductor laser diode (lambda = 685 nm), polarizing optics, and the crystal are arranged in a Pockels cell configuration. Lightning-caused electric field changes are related to small changes in the transmission of laser light through the optical cell. Several hundred lightning electric field change excursions were recorded during five thunderstorms that occurred in the summer of 1998 at the NASA Marshall Space Flight Center (MSFC) in northern Alabama.

Electro-Optic Lightning Detector

NASA Technical Reports Server (NTRS)

Koshak, Willliam; Solakiewicz, Richard

1998-01-01

The design, alignment, calibration, and field deployment of a solid-state lightning detector is described. The primary sensing component of the detector is a potassium dihydrogen phosphate (KDP) electro-optic crystal that is attached in series to a flat plate aluminum antenna; the antenna is exposed to the ambient thundercloud electric field. A semiconductor laser diode (lambda = 685 nm), polarizing optics, and the crystal are arranged in a Pockels cell configuration. Lightning-caused electric field changes are then related to small changes in the transmission of laser light through the optical cell. Several hundred lightning electric field change excursions were recorded during 4 thunderstorms that occurred in the summer of 1998 at the NASA Marshall Space Flight Center (MSFC) in Northern Alabama.

Electro-Optic Lighting Detector

NASA Technical Reports Server (NTRS)

Koshak, William J.; Solakiewicz, Richard J.

1999-01-01

The design, alignment, calibration, and field deployment of a solid-state lightning detector is described. The primary sensing component of the detector is a potassium dihydrogen phosphate electro-optic crystal that is attached in series to a flat-plate aluminum antenna; the antenna is exposed to the ambient thundercloud electric field. A semiconductor laser diode (lambda = 685 nm), polarizing optics, and the crystal are arranged in a Pockels cell configuration. Lightning-caused electric field changes are related to small changes in the transmission of laser light through the optical cell. Several hundred lightning electric field change excursions were recorded during five thunderstorms that occurred in the summer of 1998 at the NASA Marshall Space Flight Center in northern Alabama.

Lethal effect of electric fields on isolated ventricular myocytes.

PubMed

de Oliveira, Pedro Xavier; Bassani, Rosana Almada; Bassani, José Wilson Magalhães

2008-11-01

Defibrillator-type shocks may cause electric and contractile dysfunction. In this study, we determined the relationship between probability of lethal injury and electric field intensity (E in isolated rat ventricular myocytes, with emphasis on field orientation and stimulus waveform. This relationship was sigmoidal with irreversible injury for E > 50 V/cm . During both threshold and lethal stimulation, cells were twofold more sensitive to the field when it was applied longitudinally (versus transversally) to the cell major axis. For a given E, the estimated maximum variation of transmembrane potential (Delta V(max)) was greater for longitudinal stimuli, which might account for the greater sensitivity to the field. Cell death, however, occurred at lower maximum Delta V(max) values for transversal shocks. This might be explained by a less steep spatial decay of transmembrane potential predicted for transversal stimulation, which would possibly result in occurrence of electroporation in a larger membrane area. For the same stimulus duration, cells were less sensitive to field-induced injury when shocks were biphasic (versus monophasic). Ours results indicate that, although significant myocyte death may occur in the E range expected during clinical defibrillation, biphasic shocks are less likely to produce irreversible cell injury.

Penetration of Large Scale Electric Field to Inner Magnetosphere

NASA Astrophysics Data System (ADS)

Chen, S. H.; Fok, M. C. H.; Sibeck, D. G.; Wygant, J. R.; Spence, H. E.; Larsen, B.; Reeves, G. D.; Funsten, H. O.

2015-12-01

The direct penetration of large scale global electric field to the inner magnetosphere is a critical element in controlling how the background thermal plasma populates within the radiation belts. These plasma populations provide the source of particles and free energy needed for the generation and growth of various plasma waves that, at critical points of resonances in time and phase space, can scatter or energize radiation belt particles to regulate the flux level of the relativistic electrons in the system. At high geomagnetic activity levels, the distribution of large scale electric fields serves as an important indicator of how prevalence of strong wave-particle interactions extend over local times and radial distances. To understand the complex relationship between the global electric fields and thermal plasmas, particularly due to the ionospheric dynamo and the magnetospheric convection effects, and their relations to the geomagnetic activities, we analyze the electric field and cold plasma measurements from Van Allen Probes over more than two years period and simulate a geomagnetic storm event using Coupled Inner Magnetosphere-Ionosphere Model (CIMI). Our statistical analysis of the measurements from Van Allan Probes and CIMI simulations of the March 17, 2013 storm event indicate that: (1) Global dawn-dusk electric field can penetrate the inner magnetosphere inside the inner belt below L~2. (2) Stronger convections occurred in the dusk and midnight sectors than those in the noon and dawn sectors. (3) Strong convections at multiple locations exist at all activity levels but more complex at higher activity levels. (4) At the high activity levels, strongest convections occur in the midnight sectors at larger distances from the Earth and in the dusk sector at closer distances. (5) Two plasma populations of distinct ion temperature isotropies divided at L-Shell ~2, indicating distinct heating mechanisms between inner and outer radiation belts. (6) CIMI simulations reveal alternating penetration and shielding electric fields during the main phase of the geomagnetic storm, indicating an impulsive nature of the large scale penetrating electric field in regulating the gain and loss of radiation belt particles. We will present the statistical analysis and simulations results.

Dehydration process in NaCl solutions under various external electric fields

NASA Astrophysics Data System (ADS)

Kadota, Kazunori; Shimosaka, Atsuko; Shirakawa, Yoshiyuki; Hidaka, Jusuke

2007-06-01

Ionic motions at solid-liquid interface in supersaturated NaCl solutions have been investigated by molecular dynamics (MD) simulation for understanding crystal growth processes. The density profile in the vicinity of the interfaces between NaCl(100) and the supersaturated NaCl solution was calculated. Diffusion coefficients of water molecules in the solution were estimated as a function of distance from the crystal interface. It turned out that the structure and dynamics of the solution in the interfaces was different from those of bulk solution owing to electric fields depending on the surface charge. Therefore, the electric field was applied to the supersaturated solutions and dehydration phenomenon occurring in the process of the crystal growth was discussed. As the electric field increased, it was observed that the Na+ keeping strongly hydration structure broke out by the electric force. In supersaturated concentration, the solution structure is significantly different from that of dilution and has a complicated structure with hydration ions and clusters of NaCl. If the electric fields were applied to the solutions, the breakout of hydration structure was not affected with increasing the supersaturated ratio. This reason is that the cluster structures are destroyed by the electric force. The situation depends on the electric field or crystal surface structure.

Uplift of Ionospheric Oxygen Ions During Extreme Magnetic Storms

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce T.; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Huba, Joseph; Lakhina, Gurbax S.

2013-01-01

Research reported earlier in literature was conducted relating to estimation of the ionospheric electrical field, which may have occurred during the September 1859 Carrington geomagnetic storm event, with regard to modern-day consequences. In this research, the NRL SAMI2 ionospheric code has been modified and applied the estimated electric field to the dayside ionosphere. The modeling was done at 15-minute time increments to track the general ionospheric changes. Although it has been known that magnetospheric electric fields get down into the ionosphere, it has been only in the last ten years that scientists have discovered that intense magnetic storm electric fields do also. On the dayside, these dawn-to-dusk directed electric fields lift the plasma (electrons and ions) up to higher altitudes and latitudes. As plasma is removed from lower altitudes, solar UV creates new plasma, so the total plasma in the ionosphere is increased several-fold. Thus, this complex process creates super-dense plasmas at high altitudes (from 700 to 1,000 km and higher).

Geometric effects of ICMEs on geomagnetic storms

NASA Astrophysics Data System (ADS)

Cho, KyungSuk; Lee, Jae-Ok

2017-04-01

It has been known that the geomagnetic storm is occurred by the interaction between the Interplanetary Coronal Mass Ejection (ICME) and the Earth's magnetosphere; especially, the southward Bz component of ICME is thought as the main trigger. In this study, we investigate the relationship between Dst index and solar wind conditions; which are the southward Bz, electric field (VBz), and time integral of electric field as well as ICME parameters derived from toroidal fitting model in order to find what is main factor to the geomagnetic storm. We also inspect locations of Earth in ICMEs to understand the geometric effects of the Interplanetary Flux Ropes (IFRs) on the geomagnetic storms. Among 59 CDAW ICME lists, we select 30 IFR events that are available by the toroidal fitting model and classify them into two sub-groups: geomagnetic storms associated with the Magnetic Clouds (MCs) and the compression regions ahead of the MCs (sheath). The main results are as follows: (1) The time integral of electric field has a higher correlation coefficient (cc) with Dst index than the other parameters: cc=0.85 for 25 MC events and cc=0.99 for 5 sheath events. (2) The sheath associated intense storms (Dst ≤-100nT) having usually occur at flank regions of ICMEs while the MC associated intense storms occur regardless of the locations of the Earth in ICMEs. The strength of a geomagnetic storm strongly depends on electric field of IFR and durations of the IFR passages through the Earth.

Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

DOEpatents

Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

1984-04-19

In a field-effect transistor comprising a semiconductor having therein a source, a drain, a channel and a gate in operational relationship, there is provided an improvement wherein said semiconductor is a superlattice comprising alternating quantum well and barrier layers, the quantum well layers comprising a first direct gap semiconductor material which in bulk form has a certain bandgap and a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, the barrier layers comprising a second semiconductor material having a bandgap wider than that of said first semiconductor material, wherein the layer thicknesses of said quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice having a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, and wherein the thicknesses of said quantum well layers are selected to provide a superlattice curve of electron velocity versus applied electric field whereby, at applied electric fields higher than that at which the maximum electron velocity occurs in said first material when in bulk form, the electron velocities are higher in said superlattice than they are in said first semiconductor material in bulk form.

Creating and optimizing interfaces for electric-field and photon-induced charge transfer.

PubMed

Park, Byoungnam; Whitham, Kevin; Cho, Jiung; Reichmanis, Elsa

2012-11-27

We create and optimize a structurally well-defined electron donor-acceptor planar heterojunction interface in which electric-field and/or photon-induced charge transfer occurs. Electric-field-induced charge transfer in the dark and exciton dissociation at a pentacene/PCBM interface were probed by in situ thickness-dependent threshold voltage shift measurements in field-effect transistor devices during the formation of the interface. Electric-field-induced charge transfer at the interface in the dark is correlated with development of the pentacene accumulation layer close to PCBM, that is, including interface area, and dielectric relaxation time in PCBM. Further, we demonstrate an in situ test structure that allows probing of both exciton diffusion length and charge transport properties, crucial for optimizing optoelectronic devices. Competition between the optical absorption length and the exciton diffusion length in pentacene governs exciton dissociation at the interface. Charge transfer mechanisms in the dark and under illumination are detailed.

Generation of electric fields and currents by neutral flows in weakly ionized plasmas through collisional dynamos

NASA Astrophysics Data System (ADS)

Dimant, Y. S.; Oppenheim, M. M.; Fletcher, A. C.

2016-08-01

In weakly ionized plasmas neutral flows drag plasma across magnetic field lines generating intense electric fields and currents. An example occurs in the Earth's ionosphere near the geomagnetic equator. Similar processes take place in the Solar chromosphere and magnetohydrodynamic generators. This paper argues that not all convective neutral flows generate electric fields and currents and it introduces the corresponding universal criterion for their formation, ∇×(U ×B )≠∂B /∂t , where U is the neutral flow velocity, B is the magnetic field, and t is time. This criterion does not depend on the conductivity tensor, σ ̂ . For many systems, the displacement current, ∂B /∂t , is negligible making the criterion even simpler. This theory also shows that the neutral-dynamo driver that generates E-fields and currents plays the same role as the DC electric current plays for the generation of the magnetic field in the Biot-Savart law.

Unusual lightning electric field waveforms observed in Kathmandu, Nepal, and Uppsala, Sweden

NASA Astrophysics Data System (ADS)

Adhikari, Pitri Bhakta; Sharma, Shriram; Baral, Kedarnath; Rakov, Vladimir A.

2017-11-01

Unusual lightning events have been observed in Uppsala, Sweden, and Kathmandu, Nepal, using essentially the same electric field measuring system developed at Uppsala University. They occurred in the storms that also generated ;normal; lightning events. The unusual events recorded in Uppsala occurred on one thunderstorm day. Similar events were observed in Kathmandu on multiple thunderstorm days. The unusual events were analyzed in this study assuming them to be positive ground flashes (+CGs), although we cannot rule out the possibility that some or most of them were actually cloud discharges (ICs). The unusual events were each characterized by a relatively slow, negative (atmospheric electricity sign convention) electric field waveform preceded by a pronounced opposite-polarity pulse whose duration was some tens of microseconds. To the best of our knowledge, such unusual events have not been reported in the literature. The average amplitudes of the opposite-polarity pulses with respect to those of the following main waveform were found to be about 33% in Uppsala (N = 31) and about 38% in Kathmandu (N = 327). The average durations of the main waveform and the preceding opposite-polarity pulse in Uppsala were 8.24 ms and 57.1 μs, respectively, and their counterparts in Kathmandu were 421 μs and 39.7 μs. Electric field waveforms characteristic of negative ground flashes (-CGs) were also observed, and none of them exhibited an opposite-polarity pulse prior to the main waveform. Possible origins of the unusual field waveforms are discussed.

Exposure scheme separates effects of electric shock and electric field for honey bees, Apis mellifera L

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

Bindokas, V.P.; Gauger, J.R.; Greenberg, B.

Mechanisms to explain disturbance of honey bee colonies under a 765-kV, 60-Hz transmission line (electric (E) field = 7 kV/m) fall into two categories: direct bee perception of enhanced in-hive E fields, and perception of shock from induced currents. The same adverse biological effects previously observed in honey bee colonies exposed under a 765-kV transmission line can be reproduced by exposing worker bees to shock or E field within elongated hive entranceways (= tunnels). Exposure to intense E field caused disturbance only if bees were in contact with a conductive substrate. E-field and shock exposure can be separated and preciselymore » defined within tunnels, eliminating dosimetric vagaries that occur when entire hives are exposed to E field.« less

Penetration of Nonstationary Ionospheric Electric Fields into Lower Atmospheric Layers in the Global Electric Circuit Model

NASA Astrophysics Data System (ADS)

Morozov, V. N.

2018-01-01

The problem of the penetration of nonstationary ionospheric electric fields into the lower atmospheric layers is considered based on the model of the global electric circuit in the Earth's atmosphere. For the equation of the electric field potential, a solution that takes into account exponential variation in the electrical conductivity with height has been obtained. Analysis of the solution made it possible to reveal three cases of the dependence of the solution on height. The first case (the case of high frequencies) corresponds to the Coulomb approximation, when the electrical conductivity of the atmosphere can be neglected. In the case of low frequencies (when the frequency of changes in the ionosphere potential is less than the quantity reciprocal to the time of electric relaxation of the atmosphere), a quasi-stationary regime, in which the variation in the electric potential of the atmosphere is determined by the electric conduction currents, occurs. In the third case, due to the increase in the electrical conductivity of the atmosphere, two spherical regions appear: with the Coulomb approximation in the lower region and conduction currents in the upper one. For these three cases, formulas for estimating the electric field strength near the Earth's surface have been obtained.

Surface Protonics Promotes Catalysis

PubMed Central

Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

2016-01-01

Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. PMID:27905505

Pulse propagation, dispersion, and energy in magnetic materials.

PubMed

Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Bloemer, Mark J; Centini, Marco; Sibilia, Concita; Bertolotti, Mario

2005-12-01

We discuss pulse propagation effects in generic, electrically and magnetically dispersive media that may display large material discontinuities, such as a surface boundary. Using the known basic constitutive relations between the fields, and an explicit Taylor expansion to describe the dielectric susceptibility and magnetic permeability, we derive expressions for energy density and energy dissipation rates, and equations of motion for the coupled electric and magnetic fields. We then solve the equations of motion in the presence of a single interface, and find that in addition to the now-established negative refraction process an energy exchange occurs between the electric and magnetic fields as the pulse traverses the boundary.

The role of fluctuation-induced transport in a toroidal plasma with strong radial electric fields

NASA Technical Reports Server (NTRS)

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Hong, J. Y.; Kim, Y. C.

1981-01-01

Previous work employing digitally implemented spectral analysis techniques is extended to demonstrate that radial fluctuation-induced transport is the dominant ion transport mechanism in an electric field dominated toroidal plasma. Such transport can be made to occur against a density gradient, and hence may have a very beneficial effect on confinement in toroidal plasmas of fusion interest. It is shown that Bohm or classical diffusion down a density gradient, the collisional Pedersen-current mechanism, and the collisionless electric field gradient mechanism described by Cole (1976) all played a minor role, if any, in the radial transport of this plasma.

On the role of the quasi-parallel bow shock in ion pickup - A lesson from Venus?

NASA Technical Reports Server (NTRS)

Luhmann, J. G.; Russell, C. T.; Phillips, J. L.; Barnes, A.

1987-01-01

Previous observations at Venus show convincing evidence of planetary O(+) ion pickup by the largescale motional -V x B electric field in the magnetosheath when the interplanetary magnetic field is perpendicular to the solar wind flow. However, the presence of magnetic field fluctuations in the magnetosheath downstream from the quasi-parallel bow shock should allow pickup to occur even when the upstream magnetic field B and plasma velocity V are practically coaligned. Single-particle calculations are used to demonstrate the convecting magnetic field fluctuations similar to those observed in the Venus magnetosheath when the subsolar bow shock is quasi-parallel can efficiently accelerate cold planetary ions by means of the electric field associated with their transverse components. This ion pickup process, which is characterized by a spatial dependence determined by the bow shock shape and the orientation of the upstream magnetic field, is likely also to occur at Mars and may be effective at comets.

How enzymes can capture and transmit free energy from an oscillating electric field.

PubMed

Westerhoff, H V; Tsong, T Y; Chock, P B; Chen, Y D; Astumian, R D

1986-07-01

Recently, it has been demonstrated that free energy from an alternating electric field can drive the active transport of Rb+ by way of the Na+, K+-ATPase. In the present work, it is shown why many transmembrane enzymes can be expected to absorb free energy from an oscillating electric field and transduce that to chemical or transport work. In the theoretical analysis it turned out to be sufficient that (i) the catalytic process be accompanied by either net or cyclic charge translocation across the membrane and (ii) the stability of the enzyme states involved be asymmetric. Calculations based on a four-state model reveal that free-energy transduction occurs with sinusoidal, square-wave, and positive-only oscillating electric fields and for cases that exhibit either linear or exponential field-dependent rate constants. The results suggest that in addition to oscillating electric field-driven transport, the proposed mechanism can also be used to explain, in part, the "missing" free energy term in the cases in which ATP synthesis has been observed with insufficient transmembrane proton electrochemical potential difference.

How enzymes can capture and transmit free energy from an oscillating electric field.

PubMed Central

Westerhoff, H V; Tsong, T Y; Chock, P B; Chen, Y D; Astumian, R D

1986-01-01

Recently, it has been demonstrated that free energy from an alternating electric field can drive the active transport of Rb+ by way of the Na+, K+-ATPase. In the present work, it is shown why many transmembrane enzymes can be expected to absorb free energy from an oscillating electric field and transduce that to chemical or transport work. In the theoretical analysis it turned out to be sufficient that (i) the catalytic process be accompanied by either net or cyclic charge translocation across the membrane and (ii) the stability of the enzyme states involved be asymmetric. Calculations based on a four-state model reveal that free-energy transduction occurs with sinusoidal, square-wave, and positive-only oscillating electric fields and for cases that exhibit either linear or exponential field-dependent rate constants. The results suggest that in addition to oscillating electric field-driven transport, the proposed mechanism can also be used to explain, in part, the "missing" free energy term in the cases in which ATP synthesis has been observed with insufficient transmembrane proton electrochemical potential difference. PMID:2941758

Numerically simulated exposure of children and adults to pulsed gradient fields in MRI.

PubMed

Samoudi, Amine M; Vermeeren, Gunter; Tanghe, Emmeric; Van Holen, Roel; Martens, Luc; Josephs, Wout

2016-11-01

To determine exposure to gradient switching fields of adults and children in a magnetic resonance imaging (MRI) scanner by evaluating internal electric fields within realistic models of adult male, adult female, and child inside transverse and longitudinal gradient coils, and to compare these results with compliance guidelines. Patients inside x-, y-, and z-gradient coils were simulated using anatomically realistic models of adult male, adult female, and child. The induced electric fields were computed for 1 kHz sinusoidal current with a magnitude of 1 A in the gradient coils. Rheobase electric fields were then calculated and compared to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2004 and International Electrotechnical Commission (IEC) 2010 guidelines. The effect of the human body, coil type, and skin conductivity on the induced electric field was also investigated. The internal electric fields are within the first level controlled operating mode of the guidelines and range from 2.7V m -1 to 4.5V m -1 , except for the adult male inside the y-gradient coil (induced field reaches 5.4V m -1 ).The induced electric field is sensitive to the coil type (electric field in the skin of adult male: 4V m -1 , 4.6V m -1 , and 3.8V m -1 for x-, y-, and z-gradient coils, respectively), the human body model (electric field in the skin inside y-gradient coil: 4.6V m -1 , 4.2V m -1 , and 3V m -1 for adult male, adult female, and child, respectively), and the skin conductivity (electric field 2.35-4.29% higher for 0.1S m -1 skin conductivity compared to 0.2S m -1 ). The y-gradient coil induced the largest fields in the patients. The highest levels of internal electric fields occurred for the adult male model. J. Magn. Reson. Imaging 2016;44:1360-1367. © 2016 International Society for Magnetic Resonance in Medicine.

Mitigating Space Weather Impacts on the Power Grid in Real-Time: Applying 3-D EarthScope Magnetotelluric Data to Forecasting Reactive Power Loss in Power Transformers

NASA Astrophysics Data System (ADS)

Schultz, A.; Bonner, L. R., IV

2017-12-01

Current efforts to assess risk to the power grid from geomagnetic disturbances (GMDs) that result in geomagnetically induced currents (GICs) seek to identify potential "hotspots," based on statistical models of GMD storm scenarios and power distribution grounding models that assume that the electrical conductivity of the Earth's crust and mantle varies only with depth. The NSF-supported EarthScope Magnetotelluric (MT) Program operated by Oregon State University has mapped 3-D ground electrical conductivity structure across more than half of the continental US. MT data, the naturally occurring time variations in the Earth's vector electric and magnetic fields at ground level, are used to determine the MT impedance tensor for each site (the ratio of horizontal vector electric and magnetic fields at ground level expressed as a complex-valued frequency domain quantity). The impedance provides information on the 3-D electrical conductivity structure of the Earth's crust and mantle. We demonstrate that use of 3-D ground conductivity information significantly improves the fidelity of GIC predictions over existing 1-D approaches. We project real-time magnetic field data streams from US Geological Survey magnetic observatories into a set of linear filters that employ the impedance data and that generate estimates of ground level electric fields at the locations of MT stations. The resulting ground electric fields are projected to and integrated along the path of power transmission lines. This serves as inputs to power flow models that represent the power transmission grid, yielding a time-varying set of quasi-real-time estimates of reactive power loss at the power transformers that are critical infrastructure for power distribution. We demonstrate that peak reactive power loss and hence peak risk for transformer damage from GICs does not necessarily occur during peak GMD storm times, but rather depends on the time-evolution of the polarization of the GMD's inducing fields and the complex ground (3-D) electric field response, and the resulting alignment of the ground electric fields with the power transmission line paths. This is informing our efforts to provide a set of real-time tools for power grid operators to use in mitigating damage from space weather events.

The Charging of Composites in the Space Environment

NASA Technical Reports Server (NTRS)

Czepiela, Steven A.

1997-01-01

Deep dielectric charging and subsequent electrostatic discharge in composite materials used on spacecraft have become greater concerns since composite materials are being used more extensively as main structural components. Deep dielectric charging occurs when high energy particles penetrate and deposit themselves in the insulating material of spacecraft components. These deposited particles induce an electric field in the material, which causes the particles to move and thus changes the electric field. The electric field continues to change until a steady state is reached between the incoming particles from the space environment and the particles moving away due to the electric field. An electrostatic discharge occurs when the electric field is greater than the dielectric strength of the composite material. The goal of the current investigation is to investigate deep dielectric charging in composite materials and ascertain what modifications have to be made to the composite properties to alleviate any breakdown issues. A 1-D model was created. The space environment, which is calculated using the Environmental Workbench software, the composite material properties, and the electric field and voltage boundary conditions are input into the model. The output from the model is the charge density, electric field, and voltage distributions as functions of the depth into the material and time. Analysis using the model show that there should be no deep dielectric charging problem with conductive composites such as carbon fiber/epoxy. With insulating materials such as glass fiber/epoxy, Kevlar, and polymers, there is also no concern of deep dielectric charging problems with average day-to-day particle fluxes. However, problems can arise during geomagnetic substorms and solar particle events where particle flux levels increase by several orders of magnitude, and thus increase the electric field in the material by several orders of magnitude. Therefore, the second part of this investigation was an experimental attempt to measure the continuum electrical properties of a carbon fiber/epoxy composite, and to create a composite with tailorable conductivity without affecting its mechanical properties. The measurement of the conductivity and dielectric strength of carbon fiber/epoxy composites showed that these properties are surface layer dominated and difficult to measure. In the second experimental task, the conductivity of a glass fiber/epoxy composite was increased by 3 orders of magnitude, dielectric constant was increased approximately by a factor of 16, with minimal change to the mechanical properties, by adding conductive carbon black to the epoxy.

The Relation between Reconnected Flux, the Parallel Electric Field, and the Reconnection Rate in a Three-Dimensional Kinetic Simulation of Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Wendel, D. E.; Olson, D. K.; Hesse, M.; Karimabadi, H.; Daughton, W. S.

2013-12-01

We investigate the distribution of parallel electric fields and their relationship to the location and rate of magnetic reconnection of a large particle-in-cell simulation of 3D turbulent magnetic reconnection with open boundary conditions. The simulation's guide field geometry inhibits the formation of topological features such as separators and null points. Therefore, we derive the location of potential changes in magnetic connectivity by finding the field lines that experience a large relative change between their endpoints, i.e., the quasi-separatrix layer. We find a correspondence between the locus of changes in magnetic connectivity, or the quasi-separatrix layer, and the map of large gradients in the integrated parallel electric field (or quasi-potential). Furthermore, we compare the distribution of parallel electric fields along field lines with the reconnection rate. We find the reconnection rate is controlled by only the low-amplitude, zeroth and first-order trends in the parallel electric field, while the contribution from high amplitude parallel fluctuations, such as electron holes, is negligible. The results impact the determination of reconnection sites within models of 3D turbulent reconnection as well as the inference of reconnection rates from in situ spacecraft measurements. It is difficult through direct observation to isolate the locus of the reconnection parallel electric field amidst the large amplitude fluctuations. However, we demonstrate that a positive slope of the partial sum of the parallel electric field along the field line as a function of field line length indicates where reconnection is occurring along the field line.

Electric Field Screening with Backflow at Pulsar Polar Cap

NASA Astrophysics Data System (ADS)

Kisaka, Shota; Asano, Katsuaki; Terasawa, Toshio

2016-09-01

Recent γ-ray observations suggest that particle acceleration occurs at the outer region of the pulsar magnetosphere. The magnetic field lines in the outer acceleration region (OAR) are connected to the neutron star surface (NSS). If copious electron-positron pairs are produced near the NSS, such pairs flow into the OAR and screen the electric field there. To activate the OAR, the electromagnetic cascade due to the electric field near the NSS should be suppressed. However, since a return current is expected along the field lines through the OAR, the outflow extracted from the NSS alone cannot screen the electric field just above the NSS. In this paper, we analytically and numerically study the electric field screening at the NSS, taking into account the effects of the backflowing particles from the OAR. In certain limited cases, the electric field is screened without significant pair cascade if only ultra-relativistic particles (γ \\gg 1) flow back to the NSS. On the other hand, if electron-positron pairs with a significant number density and mildly relativistic temperature, expected to distribute in a wide region of the magnetosphere, flow back to the NSS, these particles adjust the current and charge densities so that the electric field can be screened without pair cascade. We obtain the condition needed for the number density of particles to screen the electric field at the NSS. We also find that in the ion-extracted case from the NSS, bunches of particles are ejected to the outer region quasi-periodically, which is a possible mechanism of observed radio emission.

Transition from a beads-on-string to a spike structure in an electrified viscoelastic jet

NASA Astrophysics Data System (ADS)

Li, Fang; Yin, Xie-Yuan; Yin, Xie-Zhen

2017-02-01

A one-dimensional numerical simulation is performed to study the nonlinear behaviors of a perfectly conducting, slightly viscoelastic liquid jet under a large radial electric field. A singular spike structure different from a beads-on-string structure is detected. The electric field is found to be the key factor for the formation of spikes. The transition from a beads-on-string to a spike structure occurs at sufficiently large electric fields. Moreover, the transition occurs more easily for smaller wave numbers. Viscosity is found to suppress spikes while elasticity promotes them. The mechanism responsible for spike formation is further explored by examining the maximum radius of the jet in the beads-on-string case. The capillary and electrostatic forces prove to be dominant in droplets, and the transition takes place when the electrostatic force exceeds the capillary force. The self-similarity in spikes is discussed. Different from the transition moment, the inertial, electrostatic, and solvent viscous forces are important in a developed spike.

Approximations useful for the prediction of electrostatic discharges for simple electrode geometries

NASA Technical Reports Server (NTRS)

Edmonds, L.

1986-01-01

The report provides approximations for estimating the capacitance and the ratio of electric field strength to potential for a certain class of electrode geometries. The geometry consists of an electrode near a grounded plane, with the electrode being a surface of revolution about the perpendicular to the plane. Some examples which show the accuracy of the capacitance estimate and the accuracy of the estimate of electric field over potential can be found in the appendix. When it is possible to estimate the potential of the electrode, knowing the ratio of electric field to potential will help to determine if an electrostatic discharge is likely to occur. Knowing the capacitance will help to determine the strength of the discharge (the energy released by it) if it does occur. A brief discussion of discharge mechanisms is given. The medium between the electrode and the grounded plane may be a neutral gas, a vacuum, or an unchanged homogeneous isotropic dielectric.

Experimental characterization and numerical modeling of tissue electrical conductivity during pulsed electric fields for irreversible electroporation treatment planning.

PubMed

Neal, Robert E; Garcia, Paulo A; Robertson, John L; Davalos, Rafael V

2012-04-01

Irreversible electroporation is a new technique to kill cells in targeted tissue, such as tumors, through a nonthermal mechanism using electric pulses to irrecoverably disrupt the cell membrane. Treatment effects relate to the tissue electric field distribution, which can be predicted with numerical modeling for therapy planning. Pulse effects will change the cell and tissue properties through thermal and electroporation (EP)-based processes. This investigation characterizes these changes by measuring the electrical conductivity and temperature of ex vivo renal porcine tissue within a single pulse and for a 200 pulse protocol. These changes are incorporated into an equivalent circuit model for cells and tissue with a variable EP-based resistance, providing a potential method to estimate conductivity as a function of electric field and pulse length for other tissues. Finally, a numerical model using a human kidney volumetric mesh evaluated how treatment predictions vary when EP- and temperature-based electrical conductivity changes are incorporated. We conclude that significant changes in predicted outcomes will occur when the experimental results are applied to the numerical model, where the direction and degree of change varies with the electric field considered.

Consideration of magnetically-induced and conservative electric fields within a loaded gradient coil.

PubMed

Mao, Weihua; Chronik, Blaine A; Feldman, Rebecca E; Smith, Michael B; Collins, Christopher M

2006-06-01

We present a method to calculate the electric (E)-fields within and surrounding a human body in a gradient coil, including E-fields induced by the changing magnetic fields and "conservative" E-fields originating with the scalar electrical potential in the coil windings. In agreement with previous numerical calculations, it is shown that magnetically-induced E-fields within the human body show no real concentration near the surface of the body, where nerve stimulation most often occurs. Both the magnetically-induced and conservative E-fields are shown to be considerably stronger just outside the human body than inside it, and under some circumstances the conservative E-fields just outside the body can be much larger than the magnetically-induced E-fields there. The order of gradient winding and the presence of conductive RF shield can greatly affect the conservative E-field distribution in these cases. Though the E-fields against the outer surface of the body are not commonly considered, understanding gradient E-fields may be important for reasons other than peripheral nerve stimulation (PNS), such as potential interaction with electrical equipment. Copyright 2006 Wiley-Liss, Inc.

Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

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

Zhang, Jingdi; Averitt, Richard D., E-mail: xinz@bu.edu, E-mail: raveritt@ucsd.edu; Department of Physics, Boston University, Boston, Massachusetts 02215

We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ∼170. Above an in-gap E-field threshold amplitude of ∼10 MV/cm{sup −1}, THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits amore » linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.« less

Lorentz factor determination for local electric fields in semiconductor devices utilizing hyper-thin dielectrics

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

McPherson, J. W., E-mail: mcpherson.reliability@yahoo.com

The local electric field (the field that distorts, polarizes, and weakens polar molecular bonds in dielectrics) has been investigated for hyper-thin dielectrics. Hyper-thin dielectrics are currently required for advanced semiconductor devices. In the work presented, it is shown that the common practice of using a Lorentz factor of L = 1/3, to describe the local electric field in a dielectric layer, remains valid for hyper-thin dielectrics. However, at the very edge of device structures, a rise in the macroscopic/Maxwell electric field E{sub diel} occurs and this causes a sharp rise in the effective Lorentz factor L{sub eff}. At capacitor and transistor edges,more » L{sub eff} is found to increase to a value 2/3 < L{sub eff} < 1. The increase in L{sub eff} results in a local electric field, at device edge, that is 50%–100% greater than in the bulk of the dielectric. This increase in local electric field serves to weaken polar bonds thus making them more susceptible to breakage by standard Boltzmann and/or current-driven processes. This has important time-dependent dielectric breakdown (TDDB) implications for all electronic devices utilizing polar materials, including GaN devices that suffer from device-edge TDDB.« less

"Diffusion" region of magnetic reconnection: electron orbits and the phase space mixing

NASA Astrophysics Data System (ADS)

Kropotkin, Alexey P.

2018-05-01

The nonlinear dynamics of electrons in the vicinity of magnetic field neutral lines during magnetic reconnection, deep inside the diffusion region where the electron motion is nonadiabatic, has been numerically analyzed. Test particle orbits are examined in that vicinity, for a prescribed planar two-dimensional magnetic field configuration and with a prescribed uniform electric field in the neutral line direction. On electron orbits, a strong particle acceleration occurs due to the reconnection electric field. Local instability of orbits in the neighborhood of the neutral line is pointed out. It combines with finiteness of orbits due to particle trapping by the magnetic field, and this should lead to the effect of mixing in the phase space, and the appearance of dynamical chaos. The latter may presumably be viewed as a mechanism producing finite conductivity in collisionless plasma near the neutral line. That conductivity is necessary to provide violation of the magnetic field frozen-in condition, i.e., for magnetic reconnection to occur in that region.

Effect of near-earth thunderstorms electric field on the intensity of ground cosmic ray positrons/electrons in Tibet

NASA Astrophysics Data System (ADS)

Zhou, X. X.; Wang, X. J.; Huang, D. H.; Jia, H. Y.

2016-11-01

Monte Carlo simulations are performed to study the correlation between the ground cosmic ray intensity and near-earth thunderstorms electric field at YBJ (located at YangBaJing, Tibet, China, 4300 m a. s. l.). The variations of the secondary cosmic ray intensity are found to be highly dependent on the strength and polarity of the electric field. In negative fields and in positive fields greater than 600 V/cm, the total number of ground comic ray positrons and electrons increases with increasing electric field strength. And these values increase more obviously when involving a shower with lower primary energy or a higher zenith angle. While in positive fields ranging from 0 to 600 V/cm, the total number of ground comic ray positrons and electrons declines and the amplitude is up to 3.1% for vertical showers. A decrease of intensity occurs in inclined showers within the range of 0-500 V/cm, which is accompanied by smaller amplitudes. In this paper, the intensity changes are analyzed, especially concerning those decreasing phenomena in positive electric fields. Our simulation results could be helpful in understanding the decreases observed in some ground-based experiments (such as the Carpet air shower array and ARGO-YBJ), and also be useful in understanding the acceleration mechanisms of secondary charged particles caused by an atmospheric electric field.

Electric-field distribution in Au-semi-insulating GaAs contact investigated by positron-lifetime technique

NASA Astrophysics Data System (ADS)

Ling, C. C.; Shek, Y. F.; Huang, A. P.; Fung, S.; Beling, C. D.

1999-02-01

Positron-lifetime spectroscopy has been used to investigate the electric-field distribution occurring at the Au-semi-insulating GaAs interface. Positrons implanted from a 22Na source and drifted back to the interface are detected through their characteristic lifetime at interface traps. The relative intensity of this fraction of interface-trapped positrons reveals that the field strength in the depletion region saturates at applied biases above 50 V, an observation that cannot be reconciled with a simple depletion approximation model. The data, are, however, shown to be fully consistent with recent direct electric-field measurements and the theoretical model proposed by McGregor et al. [J. Appl. Phys. 75, 7910 (1994)] of an enhanced EL2+ electron-capture cross section above a critical electric field that causes a dramatic reduction of the depletion region's net charge density. Two theoretically derived electric field profiles, together with an experimentally based profile, are used to estimate a positron mobility of ~95+/-35 cm2 V-1 s-1 under the saturation field. This value is higher than previous experiments would suggest, and reasons for this effect are discussed.

MUSIC for localization of thunderstorm cells

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

Mosher, J.C.; Lewis, P.S.; Rynne, T.M.

1993-12-31

Lightning represents an event detectable optically, electrically, and acoustically, and several systems are already in place to monitor such activity. Unfortunately, such detection of lightning can occur too late, since operations need to be protected in advance of the first lightning strike. Additionally, the bolt itself can traverse several kilometers before striking the ground, leaving a large region of uncertainty as to the center of the storm and its possible strike regions. NASA Kennedy Space Center has in place an array of electric field mills that monitor the (effectively) DC electric field. Prior to the first lightning strike, the surfacemore » electric fields rise as the storm generator within a thundercloud begins charging. Extending methods we developed for an analogous source localization problem in mangnetoencephalography, we present Cramer-Rao lower bounds and MUSIC scans for fitting a point-charge source model to the electric field mill data. Such techniques can allow for the identification and localization of charge centers in cloud structures.« less

Electric-field-stimulated protein mechanics

PubMed Central

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

2017-01-01

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 (LNX2PDZ2) 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. PMID:27926732

Coarse-grained model of conformation-dependent electrophoretic mobility and its influence on DNA dynamics

NASA Astrophysics Data System (ADS)

Pandey, Harsh; Underhill, Patrick T.

2015-11-01

The electrophoretic mobility of molecules such as λ -DNA depends on the conformation of the molecule. It has been shown that electrohydrodynamic interactions between parts of the molecule lead to a mobility that depends on conformation and can explain some experimental observations. We have developed a new coarse-grained model that incorporates these changes of mobility into a bead-spring chain model. Brownian dynamics simulations have been performed using this model. The model reproduces the cross-stream migration that occurs in capillary electrophoresis when pressure-driven flow is applied parallel or antiparallel to the electric field. The model also reproduces the change of mobility when the molecule is stretched significantly in an extensional field. We find that the conformation-dependent mobility can lead to a new type of unraveling of the molecule in strong fields. This occurs when different parts of the molecule have different mobilities and the electric field is large.

Exposure to magnetic fields among electrical workers in relation to leukemia risk in Los Angeles County.

PubMed

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

1994-07-01

To address the hypotheses that electrical workers are exposed to higher magnetic fields and are at higher risk of leukemia than nonelectrical workers, we performed a registry-based case-control study among men aged 20-64 years with known occupation who were diagnosed with cancer in Los Angeles County between 1972 and 1990. Controls were men with cancers other than those of the central nervous system or leukemia. Magnetic field measurements on workers in each electrical occupation and in a random sample of occupations presumed to be nonelectrical were used to estimate magnetic field exposures for each occupation. Among men in electrical occupations, 121 leukemias were diagnosed. With the exception of electrical engineers, magnetic field exposures were higher among workers in electrical occupations than in nonelectrical occupations. A weakly positive trend in leukemia risk across average occupational magnetic field exposure was observed (odds ratio [OR] per 10 milligauss increase in average magnetic field = 1.2, 95% confidence interval [CI] 1.0-1.5). A slightly stronger association was observed for chronic myloid leukemia, although only 28 cases occurred among electrical workers (OR 10 milligauss increase = 1.6, 95% CI = 1.2-2.0). The results were not materially altered by adjustment for exposure to several agents known or suspected to cause leukemia. Although not conclusive, these results are consistent with findings from studies based on job title alone that electrical workers may be at slightly increased risk of leukemia.

Modeling Plasma Formation in a Micro-gap at Microwave Frequency

NASA Astrophysics Data System (ADS)

Bowman, Arthur; Remillard, Stephen

2013-03-01

In the presence of a strong electric field, gas molecules become ionized, forming a plasma. The study of this dielectric breakdown at microwave frequency has important applications in improving the operation of radio frequency (RF) devices, where the high electric fields present in small gaps can easily ionize gases like air. A cone and tuner resonant structure was used to induce breakdown of diatomic Nitrogen in adjustable micro-gaps ranging from 13 to 1,156 μm. The electric field for plasma formation exhibited strong pressure dependence in the larger gap sizes, as predicted by previous theoretical and experimental work. Pressure is proportional to the frequency of collision between electrons and molecules, which increases with pressure when the gap is large, but levels off in the micro-gap region. A separate model of the breakdown electric field based on the characteristic diffusion length of the plasma also fit the data poorly for these smaller gap sizes. This may be explained by a hypothesis that dielectric breakdown at and below the 100 μm gap size occurs outside the gap, an argument that is supported by the observation of very high breakdown threshold electric fields in this region. Optical emissions revealed that vibrational and rotational molecular transitions of the first positive electronic system are suppressed in micro-gaps, indicating that transitions into the molecular ground state do not occur in micro-gap plasmas. Acknowledgements: National Science Foundation under NSF-REU Grant No. PHY/DMR-1004811, the Provost's Office of Hope College, and the Hope College Division of Natural and Applied Sciences.

Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

PubMed Central

Żak, Arkadiusz

2014-01-01

One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields. PMID:25136557

Chemical Detection using Electrically Open Circuits having no Electrical Connections

NASA Technical Reports Server (NTRS)

Woodward, Stanley E.; Olgesby, Donald M.; Taylor, Bryant D.; Shams, Qamar A.

2008-01-01

This paper presents investigations to date on chemical detection using a recently developed method for designing, powering and interrogating sensors as electrically open circuits having no electrical connections. In lieu of having each sensor from a closed circuit with multiple electrically connected components, an electrically conductive geometric pattern that is powered using oscillating magnetic fields and capable of storing an electric field and a magnetic field without the need of a closed circuit or electrical connections is used. When electrically active, the patterns respond with their own magnetic field whose frequency, amplitude and bandwidth can be correlated with the magnitude of the physical quantities being measured. Preliminary experimental results of using two different detection approaches will be presented. In one method, a thin film of a reactant is deposited on the surface of the open-circuit sensor. Exposure to a specific targeted reactant shifts the resonant frequency of the sensor. In the second method, a coating of conductive material is placed on a thin non-conductive plastic sheet that is placed over the surface of the sensor. There is no physical contact between the sensor and the electrically conductive material. When the conductive material is exposed to a targeted reactant, a chemical reaction occurs that renders the material non-conductive. The change in the material s electrical resistance within the magnetic field of the sensor alters the sensor s response bandwidth and amplitude, allowing detection of the reaction without having the reactants in physical contact with the sensor.

Measurements of Induced-Charge Electroosmotic Flow Around a Metallic Rod

NASA Astrophysics Data System (ADS)

Beskok, Ali; Canpolat, Cetin

2012-11-01

A cylindrical gold-coated stainless steel rod was positioned at the center of a straight microchannel connecting two fluid reservoirs on either end. The microchannel was filled with 1 mM KCl containing 0.5 micron diameter carboxylate-modified spherical particles. Induced-charge electro-osmotic (ICEO) flow occurred around the metallic rod under a sinusoidal AC electric field applied using two platinum electrodes. The ICEO flows around the metallic rod were measured using micro particle image velocimetry (micro-PIV) technique as functions of the AC electric field strength and frequency. The present study provides experimental data about ICEO flow in the weakly nonlinear limit of thin double layers, in which, the charging dynamics of the double layer cannot be presented analytically. Flow around the rod is quadrupolar, driving liquid towards the rod along the electric field and forcing it away from the rod in the direction perpendicular to the imposed electric field. The measured ICEO flow velocity is proportional to the square of the electric field strength, and depends on the applied AC frequency.

Specular Andreev reflection in thin films of topological insulators

NASA Astrophysics Data System (ADS)

Majidi, Leyla; Asgari, Reza

2016-05-01

We theoretically reveal the possibility of specular Andreev reflection in a thin film topological insulator normal-superconductor (N/S) junction in the presence of a gate electric field. The probability of specular Andreev reflection increases with the electric field, and electron-hole conversion with unit efficiency happens in a wide experimentally accessible range of the electric field. We show that perfect specular Andreev reflection can occur for all angles of incidence with a particular excitation energy value. In addition, we find that the thermal conductance of the structure displays exponential dependence on the temperature. Our results reveal the potential of the proposed topological insulator thin-film-based N/S structure for the realization of intraband specular Andreev reflection.

An example of anticorrelation of auroral particles and electric fields.

NASA Technical Reports Server (NTRS)

Maynard, N. C.; Bahnsen, A.; Christophersen, P.; Lundin, R.; Egeland, A.

1973-01-01

The question of whether correlation or anticorrelation should occur is complex and depends on many factors, e.g., the internal impedance of the source; the Pedersen conductivity, which in turn is dependent on the incident energy of the precipitated particles; whether space charge can build up; and the magnitude of the incoming flux. Data are presented from a case in which an anticorrelation between auroral particles and electric fields is especially striking. The data were obtained from a Nike Tomahawk launched from the Norwegian rocket range at Andoya. The experiments carried are described briefly. The data support the anticorrelation model as one mechanism that can affect the electric field strength in auroral regions.

Microwave transmission through metallic hole arrays: Surface electric field measurements

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

Hou Bo; Hang Zhihong; Wen Weijia

2006-09-25

The authors investigate the enhanced microwave transmission through a metal plate perforated by a square lattice of subwavelength holes, predicted to occur as a structure factor resonance phenomenon [F. J. Gracia de Abajo and J. J. Saenz, Phys. Rev. Lett. 95, 233901 (2005)]. By probing the surface electric field on the metallic plate at the peak transmission frequency, they establish the similarities and differences between the structure factor resonance and surface plasmon.

Response of ionospheric electric fields at mid-low latitudes during geomagnetic sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2014-12-01

Geomagnetic sudden commencements (SCs) are known as one of the distinct magnetospheric disturbance phenomena triggered by solar wind disturbances. Many previous studies have focused on the generation mechanism of SCs by using in-situ observations and simulations. However, the global evolution of ionospheric electric fields has primarily been estimated from the ionospheric current. Although a few studies utilized electric field data from radar observations, the coverage is limited in time, and limited component of the electric field is obtained. In this study, we investigated the response and local time dependence of the ionospheric electric field at mid-low latitudes associated with 203 SCs occurred from 1999 to 2004 by the in-situ observation of the ROCSAT-1 spacecraft. We found that the ionospheric electric field associated with SCs instantaneously responds to geomagnetic fields regardless of spacecraft local time. Our statistical analysis also showed the instantaneous response of the electric field, which indicates the global instant transmission of the electric field from polar region. In contrast, peak times in the preliminary impulse (PI) and main impulse (MI) phases were different between the ionospheric electric field and equatorial geomagnetic field (20 sec in the PI phase). Based on a comparison to the ground-ionosphere waveguide model by Kikuchi [2014], this time lag is suggested to be due to the latitudinal difference of the ionospheric conductivity. After constructing the local time distribution of the SC amplitude, we found that the dayside feature was seen at 18-22 h even the ionospheric conductivity is lower than that at dayside. We performed a magnetohydrodynamic (MHD) simulation for an ideal SC. The result of the simulation showed that the electric potential distribution is asymmetric with respect to the noon-midnight meridian, which is similar to our observational result. It appears to result from the divergence of the Hall current under the non-uniform ionospheric conductivity near the terminator as well as the auroral region.

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.

Ionic Components of Electric Current at Rat Corneal Wounds

PubMed Central

Cao, Lin; Mannis, Mark J.; Schwab, Ivan R.; Zhao, Min

2011-01-01

Background Endogenous electric fields and currents occur naturally at wounds and are a strong signal guiding cell migration into the wound to promote healing. Many cells involved in wound healing respond to small physiological electric fields in vitro. It has long been assumed that wound electric fields are produced by passive ion leakage from damaged tissue. Could these fields be actively maintained and regulated as an active wound response? What are the molecular, ionic and cellular mechanisms underlying the wound electric currents? Methodology/Principal Findings Using rat cornea wounds as a model, we measured the dynamic timecourses of individual ion fluxes with ion-selective probes. We also examined chloride channel expression before and after wounding. After wounding, Ca2+ efflux increased steadily whereas K+ showed an initial large efflux which rapidly decreased. Surprisingly, Na+ flux at wounds was inward. A most significant observation was a persistent large influx of Cl−, which had a time course similar to the net wound electric currents we have measured previously. Fixation of the tissues abolished ion fluxes. Pharmacological agents which stimulate ion transport significantly increased flux of Cl−, Na+ and K+. Injury to the cornea caused significant changes in distribution and expression of Cl− channel CLC2. Conclusions/Significance These data suggest that the outward electric currents occurring naturally at corneal wounds are carried mainly by a large influx of chloride ions, and in part by effluxes of calcium and potassium ions. Ca2+ and Cl− fluxes appear to be mainly actively regulated, while K+ flux appears to be largely due to leakage. The dynamic changes of electric currents and specific ion fluxes after wounding suggest that electrical signaling is an active response to injury and offers potential novel approaches to modulate wound healing, for example eye-drops targeting ion transport to aid in the challenging management of non-healing corneal ulcers. PMID:21364900

Nonlinear electric field structures in the inner magnetosphere

DOE PAGES

Malaspina, D. M.; Andersson, L.; Ergun, R. E.; ...

2014-08-28

Recent observations by the Van Allen Probes spacecraft have demonstrated that a variety of electric field structures and nonlinear waves frequently occur in the inner terrestrial magnetosphere, including phase space holes, kinetic field-line resonances, nonlinear whistler-mode waves, and several types of double layer. However, it is nuclear whether such structures and waves have a significant impact on the dynamics of the inner magnetosphere, including the radiation belts and ring current. To make progress toward quantifying their importance, this study statistically evaluates the correlation of such structures and waves with plasma boundaries. A strong correlation is found. These statistical results, combinedmore » with observations of electric field activity at propagating plasma boundaries, are consistent with the identification of these boundaries as the source of free energy responsible for generating the electric field structures and nonlinear waves of interest. Therefore, the ability of these structures and waves to influence plasma in the inner magnetosphere is governed by the spatial extent and dynamics of macroscopic plasma boundaries in that region.« less

Raise and collapse of pseudo Landau levels in graphene

NASA Astrophysics Data System (ADS)

Castro, Eduardo V.; Cazalilla, Miguel A.; Vozmediano, María A. H.

2017-12-01

Lattice deformations couple to the low-energy electronic excitations of graphene as vector fields similar to the electromagnetic potential. The observation of strain-induced pseudo Landau levels with scanning tunnel microscopy experiments has been one of the most exciting events in the history of graphene. Nevertheless, the experimental observation presents some ambiguities. Similar strain patterns show different images that are sometimes difficult to interpret. In this Rapid Communication, we show that, for some strain configurations, the deformation potential acts as a parallel electric field able to destabilize the Landau level structure via a mechanism identical to that occurring for real electromagnetic fields. This effect also alters the estimations of the value of the pseudomagnetic field, which can be significantly bigger. The mechanism applies equally if the electric field has an external origin, which opens the door to an electric control of giant pseudomagnetic fields in graphene.

Predicting the Electric Field Distribution in the Brain for the Treatment of Glioblastoma

PubMed Central

Miranda, Pedro C.; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J.

2014-01-01

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a “virtual lesion” in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V/cm and exceeded 1.0 V/cm in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor’s necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning. PMID:25003941

Predicting the electric field distribution in the brain for the treatment of glioblastoma

NASA Astrophysics Data System (ADS)

Miranda, Pedro C.; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J.

2014-08-01

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a ‘virtual lesion’ in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V cm - 1 and exceeded 1.0 V cm - 1 in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor’s necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning.

Predicting the electric field distribution in the brain for the treatment of glioblastoma.

PubMed

Miranda, Pedro C; Mekonnen, Abeye; Salvador, Ricardo; Basser, Peter J

2014-08-07

The use of alternating electric fields has been recently proposed for the treatment of recurrent glioblastoma. In order to predict the electric field distribution in the brain during the application of such tumor treating fields (TTF), we constructed a realistic head model from MRI data and placed transducer arrays on the scalp to mimic an FDA-approved medical device. Values for the tissue dielectric properties were taken from the literature; values for the device parameters were obtained from the manufacturer. The finite element method was used to calculate the electric field distribution in the brain. We also included a 'virtual lesion' in the model to simulate the presence of an idealized tumor. The calculated electric field in the brain varied mostly between 0.5 and 2.0 V cm( - 1) and exceeded 1.0 V cm( - 1) in 60% of the total brain volume. Regions of local field enhancement occurred near interfaces between tissues with different conductivities wherever the electric field was perpendicular to those interfaces. These increases were strongest near the ventricles but were also present outside the tumor's necrotic core and in some parts of the gray matter-white matter interface. The electric field values predicted in this model brain are in reasonably good agreement with those that have been shown to reduce cancer cell proliferation in vitro. The electric field distribution is highly non-uniform and depends on tissue geometry and dielectric properties. This could explain some of the variability in treatment outcomes. The proposed modeling framework could be used to better understand the physical basis of TTF efficacy through retrospective analysis and to improve TTF treatment planning.

Impact of disturbance electric fields in the evening on prereversal vertical drift and spread F developments in the equatorial ionosphere

NASA Astrophysics Data System (ADS)

Abdu, Mangalathayil A.; Nogueira, Paulo A. B.; Santos, Angela M.; de Souza, Jonas R.; Batista, Inez S.; Sobral, Jose H. A.

2018-04-01

Equatorial plasma bubble/spread F irregularity occurrence can present large variability depending upon the intensity of the evening prereversal enhancement in the zonal electric field (PRE), that is, the F region vertical plasma drift, which basically drives the post-sunset irregularity development. Forcing from magnetospheric disturbances is an important source of modification and variability in the PRE vertical drift and of the associated bubble development. Although the roles of magnetospheric disturbance time penetration electric fields in the bubble irregularity development have been studied in the literature, many details regarding the nature of the interaction between the penetration electric fields and the PRE vertical drift still lack our understanding. In this paper we have analyzed data on F layer heights and vertical drifts obtained from digisondes operated in Brazil to investigate the connection between magnetic disturbances occurring during and preceding sunset and the consequent variabilities in the PRE vertical drift and associated equatorial spread F (ESF) development. The impact of the prompt penetration under-shielding eastward electric field and that of the over-shielding, and disturbance dynamo, westward electric field on the evolution of the evening PRE vertical drift and thereby on the ESF development are briefly examined.

Chain of Dirac spectrum loops of nodes in crossed magnetic and electric fields

NASA Astrophysics Data System (ADS)

Gavrilenko, V. I.; Perov, A. A.; Protogenov, A. P.; Turkevich, R. V.; Chulkov, E. V.

2018-03-01

New semimetal systems along with Dirac and Weyl semimetals contain compounds, in which the energy of electron excitations vanishes not at nodes but on lines. A higher dimension of the degeneracy space changes many physical properties. We consider a chain of loops consisting of Dirac spectrum nodes in nonsymmorphic crystalline compounds placed in external mutually perpendicular magnetic and electric fields. An exact solution for the spectrum is obtained under the assumption of particle-hole symmetry. An analysis of this spectrum shows the existence of a line of critical values of the magnetic and electric fields, at which a quantum phase transition to a gapless state occurs. The use of the obtained spectrum allows also predicting a number of new oscillation and resonance effects in the field of magneto-optical phenomena.

Electron Currents and Heating in the Ion Diffusion Region of Asymmetric Reconnection

NASA Technical Reports Server (NTRS)

Graham, D. B.; Khotyaintsev, Yu. V.; Norgren, C.; Vaivads, A.; Andre, M.; Lindqvist, P. A.; Marklund, G. T.; Ergun, R. E.; Paterson, W. R.; Gershman, D. J.;

Pulsed Electromagnetic Field Assisted in vitro Electroporation: A Pilot Study

NASA Astrophysics Data System (ADS)

Novickij, Vitalij; Grainys, Audrius; Lastauskienė, Eglė; Kananavičiūtė, Rūta; Pamedytytė, Dovilė; Kalėdienė, Lilija; Novickij, Jurij; Miklavčič, Damijan

2016-09-01

Electroporation is a phenomenon occurring due to exposure of cells to Pulsed Electric Fields (PEF) which leads to increase of membrane permeability. Electroporation is used in medicine, biotechnology, and food processing. Recently, as an alternative to electroporation by PEF, Pulsed ElectroMagnetic Fields (PEMF) application causing similar biological effects was suggested. Since induced electric field in PEMF however is 2-3 magnitudes lower than in PEF electroporation, the membrane permeabilization mechanism remains hypothetical. We have designed pilot experiments where Saccharomyces cerevisiae and Candida lusitaniae cells were subjected to single 100-250 μs electrical pulse of 800 V with and without concomitant delivery of magnetic pulse (3, 6 and 9 T). As expected, after the PEF pulses only the number of Propidium Iodide (PI) fluorescent cells has increased, indicative of membrane permeabilization. We further show that single sub-millisecond magnetic field pulse did not cause detectable poration of yeast. Concomitant exposure of cells to pulsed electric (PEF) and magnetic field (PMF) however resulted in the increased number PI fluorescent cells and reduced viability. Our results show increased membrane permeability by PEF when combined with magnetic field pulse, which can explain electroporation at considerably lower electric field strengths induced by PEMF compared to classical electroporation.

Pulsed Electromagnetic Field Assisted in vitro Electroporation: A Pilot Study

PubMed Central

Novickij, Vitalij; Grainys, Audrius; Lastauskienė, Eglė; Kananavičiūtė, Rūta; Pamedytytė, Dovilė; Kalėdienė, Lilija; Novickij, Jurij; Miklavčič, Damijan

2016-01-01

Electroporation is a phenomenon occurring due to exposure of cells to Pulsed Electric Fields (PEF) which leads to increase of membrane permeability. Electroporation is used in medicine, biotechnology, and food processing. Recently, as an alternative to electroporation by PEF, Pulsed ElectroMagnetic Fields (PEMF) application causing similar biological effects was suggested. Since induced electric field in PEMF however is 2–3 magnitudes lower than in PEF electroporation, the membrane permeabilization mechanism remains hypothetical. We have designed pilot experiments where Saccharomyces cerevisiae and Candida lusitaniae cells were subjected to single 100–250 μs electrical pulse of 800 V with and without concomitant delivery of magnetic pulse (3, 6 and 9 T). As expected, after the PEF pulses only the number of Propidium Iodide (PI) fluorescent cells has increased, indicative of membrane permeabilization. We further show that single sub-millisecond magnetic field pulse did not cause detectable poration of yeast. Concomitant exposure of cells to pulsed electric (PEF) and magnetic field (PMF) however resulted in the increased number PI fluorescent cells and reduced viability. Our results show increased membrane permeability by PEF when combined with magnetic field pulse, which can explain electroporation at considerably lower electric field strengths induced by PEMF compared to classical electroporation. PMID:27634482

Partial independence of bioelectric and biomagnetic fields and its implications for encephalography and cardiography

NASA Astrophysics Data System (ADS)

Irimia, Andrei; Swinney, Kenneth R.; Wikswo, John P.

2009-05-01

In this paper, we clearly demonstrate that the electric potential and the magnetic field can contain different information about current sources in three-dimensional conducting media. Expressions for the magnetic fields of electric dipole and quadrupole current sources immersed in an infinite conducting medium are derived, and it is shown that two different point dipole distributions that are electrically equivalent have different magnetic fields. Although measurements of the electric potential are not sufficient to determine uniquely the characteristics of a quadrupolar source, the radial component of the magnetic field can supply the additional information needed to resolve these ambiguities and to determine uniquely the configuration of dipoles required to specify the electric quadrupoles. We demonstrate how the process can be extended to even higher-order terms in an electrically silent series of magnetic multipoles. In the context of a spherical brain source model, it has been mathematically demonstrated that the part of the neuronal current generating the electric potential lives in the orthogonal complement of the part of the current generating the magnetic potential. This implies a mathematical relationship of complementarity between electroencephalography and magnetoencephalography, although the theoretical result in question does not apply to the nonspherical case [G. Dassios, Math. Med. Biol. 25, 133 (2008)]. Our results have important practical applications in cases where electrically silent sources that generate measurable magnetic fields are of interest. Moreover, electrically silent, magnetically active moments of higher order can be useful when cancellation due to superposition of fields can occur, since this situation leads to a substantial reduction in the measurable amplitude of the signal. In this context, information derived from magnetic recordings of electrically silent, magnetically active multipoles can supplement electrical recordings for the purpose of studying the physiology of the brain. Magnetic fields of the electric multipole sources in a conducting medium surrounded by an insulating spherical shell are also presented and the relevance of this calculation to cardiographic and encephalographic experimentation is discussed.

Rotating magnetizations in electrical machines: Measurements and modeling

NASA Astrophysics Data System (ADS)

Thul, Andreas; Steentjes, Simon; Schauerte, Benedikt; Klimczyk, Piotr; Denke, Patrick; Hameyer, Kay

2018-05-01

This paper studies the magnetization process in electrical steel sheets for rotational magnetizations as they occur in the magnetic circuit of electrical machines. A four-pole rotational single sheet tester is used to generate the rotating magnetic flux inside the sample. A field-oriented control scheme is implemented to improve the control performance. The magnetization process of different non-oriented materials is analyzed and compared.

Electric wind in a Differential Mobility Analyzer

DOE PAGES

Palo, Marus; Meelis Eller; Uin, Janek; ...

2015-10-25

Electric wind -- the movement of gas, induced by ions moving in an electric field -- can be a distorting factor in size distribution measurements using Differential Mobility Analyzers (DMAs). The aim of this study was to determine the conditions under which electric wind occurs in the locally-built VLDMA (Very Long Differential Mobility Analyzer) and TSI Long-DMA (3081) and to describe the associated distortion of the measured spectra. Electric wind proved to be promoted by the increase of electric field strength, aerosol layer thickness, particle number concentration and particle size. The measured size spectra revealed three types of distortion: wideningmore » of the size distribution, shift of the mode of the distribution to smaller diameters and smoothing out the peaks of the multiply charged particles. Electric wind may therefore be a source of severe distortion of the spectrum when measuring large particles at high concentrations.« less

Response of the Shockley surface state to an external electrical field: A density-functional theory study of Cu(111)

NASA Astrophysics Data System (ADS)

Berland, K.; Einstein, T. L.; Hyldgaard, P.

2012-01-01

The response of the Cu(111) Shockley surface state to an external electrical field is characterized by combining a density-functional theory calculation for a slab geometry with an analysis of the Kohn-Sham wave functions. Our analysis is facilitated by a decoupling of the Kohn-Sham states via a rotation in Hilbert space. We find that the surface state displays isotropic dispersion, quadratic until the Fermi wave vector but with a significant quartic contribution beyond. We calculate the shift in energetic position and effective mass of the surface state for an electrical field perpendicular to the Cu(111) surface; the response is linear over a broad range of field strengths. We find that charge transfer occurs beyond the outermost copper atoms and that accumulation of electrons is responsible for a quarter of the screening of the electrical field. This allows us to provide well converged determinations of the field-induced changes in the surface state for a moderate number of layers in the slab geometry.

Dependence of negative ion formation on inhomogeneous electric field strength in atmospheric pressure negative corona discharge

NASA Astrophysics Data System (ADS)

Sekimoto, K.; Takayama, M.

2008-12-01

The dependence of negative ion formation on the inhomogeneous electric field strength in atmospheric pressure negative corona discharge with point-to-plane electrodes has been described. The distribution of negative ions HO-, NOx - and COx - and their abundances on the plane electrode was obtained with a mass spectrometer. The ion distribution on the plane was divided into two regions, the center region on the needle axis and peripheral region occurring the dominant NOx - and COx - ions and HO- ion, respectively. The calculated electric field strength in inhomogeneous electric field established on the needle tip surface suggested that the abundant formation of NOx - and COx - ions and HO- ion is attributed to the high field strength at the tip apex region over 108 Vm-1 and the low field strength at the tip peripheral region of the order of 107 Vm-1, respectively. The formation of HO-, NOx - and COx - has been discussed from the standpoint of negative ion evolution based on the thermochemical reaction and the kinetic energy of electron emitted from the needle tip.

Two distinct regions of response drive differential growth in Vigna root electrotropism

NASA Technical Reports Server (NTRS)

Wolverton, C.; Mullen, J. L.; Ishikawa, H.; Evans, M. L.

2000-01-01

Although exogenous electric fields have been reported to influence the orientation of plant root growth, reports of the ultimate direction of differential growth have been contradictory. Using a high-resolution image analysis approach, the kinetics of electrotropic curvature in Vigna mungo L. roots were investigated. It was found that curvature occurred in the same root toward both the anode and cathode. However, these two responses occurred in two different regions of the root, the central elongation zone (CEZ) and distal elongation zone (DEZ), respectively. These oppositely directed responses could be reproduced individually by a localized electric field application to the region of response. This indicates that both are true responses to the electric field, rather than one being a secondary response to an induced gravitropic stimulation. The individual responses differed in the type of differential growth giving rise to curvature. In the CEZ, curvature was driven by inhibition of elongation, whereas curvature in the DEZ was primarily due to stimulation of elongation. This stimulation of elongation is consistent with the growth response of the DEZ to other environmental stimuli.

Effect of Electric Field on Gas Hydrate Nucleation Kinetics: Evidence for the Enhanced Kinetics of Hydrate Nucleation by Negatively Charged Clay Surfaces.

PubMed

Park, Taehyung; Kwon, Tae-Hyuk

2018-03-06

Natural gas hydrates are found widely in oceanic clay-rich sediments, where clay-water interactions have a profound effect on the formation behavior of gas hydrates. However, it remains unclear why and how natural gas hydrates are formed in clay-rich sediments in spite of factors that limit gas hydrate formation, such as small pore size and high salinity. Herein, we show that polarized water molecules on clay surfaces clearly promote gas hydrate nucleation kinetics. When water molecules were polarized with an electric field of 10 4 V/m, gas hydrate nucleation occurred significantly faster with an induction time reduced by 5.8 times. Further, the presence of strongly polarized water layers at the water-gas interface hindered gas uptake and thus hydrate formation, when the electric field was applied prior to gas dissolution. Our findings expand our understanding of the formation habits of naturally occurring gas hydrates in clay-rich sedimentary deposits and provide insights into gas production from natural hydrate deposits.

High-latitude dayside electric fields and currents during strong northward interplanetary magnetic field - Observations and model simulation

NASA Technical Reports Server (NTRS)

Clauer, C. Robert; Friis-Christensen, Eigil

1988-01-01

On July 23, 1983 the IMF turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, the onset of the reconfiguration of the high-latitude ionospheric currents is found to occur about 3 min after the northward IMF encounters the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. These observations and the results of numerical simulations indicate that the dayside polar-cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind.

A simulation study of particle energization observed by THEMIS spacecraft during a substorm

NASA Astrophysics Data System (ADS)

Ashour-Abdalla, Maha; Bosqued, Jean-Michel; El-Alaoui, Mostafa; Peroomian, Vahe; Zhou, Meng; Richard, Robert; Walker, Raymond; Runov, Andrei; Angelopoulos, Vassilis

2009-09-01

Energetic ions with hundreds of keV energy are frequently observed in the near-Earth tail during magnetospheric substorms. We examined the sources and acceleration of ions during a magnetospheric substorm on 1 March 2008 by using Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Cluster observations and numerical simulations. Four of the THEMIS spacecraft were aligned at yGSM = 6 RE during a very large substorm (AE = 1200) while the Cluster spacecraft were located about 5 RE above the auroral ionosphere. For 2 h before the substorm, Cluster observed ionospheric oxygen flowing out into the magnetosphere. After substorm onset the THEMIS P3 and P4 spacecraft located in the near-Earth tail (xGSM = -9 RE and -8 RE, respectively) observed large fluxes of energetic ions up to 500 keV. We used calculations of millions of ions of solar wind and ionospheric origin in the time-dependent electric and magnetic fields from a global magnetohydrodynamic simulation of this event to study the source of these ions and their acceleration. The simulation did a good job of reproducing the particle observations. Both solar wind protons and ionospheric oxygen were accelerated by nonadiabatic motion across large (>˜5 mV/m) total electric fields (both potential and induced). The acceleration occurred in the "wall" region of the near-Earth tail where nonadiabatic motion dominates over convection and the particles move rapidly across the tail. The acceleration occurred mostly in regions with large electric fields and nonadiabatic motion. There was relatively little acceleration in regions with large electric fields and adiabatic motion or small electric fields and nonadiabatic motion. Prior to substorm onset, ionospheric ions were a significant contributor to the cross-tail current, but after onset, solar wind ions become more dominant.

Numerical Simulation of Non-Thermal Food Preservation

NASA Astrophysics Data System (ADS)

Rauh, C.; Krauss, J.; Ertunc, Ö.; Delgado, a.

2010-09-01

Food preservation is an important process step in food technology regarding product safety and product quality. Novel preservation techniques are currently developed, that aim at improved sensory and nutritional value but comparable safety than in conventional thermal preservation techniques. These novel non-thermal food preservation techniques are based for example on high pressures up to one GPa or pulsed electric fields. in literature studies the high potential of high pressures (HP) and of pulsed electric fields (PEF) is shown due to their high retention of valuable food components as vitamins and flavour and selective inactivation of spoiling enzymes and microorganisms. for the design of preservation processes based on the non-thermal techniques it is crucial to predict the effect of high pressure and pulsed electric fields on the food components and on the spoiling enzymes and microorganisms locally and time-dependent in the treated product. Homogenous process conditions (especially of temperature fields in HP and PEF processing and of electric fields in PEF) are aimed at to avoid the need of over-processing and the connected quality loss and to minimize safety risks due to under-processing. the present contribution presents numerical simulations of thermofluiddynamical phenomena inside of high pressure autoclaves and pulsed electric field treatment chambers. in PEF processing additionally the electric fields are considered. Implementing kinetics of occurring (bio-) chemical reactions in the numerical simulations of the temperature, flow and electric fields enables the evaluation of the process homogeneity and efficiency connected to different process parameters of the preservation techniques. Suggestions to achieve safe and high quality products are concluded out of the numerical results.

Numerical modelling of processes that occur in the selective waste disassembly installation

NASA Astrophysics Data System (ADS)

Cherecheş, T.; Lixandru, P.; Dragnea, D.; Cherecheş, D. M.

2017-08-01

This paper is the result of the attempts of quantitative approach of some of the processes that are occurring in the selective fragmentation with high voltage pulses installation. It has been formulated a methodology which customizes the general methods for the issue of transient electric field in mixed environments. The electromagnetic processes inside the fragmentation installation, the initiation and formation of the discharge channels, the thermodynamic and mechanical effects in the process vessel are complex, transient and very quick. One of the underlying principles of the fragmentation process consists in the differentiated reaction of materials in an electric field. Generally in the process vessel there can be found together three types of materials: dielectrics, metal, electrolytes. The conductivity of dielectric materials is virtually zero. Metallic materials conduct very well through electronic conductivity. Electrolytes have a more modest conductivity since they conduct through electrochemical processes. The electrical current, in this case, is the movement of ions having sizes and the masses different from the electrons. Here, the electric current includes displacements of ions and molecules, collisions and chemical reactions. Part of the electrical field’s energy is absorbed by the electrolyte in the form of mechanical and chemical energy.

Stability of parallel electroosmotic flow subject to an axial modulated electric field

NASA Astrophysics Data System (ADS)

Suresh, Vinod; Homsy, George

2001-11-01

The stability of parallel electroosmotic flow in a micro-channel subjected to an AC electric field is studied. A spatially uniform time harmonic electric field is applied along the length of a two-dimensional micro-channel containing a dilute electrolytic solution, resulting in a time periodic parallel flow. The top and bottom walls of the channel are maintained at constant potential. The base state ion concentrations and double layer potential are determined using the Poisson-Boltzmann equation in the Debye-Hückel approximation. Experiments by other workers (Santiago et. al., unpublished) have shown that such a system can exhibit instabilities that take the form of mixing motion occurring in the bulk flow outside the double layer. It is shown that such instabilities can potentially result from the coupling of disturbances in the ion concentrations or electric potential to the base state velocity or ion concentrations, respectively. The stability boundary of the system is determined using Floquet theory and its dependence on the modulation frequency and amplitude of the axial electric field is studied.

Long-term monitoring of ULF electromagnetic fields at Parkfield, CA

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

Kappler, K.N.; Morrison, H.F.; Egbert, G.D.

2009-08-01

Electric and magnetic fields in the (10{sup -4}-1.0) Hz band were monitored at two sites adjacent to the San Andreas Fault near Parkfield and Hollister, California from 1995 to present. A data window [2002-2005], enclosing the September 28, 2004 M6 Parkfield earthquake, was analyzed to determine if anomalous electric or magnetic fields, or changes in ground conductivity, occurred before the earthquake. The data were edited, removing intervals of instrument malfunction leaving 875 days in the four-year period. Frequent, spike-like disturbances were common, but were not more frequent around the time of the earthquake; these were removed before subsequent processing. Signalmore » to noise amplitude spectra, estimated via magnetotelluric processing showed the behavior of the ULF fields to be remarkably constant over the period of analysis. These first-order plots make clear that most of the recorded energy is coherent over the spatial extent of the array. Three main statistical techniques were employed to separate local anomalous electrical or magnetic fields from the dominant coherent natural fields: transfer function estimates between components at each site were employed to subtract the dominant field, and look deeper at the 'residual' fields; the data were decomposed into principal components to identify the dominant coherent array modes; and the technique of canonical coherences was employed to distinguish anomalous fields which are spatially broad from anomalies which occur at a single site only, and furthermore to distinguish anomalies which are present in both the electric and magnetic fields from those which are present in only one field type. Standard remote reference apparent resistivity estimates were generated daily at Parkfield. A significant seasonal component of variability was observed suggesting local distortion due to variations in near surface resistance. In all cases, high levels of sensitivity to subtle electromagnetic effects were demonstrated, but no effects which can be reasonably characterized as precursors to the Parkfield earthquake were found.« less

Local electric field direct writing – Electron-beam lithography and mechanism

DOE PAGES

Jiang, Nan; Su, Dong; Spence, John C. H.

2017-08-24

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Electro-rheological finishing for optical surfaces

NASA Astrophysics Data System (ADS)

Cheng, Haobo; Wang, Peng

2009-05-01

Many polishing techniques such as fixed-abrasive polishing, abrasive-free polishing and magnetorheological finishing etc., have been developed. Meanwhile, a new technique is proposed using the mixture of the electro-rheological (Er) fluid with abrasives as polishing slurry, which is a special process does not require pad. Electrorheological fluid is a special suspension liquid, whose viscosity has an approximate proportional relation with the electric strength applied. When the field strength reaches a certain limit, the phase transition occurs and the liquid acquires a solid like character, and while the electric field is removed, the fluid regains its original viscosity during the order of milliseconds. In this research work, we employed the characteristics of viscosity change of Er fluid to hold the polishing particles for micromachining. A point-contact electro-rheological finishing (Erf) tool was designed with a tip diameter 0.5~1mm. Both the anode and the cathode of the electric field were combined in the tool. The electric field could be controllable. When the tool moves across the profile of the work piece, by controlling the electric field strength as well as the other manufacturing parameters we can assure the deterministic material removal. Furthermore, the electro-rheological finishing process has been planned in detailed.

Local electric field direct writing – Electron-beam lithography and mechanism

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

Jiang, Nan; Su, Dong; Spence, John C. H.

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Tunable phase transition in single-layer TiSe2 via electric field

NASA Astrophysics Data System (ADS)

Liu, Lei; Zhuang, Houlong L.

2018-06-01

Phase transition represents an intriguing physical phenomenon that exists in a number of single-layer transition-metal dichalcogenides. This phenomenon often occurs below a critical temperature and breaks the long-range crystalline order leading to a reconstructed superstructure called the charge-density wave (CDW) structure, which can therefore be recovered by external stimuli such as temperature. Alternatively, we show here that another external stimulation, electric field can also result in the phase transition between the regular and CDW structures of a single-layer transition-metal dichalcogenide. We used single-layer TiSe2 as an example to elucidate the mechanism of the CDW followed by calculations of the electronic structure using a hybrid density functional. We found that applying electric field can tune the phase transition between the 1T and CDW phases of single-layer TiSe2. Our work opens up a route of tuning the phase transition of single-layer materials via electric field.

Nondestructive acoustic electric field probe apparatus and method

DOEpatents

Migliori, Albert

1982-01-01

The disclosure relates to a nondestructive acoustic electric field probe and its method of use. A source of acoustic pulses of arbitrary but selected shape is placed in an oil bath along with material to be tested across which a voltage is disposed and means for receiving acoustic pulses after they have passed through the material. The received pulses are compared with voltage changes across the material occurring while acoustic pulses pass through it and analysis is made thereof to determine preselected characteristics of the material.

Electric-field-induced shape transition of nematic tactoids

NASA Astrophysics Data System (ADS)

Metselaar, Luuk; Dozov, Ivan; Antonova, Krassimira; Belamie, Emmanuel; Davidson, Patrick; Yeomans, Julia M.; Doostmohammadi, Amin

2017-08-01

The occurrence of new textures of liquid crystals is an important factor in tuning their optical and photonics properties. Here, we show, both experimentally and by numerical computation, that under an electric field chitin tactoids (i.e., nematic droplets) can stretch to aspect ratios of more than 15, leading to a transition from a spindlelike to a cigarlike shape. We argue that the large extensions occur because the elastic contribution to the free energy is dominated by the anchoring. We demonstrate that the elongation involves hydrodynamic flow and is reversible: the tactoids return to their original shapes upon removing the field.

Contactless Mobility, Carrier Density, and Sheet Resistance Measurements on Si, GaN, and AlGaN/GaN High Electron Mobility Transistor (HEMT) Wafers

DTIC Science & Technology

2015-02-01

to the electrical characterization of semiconductor materials. The Hall effect occurs when an electrical conductor is placed in a magnetic field...system. The TE11 mode is caused by the Hall effect when under an applied magnetic field. This effect rotates the TE10 mode 90° where the forward...conductivity tensors σxx and σxy, where σxx and σxy are functions of the magnetic field (H). The Hall coefficient (RH) for a given H is then

Production of aligned microfibers and nanofibers and derived functional monoliths

DOEpatents

Hu, Michael Z [Knoxville, TN; DePaoli, David W [Knoxville, TN; Kuritz, Tanya [Kingston, TN; Omatete, Ogbemi [New Port Richey, FL

2007-08-14

The present invention comprises a method for producing microfibers and nanofibers and further fabricating derived solid monolithic materials having aligned uniform micro- or nanofibrils. A method for producing fibers ranging in diameter from micrometer-sized to nanometer-sized comprises the steps of producing an electric field and preparing a solid precipitative reaction media wherein the media comprises at least one chemical reactive precursor and a solvent having low electrical conductivity and wherein a solid precipitation reaction process for nucleation and growth of a solid phase occurs within the media. Then, subjecting the media to the electric field to induce in-situ growth of microfibers or nanofibers during the reaction process within the media causing precipitative growth of solid phase particles wherein the reaction conditions and reaction kinetics control the size, morphology and composition of the fibers. The fibers can then be wet pressed while under electric field into a solid monolith slab, dried and consolidated.

Reactive molecular dynamics of the initial oxidation stages of Ni111 in pure water: effect of an applied electric field.

PubMed

Assowe, O; Politano, O; Vignal, V; Arnoux, P; Diawara, B; Verners, O; van Duin, A C T

2012-12-06

Corrosion processes occurring in aqueous solutions are critically dependent upon the interaction between the metal electrode and the solvent. In this work, the interaction of a nickel substrate with water molecules has been investigated using reactive force field (ReaxFF) molecular dynamics simulations. This approach was originally developed by van Duin and co-workers to study hydrocarbon chemistry and the catalytic properties of organic compounds. To our knowledge, this method has not previously been used to study the corrosion of nickel. In this work, we studied the interaction of 480 molecules of water (ρ = 0.99 g·cm(-3)) with Ni(111) surfaces at 300 K. The results showed that a water "bilayer" was adsorbed on the nickel surface. In the absence of an applied electric field, no dissociation of water was observed. However, the nickel atoms at the surface were charged positively, whereas the first water layer was charged negatively, indicating the formation of an electric double layer. To study the corrosion of nickel in pure water, we introduced an external electric field between the metal and the solution. The electric field intensity varied between 10 and 20 MeV/cm. The presence of this electric field led to oxidation of the metal surface. The structural and morphological differences associated with the growth of this oxide film in the presence of the electric field were evaluated. The simulated atomic trajectories were used to analyze the atomic displacement during the reactive process. The growth of the oxide scale on the nickel surface was primarily due to the movement of anions toward the interior of the metal substrate and the migration of nickel toward the free surface. We found that increasing the electric field intensity sped up the corrosion of nickel. The results also showed that the oxide film thickness increased linearly with increasing electric field intensity.

Low Pressure Experimental Simulation of Electrical Discharges Above and Inside a Cloud

NASA Technical Reports Server (NTRS)

Jarzembski, Maurice A.; Srivastava, Vandana

1996-01-01

A low pressure laboratory experiment to generate sporadic electrical discharges in either a particulate dielectric or air, representing a competing path of preferred electrical breakdown, was investigated. At high pressures, discharges occurred inside the dielectric particulate; at low pressures, discharges occurred outside the dielectric particulate; at a transition pressure regime, which depends on conductivity of the dielectric particulate, discharges were simultaneously generated in both particulate dielectric and air. Unique use of a particulate dielectric was critical for sporadic discharges at lower pressures which were not identical in character to discharges without the particulate dielectric. Application of these experimental results to the field of atmospheric electricity and simulation of the above-cloud type discharges that have recently been documented, called jets and sprites, are discussed.

Observed Enhancement of Reflectivity and Electric Field in Long-Lived Florida Anvils

NASA Technical Reports Server (NTRS)

Dye, James E.; Willett, John C.

2007-01-01

A study of two long-lived Florida anvils showed that reflectivity >20 dBZ increased in area, thickness and sometimes magnitude at mid-level well downstream of the convective cores. In these same regions electric fields maintained strengths >10 kV m1 for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9 to 10 km for extended times and distances. Aggregation of ice particles enhanced by strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations further out in the anvil. The enhanced reflectivity and existence of small, medium and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. We conclude that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields >10 kV m 1 at 9 to 10 km for extended periods of time over large distances. We speculate that charge separation occurred as a result of ice-ice particle collisions (without supercooled water being present) via either a non-inductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong pre-existing electric fields and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

Spectator electric fields, de Sitter spacetime, and the Schwinger effect

NASA Astrophysics Data System (ADS)

Giovannini, Massimo

2018-03-01

During a de Sitter stage of expansion, the spectator fields of different spin are constrained by the critical density bound and by further requirements determined by their specific physical nature. The evolution of spectator electric fields in conformally flat background geometries is occasionally concocted by postulating the existence of ad hoc currents, but this apparently innocuous trick violates the second law of thermodynamics. Such a problem occurs, in particular, for those configurations (customarily employed for the analysis of the Schwinger effect in four-dimensional de Sitter backgrounds) leading to an electric energy density which is practically unaffected by the expansion of the underlying geometry. The obtained results are compared with more mundane situations where Joule heating develops in the early stages of a quasi-de Sitter phase.

Field-induced structural control of COx molecules adsorbed on graphene

NASA Astrophysics Data System (ADS)

Matsubara, Manaho; Okada, Susumu

2018-05-01

Using the density functional theory combined with both the van der Waals correction and the effective screening medium method, we investigate the energetics and electronic structures of CO and CO2 molecules adsorbed on graphene surfaces in the field-effect-transistor structure with respect to the external electric field by the excess electrons/holes. The binding energies of CO and CO2 molecules to graphene monotonically increase with increasing hole and electron concentrations. The increase occurs regardless of the molecular conformations to graphene and the counter electrode, indicating that the carrier injection substantially enhances the molecular adsorption on graphene. Injected carriers also modulate the stable molecular conformation, which is metastable in the absence of an electric field.

Modification of the coil-stretch transition by confinement

NASA Astrophysics Data System (ADS)

Doyle, Patick; Tang, Jing; Jones, Jeremy

2010-03-01

Large double stranded DNA are both a powerful system to study polymer dynamics at the single molecule level and also important molecules for genomic applications. While homogenous electric fields are routinely used to separate DNA in gels, DNA deformation in more complex fields has been less widely studied. We will demonstrate how micro/nanofluidic devices allow for the generation of electric fields with well-defined kinematics for trapping, stretching and then watching DNA relax back to equilibrium. The dimensions of the devices highly confine DNA and subsequently change both their conformation and dynamics. We will show how these confinements effects change the coil-stretch transition of a DNA being electrophoretically stretched in a purely elongational electrical field. We experimentally show that a two-stage coil stretch transition occurs and develop a simple dumbbell model which captures most of the relevant physics. We trace the origin of this phenomena to the modification of the effective spring law due to confinement.

Geomagnetic storm effects on the occurrences of ionospheric irregularities over the African equatorial/low-latitude region

NASA Astrophysics Data System (ADS)

Amaechi, P. O.; Oyeyemi, E. O.; Akala, A. O.

2018-04-01

The study investigated the effects of intense geomagnetic storms of 2015 on the occurrences of large scale ionospheric irregularities over the African equatorial/low-latitude region. Four major/intense geomagnetic storms of 2015 were analyzed for this study. These storms occurred on 17th March 2015 (-229 nT), 22nd June 2015 (-204 nT), 7th October 2015 (-124 nT), and 20th December 2015 (-170 nT). Total Electron Content (TEC) data obtained from five African Global Navigation Satellite Systems (GNSS) stations, grouped into eastern and western sectors were used to derive the ionospheric irregularities proxy indices, e.g., rate of change of TEC (ROT), ROT index (ROTI) and ROTI daily average (ROTIAVE). These indices were characterized alongside with the disturbance storm time (Dst), the Y component of the Interplanetary Electric Field (IEFy), polar cap (PC) index and the H component of the Earth's magnetic field from ground-based magnetometers. Irregularities manifested in the form of fluctuations in TEC. Prompt penetration of electric field (PPEF) and disturbance dynamo electric field (DDEF) modulated the behaviour of irregularities during the main and recovery phases of the geomagnetic storms. The effect of electric field over both sectors depends on the local time of southward turning of IMF Bz. Consequently, westward electric field inhibited irregularities during the main phase of March and October 2015 geomagnetic storms, while for the June 2015 storm, eastward electric field triggered weak irregularities over the eastern sector. The effect of electric field on irregularities during December 2015 storm was insignificant. During the recovery phase of the storms, westward DDEF suppressed irregularities.

Pre-breakdown processes in a dielectric fluid in inhomogeneous pulsed electric fields

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

Shneider, Mikhail N., E-mail: m.n.shneider@gmail.com; Pekker, Mikhail

2015-06-14

We consider the development of pre-breakdown cavitation nanopores appearing in the dielectric fluid under the influence of the electrostrictive stresses in the inhomogeneous pulsed electric field. It is shown that three characteristic regions can be distinguished near the needle electrode. In the first region, where the electric field gradient is greatest, the cavitation nanopores, occurring during the voltage nanosecond pulse, may grow to the size at which an electron accelerated by the field inside the pores can acquire enough energy for excitation and ionization of the liquid on the opposite pore wall, i.e., the breakdown conditions are satisfied. In themore » second region, the negative pressure caused by the electrostriction is large enough for the cavitation initiation (which can be registered by optical methods), but, during the voltage pulse, the pores do not reach the size at which the potential difference across their borders becomes sufficient for ionization or excitation of water molecules. And, in the third, the development of cavitation is impossible, due to an insufficient level of the negative pressure: in this area, the spontaneously occurring micropores do not grow and collapse under the influence of surface tension forces. This paper discusses the expansion dynamics of the cavitation pores and their most probable shape.« less

Regularly scheduled, day-time, slow-onset 60 Hz electric and magnetic field exposure does not depress serum melatonin concentration in nonhuman primates

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

Rogers, W.R.; Smith, H.D.; Orr, J.L.

Experiments conducted with laboratory rodents indicate that exposure to 60 Hz electric fields or magnetic fields can suppress nocturnal melatonin concentrations in pineal gland and blood. In three experiments employing three field-exposed and three sham-exposed nonhuman primates, each implanted with an indwelling venous cannula to allow repeated blood sampling, the authors studied the effects of either 6 kV/m and 50 {micro}T (0.5 G) or 30 kV/m and 100 {micro}T (1.0 G) on serum melatonin patterns. The fields were ramped on and off slowly, so that no transients occurred. Extensive quality control for the melatonin assay, computerized control and monitoring ofmore » field intensities, and consistent exposure protocols were used. No changes in nocturnal serum melatonin concentration resulted from 6 weeks of day-time exposure with slow field onset/offset and a highly regular exposure protocol. These results indicate that, under the conditions tested, day-time exposure to 60 Hz electric and magnetic fields in combination does not result in melatonin suppression in primates.« less

Utilizing Four Dimensional Lightning and Dual-Polarization Radar to Develop Lightning Initiation Forecast Guidance

DTIC Science & Technology

2015-03-26

Electrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3 Lightning Discharge ...charge is caused by falling graupel that is positively charged (Wallace and Hobbs 2006). 2.3 Lightning Discharge Lightning occurs when the electric...emission of positive corona from the surface of precipitation particles, causing the electric field to become locally enhanced and supporting the

Energy loss of ions by electric-field fluctuations in a magnetized plasma.

PubMed

Nersisyan, Hrachya B; Deutsch, Claude

2011-06-01

The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

Electromagnetically induced transparency in the case of elliptic polarization of interacting fields

NASA Astrophysics Data System (ADS)

Parshkov, Oleg M.

2018-04-01

The theoretical investigation results of disintegration effect of elliptic polarized shot probe pulses of electromagnetically induced transparency in the counterintuitive superposed elliptic polarized control field and in weak probe field approximation are presented. It is shown that this disintegration occurs because the probe field in the medium is the sum of two normal modes, which correspond to elliptic polarized pulses with different speeds of propagation. The polarization ellipses of normal modes have equal eccentricities and mutually perpendicular major axes. Major axis of polarization ellipse of one normal mode is parallel to polarization ellipse major axis of control field, and electric vector of this mode rotates in the opposite direction, than electric vector of the control field. The electric vector other normal mode rotates in the same direction that the control field electric vector. The normal mode speed of the first type aforementioned is less than that of the second type. The polarization characteristics of the normal mode depend uniquely on the polarization characteristics of elliptic polarized control field and remain changeless in the propagation process. The theoretical investigation is performed for Λ-scheme of degenerated quantum transitions between 3P0, 3P10 and 3P2 energy levels of 208Pb isotope.

Binary black hole in a double magnetic monopole field

NASA Astrophysics Data System (ADS)

Rodriguez, Maria J.

2018-01-01

Ambient magnetic fields are thought to play a critical role in black hole jet formation. Furthermore, dual electromagnetic signals could be produced during the inspiral and merger of binary black hole systems. In this paper, we derive the exact solution for the electromagnetic field occurring when a static, axisymmetric binary black hole system is placed in the field of two magnetic or electric monopoles. As a by-product of this derivation, we also find the exact solution of the binary black hole configuration in a magnetic or electric dipole field. The presence of conical singularities in the static black hole binaries represent the gravitational attraction between the black holes that also drag the external two monopole field. We show that these off-balance configurations generate no energy outflows.

Lightning-driven electric and magnetic fields measured in the stratosphere: Implications for sprites

NASA Astrophysics Data System (ADS)

Thomas, Jeremy Norman

A well accepted model for sprite production involves quasi-electrostatic fields (QSF) driven by large positive cloud-to-ground (+CG) strokes that can cause electrical breakdown in the middle atmosphere. A new high voltage, high impedance, double Langmuir probe instrument is designed specifically for measuring these large lightning-driven electric field changes at altitudes above 30 km. This High Voltage (HV) Electric Field Detector measured 200 nearby (<75 km) lightning-driven electric field changes, up to 140 V/m in magnitude, during the Brazil Sprite Balloon Campaign 2002--03. A numerical QSF model is developed and compared to the in situ measurements. It is found that the amplitudes and relaxation times of the electric fields driven by these nearby lightning events generally agree with the numerical QSF model, which suggests that the QSF approach is valid for modeling lightning-driven fields. Using the best fit parameters of this comparison, it is predicted that the electric fields at sprite altitudes (60--90 km) never surpass conventional breakdown in the mesosphere for each of these 200 nearby lightning events. Lightning-driven ELF to VLF (25 Hz--8 kHz) electric field changes were measured for each of the 2467 cloud-to-ground lightning (CGs) detected by the Brazilian Integrated Lightning Network (BIN) at distances of 75--600 km, and magnetic field changes (300 Hz--8 kHz) above the background noise were measured for about 35% (858) of these CGs. ELF pulses that occur 4--12 ms after the retarded time of the lightning sferic, which have been previously attributed to sprites, were found for 1.4% of 934 CGs examined with a strong bias towards +CGs (4.9% or 9/184) compared to -CGs (0.5% or 4/750). These results disagree with results from the Sprites99 Balloon Campaign [Bering et al., 2004b], in which the lightning-driven electric and magnetic field changes were rare, while the CG delayed ELF pulses were frequent. The Brazil Campaign results thus suggest that mesospheric currents are likely the result of the QSF driven by large charge moment strokes, which are usually +CG strokes, initiating breakdown in the middle atmosphere.

Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Hill, Carrie S.

2013-01-01

Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are useful for performing measurements in electric space thrusters and various plasma accelerator applications where a time-varying magnetic field is present. Magnetic field probes have proven to be a mainstay in diagnosing plasma thrusters where changes occur rapidly with respect to time, providing the means to measure the magnetic fields produced by time-varying currents and even an indirect measure of the plasma current density through the application of Ampère's law. Examples of applications where this measurement technique has been employed include pulsed plasma thrusters and quasi-steady magnetoplasmadynamic thrusters. The Electric Propulsion Technical Committee (EPTC) of the American Institute of Aeronautics and Astronautics (AIAA) was asked to assemble a Committee on Standards (CoS) for Electric Propulsion Testing. The assembled CoS was tasked with developing Standards and Recommended Practices for various diagnostic techniques used in the evaluation of plasma thrusters. These include measurements that can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. This paper presents a summary of the standard, describing the preferred methods for fabrication, calibration, and usage of inductive magnetic field probes for use in diagnosing plasma thrusters. Inductive magnetic field probes (also called B-dot probes throughout this document) are commonly used in electric propulsion (EP) research and testing to measure unsteady magnetic fields produced by time-varying currents. The B-dot probe is relatively simple in construction, and requires minimal cost, making it a low-cost technique that is readily accessible to most researchers. While relatively simple, the design of a B-dot probe is not trivial and there are many opportunities for errors in probe construction, calibration, and usage, and in the post-processing of data that is produced by the probe. There are typically several ways in which each of these steps can be approached, and different applications may require more or less vigorous attention to various issues.

PIC simulations of post-pulse field reversal and secondary ionization in nanosecond argon discharges

NASA Astrophysics Data System (ADS)

Kim, H. Y.; Gołkowski, M.; Gołkowski, C.; Stoltz, P.; Cohen, M. B.; Walker, M.

2018-05-01

Post-pulse electric field reversal and secondary ionization are investigated with a full kinetic treatment in argon discharges between planar electrodes on nanosecond time scales. The secondary ionization, which occurs at the falling edge of the voltage pulse, is induced by charge separation in the bulk plasma region. This process is driven by a reverse in the electric field from the cathode sheath to the formerly driven anode. Under the influence of the reverse electric field, electrons in the bulk plasma and sheath regions are accelerated toward the cathode. The electron movement manifests itself as a strong electron current generating high electron energies with significant electron dissipated power. Accelerated electrons collide with Ar molecules and an increased ionization rate is achieved even though the driving voltage is no longer applied. With this secondary ionization, in a single pulse (SP), the maximum electron density achieved is 1.5 times higher and takes a shorter time to reach using 1 kV 2 ns pulse as compared to a 1 kV direct current voltage at 1 Torr. A bipolar dual pulse excitation can increase maximum density another 50%–70% above a SP excitation and in half the time of RF sinusoidal excitation of the same period. The first field reversal is most prominent but subsequent field reversals also occur and correspond to electron temperature increases. Targeted pulse designs can be used to condition plasma density as required for fast discharge applications.

Study of polarization properties of fiber-optics probes with use of a binary phase plate.

PubMed

Alferov, S V; Khonina, S N; Karpeev, S V

2014-04-01

We conduct a theoretical and experimental study of the distribution of the electric field components in the sharp focal domain when rotating a zone plate with a π-phase jump placed in the focused beam. Comparing the theoretical and experimental results for several kinds of near-field probes, an analysis of the polarization sensitivity of different types of metal-coated aperture probes is conducted. It is demonstrated that with increasing diameter of the non-metal-coated tip part there occurs an essential redistribution of sensitivity in favor of the transverse electric field components and an increase of the probe's energy throughput.

Electric Field Profiles over Hurricanes, Tropical Cyclones, and Thunderstorms with an Instrumented ER-2 Aircraft

NASA Technical Reports Server (NTRS)

Mach, Doug M.; Blakeslee, Richard J.; Bateman, Monte G.; Bailey, Jeff C.

2007-01-01

Over the past several years, we have flown a set of calibrated electric field meters (FMs) on the NASA high altitude ER-2 aircraft over oceanic and landbased storms in a number of locations. These included tropical oceanic cyclones and hurricanes in the Caribbean and Atlantic ocean during the Third and Fourth Convection And Moisture EXperiment (CAMEX-3,1998; CAMEX-4, 2001), thunderstorms in Florida during the TExas FLorida UNderflight (TEFLUN, 1998) experiment, tropical thunderstorms in Brazil during the Tropical Rainfall Measuring Mission - Large Scale Biosphere-Atmosphere Experiment in Amazonia (TRMM LBA, 1999), and finally, hurricanes and tropical cyclones in the Caribbean and Western Pacific and thunderstorms in Central America during the Tropical Cloud Systems and Processes (TCSP, 2005) mission. Between these various missions we have well over 50 sorties that provide a unique insights on the different electrical environment, evolution and activity occurring in and around these various types of storms. In general, the electric fields over the tropical oceanic storms and hurricanes were less than a few kilovolts per meter at the ER-2 altitude, while the lightning rates were low. Land-based thunderstorms often produced high lightning activity and correspondingly higher electric fields.

On the production of Gamma rays and Relativistic Runaway Electron Avalanches from Martian dust storms

NASA Astrophysics Data System (ADS)

Arabshahi, S.; Majid, W.; Dwyer, J. R.; Rassoul, H.

2016-12-01

In Earth's atmosphere, runaway electrons are routinely produced from large electric fields such as occurs inside thunderclouds. Electrons run away when the average rate of energy loss in a medium is less than the average rate of energy gains from an electric field. These electrons can then produce more energetic electrons, and subsequently an avalanche of energetic electrons, through electron-electron Møller scattering with air atoms and molecules. The process is called a Relativistic Runaway Electron Avalanche (RREA). RREA also produces large flux of X-rays and gamma rays (e.g. Terrestrial Gamma Ray Flashes) through bremsstrahlung scattering. Theoretical modeling of electric fields inside dust devils [Farrel et al. 2006], and possible observation of large electrostatic discharges from Mars [Ruf et al. 2009] suggest that the electric fields could get close to the breakdown values for Mars' atmosphere, i.e. 25 kV/m. Using detailed Monte Carlo simulations, we have shown that for such electric fields it is possible to have a RREA-like mechanism also at work inside the Martian dust storms, capable of producing a large flux of gamma-ray photons. We have also shown that the resulting gamma ray photons could be detected using instruments either on the surface of Mars or on orbiting satellites.

Analysis of the disturbed electric field effects in the sporadic E-layers at equatorial and low latitude regions

NASA Astrophysics Data System (ADS)

Araujo Resende, Laysa Cristina; Moro, Juliano; Denardini, Clezio Marcos; Carrasco, Alexander J.; Batista, Paulo; Chen, Sony Su; Batista, Inez S.; Andrioli, Vania Fatima

2016-07-01

In the present work we analyze the disturbed electric field effects in the sporadic E-layers at equatorial regions, Jicamarca (11.57°S, 76.52°O, I: -2°) and São Luís (2°S, 44° O, I: -2.3°), and at low latitude regions, Fortaleza (3.9°S, 38.45°O, I: -9°) and Cachoeira Paulista (22.42°S, 45°O, I: -15°). We have conducted a deep analysis to investigate these effects using a theoretical model for the ionospheric E region, called MIRE. This model is able to simulate the Es layers taking into account the E region winds and electric fields. It calculates the densities for the main molecular (NO^{+}, O_{2}^{+}, N_{2}^{+}) and metallic ions (Fe^{+}, Mg^{+}) by solving the continuity and momentum equations for each species. The main purpose of this analysis is to verify the disturbed electric fields role in the occurrence or disruption of Es layers through simulations. The analysis show that the Es layer formation and dynamics can be influenced by the prompt penetration electric fields that occur during magnetic disturbances. Therefore, the simulations present interesting results that helps to improve the understanding of Es layer behavior during the disturbed periods.

Absolute and convective instabilities of a film flow down a vertical fiber subjected to a radial electric field

NASA Astrophysics Data System (ADS)

Liu, Rong; Chen, Xue; Ding, Zijing

2018-01-01

We consider the motion of a gravity-driven flow down a vertical fiber subjected to a radial electric field. This flow exhibits rich dynamics including the formation of droplets, or beads, driven by a Rayleigh-Plateau mechanism modified by the presence of gravity as well as the Maxwell stress at the interface. A spatiotemporal stability analysis is performed to investigate the effect of electric field on the absolute-convective instability (AI-CI) characteristics. We performed a numerical simulation on the nonlinear evolution of the film to examine the transition from CI to AI regime. The numerical results are in excellent agreement with the spatiotemporal stability analysis. The blowup behavior of nonlinear simulation predicts the formation of touchdown singularity of the interface due to the effect of electric field. We try to connect the blowup behavior with the AI-CI characteristics. It is found that the singularities mainly occur in the AI regime. The results indicate that the film may have a tendency to form very sharp tips due to the enhancement of the absolute instability induced by the electric field. We perform a theoretical analysis to study the behaviors of the singularities. The results show that there exists a self-similarity between the temporal and spatial distances from the singularities.

Dispersive FDTD analysis of induced electric field in human models due to electrostatic discharge.

PubMed

Hirata, Akimasa; Nagai, Toshihiro; Koyama, Teruyoshi; Hattori, Junya; Chan, Kwok Hung; Kavet, Robert

2012-07-07

Contact currents flow from/into a charged human body when touching a grounded conductive object. An electrostatic discharge (ESD) or spark may occur just before contact or upon release. The current may stimulate muscles and peripheral nerves. In order to clarify the difference in the induced electric field between different sized human models, the in-situ electric fields were computed in anatomically based models of adults and a child for a contact current in a human body following ESD. A dispersive finite-difference time-domain method was used, in which biological tissue is assumed to obey a four-pole Debye model. From our computational results, the first peak of the discharge current was almost identical across adult and child models. The decay of the induced current in the child was also faster due mainly to its smaller body capacitance compared to the adult models. The induced electric fields in the forefingers were comparable across different models. However, the electric field induced in the arm of the child model was found to be greater than that in the adult models primarily because of its smaller cross-sectional area. The tendency for greater doses in the child has also been reported for power frequency sinusoidal contact current exposures as reported by other investigators.

Electron transport and electron energy distributions within the wurtzite and zinc-blende phases of indium nitride: Response to the application of a constant and uniform electric field

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

Siddiqua, Poppy; Hadi, Walid A.; Salhotra, Amith K.

2015-03-28

Within the framework of an ensemble semi-classical three-valley Monte Carlo electron transport simulation approach, we critically contrast the nature of the electron transport that occurs within the wurtzite and zinc-blende phases of indium nitride in response to the application of a constant and uniform electric field. We use the electron energy distribution and its relationship with the electron transport characteristics in order to pursue this analysis. For the case of zinc-blende indium nitride, only a peak corresponding to the electrons within the lowest energy conduction band valley is observed, this peak being seen to broaden and shift to higher energiesmore » in response to increases in the applied electric field strength, negligible amounts of upper energy conduction band valley occupancy being observed. In contrast, for the case of wurtzite indium nitride, in addition to the aforementioned lowest energy conduction band valley peak in the electron energy distribution, and its broadening and shifting to higher energies in response to increases in the applied electric field strength, beyond a certain critical electric field strength, 30 kV/cm for the case of this particular material, upper energy conduction band valley occupancy is observed, this occupancy being further enhanced in response to further increases in the applied electric field strength. Reasons for these results are provided. The potential for device consequences is then commented upon.« less

Dipolarizing flux bundles in the cis-geosynchronous magnetosphere: relationship between electric fields and energetic particle injections

NASA Astrophysics Data System (ADS)

Liu, J.; Angelopoulos, V.; Zhang, X. J.; Turner, D. L.; Gabrielse, C.; Runov, A.; Funsten, H. O.; Spence, H. E.

2015-12-01

Dipolarizing flux bundles (DFBs) are small flux tubes (typically < 3 RE in XGSM and YGSM) in the nightside magnetosphere that have magnetic field more dipolar than the background field. Although DFBs are known to accelerate particles to create energetic particle injections, their acceleration mechanism and importance in generating injections inside geosynchronous orbit remain open questions. To answer these questions, we investigate DFBs in the inner magnetosphere by conducting a statistical study with data from the Van Allen Probes. The results show that just like DFBs outside geosynchronous orbit, those inside that orbit occur most often in the pre-midnight sector. Half the DFBs are accompanied by energetic particle injection. Statistically, DFBs with injection have an electric field three times that of those without. All the injections accompanying DFBs appear dispersionless within the temporal and energy resolution considered. These findings suggest that the injections are ushered or locally produced by the DFB, and the DFB's strong electric field is an important aspect of the injection generation mechanism.

Parallel electric fields detected via conjugate electron echoes during the Echo 7 sounding rocket flight

NASA Technical Reports Server (NTRS)

Nemzek, R. J.; Winckler, J. R.

1991-01-01

Electron detectors on the Echo 7 active sounding rocket experiment measured 'conjugate echoes' resulting from artificial electron beam injections. Analysis of the drift motion of the electrons after a complete bounce leads to measurements of the magnetospheric convection electric field mapped to ionospheric altitudes. The magnetospheric field was highly variable, changing by tens of mV/m on time scales of as little as hundreds of millisec. While the smallest-scale magnetospheric field irregularities were mapped out by ionospheric conductivity, larger-scale features were enhanced by up to 50 mV/m in the ionosphere. The mismatch between magnetospheric and ionspheric convection fields indicates a violation of the equipotential field line condition. The parallel fields occurred in regions roughly 10 km across and probably supported a total potential drop of 10-100 V.

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.

a review and an update on the winter lightning that occurred on a rotating windmill and its standalone lightning protection tower

NASA Astrophysics Data System (ADS)

Wang, D.; Takagi, N.

2012-12-01

We have observed the lightning occurred on a 100 m high windmill and its 105 m high standalone lightning-protection tower about 45 m separated from the windmill in the Hokuriku area of Japan for 7 consecutive winter seasons from 2005 to 2012. Our main observation items include: (1) Lightning current at the bottom of both the windmill and the tower. (2) Thunderstorm electric fields and the electric field changes caused by lightning at multiple sites. (3) Optical images by both low and high speed imaging systems. During the 7 winter seasons, over 100 lightning have hit either the tower or the windmill or both. All the lightning but two observed are of upward lightning. Those upward lightning can be sub-classified into self-initiated types and other-triggered types according to whether there is a discharge activity prior to the upward leaders or not. Self-initiated and other-triggered upward lightning tend to have biased percentages in terms of striking locations (windmill versus tower) and thunderstorm types (active versus weak). All the upward lightning but one contained only initial continuous current stages. In the presentation, we will first give a review on those results we have reported before [1-3]. As an update, we will report the following results. (1) The electric field change required for triggering a negative upward leader is usually more than twice bigger than that for triggering a positive upward leader. (2) An electric current pulse with an amplitude of several tens of Amperes along a high structure has been observed to occur in response to a rapid electric change generated by either a nearby return stroke or K-change. References [1] D.Wang, N.Takagi, T.Watanebe, H. Sakurano, M. Hashimoto, Observed characteristics of upward leaders that are initiated from a windmill and its lightning protection tower, Geophys. Res. Lett., Vol.35, L02803, doi:10.1029/2007GL032136, 2008. [2] W. Lu, D.Wang, Y. Zhang and N. Takagi, Two associated upward lightning flashes that produced opposite polarity electric field changes, Geophys. Res. Lett., Vol.36, L05801, doi:10.1029/2008GL036598, 2009. [3] D. Wang, N. Takagi, Characteristics of Winter Lightning that Occurred on a Windmill and its Lightning Protection Tower in Japan, IEEJ Trans. on Power and Energy, Vol. 132, No.6, pp.568-572, Doi:10.1541/ieejpes.132.568, 2012.

Kinetic Alfven wave explanation of the Hall signals in magnetic reconnection

NASA Astrophysics Data System (ADS)

Dai, L.; Wang, C.; Zhang, Y.; Duan, S.; Lavraud, B.; Burch, J. L.; Pollock, C.; Torbert, R. B.

2017-12-01

Magnetic reconnection is initiated in a small diffusion region but can drive global-scale dynamics in Earth's magnetosphere, solar flares, and astrophysical systems. Understanding the processes at work in the diffusion region remains a main challenge in space plasma physics. Recent in-situ observations from MMS and THEMIS reveal that the electric field normal to the reconnection current layer, often called the Hall electric field (En), is mainly balanced by the ion pressure gradient. Here we present theoretical explanations indicating that this observation fact is a manifestation of Kinetic Alfven Waves (KAW) physics. The ion pressure gradient represents the finite gyroradius effect of KAW, leading to ion intrusion across the magnetic field lines. Electrons stream along the magnetic field lines to track ions, resulting in field-aligned currents and the associated pattern of the out-of-plane Hall magnetic field (Bm). The ratio En/Bm is on the order of the Alfven speed, as predicted by the KAW theory. The KAW physics further provides new perspectives on how ion intrusion may trigger electric fields suitable for reconnection to occur.

Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles

PubMed Central

Ranasinghesagara, Janaka C.; Hayakawa, Carole K.; Davis, Mitchell A.; Dunn, Andrew K.; Potma, Eric O.; Venugopalan, Vasan

2014-01-01

We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens–Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell’s equations. Our HF-WEFS implementation is 2–4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

Reversible conduction block in peripheral nerve using electrical waveforms.

PubMed

Bhadra, Niloy; Vrabec, Tina L; Bhadra, Narendra; Kilgore, Kevin L

2018-01-01

Electrical nerve block uses electrical waveforms to block action potential propagation. Two key features that distinguish electrical nerve block from other nonelectrical means of nerve block: block occurs instantly, typically within 1 s; and block is fully and rapidly reversible (within seconds). Approaches for achieving electrical nerve block are reviewed, including kilohertz frequency alternating current and charge-balanced polarizing current. We conclude with a discussion of the future directions of electrical nerve block. Electrical nerve block is an emerging technique that has many significant advantages over other methods of nerve block. This field is still in its infancy, but a significant expansion in the clinical application of this technique is expected in the coming years.

Controlled alignment of carbon nanofibers in a large-scale synthesis process

NASA Astrophysics Data System (ADS)

Merkulov, Vladimir I.; Melechko, A. V.; Guillorn, M. A.; Simpson, M. L.; Lowndes, D. H.; Whealton, J. H.; Raridon, R. J.

2002-06-01

Controlled alignment of catalytically grown carbon nanofibers (CNFs) at a variable angle to the substrate during a plasma-enhanced chemical vapor deposition process is achieved. The CNF alignment is controlled by the direction of the electric field lines during the synthesis process. Off normal CNF orientations are achieved by positioning the sample in the vicinity of geometrical features of the sample holder, where bending of the electric field lines occurs. The controlled growth of kinked CNFs that consist of two parts aligned at different angles to the substrate normal also is demonstrated.

Long term electromagnetic monitoring at Parkfield, CA

NASA Astrophysics Data System (ADS)

Kappler, Karl Neil

Electric and magnetic fields in the (10-4-1.0) Hz band were monitored at two sites adjacent to the San Andreas Fault near Parkfield and Hollister, California. Observed fields typically comprise natural magnetotelluric fields, with cultural and instrument noise. A data window [2002-2005], enclosing the September 28, 2004 M6 Parkfield earthquake, was analyzed to determine if anomalous electric or magnetic fields, or changes in ground conductivity, occurred before the earthquake. The data were edited, removing intervals of instrument malfunction, leaving 875 days left in the four-year period. Frequent, local spike-like disturbances were removed. The distribution of these spikes was not biased around the time of the earthquake. Signal to noise ratios, estimated via magnetotelluric processing techniques, provided an index of data quality. Plots of signal and noise amplitude spectra, showed the behavior of the ULF fields to be remarkably constant over the period of analysis. From these first-order plots, it is clear that most of the recorded energy is coherent over the spatial extent of the array. Three main statistical techniques were employed to separate local anomalous electrical or magnetic fields from the dominant coherent natural fields: transfer function estimates between components at each site were employed to subtract the dominant field, and look deeper at the 'residual' fields; the data were decomposed into principal components to identify linear combinations of array channels, which are maximally uncorrelated; the technique of canonical coherences was employed to distinguish anomalous fields which are spatially broad from anomalies which occur at a single site only, and furthermore to distinguish anomalies which are present in both the electric and magnetic fields form those which are present in only one field type. Standard remote reference apparent resistivity estimates were generated daily at Parkfield. Most of the variation was observed to be seasonal, and frequency independent, suggesting a local seasonal distortion effect. Once corrected for distortion, nearly all of the variability in the apparent resistivity was removed. In all cases, high levels of sensitivity to subtle electromagnetic effects were demonstrated, but no effects which can be described as precursors to the Parkfield earthquake were found.

Spontaneous Mass and Charge Losses from Single Multi-Megadalton Ions Studied by Charge Detection Mass Spectrometry

NASA Astrophysics Data System (ADS)

Keifer, David Z.; Alexander, Andrew W.; Jarrold, Martin F.

2017-03-01

Spontaneous mass and charge losses from individual multi-megadalton ions have been observed with charge detection mass spectrometry (CDMS) by trapping single hepatitis B virus (HBV) capsids for 3 s. Gradual increases in the oscillation frequency of single ions in the ion trap are attributed mainly to mass loss (probably solvent, water, and/or salt). The total mass lost during the 3 s trapping period peaks at around 20 kDa for 4 MDa HBV T = 4 capsids. Discrete frequency drops punctuate the gradual increases in the oscillation frequencies. The drops are attributed to a sudden loss of charge. In most cases a single positive charge is lost along with some mass (on average around 1000 Da). Charge loss occurs for over 40% of the trapped ions. It usually occurs near the beginning of the trapping event, and it occurs preferentially in regions of the trap with strong electric fields, indicating that external electric fields promote charge loss. This process may contribute to the decrease in m/ z resolution that often occurs with megadalton ions.

Statistical Properties of Ribbon Evolution and Reconnection Electric Fields in Eruptive and Confined Flares

NASA Astrophysics Data System (ADS)

Hinterreiter, J.; Veronig, A. M.; Thalmann, J. K.; Tschernitz, J.; Pötzi, W.

2018-03-01

A statistical study of the chromospheric ribbon evolution in Hα two-ribbon flares was performed. The data set consists of 50 confined (62%) and eruptive (38%) flares that occurred from June 2000 to June 2015. The flares were selected homogeneously over the Hα and Geostationary Operational Environmental Satellite (GOES) classes, with an emphasis on including powerful confined flares and weak eruptive flares. Hα filtergrams from the Kanzelhöhe Observatory in combination with Michelson Doppler Imager (MDI) and Helioseismic and Magnetic Imager (HMI) magnetograms were used to derive the ribbon separation, the ribbon-separation velocity, the magnetic-field strength, and the reconnection electric field. We find that eruptive flares reveal statistically larger ribbon separation and higher ribbon-separation velocities than confined flares. In addition, the ribbon separation of eruptive flares correlates with the GOES SXR flux, whereas no clear dependence was found for confined flares. The maximum ribbon-separation velocity is not correlated with the GOES flux, but eruptive flares reveal on average a higher ribbon-separation velocity (by ≈ 10 km s-1). The local reconnection electric field of confined (cc=0.50 ±0.02) and eruptive (cc=0.77 ±0.03) flares correlates with the GOES flux, indicating that more powerful flares involve stronger reconnection electric fields. In addition, eruptive flares with higher electric-field strengths tend to be accompanied by faster coronal mass ejections.

Electric Fields and Enzyme Catalysis

PubMed Central

Fried, Stephen D.; Boxer, Steven G.

2017-01-01

What happens inside an enzyme’s active site to allow slow and difficult chemical reactions to occur so rapidly? This question has occupied biochemists’ attention for a long time. Computer models of increasing sophistication have predicted an important role for electrostatic interactions in enzymatic reactions, yet this hypothesis has proved vexingly difficult to test experimentally. Recent experiments utilizing the vibrational Stark effect make it possible to measure the electric field a substrate molecule experiences when bound inside its enzyme’s active site. These experiments have provided compelling evidence supporting a major electrostatic contribution to enzymatic catalysis. Here, we review these results and develop a simple model for electrostatic catalysis that enables us to incorporate disparate concepts introduced by many investigators to describe how enzymes work into a more unified framework stressing the importance of electric fields at the active site. PMID:28375745

Novel non-equilibrium modelling of a DC electric arc in argon

NASA Astrophysics Data System (ADS)

Baeva, M.; Benilov, M. S.; Almeida, N. A.; Uhrlandt, D.

2016-06-01

A novel non-equilibrium model has been developed to describe the interplay of heat and mass transfer and electric and magnetic fields in a DC electric arc. A complete diffusion treatment of particle fluxes, a generalized form of Ohm’s law, and numerical matching of the arc plasma with the space-charge sheaths adjacent to the electrodes are applied to analyze in detail the plasma parameters and the phenomena occurring in the plasma column and the near-electrode regions of a DC arc generated in atmospheric pressure argon for current levels from 20 A up to 200 A. Results comprising electric field and potential, current density, heating of the electrodes, and effects of thermal and chemical non-equilibrium are presented and discussed. The current-voltage characteristic obtained is in fair agreement with known experimental data. It indicates a minimum for arc current of about 80 A. For all current levels, a field reversal in front of the anode accompanied by a voltage drop of (0.7-2.6) V is observed. Another field reversal is observed near the cathode for arc currents below 80 A.

Electric-Field-Directed Parallel Alignment Architecting 3D Lithium-Ion Pathways within Solid Composite Electrolyte.

PubMed

Liu, Xueqing; Peng, Sha; Gao, Shuyu; Cao, Yuancheng; You, Qingliang; Zhou, Liyong; Jin, Yongcheng; Liu, Zhihong; Liu, Jiyan

2018-05-09

It is of great significance to seek high-performance solid electrolytes via a facile chemistry and simple process for meeting the requirements of solid batteries. Previous reports revealed that ion conducting pathways within ceramic-polymer composite electrolytes mainly occur at ceramic particles and the ceramic-polymer interface. Herein, one facile strategy toward ceramic particles' alignment and assembly induced by an external alternating-current (AC) electric field is presented. It was manifested by an in situ optical microscope that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 particles and poly(ethylene glycol) diacrylate in poly(dimethylsiloxane) (LATP@PEGDA@PDMS) assembled into three-dimensional connected networks on applying an external AC electric field. Scanning electron microscopy revealed that the ceramic LATP particles aligned into a necklacelike assembly. Electrochemical impedance spectroscopy confirmed that the ionic conductivity of this necklacelike alignment was significantly enhanced compared to that of the random one. It was demonstrated that this facile strategy of applying an AC electric field can be a very effective approach for architecting three-dimensional lithium-ion conductive networks within solid composite electrolyte.

Determination of the electric field strength of filamentary DBDs by CARS-based four-wave mixing

NASA Astrophysics Data System (ADS)

Böhm, P.; Kettlitz, M.; Brandenburg, R.; Höft, H.; Czarnetzki, U.

2016-10-01

It is demonstrated that a four-wave mixing technique based on coherent anti-Stokes Raman spectroscopy (CARS) can determine the electric field strength of a pulsed-driven filamentary dielectric barrier discharge (DBD) of 1 mm gap, using hydrogen as a tracer medium in nitrogen at atmospheric pressure. The measurements are presented for a hydrogen admixture of 10%, but even 5% H2 admixture delivers sufficient infrared signals. The lasers do not affect the discharge by photoionization or by other radiation-induced processes. The absolute values of the electric field strength can be determined by the calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. This procedure also enables the determination of the applied breakdown voltage. The alteration of the electric field is observed during the internal polarity reversal and the breakdown process. One advantage of the CARS technique over emission-based methods is that it can be used independently of emission, e.g. in the pre-phase and in between two consecutive discharges, where no emission occurs at all.

Electrical Manipulation of Donor Spin Qubits in Silicon and Germanium

NASA Astrophysics Data System (ADS)

Sigillito, Anthony James

Many proposals for quantum information devices rely on electronic or nuclear spins in semiconductors because of their long coherence times and compatibility with industrial fabrication processes. One of the most notable qubits is the electron spin bound to phosphorus donors in silicon, which offers coherence times exceeding seconds at low temperatures. These donors are naturally isolated from their environments to the extent that silicon has been coined a "semiconductor vacuum". While this makes for ultra-coherent qubits, it is difficult to couple two remote donors so quantum information proposals rely on high density arrays of qubits. Here, single qubit addressability becomes an issue. Ideally one would address individual qubits using electric fields which can be easily confined. Typically these schemes rely on tuning a donor spin qubit onto and off of resonance with a magnetic driving field. In this thesis, we measure the electrical tunability of phosphorus donors in silicon and use the extracted parameters to estimate the effects of electric-field noise on qubit coherence times. Our measurements show that donor ionization may set in before electron spins can be sufficiently tuned. We therefore explore two alternative options for qubit addressability. First, we demonstrate that nuclear spin qubits can be directly driven using electric fields instead of magnetic fields and show that this approach offers several advantages over magnetically driven spin resonance. In particular, spin transitions can occur at half the spin resonance frequency and double quantum transitions (magnetic-dipole forbidden) can occur. In a second approach to realizing tunable qubits in semiconductors, we explore the option of replacing silicon with germanium. We first measure the coherence and relaxation times for shallow donor spin qubits in natural and isotopically enriched germanium. We find that in isotopically enriched material, coherence times can exceed 1 ms and are limited by a single-phonon T1 process. At lower frequencies or lower temperatures the qubit coherence times should substantially increase. Finally, we measure the electric field tunability of donors in germanium and find a four order-of-magnitude enhancement in the spin-orbit Stark shift and confirm that the donors should be tunable by at least 4 times the electron spin ensemble linewidth (in isotopically enriched material). Germanium should therefore also be more sensitive to electrically driven nuclear magnetic resonance. Based on these results germanium is a promising alternative to silicon for spin qubits.

Radiation from lightning return strokes over a finitely conducting earth

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Gesell, L.; Kao, Michael

1986-01-01

The effects of the conductivity of the earth on radiation from lightning return strokes are examined theoretically using a piecewise linear transmission line model for the return stroke. First, calculations are made of the electric field radiated during the return stroke, and then this electric field is used to compute the response of conventional AM radio receivers and electric field change systems during the return stroke. The calculations apply to the entire transient waveform (they are not restricted to the initial portions of the return stroke) and yield fast field changes and RF radiation in agreement with measurements made during real lightning. This research was motivated by measurements indicating that a time delay exists between the time of arrival of the fast electric field change and the RF radiation from first return strokes. The time delay is on the order of 20 microsec for frequencies in the HF-UHF range for lightning in Florida. The time delay is obtained theoretically in this paper. It occurs when both the effects of attenuation due to conductivity of the earth, and the finite velocity of propagation of the current pulse up the return stroke channel, are taken into account in the model.

Electro-responsive polyelectrolyte-coated surfaces.

PubMed

Sénéchal, V; Saadaoui, H; Rodriguez-Hernandez, J; Drummond, C

2017-07-01

The anchoring of polymer chains at solid surfaces is an efficient way to modify interfacial properties like the stability and rheology of colloidal dispersions, lubrication and biocompatibility. Polyelectrolytes are good candidates for the building of smart materials, as the polyion chain conformation can often be tuned by manipulation of different physico-chemical variables. However, achieving efficient and reversible control of this process represents an important technological challenge. In this regard, the application of an external electrical stimulus on polyelectrolytes seems to be a convenient control strategy, for several reasons. First, it is relatively easy to apply an electric field to the material with adequate spatiotemporal control. In addition, in contrast to chemically induced changes, the molecular response to a changing electric field occurs relatively quickly. If the system is properly designed, this response can then be used to control the magnitude of surface properties. In this work we discuss the effect of an external electric field on the adhesion and lubrication properties of several polyelectrolyte-coated surfaces. The influence of the applied field is investigated at different pH and salt conditions, as the polyelectrolyte conformation is sensitive to these variables. We show that it is possible to fine tune friction and adhesion using relatively low applied fields.

Drift of charge carriers in crystalline organic semiconductors

NASA Astrophysics Data System (ADS)

Dong, Jingjuan; Si, Wei; Wu, Chang-Qin

2016-04-01

We investigate the direct-current response of crystalline organic semiconductors in the presence of finite external electric fields by the quantum-classical Ehrenfest dynamics complemented with instantaneous decoherence corrections (IDC). The IDC is carried out in the real-space representation with the energy-dependent reweighing factors to account for both intermolecular decoherence and energy relaxation by which conduction occurs. In this way, both the diffusion and drift motion of charge carriers are described in a unified framework. Based on an off-diagonal electron-phonon coupling model for pentacene, we find that the drift velocity initially increases with the electric field and then decreases at higher fields due to the Wannier-Stark localization, and a negative electric-field dependence of mobility is observed. The Einstein relation, which is a manifestation of the fluctuation-dissipation theorem, is found to be restored in electric fields up to ˜105 V/cm for a wide temperature region studied. Furthermore, we show that the incorporated decoherence and energy relaxation could explain the large discrepancy between the mobilities calculated by the Ehrenfest dynamics and the full quantum methods, which proves the effectiveness of our approach to take back these missing processes.

Drift of charge carriers in crystalline organic semiconductors.

PubMed

Dong, Jingjuan; Si, Wei; Wu, Chang-Qin

2016-04-14

We investigate the direct-current response of crystalline organic semiconductors in the presence of finite external electric fields by the quantum-classical Ehrenfest dynamics complemented with instantaneous decoherence corrections (IDC). The IDC is carried out in the real-space representation with the energy-dependent reweighing factors to account for both intermolecular decoherence and energy relaxation by which conduction occurs. In this way, both the diffusion and drift motion of charge carriers are described in a unified framework. Based on an off-diagonal electron-phonon coupling model for pentacene, we find that the drift velocity initially increases with the electric field and then decreases at higher fields due to the Wannier-Stark localization, and a negative electric-field dependence of mobility is observed. The Einstein relation, which is a manifestation of the fluctuation-dissipation theorem, is found to be restored in electric fields up to ∼10(5) V/cm for a wide temperature region studied. Furthermore, we show that the incorporated decoherence and energy relaxation could explain the large discrepancy between the mobilities calculated by the Ehrenfest dynamics and the full quantum methods, which proves the effectiveness of our approach to take back these missing processes.

Controllable spin polarization and spin filtering in a zigzag silicene nanoribbon

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

Farokhnezhad, Mohsen, E-mail: Mohsen-farokhnezhad@physics.iust.ac.ir; Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir; Pournaghavi, Nezhat

2015-05-07

Using non-equilibrium Green's function, we study the spin-dependent electron transport properties in a zigzag silicene nanoribbon. To produce and control spin polarization, it is assumed that two ferromagnetic strips are deposited on the both edges of the silicene nanoribbon and an electric field is perpendicularly applied to the nanoribbon plane. The spin polarization is studied for both parallel and anti-parallel configurations of exchange magnetic fields induced by the ferromagnetic strips. We find that complete spin polarization can take place in the presence of perpendicular electric field for anti-parallel configuration and the nanoribbon can work as a perfect spin filter. Themore » spin direction of transmitted electrons can be easily changed from up to down and vice versa by reversing the electric field direction. For parallel configuration, perfect spin filtering can occur even in the absence of electric field. In this case, the spin direction can be changed by changing the electron energy. Finally, we investigate the effects of nonmagnetic Anderson disorder on spin dependent conductance and find that the perfect spin filtering properties of nanoribbon are destroyed by strong disorder, but the nanoribbon retains these properties in the presence of weak disorder.« less

Current polarity-dependent manipulation of antiferromagnetic domains

NASA Astrophysics Data System (ADS)

Wadley, Peter; Reimers, Sonka; Grzybowski, Michal J.; Andrews, Carl; Wang, Mu; Chauhan, Jasbinder S.; Gallagher, Bryan L.; Campion, Richard P.; Edmonds, Kevin W.; Dhesi, Sarnjeet S.; Maccherozzi, Francesco; Novak, Vit; Wunderlich, Joerg; Jungwirth, Tomas

2018-05-01

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields1. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents2. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry3. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching.

Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation

PubMed Central

Cola, Adriano; Farella, Isabella

2013-01-01

Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden. PMID:23881140

Evolution of lightning in an isolated hailstorm of moderate size in the tropics

NASA Astrophysics Data System (ADS)

Kamra, A. K.; Pawar, S. D.

2007-10-01

Evolution of lightning activity in a tropical hailstorm of moderate size that developed in the premonsoon season at Pune (18°32'N, 73°51'E, 559 m above sea level) is studied from the measurements of surface electric field, the Maxwell current and thunder. Total flash rate is counted from the electric field record, and the cloud-to-ground (CG) flash rate is estimated from the visual observations. Precise timings of their occurrence were confirmed from the observations of overshoot in the Maxwell current records. The storm exhibited an almost constant rate of one CG flash every 1 to 2 min over the whole life time of the storm. The ratio of intracloud (IC) to CG flashes (IC/CG) increased with the increase in total flash rate. In the convective stage of the storm, field changes from consecutive flashes were generally found to alternate in polarity. Moreover, in this stage, field changes occur in pairs, the first field change of each pair being of negative polarity and the second one of positive polarity. The two field changes in a pair occur with an average time difference of 14.3 ± 8.4 s while two consecutive pairs appear after 29.3 ± 9.1 s. In between the convective and mature stages, our observations suggest the occurrence of the phenomenon of rain gush and the field excursion associated with falling precipitation. Development of the mature stage was marked with rapid transitions in the surface electric field and the Maxwell current polarities from negative to positive. Further, total flash rate and IC/CG ratio sharply increase, and the lightning-induced electric field changes become almost exclusively of negative polarity. Observations suggest possibly a lifting up of the charging region in mature stage of the storm. The dissipating stage of the storm witnessed hail and rain showers, sharp transition of electric field and the Maxwell current from positive to negative polarity and occurrence of a few positive CG discharges. Our observations are consistent with the general belief that that some lightning flashes, by neutralizing and depositing charge in the region of opposite polarity, change the charge distribution so as to trigger another discharge in the storm.

Electrical Behavior of Copper Mine Tailings During EKR with Modified Electric Fields.

PubMed

Rojo, Adrian; Hansen, Henrik K; Monárdez, Omara; Jorquera, Carlos; Santis, Paulina; Inostroza, Paula

2017-03-01

Electro-kinetic remediation (EKR) with sinusoidal electric field obtained simultaneously with DC/AC voltage reduce the polarization of the EKR with DC voltage. The DC voltage value defines the presence of a periodic polarity reversal of the cell and the electrical charge for electro-kinetic transport. In this case, the AC frequency favors the breaking of polarization conditions resulting from the EKR with DC voltage. However, with high frequencies a negative effect occurs where the tailings behave as a filter circuit, discriminating frequencies of an electric signal. The goal of this work is to analyse the electrical behaviour of tailings in EKR experiments. The conditions selected were: DC/AC voltages: 10/15 and 20/25 V (peak values), and AC voltage frequencies 50-2000 Hz. When the AC frequency reaches 2000 Hz, the copper removal tends to zero, indicating that the tailing behaves as a high-pass filter in which the DC voltage was filtered out.

Electric breakdown during the pulsed current spreading in the sand

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

Vasilyak, L. M., E-mail: vasilyak@ihed.ras.ru; Vetchinin, S. P.; Panov, V. A.

2016-03-15

Processes of spreading of the pulsed current from spherical electrodes and an electric breakdown in the quartz sand are studied experimentally. When the current density on the electrode exceeds the critical value, a nonlinear reduction occurs in the grounding resistance as a result of sparking in the soil. The critical electric field strengths for ionization and breakdown are determined. The ionization-overheating instability is shown to develop on the electrode, which leads to the current contraction and formation of plasma channels.

Artificial stimulation of auroral electron acceleration by intense field aligned currents

NASA Technical Reports Server (NTRS)

Holmgren, G.; Bostrom, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Bering, E. A.; Sheldon, W. R.; Fahleson, U. V.

1979-01-01

A cesium-doped high explosion was detonated at 165 km altitude in the auroral ionosphere during quiet conditions. An Alfven wave pulse with a 200-mV/m electric field was observed, with the peak occurring 135 ms after the explosion at a distance of about 1 km. The count rate of fixed energy 2-keV electron detectors abruptly increased at 140 ms, peaked at 415 ms, and indicated a downward field-aligned beam of accelerated electrons. An anomalously high-field aligned beam of backscattered electrons was also detected. The acceleration is interpreted as due to production of an electrostatic shock or double layer between 300 and 800 km altitude. The structure was probably formed by an instability of the intense field-aligned currents in the Alfven wave launched by the charge-separation electric field due to the explosion.

Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.; Hill, Carrie S.; Turchi, Peter J.; Burton, Rodney L.; Messer, Sarah; Lovberg, Ralph H.; Hallock, Ashley K.

2013-01-01

Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are often employed to perform field measurements in electric propulsion applications where there are time-varying fields. Magnetic field probes provide the means to measure these magnetic fields and can even be used to measure the plasma current density indirectly through the application of Ampere's law. Measurements of this type can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. Results of the development of a standard for B-dot probe measurements are presented, condensing the available literature on the subject into an accessible set of rules, guidelines, and techniques to standardize the performance and presentation of future measurements.

Asymmetrical electrically induced injury of rabbit ventricular myocytes.

PubMed

Knisley, S B; Grant, A O

1995-05-01

Strong defibrillation-type electric field stimulation may injure myocytes when transmembrane potentials during the pulse exceed the threshold for membrane permeabilization. The location of injury may depend on intrinsic transmembrane potential or influx of calcium by "electro-osmosis" during the stimulation pulse in addition to the transmembrane potential changes induced by the pulse. We have studied injury by examining contracture and changes in transmembrane potential-sensitive dye fluorescence induced by electric field stimulation (St) with a duration of 20 ms and strength of 16-400 V/cm in isolated rabbit ventricular myocytes. St of 100-150 V/cm produced injury in myocytes oriented parallel to the St field frequently without injuring myocytes oriented perpendicular to the field. Injury required calcium in the solution and was asymmetric, occurring first at the myocyte and facing the St anode in 100% of injured myocytes in normal Tyrode's solution. Injury depended significantly on whether the product of the electric field strength and myocyte length exceeded a threshold of 1.1 V (P < 0.05). Asymmetric injury at the end facing the anode was still present in 96% of injured myocytes for stimulation after depolarization by an action potential or 20 mM or 125 mM potassium, suggesting that intrinsic transmembrane potential is not responsible for asymmetry. In 125 mM potassium, eliminating calcium from the bathing solution during the St pulse and introducing calcium after the pulse decreased the fraction of injured myocytes in which injury occurred at the end facing the anode to 62%, suggesting that calcium influx by "electro-osmosis" at the myocyte end facing the anode contributes to asymmetry. Asymmetric injury at the end facing the anode was still present in 100% of injured myocytes after adding 1 mM tetraethylammonium chloride, indicating that asymmetry is not sensitive to the potassium channel blockade. For stimulation pulses stronger than 50 V/cm given after depolarization by an action potential, transmembrane potentials at both myocyte ends decayed after the initial deflection indicating that permeabilization occurred at both ends. In conclusion, injury depends on myocyte orientation and is asymmetric occurring first at the myocyte end facing the anode. Asymmetric injury is not explained by asymmetric permeabilization, is independent of the intrinsic transmembrane potential and may result from "electro-osmosis" during the stimulation pulse.

Observations of Pc5 micropulsation-related electric field oscillations in equatorial ionosphere

NASA Technical Reports Server (NTRS)

Reddy, C. A.; Ravindran, Sudha; Viswanathan, K. S.; Murthy, B. V. Krishna; Rao, D. R. K.; Araki, T.

1994-01-01

A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5 deg N, 77 deg E, 0.5 deg N dip angle) recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (A(sub p) = 161). Simultaneous 100-n T-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6 deg N gm) and at Narsarsuaq, Greenland (70.6 deg N gm). Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT), the amplitude of the electric field oscillation in the equatorial electrojet (EEJ) is 0.1-0.25 mV/m and it increases with height, while it is about 1.0 mV/m in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brofelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the assoicated ionospheric electric field penetrating from high latitudes to the magnetic equator.

Optimal multichannel transmission for improved cr-MREPT

NASA Astrophysics Data System (ADS)

Ariturk, Gokhan; Ziya Ider, Yusuf

2018-02-01

Magnetic resonance electrical properties tomography (MR-EPT), aiming at reconstructing the EP’s at radio frequencies, uses the H + field (both magnitude and phase) distribution within the object. One of the MR-EPT algorithms, cr-MREPT, accurately reconstructs the internal tissue boundaries, however, it faces an artifact which occurs at the regions where the convective field, \

Effect of double layers on magnetosphere-ionosphere coupling

NASA Technical Reports Server (NTRS)

Lysak, Robert L.; Hudson, Mary K.

1987-01-01

The Earth's auroral zone contains dynamic processes occurring on scales from the length of an auroral zone field line which characterizes Alfven wave propagation to the scale of microscopic processes which occur over a few Debye lengths. These processes interact in a time-dependent fashion since the current carried by the Alfven waves can excite microscopic turbulence which can in turn provide dissipation of the Alfven wave energy. This review will first describe the dynamic aspects of auroral current structures with emphasis on consequences for models of microscopic turbulence. A number of models of microscopic turbulence will be introduced into a large-scale model of Alfven wave propagation to determine the effect of various models on the overall structure of auroral currents. In particular, the effects of a double layer electric field which scales with the plasma temperature and Debye length is compared with the effect of anomalous resistivity due to electrostatic ion cyclotron turbulence in which the electric field scales with the magnetic field strength. It is found that the double layer model is less diffusive than in the resistive model leading to the possibility of narrow, intense current structures.

Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

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

Wang, Haoran; Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn; Zhou, Zhipeng

2016-08-07

In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal canmore » be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E{sup −3}, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.« less

Generation of Currents in Weakly Ionized Plasmas through a Collisional Dynamo

NASA Astrophysics Data System (ADS)

Dimant, Yakov; Oppenheim, Meers; Fletcher, Alex

2016-10-01

Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earth's ionosphere near the magnetic equator where neutral winds drive the plasma across the geomagnetic field. Similar processes take place in the Solar chromosphere and MHD generators. We argue that not all convective neutral flows generate electrojets and it introduces the corresponding universal criterion for the current formation, ∇ × (U-> × B->) ≠ ∂ B-> / ∂ t , where U-> is the neutral flow velocity, B-> is the magnetic field, and t is time. This criterion does not depend on the conductivity tensor, σ̂ . For many systems, the displacement current, ∂ B-> / ∂ t , is negligible, making the criterion even simpler. This theory also shows that the neutral-dynamo driver that generates electrojets plays the same role as the DC electric current plays for the generation of the magnetic field in the Biot-Savart law. Work supported by NSF/DOE Grant PHY-1500439.

A Generalized Electron Heat Flow Relation and its Connection to the Thermal Force and the Solar Wind Parallel Electric Field

NASA Astrophysics Data System (ADS)

Scudder, J. D.

2017-12-01

Enroute to a new formulation of the heat law for the solar wind plasma the role of the invariably neglected, but omnipresent, thermal force for the multi-fluid physics of the corona and solar wind expansion will be discussed. This force (a) controls the size of the collisional ion electron energy exchange, favoring the thermal vs supra thermal electrons; (b) occurs whenever heat flux occurs; (c) remains after the electron and ion fluids come to a no slip, zero parallel current, equilibrium; (d) enhances the equilibrium parallel electric field; but (e) has a size that is theoretically independent of the electron collision frequency - allowing its importance to persist far up into the corona where collisions are invariably ignored in first approximation. The constituent parts of the thermal force allow the derivation of a new generalized electron heat flow relation that will be presented. It depends on the separate field aligned divergences of electron and ion pressures and the gradients of the ion gravitational potential and parallel flow energies and is based upon a multi-component electron distribution function. The new terms in this heat law explicitly incorporate the astrophysical context of gradients, acceleration and external forces that make demands on the parallel electric field and quasi-neutrality; essentially all of these effects are missing in traditional formulations.

Near-membrane electric field calcium ion dehydration.

PubMed

Barger, James P; Dillon, Patrick F

2016-12-01

The dehydration of ion-water complexes prior to ion channel transit has focused on channel protein-mediated dissociation of water. Ion dehydration by the membrane electric field has not previously been considered. Near membrane electric fields have previously been shown to cause the disassociation of non-covalently bound small molecule-small molecule, small molecule-protein, and protein-protein complexes. It is well known that cosmotropic, structure making ions such as calcium and sodium significantly bind multiple water ions in solution. It is also known that these ions are often not hydrated as they pass through membrane ion channels. Using capillary electrophoresis, the range of electric fields needed to strip water molecules from calcium ions has been measured. Ion migration velocity is a linear function of the electric field. At low electric fields, the migration rate of calcium ion was shown to be linearly related to the applied electric field. Using a form of the Stoke's equation applicable to ion migration, the hydrated calcium radius was found to be 0.334nm, corresponding to a water hydration shell of 5.09 water molecules. At higher electric fields, the slope of the calcium migration velocity as a function of the electric field increased, which was modeled as a decrease in the radius of the migrating ion as the water was removed. Using a tanh function to model the transition of the ion from a hydrated to a stripped state, the transition had a midpoint at 446V/cm, and was 88% complete at 587V/cm with a correlation coefficient of 0.9996. The migration velocity of the stripped calcium ion was found to be a function of both the decrease in radius and an increase in the effective, electronic viscosity of the dipole medium through which the dehydrated ion moved. The size of the electric field needed to dehydrate calcium occurs 6-7nm from the cell membrane. Calcium ions within this distance from the membrane will be devoid of water molecules when they reach the calcium selective channel pore entrances, all known to be approximately 1-2nm from the membrane. No matter what the calcium pore structure, calcium ions reaching the channel entrance will be devoid of a water shell. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamic behaviour of the silica-water-bio electrical double layer in the presence of a divalent electrolyte.

PubMed

Lowe, B M; Maekawa, Y; Shibuta, Y; Sakata, T; Skylaris, C-K; Green, N G

2017-01-25

Electronic devices are becoming increasingly used in chemical- and bio-sensing applications and therefore understanding the silica-electrolyte interface at the atomic scale is becoming increasingly important. For example, field-effect biosensors (BioFETs) operate by measuring perturbations in the electric field produced by the electrical double layer due to biomolecules binding on the surface. In this paper, explicit-solvent atomistic calculations of this electric field are presented and the structure and dynamics of the interface are investigated in different ionic strengths using molecular dynamics simulations. Novel results from simulation of the addition of DNA molecules and divalent ions are also presented, the latter of particular importance in both physiological solutions and biosensing experiments. The simulations demonstrated evidence of charge inversion, which is known to occur experimentally for divalent electrolyte systems. A strong interaction between ions and DNA phosphate groups was demonstrated in mixed electrolyte solutions, which are relevant to experimental observations of device sensitivity in the literature. The bound DNA resulted in local changes to the electric field at the surface; however, the spatial- and temporal-mean electric field showed no significant change. This result is explained by strong screening resulting from a combination of strongly polarised water and a compact layer of counterions around the DNA and silica surface. This work suggests that the saturation of the Stern layer is an important factor in determining BioFET response to increased salt concentration and provides novel insight into the interplay between ions and the EDL.

Possible Mechanism for Damping of Electrostatic Instability Related to Inhomogeneous Distribution of Energy Density in the Auroral Ionosphere

NASA Astrophysics Data System (ADS)

Golovchanskaya, I. V.; Kozelov, B. V.; Chernyshov, A. A.; Ilyasov, A. A.; Mogilevsky, M. M.

2018-03-01

Satellite observations show that the electrostatic instability, which is expected to occur in most cases due to an inhomogeneous energy density caused by a strongly inhomogeneous transverse electric field (shear of plasma convection velocity), occasionally does not develop inside nonlinear plasma structures in the auroral ionosphere, even though the velocity shear is sufficient for its excitation. In this paper, it is shown that the instability damping can be caused by out-of-phase variations of the electric field and field-aligned current acting in these structures. Therefore, the mismatch of sources of free energy required for the wave generation nearly nullifies their common effect.

Review of ESA Experimental Research Activities for Electric Propulsion

DTIC Science & Technology

2011-01-01

detect gravitational waves, distortions of space-time occurring when a massive body is accelerated or disturbed. To achieve that goal the relative...thrusters of Electric Propulsion systems accelerate the propellant ions to velocities of tens of kilometers per second making it a propulsion option that is...expanded through nozzle Ion electrostatically accelerated . Plasma accelerated via interaction of current and magnetic field. Concept Resistojets

Human Exposure to Electromagnetic Fields from Parallel Wireless Power Transfer Systems.

PubMed

Wen, Feng; Huang, Xueliang

2017-02-08

The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated. Computational results are compared with the restrictions prescribed in the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs). The results show that the middle region between the two WPT coils is safer for the two WPT systems working in-phase, and the peripheral regions are safer around the WPT systems working anti-phase. Thin metallic plates larger than the WPT coils can shield the magnetic field leakage well, while smaller ones may worsen the situation. The orientation of the human body will influence the maximum magnitude of induced electric field and its distribution within the human body. The induced electric field centralizes in the trunk, groin, and genitals with only one exception: when the human body is standing right at the middle of the two WPT coils working in-phase, the induced electric field focuses on lower limbs. The SAR value in the lungs always seems to be greater than in other organs, while the value in the liver is minimal. Human exposure to EMFs meets the guidelines of the International Committee on Non-Ionizing Radiation Protection (ICNIRP), specifically reference levels with respect to magnetic field and basic restrictions on induced electric fields and SAR, as the charging power is lower than 3.1 kW and 55.5 kW, respectively. These results are positive with respect to the safe applications of parallel WPT systems working simultaneously.

Human Exposure to Electromagnetic Fields from Parallel Wireless Power Transfer Systems

PubMed Central

Wen, Feng; Huang, Xueliang

2017-01-01

The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated. Computational results are compared with the restrictions prescribed in the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs). The results show that the middle region between the two WPT coils is safer for the two WPT systems working in-phase, and the peripheral regions are safer around the WPT systems working anti-phase. Thin metallic plates larger than the WPT coils can shield the magnetic field leakage well, while smaller ones may worsen the situation. The orientation of the human body will influence the maximum magnitude of induced electric field and its distribution within the human body. The induced electric field centralizes in the trunk, groin, and genitals with only one exception: when the human body is standing right at the middle of the two WPT coils working in-phase, the induced electric field focuses on lower limbs. The SAR value in the lungs always seems to be greater than in other organs, while the value in the liver is minimal. Human exposure to EMFs meets the guidelines of the International Committee on Non-Ionizing Radiation Protection (ICNIRP), specifically reference levels with respect to magnetic field and basic restrictions on induced electric fields and SAR, as the charging power is lower than 3.1 kW and 55.5 kW, respectively. These results are positive with respect to the safe applications of parallel WPT systems working simultaneously. PMID:28208709

Influence of electrical fields and asymmetric application of mucilage on curvature of primary roots of Zea mays

NASA Technical Reports Server (NTRS)

Marcum, H.; Moore, R.

1990-01-01

Primary roots of Zea mays cv. Yellow Dent growing in an electric field curve towards the anode. Roots treated with EDTA and growing in electric field do not curve. When root cap mucilage is applied asymmetrically to tips of vertically-oriented roots, the roots curve toward the mucilage. Roots treated with EDTA curve toward the side receiving mucilage and toward blocks containing 10 mM CaCl2, but not toward "empty" agar blocks or the cut surfaces of severed root tips. These results suggest that 1) free calcium (Ca) is necessary for root electrotropism, 2) mucilage contains effector(s) that induce gravitropiclike curvature, and 3) mucilage can replace gravitropic effectors chelated by EDTA. These results are consistent with the hypothesis that the downward movement of gravitropic effectors to the lower sides of tips of horizontally-oriented roots occurs at least partially in the apoplast.

Toroidal Ampere-Faraday Equations Solved Consistently with the CQL3D Fokker-Planck Time-Evolution

NASA Astrophysics Data System (ADS)

Harvey, R. W.; Petrov, Yu. V.

2013-10-01

A self-consistent, time-dependent toroidal electric field calculation is a key feature of a complete 3D Fokker-Planck kinetic distribution radial transport code for f(v,theta,rho,t). In the present CQL3D finite-difference model, the electric field E(rho,t) is either prescribed, or iteratively adjusted to obtain prescribed toroidal or parallel currents. We discuss first results of an implementation of the Ampere-Faraday equation for the self-consistent toroidal electric field, as applied to the runaway electron production in tokamaks due to rapid reduction of the plasma temperature as occurs in a plasma disruption. Our previous results assuming a constant current density (Lenz' Law) model showed that prompt ``hot-tail runaways'' dominated ``knock-on'' and Dreicer ``drizzle'' runaways; we will examine modifications due to the more complete Ampere-Faraday solution. Work supported by US DOE under DE-FG02-ER54744.

Controllable rotating behavior of individual dielectric microrod in a rotating electric field.

PubMed

Liu, Weiyu; Ren, Yukun; Tao, Ye; Li, Yanbo; Chen, Xiaoming

2017-06-01

We report herein controllable rotating behavior of an individual dielectric microrod driven by a background rotating electric field. By disposing or removing structured floating microelectrode, the rigid rod suspended in electrolyte solution accordingly exhibits cofield or antifield rotating motion. In the absence of the ideally polarizable metal surface, the dielectric rod rotates opposite to propagation of electric field, with the measured rotating rate much larger than predicted by Maxwell-Wager interfacial polarization theory incorporating surface conduction of fixed bond charge. Surprisingly, with floating electrode embedded, a novel kind of cofield rotation mode occurs in the presence of induced double-layer polarization, due to the action of hydrodynamic torque from rotating induced-charge electroosmosis. This method of achieving switchable spin modes of dielectric particles would direct implications in constructing flexible electrokinetic framework for analyzing 3D profile of on-chip biomicrofluidic samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Current flow instability and nonlinear structures in dissipative two-fluid plasmas

NASA Astrophysics Data System (ADS)

Koshkarov, O.; Smolyakov, A. I.; Romadanov, I. V.; Chapurin, O.; Umansky, M. V.; Raitses, Y.; Kaganovich, I. D.

2018-01-01

The current flow in two-fluid plasma is inherently unstable if plasma components (e.g., electrons and ions) are in different collisionality regimes. A typical example is a partially magnetized E ×B plasma discharge supported by the energy released from the dissipation of the current in the direction of the applied electric field (perpendicular to the magnetic field). Ions are not magnetized so they respond to the fluctuations of the electric field ballistically on the inertial time scale. In contrast, the electron current in the direction of the applied electric field is dissipatively supported either by classical collisions or anomalous processes. The instability occurs due to a positive feedback between the electron and ion current coupled by the quasi-neutrality condition. The theory of this instability is further developed taking into account the electron inertia, finite Larmor radius and nonlinear effects. It is shown that this instability results in highly nonlinear quasi-coherent structures resembling breathing mode oscillations in Hall thrusters.

An S3-3 search for confined regions of large parallel electric fields

NASA Astrophysics Data System (ADS)

Boehm, M. H.; Mozer, F. S.

1981-06-01

S3-3 satellite passes through several hundred perpendicular shocks are searched for evidence of large, mostly parallel electric fields (several hundred millivolts per meter, total potential of several kilo-volts) in the auroral zone magnetosphere at altitudes of several thousand kilometers. The actual search criteria are that one or more E-field data points have a parallel component E sub z greater than 350 mV/m in general, or 100 mV/m for data within 10 seconds of a perpendicular shock, since double layers might be likely, in such regions. Only a few marginally convincing examples of the electric fields are found, none of which fits a double layer model well. From statistics done with the most unbiased part of the data set, upper limits are obtained on the number and size of double layers occurring in the auroral zone magnetosphere, and it is concluded that the double layers most probably cannot be responsible for the production of diffuse aurora or inverted-V events.

Lightning criteria relative to space shuttles: Currents and electric field intensity in Florida lightning

NASA Technical Reports Server (NTRS)

Uman, M. A.; Mclain, D. K.

1972-01-01

The measured electric field intensities of 161 lightning strokes in 39 flashes which occurred between 1 and 35 km from an observation point at Kennedy Space Center, Florida during June and July of 1971 have been analyzed to determine the lightning channel currents which produced the fields. In addition, typical channel currents are derived and from these typical electric fields at distances between 0.5 and 100 km are computed and presented. On the basis of the results recommendations are made for changes in the specification of lightning properties relative to space vehicle design as given in NASA TMX-64589 (Daniels, 1971). The small sample of lightning analyzed yielded several peak currents in the 100 kA range. Several current rise-times from zero to peak of 0.5 microsec or faster were found; and the fastest observed current rate-of-rise was near 200 kA/microsec. The various sources of error are discussed.

Electrochemistry and the Earth's Core-Mantle Boundary

NASA Astrophysics Data System (ADS)

Kavner, A.; Walker, D.

2001-12-01

The Earth's core-mantle boundary consists of a highly heterogeneous metal-oxide interface subjected to high temperatures, pressures, and additionally, to the presence of a temporally- and spatially-varying electrical field generated by the outer core dynamo. An understanding of the core-mantle boundary should include the nature of its electrical behavior, its electrically induced chemical partitioning, and any resultant core-mantle dynamic coupling. To this end, we have developed a method to measure the electrical behavior of metal-silicate interfaces at high pressures (15-25 kbar) and temperatures (1300-1400° C) in a piston-cylinder apparatus. Platinum electrical leads are placed at each end of the sample, which consists of a layer of iron and/or iron alloy below a layer of silicate. The sample is enclosed in a sintered MgO chamber which is then surrounded by a metal Faraday cage, allowing the sample to be electrically insulated from the AC field of the graphite heater. The platinum electric leads are threaded through the thermocouple tube and connected with an HP4284A LCR meter to measure AC impedance, or to a DC power supply to apply a field such that either the silicate or the metal end is the anode (+). AC impedance measurements performed in-situ on samples consisting of Fe, Fe-Ni-S, and a basalt-olivine mixture in series show that conductivity is strongly dependent on the electrical polarization of the silicate relative to the sulfide. When the silicate is positively charged (silicate is the anode) and when there is no applied charge, the probe-to-probe resistance displays semiconductor behavior, with conductivity ( ~10-2 S/cm) strongly thermally activated. However, when the electrical polarity is reversed, and the sulfide is the anode, the electrical conductivity between the two probes increases dramatically (to ~1 S/cm) over timescales of minutes. If the polarity is removed or reversed, the conductivity returns to its original values over similar timescales. A second set of experiments examined the behavior of iron-silicate interfaces subjected to electric fields of 1-10 V, applied for times ranging from several minutes to several days. The samples were quenched from high temperatures, mounted, and examined using both light and electron microscopy. When the iron/iron-sulfide end is charged positively (+1-2 V) with respect to the silicate, oxides form around the platinum electrode embedded within the iron metal, suggesting the reaction Fe->Fe+2+2e- occurs in the metal. When the electric field is reversed, the silicate and MgO surrounding the + electrode turns red, implying the reaction Fe+2\\rightarrowFe^{+3}+e^{-}$ occurs at the silicate (anode end) of the sample. The richness of electrical and electrically activated chemical behavior observed at metal-silicate interfaces may be relevant to the Earth's core mantle boundary.

Equatorial Plasma Bubble Development and Dynamics, and Sporadic E Layer Structuring, under Storm Time Electric Fields.

NASA Astrophysics Data System (ADS)

Abdu, M. A.; Batista, I. S.; Sobral, J. H. A.; Souza, J.; Santos, A.

2016-12-01

Equatorial and low - midlatitude ionospheric plasma dynamics and related phenomenology can be severely affected by disturbance electric fields associated with magnetic storms. Penetration electric fields, of under-shielding or over-shielding types, can cause anomalous development of plasma bubbles even during their non-occurrence season, or can lead to suppression of their normal development. Depending upon the longitude sector and local time, large relative changes in the Hall and Pedersen conductivities can occur due to storm induced extra E layer ionization or modifications in F layer plasma density, as a result of which the penetration electric fields may produce, among other effects, (1) plasma bubble zonal drift velocity reversal to westward, (2) large/abnormal F layer plasma uplift, (3) sporadic E layer disruption or its formation with instabilities. Beside these effects, the equatorial ionization anomaly is known to suffer latitudinal expansion and retraction. In this paper we will discuss some outstanding response features of the low altitude ionosphere under disturbance electric field as diagnosed by Digisondes, radars and optical imagers in the South American longitude sector, a region that is strongly influenced by the South Atlantic Magnetic anomaly (SAMA). The results will be discussed in the context of satellite observations (from C/NOFS) and modeling results based on SUPIM simulation of a realistic low latitude ionosphere.

Probing the electrostatics of active site microenvironments along the catalytic cycle for Escherichia coli dihydrofolate reductase.

PubMed

Liu, C Tony; Layfield, Joshua P; Stewart, Robert J; French, Jarrod B; Hanoian, Philip; Asbury, John B; Hammes-Schiffer, Sharon; Benkovic, Stephen J

2014-07-23

Electrostatic interactions play an important role in enzyme catalysis by guiding ligand binding and facilitating chemical reactions. These electrostatic interactions are modulated by conformational changes occurring over the catalytic cycle. Herein, the changes in active site electrostatic microenvironments are examined for all enzyme complexes along the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) by incorporation of thiocyanate probes at two site-specific locations in the active site. The electrostatics and degree of hydration of the microenvironments surrounding the probes are investigated with spectroscopic techniques and mixed quantum mechanical/molecular mechanical (QM/MM) calculations. Changes in the electrostatic microenvironments along the catalytic environment lead to different nitrile (CN) vibrational stretching frequencies and (13)C NMR chemical shifts. These environmental changes arise from protein conformational rearrangements during catalysis. The QM/MM calculations reproduce the experimentally measured vibrational frequency shifts of the thiocyanate probes across the catalyzed hydride transfer step, which spans the closed and occluded conformations of the enzyme. Analysis of the molecular dynamics trajectories provides insight into the conformational changes occurring between these two states and the resulting changes in classical electrostatics and specific hydrogen-bonding interactions. The electric fields along the CN axes of the probes are decomposed into contributions from specific residues, ligands, and solvent molecules that make up the microenvironments around the probes. Moreover, calculation of the electric field along the hydride donor-acceptor axis, along with decomposition of this field into specific contributions, indicates that the cofactor and substrate, as well as the enzyme, impose a substantial electric field that facilitates hydride transfer. Overall, experimental and theoretical data provide evidence for significant electrostatic changes in the active site microenvironments due to conformational motion occurring over the catalytic cycle of ecDHFR.

Probing the Electrostatics of Active Site Microenvironments along the Catalytic Cycle for Escherichia coli Dihydrofolate Reductase

PubMed Central

2015-01-01

Electrostatic interactions play an important role in enzyme catalysis by guiding ligand binding and facilitating chemical reactions. These electrostatic interactions are modulated by conformational changes occurring over the catalytic cycle. Herein, the changes in active site electrostatic microenvironments are examined for all enzyme complexes along the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) by incorporation of thiocyanate probes at two site-specific locations in the active site. The electrostatics and degree of hydration of the microenvironments surrounding the probes are investigated with spectroscopic techniques and mixed quantum mechanical/molecular mechanical (QM/MM) calculations. Changes in the electrostatic microenvironments along the catalytic environment lead to different nitrile (CN) vibrational stretching frequencies and 13C NMR chemical shifts. These environmental changes arise from protein conformational rearrangements during catalysis. The QM/MM calculations reproduce the experimentally measured vibrational frequency shifts of the thiocyanate probes across the catalyzed hydride transfer step, which spans the closed and occluded conformations of the enzyme. Analysis of the molecular dynamics trajectories provides insight into the conformational changes occurring between these two states and the resulting changes in classical electrostatics and specific hydrogen-bonding interactions. The electric fields along the CN axes of the probes are decomposed into contributions from specific residues, ligands, and solvent molecules that make up the microenvironments around the probes. Moreover, calculation of the electric field along the hydride donor–acceptor axis, along with decomposition of this field into specific contributions, indicates that the cofactor and substrate, as well as the enzyme, impose a substantial electric field that facilitates hydride transfer. Overall, experimental and theoretical data provide evidence for significant electrostatic changes in the active site microenvironments due to conformational motion occurring over the catalytic cycle of ecDHFR. PMID:24977791

Prediction of the Seizure Suppression Effect by Electrical Stimulation via a Computational Modeling Approach.

PubMed

Ahn, Sora; Jo, Sumin; Jun, Sang Beom; Lee, Hyang Woon; Lee, Seungjun

2017-01-01

In this paper, we identified factors that can affect seizure suppression via electrical stimulation by an integrative study based on experimental and computational approach. Preferentially, we analyzed the characteristics of seizure-like events (SLEs) using our previous in vitro experimental data. The results were analyzed in two groups classified according to the size of the effective region, in which the SLE was able to be completely suppressed by local stimulation. However, no significant differences were found between these two groups in terms of signal features or propagation characteristics (i.e., propagation delays, frequency spectrum, and phase synchrony). Thus, we further investigated important factors using a computational model that was capable of evaluating specific influences on effective region size. In the proposed model, signal transmission between neurons was based on two different mechanisms: synaptic transmission and the electrical field effect. We were able to induce SLEs having similar characteristics with differentially weighted adjustments for the two transmission methods in various noise environments. Although the SLEs had similar characteristics, their suppression effects differed. First of all, the suppression effect occurred only locally where directly received the stimulation effect in the high noise environment, but it occurred in the entire network in the low noise environment. Interestingly, in the same noise environment, the suppression effect was different depending on SLE propagation mechanism; only a local suppression effect was observed when the influence of the electrical field transmission was very weak, whereas a global effect was observed with a stronger electrical field effect. These results indicate that neuronal activities synchronized by a strong electrical field effect respond more sensitively to partial changes in the entire network. In addition, the proposed model was able to predict that stimulation of a seizure focus region is more effective for suppression. In conclusion, we confirmed the possibility of a computational model as a simulation tool to analyze the efficacy of deep brain stimulation (DBS) and investigated the key factors that determine the size of an effective region in seizure suppression via electrical stimulation.

Interface Magnetoelectric Coupling in Co/Pb(Zr,Ti)O3.

PubMed

Vlašín, Ondřej; Jarrier, Romain; Arras, Rémi; Calmels, Lionel; Warot-Fonrose, Bénédicte; Marcelot, Cécile; Jamet, Matthieu; Ohresser, Philippe; Scheurer, Fabrice; Hertel, Riccardo; Herranz, Gervasi; Cherifi-Hertel, Salia

2016-03-23

Magnetoelectric coupling at multiferroic interfaces is a promising route toward the nonvolatile electric-field control of magnetization. Here, we use optical measurements to study the static and dynamic variations of the interface magnetization induced by an electric field in Co/PbZr0.2Ti0.8O3 (Co/PZT) bilayers at room temperature. The measurements allow us to identify different coupling mechanisms. We further investigate the local electronic and magnetic structure of the interface by means of transmission electron microscopy, soft X-ray magnetic circular dichroism, and density functional theory to corroborate the coupling mechanism. The measurements demonstrate a mixed linear and quadratic optical response to the electric field, which results from a magneto-electro-optical effect. We propose a decomposition method of the optical signal to discriminate between different components involved in the electric field-induced polarization rotation of the reflected light. This allows us to extract a signal that we can ascribe to interface magnetoelectric coupling. The associated surface magnetization exhibits a clear hysteretic variation of odd symmetry with respect to the electric field and nonzero remanence. The interface coupling is remarkably stable over a wide frequency range (1-50 kHz), and the application of a bias magnetic field is not necessary for the coupling to occur. These results show the potential of exploiting interface coupling with the prospect of optimizing the performance of magnetoelectric memory devices in terms of stability, as well as fast and dissipationless operation.

Energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in electric and magnetic fields

NASA Astrophysics Data System (ADS)

Cruz, Philip Christopher S.; Bernardo, Reginald Christian S.; Esguerra, Jose Perico H.

2017-04-01

We calculate the energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in uniform electric and magnetic fields. Using separation of variables method and a change of independent variable, we show that the problem can be reduced to a one-dimensional Schrödinger equation for a periodic potential. The effects of varying the shape of the cross-section while keeping the same perimeter and the strengths of the electric and magnetic fields are investigated for elliptical, corrugated, and nearly-rectangular tubes with radial dimensions of the order of a nanometer. The geometric potential has minima at the angular positions where there is a significant amount of curvature. For the elliptical and corrugated tubes, it is shown that as the tube departs from the circular shape of cross-section the double-degeneracy between the energy levels is lifted. For the nearly-rectangular tube, it is shown that energy level crossings occur as the horizontal dimension of the tube is varied while keeping the same perimeter and radius of circular corners. The interplay between the curvature and the strength of the electric and magnetic fields determines the overall behavior of the energy levels. As the strength of the electric field increases, the overall potential gets skewed creating a potential well on the side corresponding to the more negative electric potential. The energy levels of the first few excited states approach more positive values while the ground state energy level approaches a more negative value. For large electric fields, all bound state energy levels tend to more negative values. The contribution of weak magnetic fields to the overall potential behaves in the same way as the electric field contribution but with its sign depending on the direction of the component of the momentum parallel to the cylindrical axis. Large magnetic fields lead to pairing of energy levels reminiscent of 2D Landau levels for the elliptical and nearly-rectangular tubes.

Energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in electric and magnetic fields

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

Cruz, Philip Christopher S., E-mail: pscruz1@up.edu.ph; Bernardo, Reginald Christian S., E-mail: rcbernardo@nip.upd.edu.ph; Esguerra, Jose Perico H., E-mail: jesguerra@nip.upd.edu.ph

We calculate the energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in uniform electric and magnetic fields. Using separation of variables method and a change of independent variable, we show that the problem can be reduced to a one-dimensional Schrödinger equation for a periodic potential. The effects of varying the shape of the cross-section while keeping the same perimeter and the strengths of the electric and magnetic fields are investigated for elliptical, corrugated, and nearly-rectangular tubes with radial dimensions of the order of a nanometer. The geometric potential has minima at the angular positions wheremore » there is a significant amount of curvature. For the elliptical and corrugated tubes, it is shown that as the tube departs from the circular shape of cross-section the double-degeneracy between the energy levels is lifted. For the nearly-rectangular tube, it is shown that energy level crossings occur as the horizontal dimension of the tube is varied while keeping the same perimeter and radius of circular corners. The interplay between the curvature and the strength of the electric and magnetic fields determines the overall behavior of the energy levels. As the strength of the electric field increases, the overall potential gets skewed creating a potential well on the side corresponding to the more negative electric potential. The energy levels of the first few excited states approach more positive values while the ground state energy level approaches a more negative value. For large electric fields, all bound state energy levels tend to more negative values. The contribution of weak magnetic fields to the overall potential behaves in the same way as the electric field contribution but with its sign depending on the direction of the component of the momentum parallel to the cylindrical axis. Large magnetic fields lead to pairing of energy levels reminiscent of 2D Landau levels for the elliptical and nearly-rectangular tubes.« less

Photovoltaic dependence of photorefractive grating on the externally applied dc electric field

NASA Astrophysics Data System (ADS)

Maurya, M. K.; Yadav, R. A.

2013-04-01

Photovoltaic dependence of photorefractive grating (i.e., space-charge field and phase-shift of the index grating) on the externally applied dc electric field in photovoltaic-photorefractive materials has been investigated. The influence of photovoltaic field (EPhN), diffusion field and carrier concentration ratio r (donor/acceptor impurity concentration ratio) on the space-charge field (SCF) and phase-shift of the index grating in the presence and absence of the externally applied dc electric field have also been studied in details. Our results show that, for a given value of EPhN and r, the magnitude of the SCF and phase-shift of the index grating can be enhanced significantly by employing the lower dc electric field (EON<10) across the photovoltaic-photorefractive crystal and higher value of diffusion field (EDN>40). Such an enhancement in the magnitude of the SCF and phase-shift of the index grating are responsible for the strongest beam coupling in photovoltaic-photorefractive materials. This sufficiently strong beam coupling increases the two-beam coupling gain that may be exceed the absorption and reflection losses of the photovoltaic-photorefractive sample, and optical amplification can occur. The higher value of optical amplification in photovoltaic-photorefractive sample is required for the every applications of photorefractive effect so that technology based on the photorefractive effect such as holographic storage devices, optical information processing, acousto-optic tunable filters, gyro-sensors, optical modulators, optical switches, photorefractive-photovoltaic solitons, biomedical applications, and frequency converters could be improved.

Schottky's conjecture on multiplication of field enhancement factors

NASA Astrophysics Data System (ADS)

Miller, Ryan; Lau, Y. Y.; Booske, John H.

2009-11-01

Of great interest to high power microwave, millimeter wave to terahertz sources, x-ray tubes, electrons guns, etc., is the electric field enhancement obtained from sharp emitting structures fabricated by various microfabrication methods. In this paper, we use conformal mapping to investigate the field enhancement of several rectilinear geometries, including a single rectangular ridge, a trapezoidal ridge, and their superposition, i.e., one ridge on top of another. We show that the composite field enhancement factor of the double ridge with a microprotrusion on top of a macroprotrusion is dominated by the product of the individual protrusions' field enhancement factors over a very wide range of geometric aspect ratios, as conjectured by Schottky. Simplified scaling laws are proposed. Significant deviation from Schottky's product rule occurs almost exclusively when the half-width of the macroprotrusion is less than the height of the microprotrusion. Accurate expressions of the divergent electric field near the sharp edges are derived.

Postfact phenomena of the wet-steam flow electrization in turbines

NASA Astrophysics Data System (ADS)

Tarelin, A. A.

2017-11-01

Physical processes occurring in a turbine with natural electrization of a humidity-steam flow and their effect on efficiency and reliability of the turbine operation has been considered. Causes of the electrical potential occurrence on a rotor shaft are analyzed. The wet steam's electrization exposure on the electrical potential that is one of the major factors of bearings' electroerosion has been demonstrated on the full-scale installation. Hydrogen formation in wheelspace of the turbine as a result of electrochemical processes and electric field exposure of the space charge has been considered. Hydrogen concentration dependence on a volume charge density in the steam flow has been determined. It is stated that the processes occurring behind the final stage of wet-steam turbines are similar to the ones in elaerosol ectrostatic generators. It has been demonstrated that this phenomenon causes the flow's temporal inhibition and starts pulsations. These factors' impact on power loss of the turbine has been evaluated and recommendations for their elimination have been offered. It has been determined that motions of charged drops can cause self-maintained discharges inside of the flow and between the flow and grounded surfaces that are accompanied by electromagnetic radiation of the wide spectrum. The integrated studies have shown that physical phenomena occurring due to natural electrization negatively affect efficiency and reliability of the turbine operation. Practical recommendations allowing one to minimize the negative effects of the flow natural electrization process have been offered.

Electrohydrodynamic instabilities of viscous drops*

NASA Astrophysics Data System (ADS)

Vlahovska, Petia M.

2016-10-01

A classic result due to Taylor is that a weakly conducting drop bearing zero net charge placed in a uniform electric field adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. Here I overview some intriguing symmetry-breaking instabilities occurring in strong applied dc fields: Quincke rotation resulting in drop steady tilt or tumbling, and pattern formation on the surface of a particle-coated drop.

Compositional accuracy of atom probe tomography measurements in GaN: Impact of experimental parameters and multiple evaporation events.

PubMed

Russo, E Di; Blum, I; Houard, J; Gilbert, M; Da Costa, G; Blavette, D; Rigutti, L

2018-04-01

A systematic study of the biases occurring in the measurement of the composition of GaN by Atom Probe Tomography was carried out, in which the role of surface electric field and laser pulse intensity has been investigated. Our data confirm that the electric field is the main factor influencing the measured composition, which exhibits a deficiency of N at low field and a deficiency of Ga at high field. The deficiency of Ga at high field is interpreted in terms of preferential evaporation of Ga. The detailed analysis of multiple evaporation events reveals that the measured composition is not affected by pile-up phenomena occurring in detection system. The analysis of correlation histograms yields the signature of the production of neutral N 2 due to the dissociation of GaN 3 2+ ions. However, the amount of N 2 neutral molecules that can be detected cannot account for the N deficiency found at low field. Therefore, we propose that further mechanisms of neutral N evaporation could be represented by dissociation reactions such as GaN + → Ga + + N and GaN 2+ → Ga 2 + + N. Copyright © 2018 Elsevier B.V. All rights reserved.

Ferroelastic domain switching dynamics under electrical and mechanical excitations.

PubMed

Gao, Peng; Britson, Jason; Nelson, Christopher T; Jokisaari, Jacob R; Duan, Chen; Trassin, Morgan; Baek, Seung-Hyub; Guo, Hua; Li, Linze; Wang, Yiran; Chu, Ying-Hao; Minor, Andrew M; Eom, Chang-Beom; Ramesh, Ramamoorthy; Chen, Long-Qing; Pan, Xiaoqing

2014-05-02

In thin film ferroelectric devices, switching of ferroelastic domains can significantly enhance electromechanical response. Previous studies have shown disagreement regarding the mobility or immobility of ferroelastic domain walls, indicating that switching behaviour strongly depends on specific microstructures in ferroelectric systems. Here we study the switching dynamics of individual ferroelastic domains in thin Pb(Zr0.2,Ti0.8)O3 films under electrical and mechanical excitations by using in situ transmission electron microscopy and phase-field modelling. We find that ferroelastic domains can be effectively and permanently stabilized by dislocations at the substrate interface while similar domains at free surfaces without pinning dislocations can be removed by either electric or stress fields. For both electrical and mechanical switching, ferroelastic switching is found to occur most readily at the highly active needle points in ferroelastic domains. Our results provide new insights into the understanding of polarization switching dynamics as well as the engineering of ferroelectric devices.

Ferroelastic domain switching dynamics under electrical and mechanical excitations

NASA Astrophysics Data System (ADS)

Gao, Peng; Britson, Jason; Nelson, Christopher T.; Jokisaari, Jacob R.; Duan, Chen; Trassin, Morgan; Baek, Seung-Hyub; Guo, Hua; Li, Linze; Wang, Yiran; Chu, Ying-Hao; Minor, Andrew M.; Eom, Chang-Beom; Ramesh, Ramamoorthy; Chen, Long-Qing; Pan, Xiaoqing

2014-05-01

In thin film ferroelectric devices, switching of ferroelastic domains can significantly enhance electromechanical response. Previous studies have shown disagreement regarding the mobility or immobility of ferroelastic domain walls, indicating that switching behaviour strongly depends on specific microstructures in ferroelectric systems. Here we study the switching dynamics of individual ferroelastic domains in thin Pb(Zr0.2,Ti0.8)O3 films under electrical and mechanical excitations by using in situ transmission electron microscopy and phase-field modelling. We find that ferroelastic domains can be effectively and permanently stabilized by dislocations at the substrate interface while similar domains at free surfaces without pinning dislocations can be removed by either electric or stress fields. For both electrical and mechanical switching, ferroelastic switching is found to occur most readily at the highly active needle points in ferroelastic domains. Our results provide new insights into the understanding of polarization switching dynamics as well as the engineering of ferroelectric devices.

An electrohydrodynamic flow in ac electrowetting.

PubMed

Lee, Horim; Yun, Sungchan; Ko, Sung Hee; Kang, Kwan Hyoung

2009-12-17

In ac electrowetting, hydrodynamic flows occur within a droplet. Two distinct flow patterns were observed, depending on the frequency of the applied electrical signal. The flow at low-frequency range was explained in terms of shape oscillation and a steady streaming process in conjunction with contact line oscillation. The origin of the flow at high-frequency range has not yet been explained. We suggest that the high-frequency flow originated mainly from the electrothermal effect, in which electrical charge is generated due to the gradient of electrical conductivity and permittivity, which is induced by the Joule heating of fluid medium. To support our argument, we analyzed the flow field numerically while considering the electrical body force generated by the electrothermal effect. We visualized the flow pattern and measured the flow velocity inside the droplet. The numerical results show qualitative agreement with experimental results with respect to electric field and frequency dependence of flow velocity. The effects of induced-charge electro-osmosis, natural convection, and the Marangoni flow are discussed.

Performance Improvement of Diagonal Type MHD Generator by Modification of PTO Electrode Configuration

NASA Astrophysics Data System (ADS)

Takahashi, Toru; Fujino, Takayasu; Ishikawa, Motoo

Time dependent three-dimensional numerical analysis is carried out in order to clarify causes of voltage loss occurring near power takeoff regions and to suggest how to reduce the voltage loss for the scramjet engine driven MHD generator which was developed under the hypersonic vehicle electric power system program in USA. The numerical results under the experimental condition show that the local positive electric field is induced near the power takeoff electrodes. The phenomenon is due to the electric field loss by the high electric current through the weakly ionized plasma with low temperature and also by the low electromotive force near the power takeoff electrodes. When the configuration of power takeoff electrodes is modified, the current density near the power takeoff electrodes becomes small and the electromotive force becomes strong. The electric power output under the optimum electrode configuration of power takeoff is improved by 22 percent, compared with the value under the experimental condition.

Novel Parallelized Electroporation by Electrostatic Manipulation of a Water-in-Oil Droplet as a Microreactor

PubMed Central

Takahashi, Shota; Asada, Atsushi; Matsuo, Minako; Kishikawa, Kenta; Mizuno, Akira

2015-01-01

Electroporation is the most widely used transfection method for delivery of cell-impermeable molecules into cells. We developed a novel gene transfection method, water-in-oil (W/O) droplet electroporation, using dielectric oil and an aqueous droplet containing mammalian cells and transgene DNA. When a liquid droplet suspended between a pair of electrodes in dielectric oil is exposed to a DC electric field, the droplet moves between the pair of electrodes periodically and droplet deformation occurs under the intense DC electric field. During electrostatic manipulation of the droplet, the local intense electric field and instantaneous short circuit via the droplet due to droplet deformation facilitate gene transfection. This method has several advantages over conventional transfection techniques, including co-transfection of multiple transgene DNAs into even as few as 103 cells, transfection into differentiated neural cells, and the capable establishment of stable cell lines. In addition, there have been improvements in W/O droplet electroporation electrodes for disposable 96-well plates making them suitable for concurrent performance without thermal loading by a DC electric field. This technique will lead to the development of cell transfection methods for novel regenerative medicine and gene therapy. PMID:26649904

Measurement of the magnetotail reconnection rate

NASA Astrophysics Data System (ADS)

Blanchard, G. T.; Lyons, L. R.; de la Beaujardière, O.; Doe, R. A.; Mendillo, M.

1996-07-01

A technique to measure the magnetotail reconnection rate from the ground is described and applied to 71 hours of measurements from 20 nights. The reconnection rate is obtained from the ionospheric flow across the polar cap boundary in the frame of reference of the boundary, measured by the Sondrestrom incoherent scatter radar. For our measurements, the polar cap boundary is located using 6300 Å auroral emissions and E region electron density. The average experimental uncertainty of the reconnection rate measurement is 11.6 mVm-1 in the ionospheric electric field. By using a large data set, we obtain the dependence of the reconnection rate on magnetic local time, the interplanetary magnetic field, and substorm activity, with much higher accuracy. We find that two thirds of the average polar cap potential drop occurs over the 4-hour segment of the separatrix centered on 2330 MLT, that the linear correlation between the reconnection electric field and the half-wave rectified dawn-dusk solar wind electric field VBs peaks between 1.0 and 1.5 hours, with a maximum linear correlation coefficient of 0.46 at 70 min; and that following substorm expansion phase onset, the reconnection electric field becomes larger than the experimental uncertainty, with an average delay of 23 min. The 70-min delay of the reconnection rate with respect to VBs is a typical convection time for a flux tube across the polar cap. This result indicates that reconnection in the magnetotail is influenced by the solar wind electric field VBs on the field line being reconnected.

The prevention of electrical breakdown and electrostatic voltage problems in the space shuttle and its payloads. Part 1: Theory and phenomena

NASA Technical Reports Server (NTRS)

Whitson, D. W.

1975-01-01

An introduction to the theory of corona discharge and electrostatic phenomena is presented. The theory is mainly qualitative so that workers in the field should not have to go outside this manual for an understanding of the relevant phenomena. Some of the problems that may occur with the space shuttle in regard to electrical discharge are discussed.

Laser-assisted guiding of electric discharges around objects

PubMed Central

Clerici, Matteo; Hu, Yi; Lassonde, Philippe; Milián, Carles; Couairon, Arnaud; Christodoulides, Demetrios N.; Chen, Zhigang; Razzari, Luca; Vidal, François; Légaré, François; Faccio, Daniele; Morandotti, Roberto

2015-01-01

Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight. PMID:26601188

Small-Scale Dayside Magnetic Reconnection Analysis via MMS

NASA Astrophysics Data System (ADS)

Pritchard, K. R.; Burch, J. L.; Fuselier, S. A.; Webster, J.; Genestreti, K.; Torbert, R. B.; Rager, A. C.; Phan, T.; Argall, M. R.; Le Contel, O.; Russell, C. T.; Strangeway, R. J.; Giles, B. L.

2017-12-01

The Magnetospheric Multiscale (MMS) mission has the primary objective of understanding the physics of the reconnection electron diffusion region (EDR), where magnetic energy is transformed into particle energy. In this poster, we present data from an EDR encounter that occurred in late December 2016 at approximately 11:00 MLT with a moderate guide field. The spacecraft were in a tetrahedral formation with an average inter-spacecraft distance of approximately 7 kilometers. During this event electron crescent-shaped distributions were observed in the electron stagnation region as is typical for asymmetric reconnection. Based on the observed ion velocity jets, the spacecraft traveled just south of the EDR. Because of the close spacecraft separation, fairly accurate computation of the Hall, electron pressure divergence, and electron inertia components of the reconnection electric field could be made. In the region of the crescent distributions good agreement was observed, with the strongest component being the normal electric field and the most significant sources being electron pressure divergence and the Hall electric field. While the strongest currents were in the out-of-plane direction, the dissipation was strongest in the normal direction because of the larger magnitude of the normal electric field component. These results are discussed in light of recent 3D PIC simulations performed by other groups.

Numerical evaluation of lactoperoxidase inactivation during continuous pulsed electric field processing.

PubMed

Buckow, Roman; Semrau, Julius; Sui, Qian; Wan, Jason; Knoerzer, Kai

2012-01-01

A computational fluid dynamics (CFD) model describing the flow, electric field and temperature distribution of a laboratory-scale pulsed electric field (PEF) treatment chamber with co-field electrode configuration was developed. The predicted temperature increase was validated by means of integral temperature studies using thermocouples at the outlet of each flow cell for grape juice and salt solutions. Simulations of PEF treatments revealed intensity peaks of the electric field and laminar flow conditions in the treatment chamber causing local temperature hot spots near the chamber walls. Furthermore, thermal inactivation kinetics of lactoperoxidase (LPO) dissolved in simulated milk ultrafiltrate were determined with a glass capillary method at temperatures ranging from 65 to 80 °C. Temperature dependence of first order inactivation rate constants was accurately described by the Arrhenius equation yielding an activation energy of 597.1 kJ mol(-1). The thermal impact of different PEF processes on LPO activity was estimated by coupling the derived Arrhenius model with the CFD model and the predicted enzyme inactivation was compared to experimental measurements. Results indicated that LPO inactivation during combined PEF/thermal treatments was largely due to thermal effects, but 5-12% enzyme inactivation may be related to other electro-chemical effects occurring during PEF treatments. Copyright © 2012 American Institute of Chemical Engineers (AIChE).

Mechanical Characteristics of Resin-Coated Papers and their Electrical Breakdown Characteristics in Composite Insulation Systems with Insulation Oil

NASA Astrophysics Data System (ADS)

Kurihara, Takashi; Takahashi, Toshihiro; Mizutani, Yoshinobu; Suzuki, Hiroshi; Okamoto, Tatsuki; Ogura, Nobuyuki; Iwamoto, Kazuyoshi; Kitagawa, Setsuo

Three types of resin-coated papers were investigated; kraft papers and heat-resistant kraft papers partially covered with epoxy resin, and a kraft paper covered with phenol resin; those were laminated to certain thickness. They were thermally degraded at 120°C for 240 to 1320 hours, and their mechanical characteristics such as tensile strength and average polymerization degree were measured. As a result, it was found that the tensile strength of the first and second resin-coated papers was larger than that of the pressboard, but the tensile strength of the third one was smaller. As the effect of the heating time, it was found that the tensile strength of the first resin-coated paper decreased down to that of pressboards after 500 hours of heating time while those of the second and third ones almost retained the initial values after 1320 hours of the heating time. Then, electrical breakdown characteristics of composite insulation systems with a resin-coated paper and insulation oil were investigated. In the system, an oil-filled gap was artificially introduced between a resin-coated paper and a plane electrode to induce partial discharges (PDs) at the same location. PDs occurred before breakdowns and it was found that their PD inception electric field strength was almost as high as that of the pressboard and the effect of the heating time was negligible. It was also found that the electrical breakdown field strength has similar characteristics to those of the PD inception field strength; negligible effects of the type of resin-coated papers and the heating time. Electrical breakdown occurred at the oil-filled gap and the edge of a high voltage electrode.

Electrically induced formation of uncapped, hollow polymeric microstructures

NASA Astrophysics Data System (ADS)

Lee, Sung Hun; Kim, Pilnam; Jeong, Hoon Eui; Suh, Kahp Y.

2006-11-01

Uncapped, hollow polymeric microstructures were fabricated on a silicon substrate using electric field induced stretching and detachment. Initially, square or cylinder microposts were generated using a solvent-assisted capillary molding technique, and a featureless electrode mask was positioned on the top of the microstructure with spacers maintaining an air gap (~20 µm). Upon exposure to an external electric field (1.0-3.0 V µm-1), the hollow microstructures were destabilized and stretched by the well-known electrohydrodynamic instability, resulting in contact of the top polymer surface with the mask. Subsequently, detachment of the capping layer occurred upon removal of the mask due to larger adhesion forces at the polymer/mask interface than cohesion forces of the polymer. These hollow microstructures were tested to capture the budding yeast, Saccharomyces cerevisiae, for shear protection.

Electrorheological suspensions of laponite in oil: rheometry studies.

PubMed

Parmar, K P S; Méheust, Y; Schjelderupsen, Børge; Fossum, J O

2008-03-04

We have studied the effect of an external direct current (DC) electric field ( approximately 1 kV/mm) on the rheological properties of colloidal suspensions consisting of aggregates of laponite particles in a silicone oil. Microscopy observations show that, under application of an electric field greater than a triggering electric field Ec approximately 0.6 kV/mm, laponite aggregates assemble into chain- and/or columnlike structures in the oil. Without an applied electric field, the steady-state shear behavior of such suspensions is Newtonian-like. Under application of an electric field larger than Ec, it changes dramatically as a result of the changes in the microstructure: a significant yield stress is measured, and under continuous shear the fluid is shear-thinning. The rheological properties, in particular the dynamic and static shear stress, were studied as a function of particle volume fraction for various strengths (including null) of the applied electric field. The flow curves at constant shear rate can be scaled with respect to both the particle fraction and electric field strength onto a master curve. This scaling is consistent with simple scaling arguments. The shape of the master curve accounts for the system's complexity; it approaches a standard power-law model at high Mason numbers. Both dynamic and static yield stresses are observed to depend on the particle fraction Phi and electric field E as PhibetaEalpha, with alpha approximately 1.85 and beta approximately 1 and 1.70 for the dynamic and static yield stresses, respectively. The yield stress was also determined as the critical stress at which there occurs a bifurcation in the rheological behavior of suspensions that are submitted to a constant shear stress; a scaling law with alpha approximately 1.84 and beta approximately 1.70 was obtained. The effectiveness of the latter technique confirms that such electrorheological (ER) fluids can be studied in the framework of thixotropic fluids. The method is very reproducible; we suggest that it could be used routinely for studying ER fluids. The measured overall yield stress behavior of the suspensions may be explained in terms of standard conduction models for electrorheological systems. Interesting prospects include using such systems for guided self-assembly of clay nanoparticles.

Electrohydrodynamic interactions of spherical particles under Quincke rotation

NASA Astrophysics Data System (ADS)

Das, Debasish; Saintillan, David

2012-11-01

Quincke rotation denotes the spontaneous rotation of dielectric particles immersed in a slightly dielectric liquid when subjected to a high enough DC electric field. It occurs when the charge relaxation time of the particles is greater than that of the fluid medium, causing the particles to become polarized in a direction opposite to that of the electric field and therefore giving rise to an unstable equilibrium position. When slightly perturbed, the particles start to rotate, and if the electric field exceeds a critical value the perturbations do not decay and the particle rotations reach a steady state with a constant angular velocity. We use a combination of numerical simulations and asymptotic theory to study the effect of electrohydrodynamic interactions between particles under Quincke rotation. We study the prototypical case of two equally charged spheres carrying no net charge and interacting with each other both hydrodynamically and electrically. The case of spherical particles free to roll on a horizontal grounded electrode is also described. We show that Quincke rotation results in self-propulsion of the particles in the plane of the electrode, and interactions between a pair of such ``rollers'' are analyzed.

Electro-migration of impurities in TlBr

NASA Astrophysics Data System (ADS)

Kim, Ki Hyun; Kim, Eunlim; Kim, H.; Tappero, R.; Bolotnikov, A. E.; Camarda, G. S.; Hossain, A.; Cirignano, L.; James, R. B.

2013-10-01

We observed the electro-migration of Cu, Ag, and Au impurities that exist in positive-ion states in TlBr detectors under electric field strengths typically used for device operation. The migration occurred predominantly through bulk- and specific-channels, which are presumed to be a network of grain and sub-grain boundaries. The electro-migration velocity of Cu, Ag, and Au in TlBr is about 4-8 × 10-8 cm/s at room temperature under an electric field of 500-800 V/mm. The instability and polarization effects of TlBr detectors might well be correlated with the electro-migration of residual impurities in TlBr, which alters the internal electric field over time. The effect may also have been due to migration of the electrode material itself, which would allow for the possibility of a better choice for contact material and for depositing an effective diffusion barrier. From our findings, we suggest that applying our electro-migration technique for purifying material is a promising new way to remove electrically active metallic impurities in TlBr crystals, as well as other materials.

Electron distribution functions in electric field environments

NASA Technical Reports Server (NTRS)

Rudolph, Terence H.

1991-01-01

The amount of current carried by an electric discharge in its early stages of growth is strongly dependent on its geometrical shape. Discharges with a large number of branches, each funnelling current to a common stem, tend to carry more current than those with fewer branches. The fractal character of typical discharges was simulated using stochastic models based on solutions of the Laplace equation. Extension of these models requires the use of electron distribution functions to describe the behavior of electrons in the undisturbed medium ahead of the discharge. These electrons, interacting with the electric field, determine the propagation of branches in the discharge and the way in which further branching occurs. The first phase in the extension of the referenced models , the calculation of simple electron distribution functions in an air/electric field medium, is discussed. Two techniques are investigated: (1) the solution of the Boltzmann equation in homogeneous, steady state environments, and (2) the use of Monte Carlo simulations. Distribution functions calculated from both techniques are illustrated. Advantages and disadvantages of each technique are discussed.

HIGH VOLTAGE ELECTRODES

DOEpatents

Murray, J.J.

1963-04-23

S>This patent relates to electrode structure for creating an intense direct current electric field which may have a field strength of the order of two to three times that heretofore obtained, with automatic suppression of arcing. The positive electrode is a conventional conductive material such as copper while the negative electrode is made from a special material having a resistivity greater than that of good conductors and less than that of good insulators. When an incipient arc occurs, the moderate resistivity of the negative electrode causes a momentary, localized decrease in the electric field intensity, thus suppressing the flow of electrons and avoiding arcing. Heated glass may be utilized for the negative electrode, since it provides the desired combination of resistivity, capacity, dielectric strength, mechani-cal strength, and thermal stability. (AEC)

The phenomenon of voltage controlled switching in disordered superconductors.

PubMed

Ghosh, Sanjib; De Munshi, D

2014-01-15

The superconductor-to-insulator transition (SIT) is a phenomenon occurring in highly disordered superconductors and may be useful in the development of superconducting switches. The SIT has been demonstrated to be induced by different external parameters: temperature, magnetic field, electric field, etc. However, the electric field induced SIT (ESIT), which has been experimentally demonstrated for some specific materials, holds particular promise for practical device development. Here, we demonstrate, from theoretical considerations, the occurrence of the ESIT. We also propose a general switching device architecture using the ESIT and study some of its universal behavior, such as the effects of sample size, disorder strength and temperature on the switching action. This work provides a general framework for the development of such a device.

Ground level gamma-ray and electric field enhancements during disturbed weather: Combined signatures from convective clouds, lightning and rain

NASA Astrophysics Data System (ADS)

Reuveni, Yuval; Yair, Yoav; Price, Colin; Steinitz, Gideon

2017-11-01

We report coincidences of ground-level gamma-ray enhancements with precipitation events and strong electric fields typical of thunderstorms, measured at the Emilio Segre Cosmic Ray observatory located on the western slopes of Mt. Hermon in northern Israel. The observatory hosts 2 × 2″ Nal(TI) gamma ray scintillation detectors alongside a vertical atmospheric electric field (Ez) mill and conduction current (Jz) plates. During several active thunderstorms that occurred near the Mt. Hermon station in October and November 2015, we recorded prolonged periods of gamma ray enhancements, which lasted tens of minutes and coincided with peaks both in precipitation and the vertical electric field. Two types of events were detected: slow increase (up to 300 min) of atmospheric gamma ray radiation due to radon progeny washout (or rainout) along with minutes of Ez enhancement, which were not associated with the occurrences of nearby CG lightning discharges. The second type showed 30 min bursts of gamma rays, coinciding with minutes of Ez enhancement that closely matched the occurrences of nearby CG lightning discharges, and are superimposed on the radiation from radon daughters washed out to near surface levels by precipitation. We conclude that a superposition of accelerated high energy electrons by thunderstorm electric fields and radon progeny washout (or rainout) explains the relatively fast near surface gamma-ray increase, where the minutes-scale vertical electric field enhancement are presumably caused due to nearby convective clouds. Our results show that the mean exponential half-life depletion times of the residual nuclei produced during events without lightning occurrences were between 25-65 min, compared to 55-100 min when lightning was present, indicating that different types of nuclei were involved.

Large tangential electric fields in plasmas close to temperature screening

NASA Astrophysics Data System (ADS)

Velasco, J. L.; Calvo, I.; García-Regaña, J. M.; Parra, F. I.; Satake, S.; Alonso, J. A.; the LHD team

2018-07-01

Low collisionality stellarator plasmas usually display a large negative radial electric field that has been expected to cause accumulation of impurities due to their high charge number. In this paper, two combined effects that can potentially modify this scenario are discussed. First, it is shown that, in low collisionality plasmas, the kinetic contribution of the electrons to the radial electric field can make it negative but small, bringing the plasma close to impurity temperature screening (i.e., to a situation in which the ion temperature gradient is the main drive of impurity transport and causes outward flux); in plasmas of very low collisionality, such as those of the large helical device displaying impurity hole (Ida et al (The LHD Experimental Group) 2009 Phys. Plasmas 16 056111; Yoshinuma et al (The LHD Experimental Group) 2009 Nucl. Fusion 49 062002), screening may actually occur. Second, the component of the electric field that is tangent to the flux surface (in other words, the variation of the electrostatic potential on the flux surface), although smaller than the radial component, has recently been suggested to be an additional relevant drive for radial impurity transport. Here, it is explained that, especially when the radial electric field is small, the tangential magnetic drift has to be kept in order to correctly compute the tangential electric field, that can be larger than previously expected. This can have a strong impact on impurity transport, as we illustrate by means of simulations using the newly developed code kinetic orbit-averaging-solver for stellarators, although it is not enough to explain by itself the behavior of the fluxes in situations like the impurity hole.

Electrodynamics of ionospheric weather over low latitudes

NASA Astrophysics Data System (ADS)

Abdu, Mangalathayil Ali

2016-12-01

The dynamic state of the ionosphere at low latitudes is largely controlled by electric fields originating from dynamo actions by atmospheric waves propagating from below and the solar wind-magnetosphere interaction from above. These electric fields cause structuring of the ionosphere in wide ranging spatial and temporal scales that impact on space-based communication and navigation systems constituting an important segment of our technology-based day-to-day lives. The largest of the ionosphere structures, the equatorial ionization anomaly, with global maximum of plasma densities can cause propagation delays on the GNSS signals. The sunset electrodynamics is responsible for the generation of plasma bubble wide spectrum irregularities that can cause scintillation or even disruptions of satellite communication/navigation signals. Driven basically by upward propagating tides, these electric fields can suffer significant modulations from perturbation winds due to gravity waves, planetary/Kelvin waves, and non-migrating tides, as recent observational and modeling results have demonstrated. The changing state of the plasma distribution arising from these highly variable electric fields constitutes an important component of the ionospheric weather disturbances. Another, often dominating, component arises from solar disturbances when coronal mass ejection (CME) interaction with the earth's magnetosphere results in energy transport to low latitudes in the form of storm time prompt penetration electric fields and thermospheric disturbance winds. As a result, drastic modifications can occur in the form of layer restructuring (Es-, F3 layers etc.), large total electron content (TEC) enhancements, equatorial ionization anomaly (EIA) latitudinal expansion/contraction, anomalous polarization electric fields/vertical drifts, enhanced growth/suppression of plasma structuring, etc. A brief review of our current understanding of the ionospheric weather variations and the electrodynamic processes underlying them and some outstanding questions will be presented in this paper.

Bandgap engineering in van der Waals heterostructures of blue phosphorene and MoS{sub 2}: A first principles calculation

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

Zhang, Z.Y.; Si, M.S., E-mail: sims@lzu.edu.cn; Peng, S.L.

2015-11-15

Blue phosphorene (BP) was theoretically predicted to be thermally stable recently. Considering its similar in-layer hexagonal lattice to MoS{sub 2}, MoS{sub 2} could be an appropriate substrate to grow BP in experiments. In this work, the van der Waals (vdW) heterostructures are constructed by stacking BP on top of MoS{sub 2}. The thermal stability and electronic structures are evaluated based on first principles calculations with vdW-corrected exchange-correlation functional. The formation of the heterostructures is demonstrated to be exothermic and the most stable stacking configuration is confirmed. The heterostructures BP/MoS{sub 2} preserve both the properties of BP and MoS{sub 2} butmore » exhibit relatively narrower bandgaps due to the interlayer coupling effect. The band structures can be further engineered by applying external electric fields. An indirect–direct bandgap transition in bilayer BP/MoS{sub 2} is demonstrated to be controlled by the symmetry property of the built-in electric dipole fields. - Graphical abstract: An indirect-direct band gap transition occurs in van der Waals heterostructure of MoS{sub 2}/BP under external electric fields which is demonstrated to be controlled by the symmetry of the built-in electric dipole fields. - Highlights: • The stacking of heterostructures of BP/MoS{sub 2} is demonstrated to be exothermic. • This suggests that it is possible to grow BP using MoS{sub 2} as the substrate. • The band structures of the heterostructures are exploited. • It realizes an indirect–direct gap transition under external electric fields. • The symmetry of the built-in electric dipole fields controls such gap transition.« less

Rocketborne observations of ion convection and electric fields in dayside and nightside visual auroral arcs

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

Yau, A.W.; Whalen, B.A.; Creutzberg, F.

1981-08-01

We present ionospheric ion convection measurements in a series of four rocket payloads in and near dayside and nightside auroral arcs: one at Cape Parry (75.4/sup 0/N invariant latitude) near 1300 MLT and three at Churchill (70.0/sup 0/N invariant latitude) between 1900 and 2200 MLT. Direct measurements were made of the ionospheric ion velocity distribution function, and the observed ion convection velocities and equivalent convective electric fields were correlated with the energetic particle precipitation, the optical morphology of the aurora, and the topology of the geomagnetic field. Both in the postnoon and premidnight sectors it was observed that (1) equatorwardmore » of the region(s) of precipitation the ion flow was predominantly westward, with velocity of about 1 km/s; (2) poleward of the region(s) the flow was predominantly westward, with velocity of about 1 km/s; (2) poleward of the region(s) the flow was predominantly eastward: (3) the change in the flow direction, where observed, occurred near though not exactly at the edges of the precipitation region; (4) the flow inside the precipitation region was lower; (5) the reversal of the ion flow, where observed, occurred on closed magnetic field lines; and (6) the convective electric field typically dropped from 40 to 80 mV/m outside the precipitation region to 10 to 30 mV/m within. In the dayside Cape Perry flight, where quantitative photometric measurements were available, detailed anticorrelation between the ion convection speed and the green line emission intensity was also observed.« less

Stability of Alfvén eigenmodes in the vicinity of auroral arc

NASA Astrophysics Data System (ADS)

Hiraki, Yasutaka

2013-08-01

The purpose of this study is to give a theoretical suggestion to the essential question why east-west elongated auroral arc can keep its anisotropic structure for a long time. It could be related to the stability of east-westward traveling modes in the vicinity of arc, which may develop into wavy or spiral structures, whereas north-southward modes are related to splitting of arcs. Taking into account the arc-inducing field-aligned current and magnetic shears, we examine changes in the stability of Alfvén eigenmodes that are coupled to perpendicular modes in the presence of convection electric field. It is demonstrated that the poleward current shear suppresses growth of the westward mode in case of the westward convection electric field. Only the poleward mode is still unstable because of the properties of feedback shear waves. It is suggested that this tends to promote (poleward) arc splitting as often observed during quiet times. We further draw a diagram of the westward mode growth rate as a function of convection electric field and current shear, evaluating critical fields for instabilities of lower Alfvén harmonics. It is discovered that a switching phenomenon of fast-growing mode from fundamental to the first harmonic occurs for a high electric field regime. Our stability criterion is applied to some observed situations of auroral arc current system during pre-breakup active times.

Environmental impact of the use of radiofrequency electromagnetic fields in physiotherapeutic treatment.

PubMed

Gryz, Krzysztof; Karpowicz, Jolanta

2014-01-01

Electromagnetic fields used in physiotherapeutic treatment affect not only patients, but also physiotherapists, patients not undergoing treatment and electronic medical equipment. The aim of the work was to study the parameters of the electromagnetic fields of physiotherapeutic devices with respect to requirements regarding the protection of electronic devices, including medical implants, against electromagnetic intererence, and the protection of the general public (patients not undergoing treatment and bystanders), as well as medical personnel, against the health hazards caused by electromagnetic exposure. The spatial distribution of electric and magnetic field strength was investigated near 3 capacitive short-wave and 3 long-wave diathermies and 3 ultrasound therapy units, as along with the capacitive electric currents caused by electromagnetic field interaction in the upper limbs of the physiotherapists operating these devices. The physiotherapists' exposure to electromagnetic fields depends on the spatial organisation of the workspace and their location during treatment. Electric fields able to interfere with the function of electronic medical implants and in whic anyone not undergoing treatment should not be present were measured up to 150-200 cm away from active applicators of short-wave diathermy, and up to 40-45 cm away from long-wave diathermy ones. Electric fields in which workers should not be present were measured up to 30-40 cm away from the applicators and cables of active short-wave diathermy devices. A capacitive electric current with a strength exceeding many times the international recommendations regarding workers protection was measured in the wrist while touching applicators and cables of active short-wave diathermy devices. The strongest environmental electromagnetic hazards occur near short-wave diathermy devices, and to a lesser degree near long-wave diathermy devices, but were not found near ultrasound therapy units.

Electric field measurements during the blowing snow in a cryogenic wind tunnel by a non-contact voltmeter

NASA Astrophysics Data System (ADS)

Sato, A.; Omiya, S.

2011-12-01

It is known that the average atmospheric electric field is +100V/m in fair weather (positive electric field vector points downward). An increase of atmospheric electric field is reported when the blowing snow occurred. This phenomenon is mainly explained by the fact that the blowing snow particles have negative charge in average. It is suggested that an electrostatic force, given by the product of the electric field and the charge of the particle, may influence the particle trajectory and change those movements, saltation and suspension. The purpose of this experiment is to clarify the characteristics of the electric field during blowing snow event. Experiments were carried out in the cryogenic wind tunnel of Snow and Ice Research Center, NIED. A non-contact voltmeter was used to measure the electric field. An artificial blowing snow was generated by a snow particle supply machine. The rolling brushes of the machine scratch the snow surface and supply snow particles into the airflow. This machine made it possible to supply the snow particles at an arbitrary rate. This experiment was conducted in the following experimental conditions; wind speed of 5 to 7 m/s (3 patterns), supply snow quantity of 8.7 to 34.9 g/m/s (4 patterns), air temperature of -10 degree Celsius, fetch of 10 m and hard snow surface. Measured electric field was all negative, which is opposite direction to the previous measurements. This means that the blowing snow particles had positive charges. The negative electric field tended to increase with increase of the wind speed and the mass flux. These results can be explained from the previous experiment by Omiya and Sato (2010). The snow particles gain positive charges by the friction with the rolling brush which is made from polypropylene, however the particles accumulate negative charges gradually with increase of the collisions to the snow surface. Probably, the positive charges might have remained on the snow particles that had passed over the measurement point. Moreover, it is thought that because the saltation length is longer when the wind speed is higher, fewer collision frequencies left the particles more positive charges. REFERENCE:Omiya and Sato(2010): Measurement of electrostatic charge of blowing snow particles in a wind tunnel focusing on collision frequency to the snow surface. Hokkaido University Collection of Scholarly and Academic Papers

Neutral points of skylight polarization observed during the total eclipse on 11 August 1999.

PubMed

Horváth, Gábor; Pomozi, István; Gál, József

2003-01-20

We report here on the observation of unpolarized (neutral) points in the sky during the total solar eclipse on 11 August 1999. Near the zenith a neutral point was observed at 450 nm at two different points of time during totality. Around this celestial point the distribution of the angle of polarization was heterogeneous: The electric field vectors on the one side were approximately perpendicular to those on the other side. At another moment of totality, near the zenith a local minimum of the degree of linear polarization occurred at 550 nm. Near the antisolar meridian, at a low elevation another two neutral points occurred at 450 nm at a certain moment during totality. Approximately at the position of these neutral points, at another moment of totality a local minimum of the degree of polarization occurred at 550 nm, whereas at 450 nm a neutral point was observed, around which the angle-of-polarization pattern was homogeneous: The electric field vectors were approximately horizontal on both sides of the neutral point.

Integrated structure vacuum tube: A Concept

NASA Technical Reports Server (NTRS)

Dimeff, J.; Kerwin, W. J.

1974-01-01

Cathode emission is made to occur by heating entire structure to 600 C, and positive potential is applied to anode with negative potential on grids. Electron flow takes place from ring to circular anode through electric field produced by grids.

Vesicle biomechanics in a time-varying magnetic field.

PubMed

Ye, Hui; Curcuru, Austen

2015-01-01

Cells exhibit distortion when exposed to a strong electric field, suggesting that the field imposes control over cellular biomechanics. Closed pure lipid bilayer membranes (vesicles) have been widely used for the experimental and theoretical studies of cellular biomechanics under this electrodeformation. An alternative method used to generate an electric field is by electromagnetic induction with a time-varying magnetic field. References reporting the magnetic control of cellular mechanics have recently emerged. However, theoretical analysis of the cellular mechanics under a time-varying magnetic field is inadequate. We developed an analytical theory to investigate the biomechanics of a modeled vesicle under a time-varying magnetic field. Following previous publications and to simplify the calculation, this model treated the inner and suspending media as lossy dielectrics, the membrane thickness set at zero, and the electric resistance of the membrane assumed to be negligible. This work provided the first analytical solutions for the surface charges, electric field, radial pressure, overall translational forces, and rotational torques introduced on a vesicle by the time-varying magnetic field. Frequency responses of these measures were analyzed, particularly the frequency used clinically by transcranial magnetic stimulation (TMS). The induced surface charges interacted with the electric field to produce a biomechanical impact upon the vesicle. The distribution of the induced surface charges depended on the orientation of the coil and field frequency. The densities of these charges were trivial at low frequency ranges, but significant at high frequency ranges. The direction of the radial force on the vesicle was dependent on the conductivity ratio between the vesicle and the medium. At relatively low frequencies (<200 KHz), including the frequency used in TMS, the computed radial pressure and translational forces on the vesicle were both negligible. This work provides an analytical framework and insight into factors affecting cellular biomechanics under a time-varying magnetic field. Biological effects of clinical TMS are not likely to occur via alteration of the biomechanics of brain cells.

Development of a numerical model for the electric current in burner-stabilised methane-air flames

NASA Astrophysics Data System (ADS)

Speelman, N.; de Goey, L. P. H.; van Oijen, J. A.

2015-03-01

This study presents a new model to simulate the electric behaviour of one-dimensional ionised flames and to predict the electric currents in these flames. The model utilises Poisson's equation to compute the electric potential. A multi-component diffusion model, including the influence of an electric field, is used to model the diffusion of neutral and charged species. The model is incorporated into the existing CHEM1D flame simulation software. A comparison between the computed electric currents and experimental values from the literature shows good qualitative agreement for the voltage-current characteristic. Physical phenomena, such as saturation and the diodic effect, are captured by the model. The dependence of the saturation current on the equivalence ratio is also captured well for equivalence ratios between 0.6 and 1.2. Simulations show a clear relation between the saturation current and the total number of charged particles created. The model shows that the potential at which the electric field saturates is strongly dependent on the recombination rate and the diffusivity of the charged particles. The onset of saturation occurs because most created charged particles are withdrawn from the flame and because the electric field effects start dominating over mass based diffusion. It is shown that this knowledge can be used to optimise ionisation chemistry mechanisms. It is shown numerically that the so-called diodic effect is caused primarily by the distance the heavier cations have to travel to the cathode.

Highly tunable charge and spin transport in silicene junctions: phase transitions and half-metallic states.

PubMed

Mahdavifar, Maryam; Khoeini, Farhad

2018-08-10

We report peculiar charge and spin transport properties in S-shaped silicene junctions with the Kane-Mele tight-binding model. In this work, we investigate the effects of electric and exchange fields on the charge and spin transport properties. Our results show that by applying a perpendicular electric field, metal-semiconductor and also semimetal-semiconductor phase transitions occur in our systems. Furthermore, full spin current can be obtained in the structures, so the half-metallic states are observable. Our results enable us to control charge and spin currents and provide new opportunities and applications in silicene-based electronics, optoelectronics, and spintronics.

The joint use of the tangential electric field and surface Laplacian in EEG classification.

PubMed

Carvalhaes, C G; de Barros, J Acacio; Perreau-Guimaraes, M; Suppes, P

2014-01-01

We investigate the joint use of the tangential electric field (EF) and the surface Laplacian (SL) derivation as a method to improve the classification of EEG signals. We considered five classification tasks to test the validity of such approach. In all five tasks, the joint use of the components of the EF and the SL outperformed the scalar potential. The smallest effect occurred in the classification of a mental task, wherein the average classification rate was improved by 0.5 standard deviations. The largest effect was obtained in the classification of visual stimuli and corresponded to an improvement of 2.1 standard deviations.

Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device.

PubMed

Ida, K; Funaba, H; Kado, S; Narihara, K; Tanaka, K; Takeiri, Y; Nakamura, Y; Ohyabu, N; Yamazaki, K; Yokoyama, M; Murakami, S; Ashikawa, N; deVries, P C; Emoto, M; Goto, M; Idei, H; Ikeda, K; Inagaki, S; Inoue, N; Isobe, M; Itoh, K; Kaneko, O; Kawahata, K; Khlopenkov, K; Komori, A; Kubo, S; Kumazawa, R; Liang, Y; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Mutoh, T; Muto, S; Nagayama, Y; Nakanishi, H; Nishimura, K; Noda, N; Notake, T; Kobuchi, T; Ohdachi, S; Ohkubo, K; Oka, Y; Osakabe, M; Ozaki, T; Pavlichenko, R O; Peterson, B J; Sagara, A; Saito, K; Sakakibara, S; Sakamoto, R; Sanuki, H; Sasao, H; Sasao, M; Sato, K; Sato, M; Seki, T; Shimozuma, T; Shoji, M; Suzuki, H; Sudo, S; Tamura, N; Toi, K; Tokuzawa, T; Torii, Y; Tsumori, K; Yamamoto, T; Yamada, H; Yamada, I; Yamaguchi, S; Yamamoto, S; Yoshimura, Y; Watanabe, K Y; Watari, T; Hamada, Y; Motojima, O; Fujiwara, M

2001-06-04

Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

Small-scale plasma irregularities in the nightside Venus ionosphere

NASA Astrophysics Data System (ADS)

Grebowsky, J. M.; Curtis, S. A.; Brace, L. H.

1991-12-01

The individual volt-ampere curves from the Pioneer Venus Orbiter electron temperature probe showed evidence for small-scale density irregularities, or short-period plasma waves, in regions of the nightside ionosphere where the Orbiter electric field detector observed waves in its 100-Hz channel. A survey of the nightside volt-ampere curves has revealed several hundred examples of such irregularities. The I-V structures correspond to plasma density structure with spatial scale sizes in the range of about 100-2000 m, or alternatively they could be viewed as waves having frequencies extending toward 100 Hz. They are often seen as isolated events, with spatial extent along the orbit frequently less than 80 km. The density irregularities or waves occur in or near prominent gradients in the ambient plasma concentrations both at low altitudes where molecular ions are dominant and at higher altitudes in regions of reduced plasma density where O(+) is the major ion. Electric field 100-Hz bursts occur simultaneously, with the majority of the structured I-V curves providing demonstrative evidence that at least some of the E field signals are produced within the ionosphere.

Lightning generation in Titan due to the electrical self-polarization properties of Methane

NASA Astrophysics Data System (ADS)

Quintero, A.; Falcón, N.

2009-05-01

We describe an electrical charge process in Titan's thunderclouds, due to the self-polarization properties or pyroelectricity of methane, which increases the internal electric field in thunderclouds and facilitates the charge generation and separation processes. Microphysics that generates lightning flashes is associated with the physical and chemical properties of the local atmosphere, so methane could be the principal agent of the electrical activity because of its great concentration in Titan's atmosphere. Besides, Titan's electrical activity should not be very influenced by Saturn's magnetosphere because lightning occurs at very low altitude above Titan's surface, compared with the greater distance of Saturn's magnetosphere and Titan's troposphere. Using an electrostatic treatment, we calculate the internal electric field of Titan's thunderclouds due to methane's pyroelectrical properties, 7.05×10^11 Vm^-1; and using the telluric capacitor approximation for thunderclouds, we calculate the total charge obtained for a typical Titan thundercloud, 2.67×10^9 C. However, it is not right to use an electrostatic treatment because charge times are very fast due to the large methane concentration in Titan's clouds and the life time of thunderclouds is very low (around 2 hours). We consider a time dependent mechanism, employing common Earth atmospheric approaches, because of the similitude in chemical composition of both atmospheres (mainly nitrogen), so the typical charge of a thundercloud in Titan should reach between 20 C to 40 C, like on Earth. We obtain that lightning occurs with a frequency between 2 and 6 KHz. In Titan's atmosphere, methane concentration is higher than on Earth, and atmospheric electrical activity is stronger, so this model could be consistent with the observed phenomenology.

Statistical Properties of Ribbon Evolution and Reconnection Electric Fields in Eruptive and Confined Flares.

PubMed

Hinterreiter, J; Veronig, A M; Thalmann, J K; Tschernitz, J; Pötzi, W

2018-01-01

A statistical study of the chromospheric ribbon evolution in H[Formula: see text] two-ribbon flares was performed. The data set consists of 50 confined (62%) and eruptive (38%) flares that occurred from June 2000 to June 2015. The flares were selected homogeneously over the H[Formula: see text] and Geostationary Operational Environmental Satellite (GOES) classes, with an emphasis on including powerful confined flares and weak eruptive flares. H[Formula: see text] filtergrams from the Kanzelhöhe Observatory in combination with Michelson Doppler Imager (MDI) and Helioseismic and Magnetic Imager (HMI) magnetograms were used to derive the ribbon separation, the ribbon-separation velocity, the magnetic-field strength, and the reconnection electric field. We find that eruptive flares reveal statistically larger ribbon separation and higher ribbon-separation velocities than confined flares. In addition, the ribbon separation of eruptive flares correlates with the GOES SXR flux, whereas no clear dependence was found for confined flares. The maximum ribbon-separation velocity is not correlated with the GOES flux, but eruptive flares reveal on average a higher ribbon-separation velocity (by ≈ 10 km s -1 ). The local reconnection electric field of confined ([Formula: see text]) and eruptive ([Formula: see text]) flares correlates with the GOES flux, indicating that more powerful flares involve stronger reconnection electric fields. In addition, eruptive flares with higher electric-field strengths tend to be accompanied by faster coronal mass ejections. The online version of this article (10.1007/s11207-018-1253-1) contains supplementary material, which is available to authorized users.

Electroporation System for Sterilizing Water

NASA Technical Reports Server (NTRS)

Schlager, Kenneth J.

2005-01-01

A prototype of an electroporation system for sterilizing wastewater or drinking water has been developed. In electroporation, applied electric fields cause transient and/or permanent changes in the porosities of living cells. Electroporation at lower field strengths can be exploited to increase the efficiency of chemical disinfection (as in chlorination). Electroporation at higher field strengths is capable of inactivating and even killing bacteria and other pathogens, without use of chemicals. Hence, electroporation is at least a partial alternative to chlorination. The transient changes that occur in micro-organisms at lower electric-field strengths include significantly increased uptake of ions and molecules. Such increased uptake makes it possible to achieve disinfection at lower doses of chemicals (e.g., chlorine or ozone) than would otherwise be needed. Lower doses translate to lower costs and reduced concentrations of such carcinogenic chemical byproducts as trichloromethane. Higher electric fields cause cell membranes to lose semipermeability and thereby become unable to function as selective osmotic barriers between the cells and the environment. This loss of function is the cause of the cell death at higher electric-field intensities. Experimental evidence does not indicate cell lysis but, rather, combined leaking of cell proteins out of the cells as well as invasion of foreign chemical compounds into the cells. The concept of electroporation is not new: it has been applied in molecular biology and genetic engineering for decades. However, the laboratory-scale electroporators used heretofore have been built around small (400-microliter) cuvettes, partly because the smallness facilitates the generation of electric fields of sufficient magnitude to cause electroporation. Moreover, most laboratory- scale electroporators have been designed for testing static water. In contrast, the treatment cell in the present system is much larger and features a flow-through geometry, such that electric fields strong enough to effect 99.9- percent disinfection can be applied to water flowing in a pipe.

Topological responses from chiral anomaly in multi-Weyl semimetals

NASA Astrophysics Data System (ADS)

Huang, Ze-Min; Zhou, Jianhui; Shen, Shun-Qing

2017-08-01

Multi-Weyl semimetals are a kind of topological phase of matter with discrete Weyl nodes characterized by multiple monopole charges, in which the chiral anomaly, the anomalous nonconservation of an axial current, occurs in the presence of electric and magnetic fields. Electronic transport properties related to the chiral anomaly in the presence of both electromagnetic fields and axial electromagnetic fields in multi-Weyl semimetals are systematically studied. It has been found that the anomalous Hall conductivity has a modification linear in the axial vector potential from inhomogeneous strains. The axial electric field leads to an axial Hall current that is proportional to the distance of Weyl nodes in momentum space. This axial current may generate chirality accumulation of Weyl fermions through delicately engineering the axial electromagnetic fields even in the absence of external electromagnetic fields. Therefore this work provides a nonmagnetic mechanism of generation of chirality accumulation in Weyl semimetals and might shed new light on the application of Weyl semimetals in the emerging field of valleytronics.

Particle production in a gravitational wave background

NASA Astrophysics Data System (ADS)

Jones, Preston; McDougall, Patrick; Singleton, Douglas

2017-03-01

We study the possibility that massless particles, such as photons, are produced by a gravitational wave. That such a process should occur is implied by tree-level Feynman diagrams such as two gravitons turning into two photons, i.e., g +g →γ +γ . Here we calculate the rate at which a gravitational wave creates a massless scalar field. This is done by placing the scalar field in the background of a plane gravitational wave and calculating the 4-current of the scalar field. Even in the vacuum limit of the scalar field it has a nonzero vacuum expectation value (similar to what occurs in the Higgs mechanism) and a nonzero current. We associate this with the production of scalar field quanta by the gravitational field. This effect has potential consequences for the attenuation of gravitational waves since the massless field is being produced at the expense of the gravitational field. This is related to the time-dependent Schwinger effect, but with the electric field replaced by the gravitational wave background and the electron/positron field quanta replaced by massless scalar "photons." Since the produced scalar quanta are massless there is no exponential suppression, as occurs in the Schwinger effect due to the electron mass.

Timing Actions to Avoid Refractoriness: A Simple Solution for Streaming Sensory Signals

PubMed Central

Nogueira, Javier; Caputi, Ángel Ariel

2011-01-01

Segmenting self- from allo-generated signals is crucial for active sensory processing. We report a dynamic filter used by South American pulse electric fish to distinguish active electro-sensory signals carried by their own electric discharges from other concomitant electrical stimuli (i.e. communication signals). The filter has a sensory component, consisting of an onset type central electro-sensory neuron, and a motor component, consisting of a change in the fish's discharge rate when allo-generated electrical events occur in temporal proximity to the fish's own discharge. We investigated the sensory component of the filter by in vitro mimicking synaptic inputs occurring during behavioral responses to allo-generated interfering signals. We found that active control of the discharge enhances self-generated over allo-generated responses by forcing allo-generated signals into a central refractory period. This hypothesis was confirmed by field potential recordings in freely discharging fish. Similar sensory-motor mechanisms may also contribute to signal segmentation in other sensory systems. PMID:21789228

Evaluating sensitivity of complex electrical methods for monitoring CO2 intrusion into a shallow groundwater system and associated geochemical transformations

NASA Astrophysics Data System (ADS)

Dafflon, B.; Wu, Y.; Hubbard, S. S.; Birkholzer, J. T.; Daley, T. M.; Pugh, J. D.; Peterson, J.; Trautz, R. C.

2011-12-01

A risk factor of CO2 storage in deep geological formations includes its potential to leak into shallow formations and impact groundwater geochemistry and quality. In particular, CO2 decreases groundwater pH, which can potentially mobilize naturally occurring trace metals and ions commonly absorbed to or contained in sediments. Here, geophysical studies (primarily complex electrical method) are being carried out at both laboratory and field scales to evaluate the sensitivity of geophysical methods for monitoring dissolved CO2 distribution and geochemical transformations that may impact water quality. Our research is performed in association with a field test that is exploring the effects of dissolved CO2 intrusion on groundwater geochemistry. Laboratory experiments using site sediments (silica sand and some fraction of clay minerals) and groundwater were initially conducted under field relevant CO2 partial pressures (pCO2). A significant pH drop was observed with inline sensors with concurrent changes in fluid conductivity caused by CO2 dissolution. Electrical resistivity and electrical phase responses correlated well with the CO2 dissolution process at various pCO2. Specifically, resistivity decreased initially at low pCO2 condition resulting from CO2 dissolution followed by a slight rebound because of the transition of bicarbonate into non-dissociated carbonic acid at lower pH slightly reducing the total concentration of dissociated species. Continuous electrical phase decreases were also observed, which are interpreted to be driven by the decrease of surface charge density (due to the decrease of pH, which approaches the PZC of the sediments). In general, laboratory experiments revealed the sensitivity of electrical signals to CO2 intrusion into groundwater formations and can be used to guide field data interpretation. Cross well complex electrical data are currently being collected periodically throughout a field experiment involving the controlled release of dissolved CO2 into groundwater. The objective of the geophysical cross well monitoring effort is to evaluate the sensitivity of complex electrical methods to dissolved CO2 at the field scale. Here, we report on the ability to translate laboratory-based petrophysical information from lab to field scales, and on the potential of field complex electrical methods for remotely monitoring CO2-induced geochemical transformations.

Dipolarizing flux bundles in the cis-geosynchronous magnetosphere: Relationship between electric fields and energetic particle injections

NASA Astrophysics Data System (ADS)

Liu, Jiang; Angelopoulos, V.; Zhang, Xiao-Jia; Turner, D. L.; Gabrielse, C.; Runov, A.; Li, Jinxing; Funsten, H. O.; Spence, H. E.

2016-02-01

Dipolarizing flux bundles (DFBs) are small flux tubes (typically <3 RE in XGSM and YGSM) in the nightside magnetosphere that have magnetic field more dipolar than the background. Although DFBs are known to accelerate particles, creating energetic particle injections outside geosynchronous orbit (trans-GEO), the nature of the acceleration mechanism and the importance of DFBs in generating injections inside geosynchronous orbit (cis-GEO) are unclear. Our statistical study of cis-GEO DFBs using data from the Van Allen Probes reveals that just like trans-GEO DFBs, cis-GEO DFBs occur most often in the premidnight sector, but their occurrence rate is ~1/3 that of trans-GEO DFBs. Half the cis-GEO DFBs are accompanied by an energetic particle injection and have an electric field 3 times stronger than that of the injectionless half. All DFB injections are dispersionless within the temporal resolution considered (11 s). Our findings suggest that these injections are ushered or produced locally by the DFB, and the DFB's strong electric field is an important aspect of the injection generation mechanism.

Internal Electrostatic Discharge Monitor - IESDM

NASA Technical Reports Server (NTRS)

Kim, Wousik; Goebel, Dan M.; Jun, Insoo; Garrett, Henry B.

2011-01-01

A document discusses an innovation designed to effectively monitor dielectric charging in spacecraft components to measure the potential for discharge in order to prevent damage from internal electrostatic discharge (IESD). High-energy electrons penetrate the structural materials and shielding of a spacecraft and then stop inside dielectrics and keep accumulating. Those deposited charges generate an electric field. If the electric field becomes higher than the breakdown threshold (approx. =2 x 10(exp 5) V/cm), discharge occurs. This monitor measures potentials as a function of dielectric depth. Differentiation of potential with respect to the depth yields electric field. Direct measurement of the depth profile of the potential in a dielectric makes real-time electronic field evaluation possible without simulations. The IESDM has been designed to emulate a multi-layer circuit board, to insert very thin metallic layers between the dielectric layers. The conductors serve as diagnostic monitoring locations to measure the deposited electron-charge and the charge dynamics. Measurement of the time-dependent potential of the metal layers provides information on the amount of charge deposited in the dielectrics and the movement of that charge with time (dynamics).

A current disruption mechanism in the neutral sheet - A possible trigger for substorm expansions

NASA Technical Reports Server (NTRS)

Lui, A. T. Y.; Mankofsky, A.; Chang, C.-L.; Papadopoulos, K.; Wu, C. S.

1990-01-01

A linear analysis is performed to investigate the kinetic cross-field streaming instability in the earth's magnetotail neutral sheet region. Numerical solution of the dispersion equation shows that the instability can occur under conditions expected for the neutral sheet just prior to the onset of substorm expansion. The excited waves are obliquely propagating whistlers with a mixed polarization in the lower hybrid frequency range. The ensuing turbulence of this instability can lead to a local reduction of the cross-tail current causing it to continue through the ionosphere to form a substorm current wedge. A substorm expansion onset scenario is proposed based on this instability in which the relative drift between ions and electrons is primarily due to unmagnetized ions undergoing current sheet acceleration in the presence of a cross-tail electric field. The required electric field strength is within the range of electric field values detected in the neutral sheet region during substorm intervals. The skew in local time of substorm onset location and the three conditions under which substorm onset is observed can be understood on the basis of the proposed scenario.

Nonlinear dielectric effects in liquids: a guided tour

NASA Astrophysics Data System (ADS)

Richert, Ranko

2017-09-01

Dielectric relaxation measurements probe how the polarization of a material responds to the application of an external electric field, providing information on structure and dynamics of the sample. In the limit of small fields and thus linear response, such experiments reveal the properties of the material in the same thermodynamic state it would have in the absence of the external field. At sufficiently high fields, reversible changes in enthalpy and entropy of the system occur even at constant temperature, and these will in turn alter the polarization responses. The resulting nonlinear dielectric effects feature field induced suppressions (saturation) and enhancements (chemical effect) of the amplitudes, as well as time constant shifts towards faster (energy absorption) and slower (entropy reduction) dynamics. This review focuses on the effects of high electric fields that are reversible and observed at constant temperature for single component glass-forming liquids. The experimental challenges involved in nonlinear dielectric experiments, the approaches to separating and identifying the different sources of nonlinear behavior, and the current understanding of how high electric fields affect dielectric materials will be discussed. Covering studies from Debye’s initial approach to the present state-of-the-art, it will be emphasized what insight can be gained from the nonlinear responses that are not available from dielectric relaxation results obtained in the linear regime.

Dark sector impact on gravitational collapse of an electrically charged scalar field

NASA Astrophysics Data System (ADS)

Nakonieczna, Anna; Rogatko, Marek; Nakonieczny, Łukasz

2015-11-01

Dark matter and dark energy are dominating components of the Universe. Their presence affects the course and results of processes, which are driven by the gravitational interaction. The objective of the paper was to examine the influence of the dark sector on the gravitational collapse of an electrically charged scalar field. A phantom scalar field was used as a model of dark energy in the system. Dark matter was modeled by a complex scalar field with a quartic potential, charged under a U(1)-gauge field. The dark components were coupled to the electrically charged scalar field via the exponential coupling and the gauge field-Maxwell field kinetic mixing, respectively. Complete non-linear simulations of the investigated process were performed. They were conducted from regular initial data to the end state, which was the matter dispersal or a singularity formation in a spacetime. During the collapse in the presence of dark energy dynamical wormholes and naked singularities were formed in emerging spacetimes. The wormhole throats were stabilized by the violation of the null energy condition, which occurred due to a significant increase of a value of the phantom scalar field function in its vicinity. The square of mass parameter of the dark matter scalar field potential controlled the formation of a Cauchy horizon or wormhole throats in the spacetime. The joint impact of dark energy and dark matter on the examined process indicated that the former decides what type of an object forms, while the latter controls the amount of time needed for the object to form. Additionally, the dark sector suppresses the natural tendency of an electrically charged scalar field to form a dynamical Reissner-Nordström spacetime during the gravitational collapse.

Theoretical Investigations of Dielectric Breakdown in CO2: Implications for Atmospheric Discharges on Mars (and Venus)

NASA Astrophysics Data System (ADS)

Riousset, J. A.

2017-12-01

The detection of an atmospheric discharge in the Martian atmosphere by Ruf et al. [GRL, 36, L13202, 2009] supports the idea of a Martian atmospheric electric circuit [Farrell and Desch, JGR, 106, E4, 2001]. However, the lack of subsequent detection of similar events raises the question of the conditions of their initiation, and the existence of Martian lightning remains a controversial question. On Earth, atmospheric electricity manifests itself in the form of glow, corona, streamer, and leader discharges observed as Saint Elmo's fire, sprites, lightning and jets discharges, and other Transient Luminous Events (TLEs). All of these are dielectric breakdown governed by different physics. Their initiation is associated with the crossing of specific electric field thresholds: relativistic runaway, streamer propagation, conventional breakdown, or thermal runaway thresholds, some better understood than others. For example, the initiation of a lightning discharge is known to occur when the local electric field exceeds a value similar to relativistic runaway field, but the exact threshold, as well as the physical mechanisms at work, remain unclear to date. Scaling laws for electric fields (and other quantities) have been established by Pasko et al. [GRL, 25(12), 2123-2126, 1998] and Pasko [NATO Sci. Series, Springer, 253-311, 2006]. In this work, we develop profiles for initiation criteria in air and in other atmospheric environments. We further calculate their associated scaling laws to determine the ability to trigger lightning flashes and TLEs on Mars. This lets us predict the likelihood of electrical discharges and calculate the expected electric field conditions, under which discharges could be observed. We develop the analogy between Earth sand storm [Nicoll et al., Env. Res. Lett., 6, 014001, 2001] and Martian dust storms [Melnik and Parrot, JGR, 103(A12), 1998] to investigate the charge structure and resulting electric fields necessary to initiate dielectric breakdown in the Martian atmosphere. Initiation of electric discharges will be susceptible to local pressure, density, atmospheric composition, and charge structure, and will impact charge moment variations detectable by remote sensing.

Atomistic study of mixing at high Z / low Z interfaces at Warm Dense Matter Conditions

NASA Astrophysics Data System (ADS)

Haxhimali, Tomorr; Glosli, James; Rudd, Robert; Lawrence Livermore National Laboratory Team

2016-10-01

We use atomistic simulations to study different aspects of mixing occurring at an initially sharp interface of high Z and low Z plasmas in the Warm/Hot Dense Matter regime. We consider a system of Diamond (the low Z component) in contact with Ag (the high Z component), which undergoes rapid isochoric heating from room temperature up to 10 eV, rapidly changing the solids into warm dense matter at solid density. We simulate the motion of ions via the screened Coulomb potential. The electric field, the electron density and ionizations level are computed on the fly by solving Poisson equation. The spatially varying screening lengths computed from the electron cloud are included in this effective interaction; the electrons are not simulated explicitly. We compute the electric field generated at the Ag-C interface as well as the dynamics of the ions during the mixing process occurring at the plasma interface. Preliminary results indicate an anomalous transport of high Z ions (Ag) into the low Z component (C); a phenomenon that is partially related to the enhanced transport of ions due to the generated electric field. These results are in agreement with recent experimental observation on Au-diamond plasma interface. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.

Airway smooth muscle responsiveness from dogs with airway hyperresponsiveness after O/sub 3/ inhalation

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

Jones, G.L.; O'Byrne, P.M.; Pashley, M.

1988-07-01

Airway hyperresponsiveness occurs after inhalation of O3 in dogs. The purpose of this study was to examine the responsiveness of trachealis smooth muscle in vitro to electrical field stimulation, exogenous acetylcholine, and potassium chloride from dogs with airway hyperresponsiveness after inhaled O3 in vivo and to compare this with the responsiveness of trachealis muscle from control dogs. In addition, excitatory junction potentials were measured with the use of single and double sucrose gap techniques in both groups of dogs to determine whether inhaled O3 affects the release of acetylcholine from parasympathetic nerves in trachealis muscle. Airway hyperresponsiveness developed in allmore » dogs after inhaled O3 (3 ppm for 30 min). The acetylcholine provocative concentration decreased from 4.11 mg/ml before O3 inhalation to 0.66 mg/ml after O3 (P less than 0.0001). The acetylcholine provocative concentration increased slightly after control inhalation of dry room air. Airway smooth muscle showed increased responses to both electrical field stimulation and exogenous acetylcholine but not to potassium chloride in preparations from dogs with airway hyperresponsiveness in vivo. The increased response to electrical field stimulation was not associated with a change in excitatory junctional potentials. These results suggest that a postjunctional alteration in trachealis muscle function occurs after inhaled O3 in dogs, which may account for airway hyperresponsiveness after O3 in vivo.« less

Particle-in-cell simulations of asymmetric guide-field reconnection: quadrupolar structure of Hall magnetic field

NASA Astrophysics Data System (ADS)

Schmitz, R. G.; Alves, M. V.; Barbosa, M. V. G.

2017-12-01

One of the most important processes that occurs in Earth's magnetosphere is known as magnetic reconnection (MR). This process can be symmetric or asymmetric, depending basically on the plasma density and magnetic field in both sides of the current sheet. A good example of symmetric reconnection in terrestrial magnetosphere occurs in the magnetotail, where these quantities are similar on the north and south lobes. In the dayside magnetopause MR is asymmetric, since the plasma regimes and magnetic fields of magnetosheath and magnetosphere are quite different. Symmetric reconnection has some unique signatures. For example, the formation of a quadrupolar structure of Hall magnetic field and a bipolar Hall electric field that points to the center of the current sheet. The different particle motions in the presence of asymmetries change these signatures, causing the quadrupolar pattern to be distorted and forming a bipolar structure. Also, the bipolar Hall electric field is modified and gives rise to a single peak pointing toward the magnetosheat, considering an example of magnetopause reconnection. The presence of a guide-field can also distort the quadrupolar pattern, by giving a shear angle across the current sheet and altering the symmetric patterns, according to previous simulations and observations. Recently, a quadrupolar structure was observed in an asymmetric guide-field MR event using MMS (Magnetospheric Multiscale) mission data [Peng et al., JGR, 2017]. This event shows clearly that the density asymmetry and the guide-field were not sufficient to form signatures of asymmetric reconnection. Using the particle-in-cell code iPIC3D [Markidis et al, Mathematics and Computers in Simulation, 2010] with the MMS data from this event used to define input parameters, we found a quadrupolar structure of Hall magnetic field and a bipolar pattern of Hall electric field in ion scales, showing that our results are in an excellent agreement with the MMS observations. To our knowledge, this is the first time PIC simulations show this kind of results, since previous simulations have predicted bipolar pattern in the asymmetric guide-field reconnection.

Coarsening behavior of γ' and γ″ phases in GH4169 superalloy by electric field treatment

NASA Astrophysics Data System (ADS)

Wang, Lei; Wang, Yao; Liu, Yang; Song, Xiu; Lü, Xu-dong; Zhang, Bei-jiang

2013-09-01

The coarsening behaviors of γ' and γ″ phases in GH4169 alloy aged at 1023 and 1073 K with electric field treatment (EFT) were investigated by transmission electron microscopy (TEM) and positron annihilation lifetime spectroscopy (PALS). It is demonstrated that precipitation coarsening occurs, and the growth activation energies of γ' and γ″ phases can be decreased to 115.6 and 198.1 kJ·mol-1, respectively, by applying the electric field. The formation of a large number of vacancies in the matrix is induced by EFT. Due to the occurrence of vacancy migration, the diffusion coefficients of Al and Nb atoms are increased to be 1.6-5.0 times larger than those without EFT at 1023 or 1073 K. Furthermore, the formation of vacancy clusters is promoted by EFT, and the increase in strain energy for the coarsening of γ' and γ″ phases can be counterbalanced by the formation of vacancy clusters.

Preliminary Breakdown: Physical Mechanisms and Potential for Energetic Emissions

NASA Astrophysics Data System (ADS)

Petersen, D.; Beasley, W. H.

2014-12-01

Observations and analysis of the preliminary breakdown phase of virgin negative cloud-to-ground (-CG) lightning strokes will be presented. Of primary interest are the physical processes responsible for the fast electric field "characteristic" pulses that are often observed during this phase. The pulse widths of characteristic pulses are shown to occur as a superposed bimodal distribution, with the short and long modes having characteristic timescales on the order of 1 microsecond and 10 microseconds, respectively. Analysis of these pulses is based on comparison with laboratory observations of long spark discharge processes and with recently acquired high-speed video observations of a single -CG event. It will be argued that the fast electric field bimodal distribution is the result of conventional discharge processes operating in an extensive strong ambient electric field environment. An important related topic will also be discussed, where it will be argued that preliminary breakdown discharges are capable of generating energetic electrons and may therefore seed relativistic electron avalanches that go on to produce pulsed energetic photon emissions.

Investigating Perturbation Electric Fields and Their Effects on the Coupled Low-, Mid- and High-latitude Ionosphere

DTIC Science & Technology

2015-08-14

stream (SAPS) E field had been strong. During these E field events, the repeated development of equatorial ionization anomaly ( EIA ), storm-enhanced...density (SED) bulge and SED plume occurred in those longitude sectors that covered the local dusk-midnight hours. Thus, a well-formed EIA - SED...Observational results and CTIPe simulated wind vector maps suggest that 1) the enhanced growth of the EIA transported solar produced plasma to the

Electrical Aspects of Flames in Microgravity Combustion

NASA Technical Reports Server (NTRS)

Dunn-Rankin, D.; Strayer, B.; Weinberg, F.; Carleton, F.

1999-01-01

A principal characteristic of combustion in microgravity is the absence of buoyancy driven flows. In some cases, such as for spherically symmetrical droplet burning, the absence of buoyancy is desirable for matching analytical treatments with experiments. In other cases, however, it can be more valuable to arbitrarily control the flame's convective environment independent of the environmental gravitational condition. To accomplish this, we propose the use of ion generated winds driven by electric fields to control local convection of flames. Such control can produce reduced buoyancy (effectively zero buoyancy) conditions in the laboratory in 1-g facilitating a wide range of laser diagnostics that can probe the system without special packaging required for drop tower or flight tests. In addition, the electric field generated ionic winds allow varying gravitational convection equivalents even if the test occurs in reduced gravity environments.

The Initiation of Lightning and the Growth of Electric Fields in Thunderstorms

DTIC Science & Technology

1992-12-01

characteristics and the temperature in the regions of strongest fields; which features are themselves dependent on air- mass characteristics and...climatological condsiderations. A recently identified unresolved question is why, in continental Northern Hemisphere thunderclouds at least, the sign of the... questions of primary and secondary ice production, and the development of precipitation particles. Primary ice nucleation was found to occur when the cloud

Localized Oscillatory Energy Conversion in Magnetopause Reconnection

NASA Astrophysics Data System (ADS)

Burch, J. L.; Ergun, R. E.; Cassak, P. A.; Webster, J. M.; Torbert, R. B.; Giles, B. L.; Dorelli, J. C.; Rager, A. C.; Hwang, K.-J.; Phan, T. D.; Genestreti, K. J.; Allen, R. C.; Chen, L.-J.; Wang, S.; Gershman, D.; Le Contel, O.; Russell, C. T.; Strangeway, R. J.; Wilder, F. D.; Graham, D. B.; Hesse, M.; Drake, J. F.; Swisdak, M.; Price, L. M.; Shay, M. A.; Lindqvist, P.-A.; Pollock, C. J.; Denton, R. E.; Newman, D. L.

2018-02-01

Data from the NASA Magnetospheric Multiscale mission are used to investigate asymmetric magnetic reconnection at the dayside boundary between the Earth's magnetosphere and the solar wind. High-resolution measurements of plasmas and fields are used to identify highly localized ( 15 electron Debye lengths) standing wave structures with large electric field amplitudes (up to 100 mV/m). These wave structures are associated with spatially oscillatory energy conversion, which appears as alternatingly positive and negative values of J · E. For small guide magnetic fields the wave structures occur in the electron stagnation region at the magnetosphere edge of the electron diffusion region. For larger guide fields the structures also occur near the reconnection X-line. This difference is explained in terms of channels for the out-of-plane current (agyrotropic electrons at the stagnation point and guide field-aligned electrons at the X-line).

Propagation of large-amplitude waves on dielectric liquid sheets in a tangential electric field: exact solutions in three-dimensional geometry.

PubMed

Zubarev, Nikolay M; Zubareva, Olga V

2010-10-01

Nonlinear waves on sheets of dielectric liquid in the presence of an external tangential electric field are studied theoretically. It is shown that waves of arbitrary shape in three-dimensional geometry can propagate along (or against) the electric field direction without distortion, i.e., the equations of motion admit a wide class of exact traveling wave solutions. This unusual situation occurs for nonconducting ideal liquids with high dielectric constants in the case of a sufficiently strong field strength. Governing equations for evolution of plane symmetric waves on fluid sheets are derived using conformal variables. A dispersion relation for the evolution of small perturbations of the traveling wave solutions is obtained. It follows from this relation that, regardless of the wave shape, the amplitudes of small-scale perturbations do not increase with time and, hence, the traveling waves are stable. We also study the interaction of counterpropagating symmetric waves with small but finite amplitudes. The corresponding solution of the equations of motion describes the nonlinear superposition of the oppositely directed waves. The results obtained are applicable for the description of long waves on fluid sheets in a horizontal magnetic field.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

PubMed

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

The relationship of total Birkeland currents to the merging electric field

NASA Technical Reports Server (NTRS)

Bythrow, P. F.; Potemra, T. A.

1983-01-01

Magsat data were used to examine the behavior of Birkeland currents during 1100-2000 UT in consecutive orbits passing near the dawn-dusk meridian. The field was measured with a three-axis fluxgate instrument with a resolution of within 0.5 nT, with the sampling occurring every 1/16th sec. A total of 32 crossings of the Northern Hemisphere auroral zone were available for analysis. The changes in the magnetic readings were correlated more closely with variation in the IMF parameters than to the latitudinal width of the changes. Evidence was found for a relationship between the reconnection electric field and the intensity of the large-scale Birkeland current system. The total conductance of the auroral zone was calculated to be about 18.7 mhos.

Seasonal Patterns of Melatonin, Cortisol, and Progesterone Secretion in Female Lambs Raised Beneath a 500-kV Transmission Line.

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

Lee, Jack M.

Although several kinds of biological effects of electric and magnetic fields have been reported from laboratory studies, few have been independently replicated. When this study was being planned, the suppression of nighttime melatonin in rodents was thought to represent one of the strongest known effects of these fields. The effect had been replicated by a single laboratory for 60-Hz electric fields, and by multiple laboratories for d-c magnetic fields. The primary objective of this study was to determine whether the effect of electric and magnetic fields on melatonin would also occur in sheep exposed to a high voltage transmission line.more » The specific hypothesis tested by this experiment was as follows: The electrical environment produced by a 60-Hz, 500-kV transmission line causes a depression in nocturnal melatonin in chronically exposed female lambs. This may mimic effects of pinealectomy or constant long-day photoperiods, thus delaying the onset of reproductive cycles. Results of the study do not provide evidence to support the hypothesis. Melatonin concentrations in the sheep exposed to the transmission line showed the normal pattern of low daytime and high nighttime serum levels. As compared to the control group, there were no statistically significant group differences in the mean amplitude, phase, or duration of the nighttime melatonin elevation.« less

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

Skordas, E. S., E-mail: eskordas@phys.uoa.gr

By applying Detrended Fluctuation Analysis (DFA) to the time series of the geomagnetic data recorded at three measuring stations in Japan, Rong et al. in 2012 recently reported that anomalous magnetic field variations were identified well before the occurrence of the disastrous Tohoku M{sub w}9.0 earthquake that occurred on 11 March 2011 in Japan exhibiting increased “non-uniform” scaling behavior. Here, we provide an explanation for the appearance of this increase of “non-uniform” scaling on the following grounds: These magnetic field variations are the ones that accompany the electric field variations termed Seismic Electric Signals (SES) activity which have been repeatedlymore » reported that precede major earthquakes. DFA as well as multifractal DFA reveal that the latter electric field variations exhibit scaling behavior as shown by analyzing SES activities observed before major earthquakes in Greece. Hence, when these variations are superimposed on a background of pseudosinusoidal trend, their long range correlation properties—quantified by DFA—are affected resulting in an increase of the “non-uniform” scaling behavior. The same is expected to hold for the former magnetic field variations. This explanation is strengthened by recent findings showing that the fluctuations of the order parameter of seismicity exhibited an unprecedented minimum almost two months before the Tohoku earthquake occurrence which is characteristic for an almost simultaneous emission of Seismic Electric Signals activity.« less

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: circuitry and mechanical design.

PubMed

Kia, Kaveh Kazemi; Bonabi, Fahimeh

2012-12-01

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

Removal of phenol by activated alumina bed in pulsed high-voltage electric field.

PubMed

Zhu, Li-nan; Ma, Jun; Yang, Shi-dong

2007-01-01

A new process for removing the pollutants in aqueous solution-activated alumina bed in pulsed high-voltage electric field was investigated for the removal of phenol under different conditions. The experimental results indicated the increase in removal rate with increasing applied voltage, increasing pH value of the solution, aeration, and adding Fe2+. The removal rate of phenol could reach 72.1% when air aeration flow rate was 1200 ml/min, and 88.2% when 0.05 mmol/L Fe2+ was added into the solution under the conditions of applied voltage 25 kV, initial phenol concentration of 5 mg/L, and initial pH value 5.5. The addition of sodium carbonate reduced the phenol removal rate. In the pulsed high-voltage electric field, local discharge occurred at the surface of activated alumina, which promoted phenol degradation in the thin water film. At the same time, the space-time distribution of gas-liquid phases was more uniform and the contact areas of the activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed. The synthetical effects of the pulsed high-voltage electric field and the activated alumina particles accelerated phenol degradation.

Periodic variations of atmospheric electric field on fair weather conditions at YBJ, Tibet

NASA Astrophysics Data System (ADS)

Xu, Bin; Zou, Dan; Chen, Ben Yuan; Zhang, Jin Ye; Xu, Guo Wang

2013-05-01

Observations of atmospheric electric field on fair weather conditions from the plateau station, YBJ, Tibet (90°31‧50″ E, 30°06‧38″ N), over the period from 2006 to 2011, are presented in this work. Its periodic modulations are analyzed in frequency-domain by Lomb-Scargle Periodogram method and in time-domain by folding method. The results show that the fair weather atmospheric electric field intensity is modulated weakly by annual cycle, solar diurnal cycle and its several harmonic components. The modulating amplitude of annual cycle is bigger than that of solar diurnal cycle. The annual minimum/maximum nearly coincides with spring/autumn equinox. The detailed spectrum analysis show that the secondary peaks (i.e. sidereal diurnal cycle and semi-sidereal diurnal cycle) nearly disappear along with their primary peaks when the primary signals are subtracted from electric field data sequence. The average daily variation curve exhibits dual-fluctuations, and has obviously seasonal dependence. The mean value is bigger in summer and autumn, but smaller in spring and winter. The daytime fluctuation is affected by the sunrise and sunset effect, the occurring time of which have a little shift with seasons. However, the nightly one has a great dependence on season conditions.

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

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

Kia, Kaveh Kazemi; Bonabi, Fahimeh

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 {mu}s. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through themore » graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.« less

Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

NASA Astrophysics Data System (ADS)

Kia, Kaveh Kazemi; Bonabi, Fahimeh

2012-12-01

A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

Electric field stabilization of viscous liquid layers coating the underside of a surface

NASA Astrophysics Data System (ADS)

Anderson, Thomas G.; Cimpeanu, Radu; Papageorgiou, Demetrios T.; Petropoulos, Peter G.

2017-05-01

We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a horizontal surface in the presence of an electric field applied parallel to the surface. The model includes the effect of bounding solid dielectric regions above and below the liquid-air system that are typically found in experiments. The competition between gravitational forces, surface tension, and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semispectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations using the volume-of-fluid methodology and assess the accuracy of the obtained solutions in the long-wave (thin-film) regime when varying the electric field strength from zero up to the point when complete stabilization occurs. We employ DNS to examine the limitations of the asymptotically derived behavior as the liquid layer thickness increases and find excellent agreement even beyond the regime of strict applicability of the asymptotic solution. Finally, the asymptotic and computational approaches are utilized to identify robust and efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.

Anisotropy of synthetic quartz electrical conductivity at high pressure and temperature

NASA Astrophysics Data System (ADS)

Wang, Duojun; Li, Heping; Yi, Li; Matsuzaki, Takuya; Yoshino, Takashi

2010-09-01

AC measurements of the electrical conductivity of synthetic quartz along various orientations were made between 0.1 and 1 MHz, at ˜855˜1601 K and at 1.0 GPa. In addition, the electrical conductivity of quartz along the c axis has been studied at 1.0-3.0 GPa. The impedance arcs representing bulk conductivity occur in the frequency range of 103-106 Hz, and the electrical responses of the interface between the sample and the electrode occur in the 0.1˜103 Hz range. The pressure has a weak effect on the electrical conductivity. The electrical conductivity experiences no abrupt change near the α - β phase transition point. The electrical conductivity of quartz is highly anisotropic; the electrical conductivity along the c axis is strongest and several orders of magnitude larger than in other directions. The activation enthalpies along various orientations are determined to be 0.6 and 1.2 eV orders of magnitude, respectively. The interpretation of the former is based on the contribution of alkali ions, while the latter effect is attributed to additional unassociated aluminum ions. Comparison of determined anisotropic conductivity of quartz determined with those from field geophysical models shows that the quartz may potentially provide explanations for the behavior of electrical conductivity of anisotropy in the crust that are inferred from the transverse magnetic mode.

Radiofrequency ablation: importance of background tissue electrical conductivity--an agar phantom and computer modeling study.

PubMed

Solazzo, Stephanie A; Liu, Zhengjun; Lobo, S Melvyn; Ahmed, Muneeb; Hines-Peralta, Andrew U; Lenkinski, Robert E; Goldberg, S Nahum

2005-08-01

To determine whether radiofrequency (RF)-induced heating can be correlated with background electrical conductivity in a controlled experimental phantom environment mimicking different background tissue electrical conductivities and to determine the potential electrical and physical basis for such a correlation by using computer modeling. The effect of background tissue electrical conductivity on RF-induced heating was studied in a controlled system of 80 two-compartment agar phantoms (with inner wells of 0.3%, 1.0%, or 36.0% NaCl) with background conductivity that varied from 0.6% to 5.0% NaCl. Mathematical modeling of the relationship between electrical conductivity and temperatures 2 cm from the electrode (T2cm) was performed. Next, computer simulation of RF heating by using two-dimensional finite-element analysis (ETherm) was performed with parameters selected to approximate the agar phantoms. Resultant heating, in terms of both the T2cm and the distance of defined thermal isotherms from the electrode surface, was calculated and compared with the phantom data. Additionally, electrical and thermal profiles were determined by using the computer modeling data and correlated by using linear regression analysis. For each inner compartment NaCl concentration, a negative exponential relationship was established between increased background NaCl concentration and the T2cm (R2= 0.64-0.78). Similar negative exponential relationships (r2 > 0.97%) were observed for the computer modeling. Correlation values (R2) between the computer and experimental data were 0.9, 0.9, and 0.55 for the 0.3%, 1.0%, and 36.0% inner NaCl concentrations, respectively. Plotting of the electrical field generated around the RF electrode identified the potential for a dramatic local change in electrical field distribution (ie, a second electrical peak ["E-peak"]) occurring at the interface between the two compartments of varied electrical background conductivity. Linear correlations between the E-peak and heating at T2cm (R2= 0.98-1.00) and the 50 degrees C isotherm (R2= 0.99-1.00) were established. These results demonstrate the strong relationship between background tissue conductivity and RF heating and further explain electrical phenomena that occur in a two-compartment system.

Low-Loss and Broadband Metamaterials for Negative Index and Transformational Optics Applications

DTIC Science & Technology

2012-05-22

the temporal electric field, multiplying by ǫ(ω), and then inverse Fourier transforming the result. The quantities ∂wE/∂t and ∂qE/∂t were formed...force occurs in a material with gain. Imaging and antenna opportunities are described for metal-insulator stack lenses, and analytic models are...and Transformational Optics Applications Award Number: W911NF-10-1-0492 Kevin J. Webb School of Electrical and Computer Engineering Purdue University

Theory of controlling band-width broadening in terahertz sideband generation in semiconductors by a direct current electric field

NASA Astrophysics Data System (ADS)

Liu, Houquan; Zhang, Xingchu

2017-03-01

In a semiconductor, optically excited electron-hole pairs, driven by a strong terahertz (THz) field, can recombine to create THz sidebands in the optical spectrum. The sideband spectrum exhibits a "plateau" up to a cutoff frequency of 3.17Up, where Up is the ponderomotive energy. In this letter, we predict that the bandwidth of this sideband spectrum plateau can be broadened by applying an additional direct-current (DC) electric field. We find that if applying a DC field of EDC=0.2ETHz (where EDC and ETHz are the amplitudes of the DC field and THz field, respectively), the sideband spectrum presents three plateaus with 5.8Up, 10.05Up and 16Up being the cutoff frequencies of the first, second and third plateaus, respectively. This bandwidth broadening occurs because the DC field can increase the kinetic energy that an electron-hole pair can gain from the THz field. This effect means that the bandwidth of the sideband spectrum can be controlled flexibly by changing the DC field, thereby facilitating the ultrafast electro-optical applications of THz sideband generation.

Vertical Electromagnetic Pulse (VEMP) Testing

DTIC Science & Technology

2009-09-11

3) MIL-STD-2169B: High Altitude Electromagnetic Pulse ( HEMP ) Environment. The final survivability analysis of the baseline system...Electromagnetic Pulse ( HEMP ). The first EMP situation, SREMP, occurs within the atmosphere at an altitude of less than 40 km above sea level, and possesses an...The second EMP situation, HEMP , occurs at an altitude greater than 40 km above sea level, and possesses a large electric and magnetic field over a

An analysis of the gradient-induced electric fields and current densities in human models when situated in a hybrid MRI-LINAC system

NASA Astrophysics Data System (ADS)

Liu, Limei; Trakic, Adnan; Sanchez-Lopez, Hector; Liu, Feng; Crozier, Stuart

2014-01-01

MRI-LINAC is a new image-guided radiotherapy treatment system that combines magnetic resonance imaging (MRI) with a linear accelerator (LINAC) in a single unit. One drawback is that the pulsing of the split gradient coils of the system induces an electric field and currents in the patient which need to be predicted and evaluated for patient safety. In this novel numerical study the in situ electric fields and associated current densities were evaluated inside tissue-accurate male and female human voxel models when a number of different split-geometry gradient coils were operated. The body models were located in the MRI-LINAC system along the axial and radial directions in three different body positions. Each model had a region of interest (ROI) suitable for image-guided radiotherapy. The simulation results show that the amplitudes and distributions of the field and current density induced by different split x-gradient coils were similar with one another in the ROI of the body model, but varied outside of the region. The fields and current densities induced by a split classic coil with the surface unconnected showed the largest deviation from those given by the conventional non-split coils. Another finding indicated that the distributions of the peak current densities varied when the body position, orientation or gender changed, while the peak electric fields mainly occurred in the skin and fat tissues.

Electron plasma oscillations in the Venus foreshock

NASA Technical Reports Server (NTRS)

Crawford, G. K.; Strangeway, R. J.; Russell, C. T.

1990-01-01

Plasma waves are observed in the solar wind upstream of the Venus bow shock by the Pioneer Venus Orbiter. These wave signatures occur during periods when the interplanetary magnetic field through the spacecraft position intersects the bow shock, thereby placing the spacecraft in the foreshock region. The electron foreshock boundary is clearly evident in the data as a sharp onset in wave activity and a peak in intensity. Wave intensity is seen to drop rapidly with increasing penetration into the foreshock. The peak wave electric field strength at the electron foreshock boundary is found to be similar to terrestrial observations. A normalized wave spectrum was constructed using measurements of the electron plasma frequency and the spectrum was found to be centered about this value. These results, along with polarization studies showing the wave electric field to be field aligned, are consistent with the interpretation of the waves as electron plasma oscillations.

Atmospheric Electric Field Measurements at 100 Hz and High Frequency Electric Phenomena

NASA Astrophysics Data System (ADS)

Conceição, Ricardo; Gonçalves da Silva, Hugo; Matthews, James; Bennett, Alec; Chubb, John

2016-04-01

Spectral response of Atmospheric Electric Potential Gradient (PG), symmetric to the Atmospheric Electric Field, gives important information about phenomena affecting these measurements with characteristic time-scales that appear in the spectra as specific periodicities. This is the case of urban pollution that has a clear weekly dependence and reveals itself on PG measurements by a ~7 day periodicity (Silva et al., 2014). While long-term time-scales (low frequencies) have been exhaustively explored in literature, short-term time-scales (high frequencies), above 1 Hz, have comparatively received much less attention (Anisimov et al., 1999). This is mainly because of the technical difficulties related with the storage of such a huge amount of data (for 100 Hz sampling two days of data uses a ~1 Gb file) and the response degradation of the field-meters at such frequencies. Nevertheless, important Electric Phenomena occurs for frequencies above 1 Hz that are worth pursuing, e.g. the Schumann Resonances have a signature of worldwide thunderstorm activity at frequencies that go from ~8 up to ~40 Hz. To that end the present work shows preliminary results on PG measurements at 100 Hz that took place on two clear-sky days (17th and 18th June 2015) on the South of Portugal, Évora (38.50° N, 7.91° W). The field-mill used is a JCI 131F installed in the University of Évora campus (at 2 m height) with a few trees and two buildings in its surroundings (~50 m away). This device was developed by John Chubb (Chubb, 2014) and manufactured by Chilworth (UK). It was calibrated in December 2013 and recent work by the author (who is honored in this study for his overwhelming contribution to atmospheric electricity) reveals basically a flat spectral response of the device up to frequencies of 100 Hz (Chubb, 2015). This makes this device suitable for the study of High Frequency Electric Phenomena. Anisimov, S.V., et al. (1999). On the generation and evolution of aeroelectric structures in the surface layer. J. Geophys. Res., 104(D12), 14359-14367. Chubb, J. (2014). The measurement of atmospheric electric fields using pole mounted electrostatic fieldmeters. Journal of Electrostatics 72, 295-300. Chubb, J. (2015). Limitations on the performance of 'field mill' fieldmeters with alternating electric fields. Journal of Electrostatics 78, 1-3. Silva, H.G. et al. (2014). Atmospheric electric field measurements in urban environment and the pollutant aerosol weekly dependence. Environment Research Letters, 9, 114025.

Swarm Observation of Field-Aligned Currents Associated With Multiple Auroral Arc Systems

NASA Astrophysics Data System (ADS)

Wu, J.; Knudsen, D. J.; Gillies, D. M.; Donovan, E. F.; Burchill, J. K.

2017-10-01

Auroral arcs occur in regions of upward field-aligned currents (FACs); however, the relation is not one to one, since kinetic energy of the current-carrying electrons is also important in the production of auroral luminosity. Multiple auroral arc systems provide an opportunity to study the relation between FACs and auroral brightness in detail. In this study, we have identified two types of FAC configurations in multiple parallel arc systems using ground-based optical data from the Time History of Events and Macroscale Interactions during Substorms all-sky imagers, magnetometers and electric field instruments on board the Swarm satellites. In "unipolar FAC" events, each arc is an intensification within a broad, unipolar current sheet and downward return currents occur outside of this broad sheet. In "multipolar FAC" events, multiple arc systems represent a collection of multiple up/down current pairs. By collecting 17 events with unipolar FAC and 12 events with multipolar FACs, we find that (1) unipolar FAC events occur most frequently between 20 and 21 magnetic local time and multipolar FAC events tend to occur around local midnight and within 1 h after substorm onset. (2) Arcs in unipolar FAC systems have a typical width of 10-20 km and a spacing of 25-50 km. Arcs in multipolar FAC systems are wider and more separated. (3) Upward currents with more arcs embedded have larger intensities and widths. (4) Electric fields are strong and highly structured on the edges of multiple arc system with unipolar FAC. The fact that arcs with unipolar FAC are much more highly structured than the associated currents suggests that arc multiplicity is indicative not of a structured generator deep in the magnetosphere, but rather of the magnetosphere-ionosphere coupling process.

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.

Ultra-capacitor flexible films with tailored dielectric constants using electric field assisted assembly of nanoparticles.

PubMed

Batra, Saurabh; Cakmak, Miko

2015-12-28

In this study, the chaining and preferential alignment of barium titanate nanoparticles (100 nm) through the thickness direction of a polymer matrix in the presence of an electric field is shown. Application of an AC electric field in a well-dispersed solution leads to the formation of chains of nanoparticles in discrete rows oriented with their primary axis in the E-field direction due to dielectrophoresis. The change in the orientation of these chains was quantified through statistical analysis of SEM images and was found to be dependent on E-field, frequency and viscosity. When a DC field is applied a distinct layer consisting of dense particles was observed with micro-computed tomography. These studies show that the increase in DC voltage leads to increase in the thickness of the particle rich layer along with the packing density also increasing. Increasing the mutual interactions between particles due to the formation of particle chains in the "Z"-direction decreases the critical percolation concentration above which substantial enhancement of properties occurs. This manufacturing method therefore shows promise to lower the cost of the products for a range of applications including capacitors by either enhancing the dielectric properties for a given concentration or reduces the concentration of nanoparticles needed for a given property.

Perfect Circular Dichroism in the Haldane Model

NASA Astrophysics Data System (ADS)

Ghalamkari, Kazu; Tatsumi, Yuki; Saito, Riichiro

2018-06-01

We theoretically show that perfect circular dichroism (CD) occurs in the Haldane model in which the two-dimensional (2D) material absorbs only either left-handed or right-handed circularly polarized light. Perfect CD occurs in the phase diagram of the Haldane model when the zero-field quantum Hall conductivity has a nonzero value. The coincidence of the occurrence of perfect CD and zero-field quantum Hall effect is attributed to the fact that the effect of broken time-reversal symmetry is larger than the effect of broken inversion symmetry. On the other hand, valley polarization and perfect CD occur exclusively in the phase diagram. Further, for the four regions of the phase diagram, pseudospin polarization occurs at the K and K' points in the hexagonal Brillouin zone with either the same sign or opposite sign for the K and K' points and for the valence and conduction bands. This theoretical prediction may have an impact on search for a new optical device that selects circularly polarized light controlled by the electric field.

Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

NASA Technical Reports Server (NTRS)

Pfaff, R. F.

2009-01-01

On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

``Hiss, clicks and pops'' - The enigmatic sounds of meteors

NASA Astrophysics Data System (ADS)

Finnegan, J. A.

2015-04-01

The improbability of sounds heard simultaneously with meteors allows the phenomenon to remain on the margins of scientific interest and research. This is unjustified, since these audibly perceived electric field effects indicate complex, inconsistent and still unresolved electric-magnetic coupling and charge dynamics; interacting between the meteor; the ionosphere and mesosphere; stratosphere; troposphere and the surface of the earth. This paper reviews meteor acoustic effects, presents illustrating reports and hypotheses and includes a summary of similar and additional phenomena observed during the 2013 February 15 asteroid fragment disintegration above the Russian district of Chelyabinsk. An augmenting theory involving near ground, non uniform electric field production of Ozone, as a stimulated geo-physical phenomenon to explain some hissing `meteor sounds' is suggested in section 2.2. Unlike previous theories, electric-magnetic field fluctuation rates are not required to occur in the audio frequency range for this process to acoustically emit hissing and intermittent impulsive sounds; removing the requirements of direct conversion, passive human transduction or excited, localised acoustic `emitters'. Links to the Armagh Observatory All-sky meteor cameras, electrophonic meteor research and full construction plans for an extremely low frequency (ELF) receiver are also included.

Global Dayside Ionospheric Uplift and Enhancement Associated with Interplanetary Electric Fields

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce; Mannucci, Anthony; Iijima, Byron; Abdu, Mangalathayil Ali; Sobral, Jose Humberto A.; Gonzalez, Walter; Guarnieri, Fernando; Tsuda, Toshitaka; Saito, Akinori; Yumoto, Kiyohumi;

Risk on the Horizon, Rig for Dark: Solutions to Mitigate DoD’s Reliance on the Fragile Electric Grid

DTIC Science & Technology

2013-04-01

occurring event that could disrupt the production and delivery of power is a solar storm. Solar storms can create effects in the earth’s magnetic fields ...solar storms, their potential for disruption is evident. The magnetic fields within the sun undergo a 22-year cycle during which the magnetic poles...sunspots.27 Contained in this CME are low- to medium-charged 25 “The Sun’s Magnetic Field ,” NASA’s

The Electrical Structure of Thunderstorms

NASA Technical Reports Server (NTRS)

Workman, E J; Helzer, R E; Pelsor, G T

1942-01-01

The time histories of thunderstorm charge distribution during three storms occurring during the summer of 1940 in the vicinity of the Albuquerque Airport were investigated by the use of eight synchronized recording electrometers arranged in a particular pattern over a field 1.6 kilometers above sea level.

Electric fields, electron production, and electron motion at the stripper foil in the Los Alamos Proton Storage Ring

NASA Astrophysics Data System (ADS)

Plum, M.

The beam instability at the Los Alamos Proton Storage Ring (PSR) most likely involves coupled oscillations between electrons and protons. For this instability to occur, there must be a strong source of electrons. Investigation of the various sources of electrons in the PSR had begun. Copious electron production is expected in the injection section because this section contains the stripper foil. This foil is mounted near the center of the beam pipe, and both circulating and injected protons pass through it, thus allowing ample opportunity for electron production. This paper discusses various mechanisms for electron production, beam-induced electric fields, and electron motion in the vicinity of the foil.

Tunable electronic properties of silicene/GaP heterobilayer: Effects of electric field or biaxial tensile strain

NASA Astrophysics Data System (ADS)

Zhang, Peng; Yang, Xibin; Wu, Wei; Tian, Lifen; Cui, Heping; Zheng, Kai; Jiang, Junke; Chen, Xianping; Ye, Huaiyu

2018-05-01

We systematically investigate the electronic properties the two-dimensional (2D) silicene/GaP heterobilayer by using density functional theory calculations. We find the silicene and GaP monolayer are bounded to each other via orbital hybridization, and the charge redistribution occurring at the silicene/GaP interface leads to the opening of a direct energy band gap of about 0.997 eV in silicene. Importantly, by applying external electric field, the band structure of silicene/GaP heterostructure can be effectively modulated, and a semiconductor-metal transition even emerges. These intriguing properties make the silicene/GaP heterobilayer a promising 2D material for future electronics and strain sensors.

Anti-parallel polarization switching in a triglycine sulfate organic ferroelectric insulator: The role of surface charges

NASA Astrophysics Data System (ADS)

Ma, He; Wu, Zhuangchun; Peng, Dongwen; Wang, Yaojin; Wang, Yiping; Yang, Ying; Yuan, Guoliang

2018-04-01

Four consecutive ferroelectric polarization switchings and an abnormal ring-like domain pattern can be introduced by a single tip bias of a piezoresponse force microscope in the (010) triglycine sulfate (TGS) crystal. The external electric field anti-parallel to the original polarization induces the first polarization switching; however, the surface charges of TGS can move toward the tip location and induce the second polarization switching once the tip bias is removed. The two switchings allow a ring-like pattern composed of the central domain with downward polarization and the outer domain with upward polarization. Once the two domains disappear gradually as a result of depolarization, the other two polarization switchings occur one by one at the TGS where the tip contacts. However, the backswitching phenomenon does not occur when the external electric field is parallel to the original polarization. These results can be explained according to the surface charges instead of the charges injected inside.

Observations of field-aligned currents, waves, and electric fields at substorm onset

NASA Technical Reports Server (NTRS)

Smits, D. P.; Hughes, W. J.; Cattell, C. A.; Russell, C. T.

1986-01-01

Substorm onsets, identified Pi 2 pulsations observed on the Air Force Geophysics Laboratory Magnetometer Network, are studied using magnetometer and electric field data from ISEE 1 as well as magnetometer data from the geosynchronous satellites GOES 2 and 3. The mid-latitude magnetometer data provides the means of both timing and locating the substorm onset so that the spacecraft locations with respect to the substorm current systems are known. During two intervals, each containing several onsets or intensifications, ISEE 1 observed field-aligned current signatures beginning simultaneously with the mid-latitude Pi 2 pulsation. Close to the earth broadband bursts of wave noise were observed in the electric field data whenever field-aligned currents were detected. One onset occurred when ISEE 1 and GOES 2 were on the same field line but in opposite hemispheres. During this onset ISEE 1 and GOES 2 saw magnetic signatures which appear to be due to conjugate field-aligned currents flowing out of the western end of the westward auroral electrojets. The ISEE 1 signature is of a line current moving westward past the spacecraft. During the other interval, ISEE 1 was in the near-tail region near the midnight meridian. Plasma data confirms that the plasma sheet thinned and subsequently expanded at onset. Electric field data shows that the plasma moved in the opposite direction to the plasma sheet boundary as the boundary expanded which implies that there must have been an abundant source of hot plasma present. The plasma motion was towards the center of the plasma sheet and earthwards and consisted of a series of pulses rather than a steady flow.

Scaling of Dielectric Breakdown Thresholds in Earth's and CO2-rich atmospheres: Impact for Predictions of Extraterrestrial Transient Luminous Events and Lightning Discharges

NASA Astrophysics Data System (ADS)

Riousset, J. A.

2016-12-01

Earth's atmospheric electricity manifests itself in the form of glow, corona, streamer, and leader discharges observed as Saint Elmo's fire, sprites, lightning and jets discharges, and other Transient Luminous Events (TLEs). All of these are types of dielectric breakdown, but are governed by different physics. In particular, their initiation is associated with the crossing of specific electric field thresholds: relativistic runaway, streamer propagation, conventional breakdown, or thermal runaway thresholds, some better understood than others. For example, the initiation of a lightning discharge is known to occur when the local electric field exceeds a value similar to relativistic runaway field, but the exact threshold, as well as the physical mechanisms at work, remain rather unclear to date. Scaling laws for electric fields (and other quantities) have been established by Pasko et al. [GRL, 25(12), 2123-2126, 1998] and Pasko [NATO Sci. Series, Springer, 253-311, 2006]. In this work, we develop profiles for initiation criteria in air and in other atmospheric environments. We further calculate their associated scaling laws to determine the ability to trigger lightning flashes and TLEs in our solar system. This lets us predict the likelihood of electrical discharges on, e.g., Mars, Venus and Titan, and calculate the expected electric field conditions, under which discharges have been observed on Jupiter, Saturn, Uranus, and Neptune [Leblanc et al., ISSI Spa. Sci. Series, Springer, 2008, Yair, Adv. Space Res., 50(3), 293-310, 2012]. Our results anticipate the arrival of ExoMars 2016's Schiaparelli module, which will provide the first records of electric field at the surface of the planet [Déprez et al., EGU GA, 16, 16613, 2014]. This research is also motived by the increasing probability of manned missions to Mars and the potential electrostatic hazards it may face [Yair, 2012], and by the role of electrical discharges in the creation of active radicals, some of which may be of biological importance [Miller, Science, 117, 528-529, 1953; Biochem. Biophys. Acta, 23, 480-489, 1957].

Mechanism of biological effects observed in honey bees (Apis mellifera, L. ) hived under extra-high-voltage transmission lines: implications derived from bee exposure to simulated intense electric fields and shocks

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

Bindokas, V.P.; Gauger, J.R.; Greenberg, B.

This work explores mechanisms for disturbance of honey bee colonies under a 765 kV, 60-Hz transmission line (electric (E) field = 7 kV/m) observed in previous studies. Proposed mechanisms fell into two categories: direct bee perception of enhanced in-hive E fields and perception of shock from induced currents. The adverse biological effects could be reproduced in simulations where only the worker bees were exposed to shock or to E field in elongated hive entranceways (= tunnels). We now report the results of full-scale experiments using the tunnel exposure scheme, which assesses the contribution of shock and intense E field tomore » colony disturbance. Exposure of worker bees (1400 h) to 60-Hz E fields including 100 kV/m under moisture-free conditions within a nonconductive tunnel causes no deleterious affect on colony behavior. Exposure of bees in conductive (e.g., wet) tunnels produces bee disturbance, increased mortality, abnormal propolization, and possible impairment of colony growth. We propose that this substrate dependence of bee disturbance is the result of perception of shock from coupled body currents and enhanced current densities postulated to exist in the legs and thorax of bees on conductors. Similarly, disturbance occurs when bees are exposed to step-potential-induced currents. At 275-350 nA single bees are disturbed; at 600 nA bees begin abnormal propolization behavior; and stinging occurs at 900 nA. We conclude that biological effects seen in bee colonies under a transmission line are primarily the result of electric shock from induced hive currents. This evaluation is based on the limited effects of E-field exposure in tunnels, the observed disturbance thresholds caused by shocks in tunnels, and the ability of hives exposed under a transmission line to source currents 100-1,000 times the shock thresholds.« less

Thermal and electrical transport across a magnetic quantum critical point.

PubMed

Pfau, Heike; Hartmann, Stefanie; Stockert, Ulrike; Sun, Peijie; Lausberg, Stefan; Brando, Manuel; Friedemann, Sven; Krellner, Cornelius; Geibel, Christoph; Wirth, Steffen; Kirchner, Stefan; Abrahams, Elihu; Si, Qimiao; Steglich, Frank

2012-04-25

A quantum critical point (QCP) arises when a continuous transition between competing phases occurs at zero temperature. Collective excitations at magnetic QCPs give rise to metallic properties that strongly deviate from the expectations of Landau's Fermi-liquid description, which is the standard theory of electron correlations in metals. Central to this theory is the notion of quasiparticles, electronic excitations that possess the quantum numbers of the non-interacting electrons. Here we report measurements of thermal and electrical transport across the field-induced magnetic QCP in the heavy-fermion compound YbRh(2)Si(2) (refs 2, 3). We show that the ratio of the thermal to electrical conductivities at the zero-temperature limit obeys the Wiedemann-Franz law for magnetic fields above the critical field at which the QCP is attained. This is also expected for magnetic fields below the critical field, where weak antiferromagnetic order and a Fermi-liquid phase form below 0.07 K (at zero field). At the critical field, however, the low-temperature electrical conductivity exceeds the thermal conductivity by about 10 per cent, suggestive of a non-Fermi-liquid ground state. This apparent violation of the Wiedemann-Franz law provides evidence for an unconventional type of QCP at which the fundamental concept of Landau quasiparticles no longer holds. These results imply that Landau quasiparticles break up, and that the origin of this disintegration is inelastic scattering associated with electronic quantum critical fluctuations--these insights could be relevant to understanding other deviations from Fermi-liquid behaviour frequently observed in various classes of correlated materials.

On the importance of body posture and skin modelling with respect to in situ electric field strengths in magnetic field exposure scenarios

NASA Astrophysics Data System (ADS)

Schmid, Gernot; Hirtl, Rene

2016-06-01

The reference levels and maximum permissible exposure values for magnetic fields that are currently used have been derived from basic restrictions under the assumption of upright standing body models in a standard posture, i.e. with arms laterally down and without contact with metallic objects. Moreover, if anatomical modelling of the body was used at all, the skin was represented as a single homogeneous tissue layer. In the present paper we addressed the possible impacts of posture and skin modelling in scenarios of exposure to a 50 Hz uniform magnetic field on the in situ electric field strength in peripheral tissues, which must be limited in order to avoid peripheral nerve stimulation. We considered different body postures including situations where body parts form large induction loops (e.g. clasped hands) with skin-to-skin and skin-to-metal contact spots and compared the results obtained with a homogeneous single-layer skin model to results obtained with a more realistic two-layer skin representation consisting of a low-conductivity stratum corneum layer on top of a combined layer for the cellular epidermis and dermis. Our results clearly indicated that postures with loops formed of body parts may lead to substantially higher maximum values of induced in situ electric field strengths than in the case of standard postures due to a highly concentrated current density and in situ electric field strength in the skin-to-skin and skin-to-metal contact regions. With a homogeneous single-layer skin, as is used for even the most recent anatomical body models in exposure assessment, the in situ electric field strength may exceed the basic restrictions in such situations, even when the reference levels and maximum permissible exposure values are not exceeded. However, when using the more realistic two-layer skin model the obtained in situ electric field strengths were substantially lower and no violations of the basic restrictions occurred, which can be explained by the current-limiting effect of the low-conductivity stratum corneum layer.

Polar Spacecraft Based Comparisons of Intense Electric Fields and Poynting Flux Near and Within the Plasma Sheet-Tail Lobe Boundary to UVI Images: An Energy Source for the Aurora

NASA Technical Reports Server (NTRS)

Wygant, J. R.; Keiling, A.; Cattell, C. A.; Johnson, M.; Lysak, R. L.; Temerin, M.; Mozer, F. S.; Kletzing, C. A.; Scudder, J. D.; Peterson, W.;

Polar spacecraft based comparisons of intense electric fields and Poynting flux near and within the plasma sheet-tail lobe boundary to UVI images: An energy source for the aurora

NASA Astrophysics Data System (ADS)

Wygant, J. R.; Keiling, A.; Cattell, C. A.; Johnson, M.; Lysak, R. L.; Temerin, M.; Mozer, F. S.; Kletzing, C. A.; Scudder, J. D.; Peterson, W.; Russell, C. T.; Parks, G.; Brittnacher, M.; Germany, G.; Spann, J.

2000-08-01

In this paper, we present measurements from two passes of the Polar spacecraft of intense electric and magnetic field structures associated with Alfven waves at and within the outer boundary of the plasma sheet at geocentric distances of 4-6 RE near local midnight. The electric field variations have maximum values exceeding 100 mV/m and are typically polarized approximately normal to the plasma sheet boundary. The electric field structures investigated vary over timescales (in the spacecraft frame) ranging from 1 to 30 s. They are associated with strong magnetic field fluctuations with amplitudes of 10-40 nT which lie predominantly in the plane of the plasma sheet and are perpendicular to the local magnetic field. The Poynting flux associated with the perturbation fields measured at these altitudes is about 1-2 ergs cm-2 s-1 and is directed along the average magnetic field direction toward the ionosphere. If the measured Poynting flux is mapped to ionospheric altitudes along converging magnetic field lines, the resulting energy flux ranges up to 100 ergs cm-2s-1. These strongly enhanced Poynting fluxes appear to occur in layers which are observed when the spacecraft is magnetically conjugate (to within a 1° mapping accuracy) to intense auroral structures as detected by the Polar UV Imager (UVI). The electron energy flux (averaged over a spatial resolution of 0.5° ) deposited in the ionosphere due to auroral electron beams as estimated from the intensity in the UVI Lyman-Birge-Hopfield-long filters is 15-30 ergs cm-2s-1. Thus there is evidence that these electric field structures provide sufficient Poynting flux to power the acceleration of auroral electrons (as well as the energization of upflowing ions and Joule heating of the ionosphere). During some events the phasing and ratio of the transverse electric and magnetic field variations are consistent with earthward propagation of Alfven surface waves with phase velocities of 4000-10000 km/s. During other events the phase shifts between electric and magnetic fields suggest interference between upward and downward propagating Alfven waves. The E/B ratios are about an order of magnitude larger than typical values of c/Σp, where Σp is the height integrated Pedersen conductivity. The contribution to the total energy flux at these altitudes from Poynting flux associated with Alfven waves is comparable to or larger than the contribution from the particle energy flux and 1-2 orders of magnitude larger than that estimated from the large-scale steady state convection electric field and field-aligned current system.

Interplay between Rashba interaction and electromagnetic field in the edge states of a two-dimensional topological insulator

NASA Astrophysics Data System (ADS)

Dolcini, Fabrizio

2017-02-01

The effects of Rashba interaction and electromagnetic field on the edge states of a two-dimensional topological insulator are investigated in a nonperturbative way. We show that the electron dynamics is equivalent to a problem of massless Dirac fermions propagating with an inhomogeneous velocity, enhanced by the Rashba profile with respect to the bare Fermi value vF. Despite the inelastic and time-reversal breaking processes induced by the electromagnetic field, no backscattering occurs without interaction. The photoexcited electron densities are explicitly obtained in terms of the electric field and the Rashba interaction, and are shown to fulfill generalized chiral anomaly equations. The case of a Gaussian electromagnetic pulse is analyzed in detail. When the photoexcitation occurs far from the Rashba region, the latter effectively acts as a "superluminal gate" boosting the photoexcited wave packet outside the light-cone determined by vF. In contrast, for an electric pulse overlapping the Rashba region, the emerging wave packets are squeezed in a manner that depends on the overlap area. The electron-electron interaction effects are also discussed, for both intraspin and interspin density-density coupling. The results suggest that Rashba interaction, often considered as an unwanted disorder effect, may be exploited to tailor the shape and the propagation time of photoexcited spin-polarized wave packets.

On the behavior of return stroke current and the remotely detected electric field change waveform

NASA Astrophysics Data System (ADS)

Shao, Xuan-Min; Lay, Erin; Jacobson, Abram R.

2012-04-01

After accumulating a large number of remotely recorded negative return stroke electric field change waveforms, a subtle but persistent kink was found following the main return stroke peak by several microseconds. To understand the corresponding return stroke current properties behind the kink and the general return stroke radiation waveform, we analyze strokes occurring in triggered lightning flashes for which have been measured both the channel base current and simultaneous remote electric radiation field. In this study, the channel base current is assumed to propagate along the return stroke channel in a dispersive and lossy manner. The measured channel base current is band-pass filtered, and the higher-frequency component is assumed to attenuate faster than the lower-frequency component. The radiation electric field is computed for such a current behavior and is then propagated to distant sensors. It is found that such a return stroke model is capable of very closely reproducing the measured electric waveforms at multiple stations for the triggered return strokes, and such a model is considered applicable to the common behavior of the natural return stroke as well. On the basis of the analysis, a number of other observables are derived. The time-evolving current dispersion and attenuation compare well with previously reported optical observations. The observable speed tends to agree with optical and VHF observations. Line charge density that is removed or deposited by the return stroke is derived, and the implication of the charge density distribution on leader channel decay is discussed.

A new theoretical formulation of coupling thermo-electric breakdown in LDPE film under dc high applied fields

NASA Astrophysics Data System (ADS)

Boughariou, F.; Chouikhi, S.; Kallel, A.; Belgaroui, E.

2015-12-01

In this paper, we present a new theoretical and numerical formulation for the electrical and thermal breakdown phenomena, induced by charge packet dynamics, in low-density polyethylene (LDPE) insulating film under dc high applied field. The theoretical physical formulation is composed by the equations of bipolar charge transport as well as by the thermo-electric coupled equation associated for the first time in modeling to the bipolar transport problem. This coupled equation is resolved by the finite-element numerical model. For the first time, all bipolar transport results are obtained under non-uniform temperature distributions in the sample bulk. The principal original results show the occurring of very sudden abrupt increase in local temperature associated to a very sharp increase in external and conduction current densities appearing during the steady state. The coupling between these electrical and thermal instabilities reflects physically the local coupling between electrical conduction and thermal joule effect. The results of non-uniform temperature distributions induced by non-uniform electrical conduction current are also presented for several times. According to our formulation, the strong injection current is the principal factor of the electrical and thermal breakdown of polymer insulating material. This result is shown in this work. Our formulation is also validated experimentally.

Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy.

PubMed

Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

2016-11-01

MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0-35 G in the perpendicular direction. The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater sensitivity to in-line magnetic fields than previously presented models, and different operating modes show different sensitivity.

Performance of a clinical gridded electron gun in magnetic fields: Implications for MRI-linac therapy

PubMed Central

Whelan, Brendan; Holloway, Lois; Constantin, Dragos; Oborn, Brad; Bazalova-Carter, Magdalena; Fahrig, Rebecca; Keall, Paul

2016-01-01

Purpose: MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields. Methods: The geometry of a Varian electron gun was measured using 3D laser scanning and digital calipers. The electric potentials and emission current of these guns were measured directly from six dose matched true beam linacs for the 6X, 10X, and 15X modes of operation. Based on these measurements, a finite element model (FEM) of the gun was developed using the commercial software opera/scala. The performance of the FEM model in magnetic fields was characterized using parallel fields ranging from 0 to 200 G in the in-line direction, and 0–35 G in the perpendicular direction. Results: The FEM model matched the average measured emission current to within 5% across all three modes of operation. Different high voltage settings are used for the different modes; the 6X, 10X, and 15X modes have an average high voltage setting of 15, 10, and 11 kV. Due to these differences, different operating modes show different sensitivities in magnetic fields. For in line fields, the first current loss occurs at 40, 20, and 30 G for each mode. This is a much greater sensitivity than has previously been observed. For perpendicular fields, first beam loss occurred at 8, 5, and 5 G and total beam loss at 27, 22, and 20 G. Conclusions: A validated FEM model of a clinical triode electron gun has been developed based on accurate geometric and electrical measurements. Three different operating modes were simulated, with a maximum mean error of 5%. This gun shows greater sensitivity to in-line magnetic fields than previously presented models, and different operating modes show different sensitivity. PMID:27806583

A coordinated study of a storm system over the South American continent. 1. Weather information and quasi-DC stratospheric electric field data

NASA Astrophysics Data System (ADS)

Pinto, O.; Pinto, I. R. C. A.; Gin, R. B. B.; Mendes, O.

1992-11-01

This paper reports on a coordinated campaign conducted in Brazil, December 13, 1989, to study the electrical signatures associated with a large storm system over the South American continent. Inside the storm, large convective cells developed extending up to the tropopause, as revealed from meteorological balloon soundings. Quasi-DC vertical electric field and temperature were measured by zero-pressure balloon-borne payload launched from Cachoeira Paulista, Brazil. The data were supported by radar and GOES satellite observations, as well as by a lightning position and tracking system (LPATS). The analysis of infrared imagery supports the general tendency for lightning strikes to be near to but not exactly under the coldest cloud tops. In turn, the radar maps located the strikes near to but outside of the most intense areas of precipitation (reflectivity levels above 40 dBz). The balloon altitude and stratospheric temperature show significant variations in association with the storm. The quasi-DC vertical electric field remained almost during the whole flight in a reversed direction relative to the usual fair weather downward orientation with values as large as 4 V/m. A simple calculation based on a static dipole model of electrical cloud structure gives charges of some tens of coulombs. In contrast with most electric field measurements in other regions, no indication of an intensification of the vertical field in the downward fair weather orientation was observed. This fact is in agreement with past observations in the South American region and seems to be related to a particular type of storm that would occur with more frequency in this region. If so, such a difference may have an important role in the global atmospheric electrical circuit, considering that South America is believed to give a significant current contribution to the global circuit.

Numerical simulation of a helical shape electric arc in the external axial magnetic field

NASA Astrophysics Data System (ADS)

Urusov, R. M.; Urusova, I. R.

2016-10-01

Within the frameworks of non-stationary three-dimensional mathematical model, in approximation of a partial local thermodynamic equilibrium, a numerical calculation was made of characteristics of DC electric arc burning in a cylindrical channel in the uniform external axial magnetic field. The method of numerical simulation of the arc of helical shape in a uniform external axial magnetic field was proposed. This method consists in that that in the computational algorithm, a "scheme" analog of fluctuations for electrons temperature is supplemented. The "scheme" analogue of fluctuations increases a weak numerical asymmetry of electrons temperature distribution, which occurs randomly in the course of computing. This asymmetry can be "picked up" by the external magnetic field that continues to increase up to a certain value, which is sufficient for the formation of helical structure of the arc column. In the absence of fluctuations in the computational algorithm, the arc column in the external axial magnetic field maintains cylindrical axial symmetry, and a helical form of the arc is not observed.

Particle acceleration in the dynamic magnetotail: Orbits in self-consistent three-dimensional MHD fields

NASA Technical Reports Server (NTRS)

Birn, Joachim; Hesse, Michael

1994-01-01

The acceleration of protons in a dynamically evolving magnetotail is investigated by tracing particles in the fields obtained from a three-dimensional resistive magnetohydrodynamic (MHD) simulation. The MHD simulation, representing plasmoid formation and ejection through a near-Earth reconnection process, leads to cross-tail electric fields of up to approximately 4 mV/m with integrated voltages across the tail of up to approximately 200 kV. Energization of particles takes place over a wide range along the tail, due to the large spatial extent of the increased electric field together with the finite cross-tail extent of the electric field region. Such accelerated particles appear earthward of the neutral line over a significant portion of the closed field line region inside of the separatrix, not just in the vicinity of the separatrix. Two different acceleration processes are identified: a 'quasi-potential' acceleration, due to particle motion in the direction of the cross-tail electric field, and a 'quasi-betatron' effect, which consists of multiple energy gains from repeated crossings of the acceleration region, mostly on Speiser-type orbits, in the spatially varying induced electric field. The major source region for accelerated particles in the hundreds of keV range is the central plasma sheet at the dawn flank outside the reconnection site. Since this source plasma is already hot and dense, its moderate energization by a factor of approximately 2 may be sufficient to explain the observed increases in the energetic particle fluxes. Particles from the tail are the source of beams at the plasma sheet/lobe boundary. The temporal increase in the energetic particle fluxes, estimated from the increase in energy gain, occurs on a fast timescale of a few minutes, coincident with a strong increase in B(sub z), despite the fact that the inner boundary ('injection boundary') of the distribution of energized particles is fairly smooth.

Field induced metastable ferroelectric phase in Pb 0.97La 0.03(Zr 0.90Ti 0.10) 0.9925O 3 ceramics

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

Ciuchi, I. V.; Chung, C. C.; Fancher, C. M.

2017-11-06

Pb 0.97La 0.03(Zr 0.9T i0.1)0.9925O3 (PLZT 3/90/10) ceramics prepared by solid-state reaction with the compositions near the antiferroelectric/ferroelectric (FE/AFE) phase boundary were studied. From the polarization–electric field P(E) dependence and ex situ X-ray study, an irreversible electric field induced AFE-to-FE phase transition is verified at room temperature. Dielectric and in situ temperature dependent X-ray analysis evidence that the phase transition sequence in PLZT 3/90/10-based ceramics can be readily altered by poling. A first order antiferroelectric-paraelectric (AFE-to-PE) transition occurred at ~190 °C in virgin sample and at ~180 °C in poled sample. In addition, a FE-to-AFE transition occurs in the poledmore » ceramic at much lower temperatures (~120 °C) with respect to the Curie range (~190 °C). The temperature-induced FE-to-AFE transition is diffuse and takes place in a broad temperature range of 72–135 °C. Lastly, the recovery of AFE is accompanied by an enhancement in the piezoelectric properties.« less

Kinetic Electric Field Signatures Associated with Magnetic Turbulence and Their Impact on Space Plasma Environments

NASA Astrophysics Data System (ADS)

Goodrich, K. A.

Magnetic turbulence is a universal phenomenon that occurs in space plasma physics, the small-scale processes of which is not well understood. This thesis presents on observational analysis of kinetic electric field signatures associated with magnetic turbulence, in an attempt to examine its underlying microphysics. Such kinetic signatures include small-scale magnetic holes, double layers, and phase-space holes. The first and second parts of this thesis presents observations of small-scale magnetic holes, observed depressions in total magnetic field strength with spatial widths on the order of or less than the ion Larmor radius, in the near-Earth plasmasheet. Here I demonstrate electric field signatures associated small-scale magnetic holes are consistent with the presence of electron Hall currents, currents oriented perpendicularly to the magnetic field. Further investigation of these fields indicates that the Hall electron current is primarily responsible for the depletion of | B| associated with small-scale magnetic holes. I then present evidence that suggests these currents can descend to smaller spatial scales, indicating they participate in a turbulent cascade to smaller scales, a link that has not been observable suggested until now. The last part of this thesis investigates the presence of double layers and phase-space holes in a magnetically turbulent region of the terrestrial bow shock. In this part, I present evidence that these same signatures can be generated via field-aligned currents generated by strong magnetic fluctuations. I also show that double layers and phase-space holes, embedded within localized nonlinear ion acoustic waves, correlate with localized electron heating and possible ion deceleration, indicating they play a role in turbulent dissipation of kinetic to thermal energy. This thesis clearly demonstrates that energy dissipation in turbulent plasma is closely linked to the small-scale electric field environment.

Characterizing charge centroids from lightning using a slow antenna network and the Levenberg-Marquardt inverse method

NASA Astrophysics Data System (ADS)

Lapierre, J. L.; Sonnenfeld, R. G.; Hager, W. W.; Morris, K.

2011-12-01

Researchers have long studied the copious and complex electric field waveforms caused by lightning. By combining electric-field measurements taken at many different locations on the ground simultaneously [Krehbiel et al., 1979], we hope to learn more about charge sources for lightning flashes. The Langmuir Electric Field Array (LEFA) is a network of nine field-change measurement stations (slow-antennas) arranged around Langmuir Laboratory near Magdalena, New Mexico. Using a mathematical method called the Levenberg-Marquardt (LM) method, we can invert the electric field data to determine the magnitude and position of the charge centroid removed from the cloud. We analyzed three return strokes (RS) following a dart-leader from a storm occurring on October 21st 2011. RS 'A' occurred at 07:17:00.63 UT. The altitude of the charge centroid was estimated to be 5 km via LMA data. Because the LM method requires a prediction, the code was run with a wide range of values to verify the robustness of the method. Predictions varied from ±3 C for the charge magnitude and ±20 km N-S and E-W for the position (with the coordinate origin being the Langmuir Laboratory Annex). The LM method converged to a charge magnitude of -5.5 C and a centroid position of 3.3 km E-W and 12 km, N-S for that RS. RS 'B' occurred at 07:20:05.9 UT. With an altitude of 4 km, the predictions were again varied; ±3 C, ±15 km N-S and E-W. Most runs converged to -27.5 C, 4 km E-W, and 10.9 km N-S. Finally, while results seem best for events right over the array, success was had locating more distant events. RS 'C' occurred at 02:42:46.8 UT. Assuming an altitude of 5 km and varying the predictions as with RS 'A', the results converged to -9.2 C, 35.5 km E-W, and 9 km N-S. All of these results are broadly consistent with the LMA and the NLDN. By continuing this type of analysis, we hope to learn more about how lightning channels propagate and how the charges in the cloud respond to the sudden change in charge distribution after a CG flash. Reference Krehbiel, P.R., M. Brook, and R. A. McCrory (1979), An analysis of the charge structure of lightning discharges to ground, J. Geophys. Res., 84(C5), 2432-2456. We gratefully acknowledge support from the National Science Foundation Grant No. 0724771.

Rapid fluid disruption: A source for self-potential anomalies on volcanoes

USGS Publications Warehouse

Johnston, M.J.S.; Byerlee, J.D.; Lockner, D.

2001-01-01

Self-potential (SP) anomalies observed above suspected magma reservoirs, dikes, etc., on various volcanoes (Kilauea, Hawaii; Mount Unzen, Japan; Piton de la Fournaise, Reunion Island, Miyake Jima, Japan) result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity. These SP anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained. We propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization/disruption. As liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions, both charge generation and local increase in electrical resistivity by removal of fluids should occur. We report laboratory observations of electric fields in hot rock samples generated by pulses of fluid (water) through the rock at atmospheric pressure. These indicate the relative amplitudes of rapid fluid disruption (RFD) potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign. Above vaporization temperatures, RFD effects of positive sign in the direction of gas flow dominate, whereas below these temperatures, effects of negative sign dominate. This suggests that the primary contribution to observed self-potential anomalies arises from gas-related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport. At lower temperatures, the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and RFD effects from high-pressure but low-temperature CO2 and SO2 gas flow ripping water molecules from saturated crustal rocks. If charge generation is continuous, as could well occur above a newly emplaced dike, positive static potentials will be set up that could be sustained for many years, and the simplest method for identifying these hot, active regions would be to identify the SP anomalies they generate.

Cursory examination of the zeta potential behaviors of two optical materials

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

Tesar, A.; Oja, T.

1992-01-02

When an oxide surface is placed in water, a difference in potential across the interface occurs due to dipole orientation. Hydroxyl groups or bound oxygen atoms on the oxide surface will orient adjacent water molecules which balance the dipole charge. This occurs over some small distance called the electrical double layer. Trace amounts of high field strength ions present in the vicinity of the double layer can have significant effects on the double layer. When there is movement of the oxide surface with respect to the water, a shearing of the double layer occurs. The electrical potential at this surfacemore » of shear is termed the zeta potential. The impetus for this study was to document the zeta potential behavior in water of two optical materials. (1) a multicomponent phosphate glass; and (2) Zerodur, a silicate glass-ceramic.« less

The FIELDS experiment for Solar Probe Plus

NASA Astrophysics Data System (ADS)

Bale, S.; Spp/Fields Team

2010-12-01

Many of our basic ideas on the plasma physics of acceleration, energy flow, and dissipation, and structure of the solar wind have never been rigorously confronted by direct experimental measurements in the region where these processes are actually occurring. Although Alfven waves, shocks, and magnetic reconnection are often invoked as heating mechanisms, there have never been any direct measurements of Alfvenic waves nor the associated Poynting flux nor any measurements of ion or electron kinetic energy flux in the region from 10 R_s to 30 R_s where the final stages of wind acceleration are believed to occur. The radial profiles of both slow and fast solar wind acceleration are based on remote-sensing measurements and have been obtained for only a few selected events. Thus, the spatial radial and perpendicular scales of the acceleration process have been averaged by line-of-sight effects and the possibility of intense localized acceleration cannot be ruled out. The Solar Probe Plus (SPP) mission calls for the high quality fields and particles measurements required to solve the coronal heating and wind acceleration problem. The SPP 'FIELDS' experiment measures the electric and magnetic fields fundamental to the plasma physics of the structured and turbulent solar wind, flux ropes, collisionless shocks, and magnetic reconnection. FIELDS will make the first-ever measurements of the DC/Low-Frequency electric field inside of 1 AU allowing for in situ, high cadence measurements of the Poynting vector, the Elsasser variables, and E/B diagnostics of the wave spectrum to fce in the solar wind. SPP/FIELDS measures the radio wave (type III and II) signatures of microflares, energized electrons, and CME propagation. SPP/ FIELDS measures the plasma electron density to ~2% accuracy and the core electron temperature to ~5-10% accuracy more than 90% of the time at perihelion. FIELDS will also measure the in situ density fluctuation spectrum and structures at a very high cadence (≤ 10 kHz) and provide definitive signatures of the turbulent nature and heating of the solar wind plasma. Furthermore, SPP/FIELDS measures the impact rate and sig- natures of dust from micron- to nano-scales, by measuring the voltage signature of dust impacts on the spacecraft. FIELDS will also measure the floating potential of the SPP spacecraft, which is essential for correcting in situ electron data. The SPP/FIELDS experiment combines four (4) deployable electric antennas, fluxgate and search coil magnetometers and the associated signal processing electronics into a scientifically and technically integrated package. SPP/FIELDS makes very high cadence measurements of fields and density and employs an internal burst memory for intelligent data selection. FIELDS is required to measure very large plasma potentials and electric fields (~10V) and uses floating ground (+/- 100V) power preamplifiers. The SPP/FIELDS team has performed 3D plasma simulations of the SPP spacecraft plasma environ- ment, which reveal enormous voltage fluctuation levels in the plasma wake behind the spacecraft. This voltage noise dominates the true signal by orders of magnitude in the critical DC/LF frequency range. Therefore, we are proposing a design which places the four (4) electric antennas in front of the spacecraft ahead of the heat shield.

Ferroelectric properties of a triphenylene derivative with polar functional groups in the crystalline state

NASA Astrophysics Data System (ADS)

Sugita, Atsushi; Suzuki, Kyoko; Tasaka, Shigeru

2004-06-01

We studied ferroelectric ordering in a triphenylene derivative embedded with electric dipoles [2,3,6,7,10,11-hexakis (4-octyloxy-benzoyloxy) triphenylene (HOBPT)] in a crystalline state. Experimental results indicate that the ferroelectricity in HOBPT is caused by an ordered orientation of CO dipoles. Our experiments also reveal that dielectric anomaly due to ferroelectric paraelectric phase transition occurs at 380 K . A photovoltaic effect was observed in an electrically treated thin film of HOBPT. The phenomenon results from a high charge mobility due to the π-π stack between adjacent molecules as well as an internal electric field derived by the residual polarization.

Ion evaporation from the surface of a Taylor cone.

PubMed

Higuera, F J

2003-07-01

An analysis is carried out of the electric field-induced evaporation of ions from the surface of a polar liquid that is being electrosprayed in a vacuum. The high-field cone-to-jet transition region of the electrospray, where ion evaporation occurs, is studied taking advantage of its small size and neglecting the inertia of the liquid and the space charge around the liquid. Evaporated ions and charged drops coexist in a range of flow rates, which is investigated numerically. The structure of the cone-to-jet transition comprises: a hydrodynamic region where the nearly equipotential surface of the liquid departs from a Taylor cone and becomes a jet; a slender region where the radius of the jet decreases and the electric field increases while the pressure and the viscous stress balance the electric stress at the surface; the ion evaporation region of high, nearly constant field; and a charged, continuously strained jet that will eventually break into drops. Estimates of the ion and drop contributions to the total, conduction-limited current show that the first of these contributions dominates for small flow rates, while most of the mass is still carried by the drops.

Two substorm studies of relations between westward electric fields in the outer plasmasphere, auroral activity, and geomagnetic perturbations

NASA Technical Reports Server (NTRS)

Carpenter, D. L.; Akasofu, S.

1972-01-01

Temporal variations of the westward component of the magnetospheric convection electric field in the outer plasmasphere were compared to auroral activity near L = 7, and to variations in the geomagnetic field at middle and high latitudes. The substorms occurred on July 29, 1965 near 0530 UT and on August 20, 1965 near 0730 UT. The results on westward electric field E(w) were obtained by the whistler method using data from Eights, Antarctica (L is approximately 4). All sky camera records were obtained from Byrd, Antarctica, (L is approximately 7), located within about 1 hour of Eights in magnetic local time. It was found that E(w) within the outer plasmasphere increased rapidly to substorm levels about the time of auroral expansion at nearby longitudes. This behavior is shown to differ from results on E(w) from balloons, which show E(w) reaching enhanced levels prior to the expansion. A close temporal relation was found between the rapid, substorm associated increases in E(w) and a well known type of nightside geomagnetic perturbation. Particularly well defined was the correlation of E(w) rise and a large deviation of the D component at middle latitudes.

Sampling and Reconstruction of the Pupil and Electric Field for Phase Retrieval

NASA Technical Reports Server (NTRS)

Dean, Bruce; Smith, Jeffrey; Aronstein, David

2012-01-01

This technology is based on sampling considerations for a band-limited function, which has application to optical estimation generally, and to phase retrieval specifically. The analysis begins with the observation that the Fourier transform of an optical aperture function (pupil) can be implemented with minimal aliasing for Q values down to Q = 1. The sampling ratio, Q, is defined as the ratio of the sampling frequency to the band-limited cut-off frequency. The analytical results are given using a 1-d aperture function, and with the electric field defined by the band-limited sinc(x) function. Perfect reconstruction of the Fourier transform (electric field) is derived using the Whittaker-Shannon sampling theorem for 1

Electrical model of dielectric barrier discharge homogenous and filamentary modes

NASA Astrophysics Data System (ADS)

López-Fernandez, J. A.; Peña-Eguiluz, R.; López-Callejas, R.; Mercado-Cabrera, A.; Valencia-Alvarado, R.; Muñoz-Castro, A.; Rodríguez-Méndez, B. G.

2017-01-01

This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results.

Partially disordered antiferromagnetism and multiferroic behavior in a frustrated Ising system CoCl 2 – 2 SC ( NH 2 ) 2

DOE PAGES

Mun, Eundeok; Weickert, Dagmar Franziska; Kim, Jaewook; ...

2016-03-01

We investigate partially disordered antiferromagnetism in CoCl 2-2SC(NH 2) 2, in which ab-plane hexagonal layers are staggered along the c axis rather than stacked. A robust 1/3 state forms in applied magnetic fields in which the spins are locked, varying as a function of neither temperature nor field. By contrast, in zero field and applied fields at higher temperatures, partial antiferromagnetic order occurs, in which free spins are available to create a Curie-like magnetic susceptibility. We report measurements of the crystallographic structure and the specific heat, magnetization, and electric polarization down to T = 50mK and up to μ0H =more » 60T. The Co 2+ S = 3/2 spins are Ising-like and form distorted hexagonal layers. The Ising energy scale is well separated from the magnetic exchange, and both energy scales are accessible to the measurements, allowing us to cleanly parametrize them. In transverse fields, a quantum Ising phase transition can be observed at 2 T. Lastly, we find that magnetic exchange striction induces changes in the electric polarization up to 3μC/m 2, and single-ion magnetic anisotropy effects induce a much larger electric polarization change of 300μC/m 2.« less

Immunity of medical electrical equipment to radiated RF disturbances

NASA Astrophysics Data System (ADS)

Mocha, Jan; Wójcik, Dariusz; Surma, Maciej

2018-04-01

Immunity of medical equipment to radiated radio frequency (RF) electromagnetic (EM) fields is a priority issue owing to the functions that the equipment is intended to perform. This is reflected in increasingly stringent normative requirements that medical electrical equipment has to conform to. A new version of the standard concerning electromagnetic compatibility of medical electrical equipment IEC 60601-1-2:2014 has recently been published. The paper discusses major changes introduced in this edition of the standard. The changes comprise more rigorous immunity requirements for medical equipment as regards radiated RF EM fields and a new requirement for testing the immunity of medical electrical equipment to disturbances coming from digital radio communication systems. Further on, the paper presents two typical designs of the input block: involving a multi-level filtering and amplification circuit and including a solution which integrates an input amplifier and an analog-to-digital converter in one circuit. Regardless of the applied solution, presence of electromagnetic disturbances in the input block leads to demodulation of the disturbance signal envelope. The article elaborates on mechanisms of amplitude detection occurring in such cases. Electromagnetic interferences penetration from the amplifier's input to the output is also described in the paper. If the aforementioned phenomena are taken into account, engineers will be able to develop a more conscious approach towards the issue of immunity to RF EM fields in the process of designing input circuits in medical electrical equipment.

Linear Stability of Relativistic Space-Charge Flow in a Magnetically Insulated Transmission Line Oscillator

DTIC Science & Technology

1989-04-01

MILO Magnetica fy insulated transmission line Slow-wave structure Relativistic Brillouin flow Space-charge waves Slow electromagnetic waves (over) 19... resonant layer always see a decelerating axial electric field. Consequently, field energy increases at the expense of particle energy. 17 AFWL-TR-88-103...Ve). If ve is greater than the structure coupling velocity, a resonant layer of electrons will always be present, and oscillations will occur at any

Investigation of the inverse piezoelectric effect of trabecular bone on a micrometer length scale using synchrotron radiation.

PubMed

Wieland, D C F; Krywka, C; Mick, E; Willumeit-Römer, R; Bader, R; Kluess, D

2015-10-01

In the present paper we have investigated the impact of electro stimulation on microstructural parameters of the major constituents of bone, hydroxyapatite and collagen. Therapeutic approaches exhibit an improved healing rate under electric fields. However, the underlying mechanism is not fully understood so far. In this context one possible effect which could be responsible is the inverse piezo electric effect at bone structures. Therefore, we have carried out scanning X-ray microdiffraction experiments, i.e. we recorded X-ray diffraction data with micrometer resolution using synchrotron radiation from trabecular bone samples in order to investigate how the bone matrix reacts to an applied electric field. Different samples were investigated, where the orientation of the collagen matrix differed with respect to the applied electric field. Our experiments aimed to determine whether the inverse piezo electric effect could have a significant impact on the improved bone regeneration owing to electrostimulative therapy. Our data suggest that strain is in fact induced in bone by the collagen matrix via the inverse piezo electric effect which occurs in the presence of an adequately oriented electric field. The magnitude of the underlying strain is in a range where bone cells are able to detect it. In our study we report on the piezoelectric effect in bone which was already discovered and explored on a macro scale in the 1950. Clinical approaches utilize successfully electro stimulation to enhance bone healing but the exact mechanisms taking place are still a matter of debate. We have measured the stress distribution with micron resolution in trabecular bone to determine the piezo electric induced stress. Our results show that the magnitude of the induced stress is big enough to be sensed by cells and therefore, could be a trigger for bone remodeling and growth. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Electron Demagnetization and Collisionless Magnetic Reconnection in βe ≪ 1 Plasmas: Theory and Observations

NASA Astrophysics Data System (ADS)

Scudder, J. D.; Mozer, F. S.

2005-05-01

Abrupt, intense bipolar and unipolar electric spikes with E > 100mV/m surveyed over 3 years of Polar data (Mozer et al 2005) have been organized to answer the limited question: can they be involved in the local demagnetization of thermal electrons? We determine a lower bound on the electric strength sufficient to cause non-gyrotropic effects on the electron pressure tensor of the form E>E*=B{we}/{8c Im}, where B is the ambient magnetic field strength, we=√2kTe/me, c is the speed of light, and Im is an electron velocity space weighted average displacement along the electric field while transiting the layer (assumed localized with a scale Δ x=a ρe, where ρe is the electron thermal gyroradius). The variation of Im as a function of a for equal mean energy Maxwellian and more typical κ distributions seen in the Earth's magnetosphere provides strong evidence that the surveyed electric field spikes are generally smaller than E* (assuming ≍ 1), although 23% (n=57) exceed E* . Only 11% (n=6) of the bipolar class exceed E* ; the frequency of occurrence distribution for the bipolar class of spikes is peaked at 0.1E*. The unipolar occurrence is flat below E*, but has a significant 26% subgroup (n=51) that exceed E* . While E* does not depend on the ambient density, the occurrence distribution of all demagnetizing events is well organized by the ratio ℜ=λDe/ρe=&Omegace/ωpe, residing almost exclusively in the regime ℜ <1. Spikes with E < E* generally occur with ℜ >1 . All the electrostatic spike events surveyed occur in the regime 10-8≤βe≤3×10-2. The demagnetizing events of either class occupy the more restricted low beta regime 10-3≤βe≤3×10-2. Because these demagnetizing events occur in βe ≪ 1 they would not, however, be considered unmagnetized at current channels as thin as the electron skin depth, de, since for such current channels ρe ≡ βe-1/2de ≪ de. As a group the subset of unipolar events with E > E* are consistently understood as sites where the electron pressure tensor could become deformed from cylindrical symmetry by electric field enhancement in layers with scale sizes up to the local thermal electron's gyroradius. Such a deformation is critical for a viable mechanism that supports collisionless reconnection. After selecting events as demagnetizing based on the size of the relevant forces and work done, the geophysical locale of their detection has been investigated. Previously, all E spikes in this survey were found near the invariant latitudes Λ of the earth's magnetic cusps but at all magnetic local times. The demagnetizing events identified here via E* are strongly organized at magnetic local noon (with a secondary, much shallower maximum at local magnetic midnight), occur preferentially at orbit apogee, and without significant preference for the magnetic latitude of the spacecraft. These geophysical organizations are consistent with the demagnetizing E spikes as indices of ongoing, collisionless reconnection in low βe regimes at the earth's subsolar magnetopause. The identification of this sub-class of electric spikes at low βe with E>E* widens the observed venues in the E and B fields where topology changing departures from ideal MHD should be anticipated in collisionless astrophysical plasmas.

Zonal Drift Variations and Suppression of Ionospheric Scintillation During St. Patrick's Day Storm Observed by Pingtung SCINDA Station in Taiwan

NASA Astrophysics Data System (ADS)

Su, S. Y.; Nayak, C.; Tsai, L. C.; Caton, R. G.; Groves, K. M.

2016-12-01

Variations of zonal drift and ionospheric VHF scintillations observed by a SCINDA station in Southern Taiwan during the St. Patrick's day geomagnetic storm are studied. Although scintillations were observed for 6 consecutive days before the storm, they were absence during the storm period. Data from VHF receivers, ionosonde and in situ plasma density observations from ESA's SWARM constellation are used to study the ionospheric irregularity/scintillation events in the Taiwanese sector to compare with what happened in the Indian sectors. The absence of scintillation in the Taiwanese sector during the storm period seems to be caused by a reduced pre-reversal enhancement (PRE) electric field from a westward prompt-penetration electric field (PPEF) during the storm. A low post-sunset ionosphere thus becomes unfavorable for the Rayleigh-Taylor instability to occur. On the contrary, the PPEFs were found to strongly enhance the PRE electric field in the Indian sector to cause the ionospheric irregularities/scintillations in the post-sunset sector. Zonal drift variations during the storm time are also discussed in conjunction with the irregularity/scintillation occurrences.

The Effect of a Guide Field on Local Energy Conversion During Asymmetric Magnetic Reconnection: Particle-in-Cell Simulations

NASA Astrophysics Data System (ADS)

Cassak, P. A.; Genestreti, K. J.; Burch, J. L.; Phan, T.-D.; Shay, M. A.; Swisdak, M.; Drake, J. F.; Price, L.; Eriksson, S.; Ergun, R. E.; Anderson, B. J.; Merkin, V. G.; Komar, C. M.

2017-11-01

We use theory and simulations to study how the out-of-plane (guide) magnetic field strength modifies the location where the energy conversion rate between the electric field and the plasma is appreciable during asymmetric magnetic reconnection, motivated by observations (Genestreti et al., 2017). For weak guide fields, energy conversion is maximum on the magnetospheric side of the X line, midway between the X line and electron stagnation point. As the guide field increases, the electron stagnation point gets closer to the X line, and energy conversion occurs closer to the electron stagnation point. We motivate one possible nonrigorous approach to extend the theory of the stagnation point location to include a guide field. The predictions are compared to two-dimensional particle-in-cell (PIC) simulations with vastly different guide fields. The simulations have upstream parameters corresponding to three events observed with Magnetospheric Multiscale (MMS). The predictions agree reasonably well with the simulation results, capturing trends with the guide field. The theory correctly predicts that the X line and stagnation points approach each other as the guide field increases. The results are compared to MMS observations, Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) observations of each event, and a global resistive-magnetohydrodynamics simulation of the 16 October 2015 event. The PIC simulation results agree well with the global observations and simulation but differ in the strong electric fields and energy conversion rates found in MMS observations. The observational, theoretical, and numerical results suggest that the strong electric fields observed by MMS do not represent a steady global reconnection rate.

Conductivity versus Dielectric Mechanisms for Electrorheology

NASA Astrophysics Data System (ADS)

Davis, L. C.

1997-03-01

Electrorheological (ER) fluids are continuously and rapidly controllable by an electric field. Controllability of these materials permits the construction of novel intelligent systems such as semiactively controlled shock absorbers and vibration dampers, tunable composite beams and panels, and even reconfigurable Braille arrays. The eventual success of these applications depends in part on developing improved ER fluids, which requires a fundamental understanding of the physics and chemistry of these materials. ER fluids generally consist of highly polarizable colloidal particles suspended in an insulating oil. Particles are typically 1-10 microns in diameter and can be of a wide variety of materials including zeolites, barium titanate, conducting polymers, and oxide-coated metals. Electric fields of magnitude 1-5 kV/mm induce particle chaining and concomitant shear stresses of order 1 kPa. Recent experiments (J. M. Ginder and S. L. Ceccio, J. Rheol. 39, 211 (1995)) using square-wave electric-field excitation have helped to elucidate the mechanisms of ER activity. Immediately after a step-function increase of electric field, chaining occurs due to particle-particle forces arising from dielectric polarization (dipoles and higher multipoles), i.e., it is controlled by the dielectric mismatch between particles and fluid. On a longer time scale, currents flow in the fluid and in the particles so that the forces are eventually dominated by the conductivity mismatch. Characteristic times for the transition between the two regimes are 10-50 ms. Likewise, in the frequency domain, conductivity mismatch dominates the dc response of ER fluids whereas dielectric effects dominate for high frequencies. A theory of ER fluids is given including a model for non-linear effects at high electric fields.

Probing resonant energy transfer in collisions of ammonia with Rydberg helium atoms by microwave spectroscopy

NASA Astrophysics Data System (ADS)

Zhelyazkova, V.; Hogan, S. D.

2017-12-01

We present the results of experiments demonstrating the spectroscopic detection of Förster resonance energy transfer from NH3 in the X1A1 ground electronic state to helium atoms in 1sns 3S1 Rydberg levels, where n = 37 and n = 40. For these values of n, the 1sns 3S1 → 1snp 3PJ transitions in helium lie close to resonance with the ground-state inversion transitions in NH3 and can be tuned through resonance using electric fields of less than 10 V/cm. In the experiments, energy transfer was detected by direct state-selective electric field ionization of the 3S1 and 3PJ Rydberg levels and by monitoring the population of the 3DJ levels following pulsed microwave transfer from the 3PJ levels. Detection by microwave spectroscopic methods represents a highly state selective, low-background approach to probing the collisional energy transfer process and the environment in which the atom-molecule interactions occur. The experimentally observed electric-field dependence of the resonant energy transfer process, probed both by direct electric field ionization and by microwave transfer, agrees well with the results of calculations performed using a simple theoretical model of the energy transfer process. For measurements performed in zero electric field with atoms prepared in the 1s40s 3S1 level, the transition from a regime in which a single energy transfer channel can be isolated for detection to one in which multiple collision channels begin to play a role has been identified as the NH3 density was increased.

Ephemeral Electric Potential and Electric Field Sensor

NASA Technical Reports Server (NTRS)

Generazio, Edward R. (Inventor)

2017-01-01

Systems, methods, and devices of the various embodiments provide for the minimization of the effects of intrinsic and extrinsic leakage electrical currents enabling true measurements of electric potentials and electric fields. In an embodiment, an ephemeral electric potential and electric field sensor system may have at least one electric field sensor and a rotator coupled to the electric field sensor and be configured to rotate the electric field sensor at a quasi-static frequency. In an embodiment, ephemeral electric potential and electric field measurements may be taken by rotating at least one electric field sensor at a quasi-static frequency, receiving electrical potential measurements from the electric field sensor when the electric field sensor is rotating at the quasi-static frequency, and generating and outputting images based at least in part on the received electrical potential measurements.

Occupational exposure to electromagnetic fields from medical sources

PubMed Central

STAM, Rianne; YAMAGUCHI-SEKINO, Sachiko

2017-01-01

High exposures to electromagnetic fields (EMF) can occur near certain medical devices in the hospital environment. A systematic assessment of medical occupational EMF exposure could help to clarify where more attention to occupational safety may be needed. This paper seeks to identify sources of high exposure for hospital workers and compare the published exposure data to occupational limits in the European Union. A systematic search for peer-reviewed publications was conducted via PubMed and Scopus databases. Relevant grey literature was collected via a web search. For each publication, the highest measured magnetic flux density or internal electric field strength per device and main frequency component was extracted. For low frequency fields, high action levels may be exceeded for magnetic stimulation, MRI gradient fields and movement in MRI static fields. For radiofrequency fields, the action levels may be exceeded near devices for diathermy, electrosurgery and hyperthermia and in the radiofrequency field inside MRI scanners. The exposure limit values for internal electric field may be exceeded for MRI and magnetic stimulation. For MRI and magnetic stimulation, practical measures can limit worker exposure. For diathermy, electrosurgery and hyperthermia, additional calculations are necessary to determine if SAR limits may be exceeded in some scenarios. PMID:29109357

The Peculiar Electrical Properties of the 8-12th September, 2015 Massive Dust Outbreak Over the Levant

NASA Astrophysics Data System (ADS)

Yair, Y.; Katz, S.; Price, C.; Ziv, B.; Yaniv, R.

2016-12-01

Dust storms over the Levant and Eastern Mediterranean region are common and occur several times a year, depending on synoptic systems and meteorological parameters. Such storms are often accompanied by large electrical charging, most likely due to triboelectric processes (Esposito et al., 2016). The effects of dust storms on atmospheric electricity parameters such as the fair weather electric field (Ez) and current density (Jz) are well documented, but have not been extensively studied for the Levant region. We report new measurements conducted during the massive dust outbreak that occurred over the region in September 08-12, 2015. That event was one of the strongest dust storms on record and engulfed the entire region for 5 consecutive days, from Iraq through Syria, Jordan, Israel, Lebanon, the Eastern Mediterranean Sea, Cyprus and Egypt. Ground-based measurements of Ez and Jz were conducted at the Wise Observatory (WO) in Mizpe-Ramon (30035'N, 34045'E) and at Mt. Hermon (30024'N, 35051'E). The Aerosol Optical Thickness (AOT) obtained from the AERONET station in Sde-Boker reached values up to 4.0. During the dust outbreak very large fluctuations in the electrical parameters were measured at both stations, however remarkable differences were noted. While at the Mt. Hermon station we registered strong positive values of the electric field and current density, the values registered at WO were significantly smaller and more negative. The Mt. Hermon site showed Ez and Jz values fluctuating between -460 and +570 V m-1 and -14.5 and +18 pA m-2 respectively. In contrast, Ez values registered at WO were between -430 and +10 V m-1, while the Jz fluctuated between -6 and +3 pA m-2 .When compared with the February 2015 electrified dust storm reported by Yair et al. (2016), we note substantial differences in the electric parameters variability, amplitude and polarity. The possible reasons for these differences will be discussed.

The University of Iowa Helios solar wind plasma wave experiment /E 5a/. [using spectrum analyzer-electric field antenna system

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Anderson, R. R.; Odem, D. L.

1975-01-01

This document describes the University of Iowa solar wind plasma wave experiment for the Helios missions (Experiment 5a). The objective of this experiment is the investigation of naturally occurring plasma instabilities and electromagnetic waves in the solar wind. To carry out this investigation, the experiment consists primarily of a 16-channel spectrum analyzer connected to the electric field antennas. The spectrum analyzer covers the frequency range from 20 Hz to 200 kHz and has an amplitude dynamic range which extends from .3 microvolts/m to 30 mV/m per channel. This spectrum analyzer, the antenna potential measurements, the shock alarm system and the supporting electronics are discussed in detail.

Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios

NASA Astrophysics Data System (ADS)

van den Ende, D. A.; Maier, R. A.; van Neer, P. L. M. J.; van der Zwaag, S.; Randall, C. A.; Groen, W. A.

2013-01-01

In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT—polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the composites are compared to those of PZT-polymer composites with equiaxed particles, continuous PZT fiber-polymer composites, and bulk PZT ceramics. From high-field polarization and strain measurements, the effective field dependent permittivity and piezoelectric charge constant in the poling direction are determined for dielectrophoresis structured PZT-polymer composites, continuous PZT fiber-polymer composites, and bulk PZT ceramics. The changes in dielectric properties of the inclusions and the matrix at high fields influence the dielectric and piezoelectric properties of the composites. It is found that the permittivity and piezoelectric charge constants increase towards a maximum at an applied field of around 2.5-5 kV/mm. The electric field at which the maximum occurs depends on the aspect ratio and degree of alignment of the inclusions. Experimental values of d33 at low and high applied fields are compared to a model describing the composites as a continuous polymer matrix containing PZT particles of various aspect ratios arranged into chains. Thickness mode coupling factors were determined from measured impedance data using fitted equivalent circuit model simulations. The relatively high piezoelectric strain constants, voltage constants, and thickness coupling factors indicate that such aligned short fiber composites could be useful as flexible large area transducers.

Spatial and temporal dependence of the convective electric field in Saturn’s inner magnetosphere

NASA Astrophysics Data System (ADS)

Andriopoulou, M.; Roussos, E.; Krupp, N.; Paranicas, C.; Thomsen, M.; Krimigis, S.; Dougherty, M. K.; Glassmeier, K.-H.

2014-02-01

The recently established presence of a convective electric field in Saturn’s inner and middle magnetosphere, with an average pointing approximately towards midnight and an intensity less than 1 mV/m, is one of the most puzzling findings by the Cassini spacecraft. In order to better characterize the properties of this electric field, we augmented the original analysis method used to identify it (Andriopoulou et al., 2012) and applied it to an extended energetic electron microsignature dataset, constructed from observations at the vicinity of four saturnian moons. We study the average characteristics of the convective pattern and additionally its temporal and spatial variations. In our updated dataset we include data from the recent Cassini orbits and also microsignatures from the two moons, Rhea and Enceladus, allowing us to further extend this analysis to cover a greater time period as well as larger radial distances within the saturnian magnetosphere. When data from the larger radial range and more recent orbits are included, we find that the originally inferred electric field pattern persists, and in fact penetrates at least as far in as the orbit of Enceladus, a region of particular interest due to the plasma loading that takes place there. We perform our electric field calculations by setting the orientation of the electric field as a free, time-dependent parameter, removing the pointing constraints from previous works. Analytical but also numerical techniques have been employed, that help us overcome possible errors that could have been introduced from simplified assumptions used previously. We find that the average electric field pointing is not directed exactly at midnight, as we initially assumed, but is found to be stably displaced by approximately 12-32° from midnight, towards dawn. The fact, however, that the field’s pointing is much more variable in short time scales, in addition to our observations that it penetrates inside the orbit of Enceladus (∼4 Rs), may suggest that the convective pattern is dominating all the way down to the main rings (2.2 Rs), when data from the Saturn Orbit Insertion are factored in. We also report changes of the electric field strength and pointing over the course of time, possibly related to seasonal effects, with the largest changes occurring during a period that envelopes the saturnian equinox. Finally, the average electric field strength seems to be sensitive to radial distance, exhibiting a drop as we move further out in the magnetosphere, confirming earlier results. This drop-off, however, appears to be more intense in the earlier years of the mission. Between 2010 and 2012 the electric field is quasi-uniform, at least between the L-shells of Tethys and Dione. These new findings provide constraints in the possible electric field sources that might be causing such a convection pattern that has not been observed before in other planetary magnetospheres. The very well defined values of the field’s average properties may suggest a periodic variation of the convective pattern, which can average out very effectively the much larger changes in both pointing and intensity over short time scales, although this period cannot be defined. The slight evidence of changes in the properties across the equinox (seasonal control), may also hint that the source of the electric field resides in the planet’s atmosphere/ionosphere system.

Finite element analysis of hysteresis effects in piezoelectric transducers

NASA Astrophysics Data System (ADS)

Simkovics, Reinhard; Landes, Hermann; Kaltenbacher, Manfred; Hoffelner, Johann; Lerch, Reinhard

2000-06-01

The design of ultrasonic transducers for high power applications, e.g. in medical therapy or production engineering, asks for effective computer aided design tools to analyze the occurring nonlinear effects. In this paper the finite-element-boundary-element package CAPA is presented that allows to model different types of electromechanical sensors and actuators. These transducers are based on various physical coupling effects, such as piezoelectricity or magneto- mechanical interactions. Their computer modeling requires the numerical solution of a multifield problem, such as coupled electric-mechanical fields or magnetic-mechanical fields as well as coupled mechanical-acoustic fields. With the reported software environment we are able to compute the dynamic behavior of electromechanical sensors and actuators by taking into account geometric nonlinearities, nonlinear wave propagation and ferroelectric as well as magnetic material nonlinearities. After a short introduction to the basic theory of the numerical calculation schemes, two practical examples will demonstrate the applicability of the numerical simulation tool. As a first example an ultrasonic thickness mode transducer consisting of a piezoceramic material used for high power ultrasound production is examined. Due to ferroelectric hysteresis, higher order harmonics can be detected in the actuators input current. Also in case of electrical and mechanical prestressing a resonance frequency shift occurs, caused by ferroelectric hysteresis and nonlinear dependencies of the material coefficients on electric field and mechanical stresses. As a second example, a power ultrasound transducer used in HIFU-therapy (high intensity focused ultrasound) is presented. Due to the compressibility and losses in the propagating fluid a nonlinear shock wave generation can be observed. For both examples a good agreement between numerical simulation and experimental data has been achieved.

Impact of a static magnetic field on the electricity production of Shewanella-inoculated microbial fuel cells.

PubMed

Li, Wen-Wei; Sheng, Guo-Ping; Liu, Xian-Wei; Cai, Pei-Jie; Sun, Min; Xiao, Xiang; Wang, Yun-Kun; Tong, Zhong-Hua; Dong, Fang; Yu, Han-Qing

2011-06-15

The electricity production of Shewanella-inoculated microbial fuel cells (MFCs) under magnetic field (MF) exposure was investigated in different reactor systems. The persistency of the MF effect and the influences of MF intensity and direction on MFC performance were also studied. Application of a 100-mT static MF to the MFCs improved electricity production considerably, with an increase in the maximum voltage by 20-27% in both single- and two-chamber MFCs, while a more conspicuous improvement in the electricity generation was observed in a three-electrode cell. The MF effects were found to be immediate and reversible, and adverse effects seemed to occur when the MF was suddenly removed. The medium components analysis demonstrated that the application of MF led to an enhanced bioelectrochemical activity of Shewanella, and no significant promotion in mediator secretion was found. The improvement in the electricity production of MFCs under MF was mainly attributed to the enhanced bioelectrochemical activity, possibly through the oxidative stress mechanism. An accelerated cell growth under MF might also contribute to the enhanced substrate degradation and power generation. Copyright © 2010 Elsevier B.V. All rights reserved.

Electric-field sensors for bullet detection systems

NASA Astrophysics Data System (ADS)

Vinci, Stephen; Hull, David; Ghionea, Simon; Ludwig, William; Deligeorges, Socrates; Gudmundsson, Thorkell; Noras, Maciej

2014-06-01

Research and experimental trials have shown that electric-field (E-field) sensors are effective at detecting charged projectiles. E-field sensors can likely complement traditional acoustic sensors, and help provide a more robust and effective solution for bullet detection and tracking. By far, the acoustic sensor is the most prevalent technology in use today for hostile fire defeat systems due to compact size and low cost, yet they come with a number of challenges that include multipath, reverberant environments, false positives and low signal-to-noise. Studies have shown that these systems can benefit from additional sensor modalities such as E-field sensors. However, E-field sensors are a newer technology that is relatively untested beyond basic experimental trials; this technology has not been deployed in any fielded systems. The U.S. Army Research Laboratory (ARL) has conducted live-fire experiments at Aberdeen Proving Grounds (APG) to collect data from E-field sensors. Three types of E-field sensors were included in these experiments: (a) an electric potential gradiometer manufactured by Quasar Federal Systems (QFS), (b) electric charge induction, or "D-dot" sensors designed and built by the Army Research Lab (ARL), and (c) a varactor based E-field sensor prototype designed by University of North Carolina-Charlotte (UNCC). Sensors were placed in strategic locations near the bullet trajectories, and their data were recorded. We analyzed the performance of each E-field sensor type in regard to small-arms bullet detection capability. The most recent experiment in October 2013 allowed demonstration of improved versions of the varactor and D-dot sensor types. Results of new real-time analysis hardware employing detection algorithms were also tested. The algorithms were used to process the raw data streams to determine when bullet detections occurred. Performance among the sensor types and algorithm effectiveness were compared to estimates from acoustics signatures and known ground truth. Results, techniques and configurations that might work best for a given sensor platform are discussed.

Effects of convection electric field on the distribution of ring current type protons

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.; Chen, A. J.

1975-01-01

The topology of the boundaries of penetration (or, inversely, the boundaries of the forbidden regions) of 90-deg pitch-angle equatorial protons with energies less than 100 keV are explored for an equatorial convection E-field which is directed in general from dawn to dusk. Due to the dependence of drift path on energy (or magnetic moment), complex structural features are expected in the proton energy spectra detected by satellites since the penetration distance of a proton is not a monotonically increasing or decreasing function of energy. During a storm when the convection E is enhanced, model calculations predict elongations of the forbidden regions analogous to tail extensions of the plasmasphere. Following a reduction in the convection field, spiral-structured forbidden regions can occur. Structural features inherent to large-scale convection field changes may be seen in the nose-like proton spectrograms observed near dusk by instrumentation on Explorer 45. These nose events are modelled by using an electric field model developed originally by Volland (1973). The strength of the field is related to the Kp index through night-time equatorial plasmapause measurements.

The effect of an electric field on electron attachment to SF6 in non-polar liquids

NASA Astrophysics Data System (ADS)

Bakale, G.; Schmidt, W. F.

Sulfur hexafluoride is widely used as a gaseous insulator in high voltage equipment which is primarily attributable to the electronegative nature of the SF6 molecule. Due to this property, electrons readily attach to SF6 and potential electron avalanches are thereby quenched. Several reports have been published in which the effect of SF6 on the insulating behavior of transformer oil was investigated and where SF6 was found to influence breakdown at different stages of the discharge. In view of the finding that the electron attachment rate constant, k/sub s/, becomes field dependent in liquid Ar and Xe at fields where u/sub e/ is field dependent, it was of obvious interest to determine if the same phenomena occurred in liquid hydrocarbons. Therefore, the effect of the electric field, F, on k/sub s/, at F = 50 to 200 kV/cm was studied in the two liquids in which detailed field dependent studies of u/sub e/7, 8/ had been made, viz. ethane and propane. Results are presented and discussed.

Simulating TGF and gamma ray emission above and within stormclouds due to the interaction of TeV cosmic ray shower electrons/positrons/photons with plausible electric field geometries generated in stormclouds.

NASA Astrophysics Data System (ADS)

Connell, P. H.

2017-12-01

The University of Valencia has developed a software simulator LEPTRACK to simulate lepton and photon scattering in any kind of media with a variable density, and permeated by electric/magnetic fields of any geometry, and which can handle an exponential runaway avalanche. Here we show results of simulating the interaction of electrons/positrons/photons in an incoming TeV cosmic ray shower with the kind of electric fields expected in a stormcloud after a CG discharge which removes much of the positive charge build up at the centre of the cloud. The point is to show not just a Relativistic Runaway Electron Avalanche (RREA) above the upper negative shielding layer at 12 km but other gamma ray emission due to electron/positron interaction in the remaining positive charge around 9km and the lower negative charge at 6km altitude. We present here images, lightcurves, altitude profiles, spectra and videos showing the different ionization, excitation and photon density fields produced, their time evolution, and how they depend critically on where the cosmic ray shower beam intercepts the electric field geometry. We also show a new effect of incoming positrons, which make up a significant fraction of the shower, where they appear to "orbit" within the high altitude negative shielding layer, and which has been conjectured to produce significant microwave emission, as well as a short range 511 keV annihilation line. The interesting question is if this conjectured emission can be observed and correlated with TGF orbital observations to prove that a TGF originates in the macro-fields of stormclouds or the micro-fields of light leaders and streamers where this "positron orbiting" is not likely to occur.

Non-Gaussian Multi-resolution Modeling of Magnetosphere-Ionosphere Coupling Processes

NASA Astrophysics Data System (ADS)

Fan, M.; Paul, D.; Lee, T. C. M.; Matsuo, T.

2016-12-01

The most dynamic coupling between the magnetosphere and ionosphere occurs in the Earth's polar atmosphere. Our objective is to model scale-dependent stochastic characteristics of high-latitude ionospheric electric fields that originate from solar wind magnetosphere-ionosphere interactions. The Earth's high-latitude ionospheric electric field exhibits considerable variability, with increasing non-Gaussian characteristics at decreasing spatio-temporal scales. Accurately representing the underlying stochastic physical process through random field modeling is crucial not only for scientific understanding of the energy, momentum and mass exchanges between the Earth's magnetosphere and ionosphere, but also for modern technological systems including telecommunication, navigation, positioning and satellite tracking. While a lot of efforts have been made to characterize the large-scale variability of the electric field in the context of Gaussian processes, no attempt has been made so far to model the small-scale non-Gaussian stochastic process observed in the high-latitude ionosphere. We construct a novel random field model using spherical needlets as building blocks. The double localization of spherical needlets in both spatial and frequency domains enables the model to capture the non-Gaussian and multi-resolutional characteristics of the small-scale variability. The estimation procedure is computationally feasible due to the utilization of an adaptive Gibbs sampler. We apply the proposed methodology to the computational simulation output from the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) magnetosphere model. Our non-Gaussian multi-resolution model results in characterizing significantly more energy associated with the small-scale ionospheric electric field variability in comparison to Gaussian models. By accurately representing unaccounted-for additional energy and momentum sources to the Earth's upper atmosphere, our novel random field modeling approach will provide a viable remedy to the current numerical models' systematic biases resulting from the underestimation of high-latitude energy and momentum sources.

An optical levitation system for a physics teaching laboratory

NASA Astrophysics Data System (ADS)

Isaksson, Oscar; Karlsteen, Magnus; Rostedt, Mats; Hanstorp, Dag

2018-02-01

We describe an experimental system based on optical levitation of an oil droplet. When combined with an applied electric field and a source of ionizing radiation, the setup permits the investigation of physical phenomena such as radiation pressure, light diffraction, the motion of a charged particle in an oscillating electric field, and the interaction of ionizing radiation with matter. The trapping occurs by creating an equilibrium between a radiation pressure force and the force of gravity. We have found that an oil droplet can be trapped for at least nine hours. The system can be used to measure the size and total electric charge on the trapped droplet. The intensity of the light from the trapping laser that is scattered by the droplet is sufficient to allow the droplet to be easily seen with the naked eye, covered by laser alignment goggles. When oscillating under the influence of an ac electric field, the motion of the droplet can be described as that of a driven, damped harmonic oscillator. The magnitude and polarity of the charge can be altered by exposing the droplet to ionizing radiation from a low-activity radioactive source. Our goal was to design a hands-on setup that allows undergraduate and graduate students to observe and better understand fundamental physical processes.

Spontaneous Droplet Jump with Electro-Bouncing

NASA Astrophysics Data System (ADS)

Schmidt, Erin; Weislogel, Mark

2016-11-01

We investigate the dynamics of water droplet jumps from superhydrophobic surfaces in the presence of an electric field during a step reduction in gravity level. In the brief free-fall environment of a drop tower, when a strong non-homogeneous electric field (with a measured strength between 0 . 39 and 2 . 36 kV/cm) is imposed, body forces acting on the jumped droplets are primarily supplied by polarization stress and Coulombic attraction instead of gravity. The droplet charge, measured to be on the order of 2 . 3 . (10-11) C, originates by electro-osmosis of charged species at the (PTFE coated) hydrophobic surface interface. This electric body force leads to a droplet bouncing behavior similar to well-known phenomena in 1-g, though occurring for larger drops 0.1 mL for a given range of impact Weber numbers, We < 20 . In 1-g, for We > 0 . 4 , impact recoil behavior on a super-hydrophobic surface is normally dominated by damping from contact line hysteresis and by air-layer interactions. However, in the strong electric field, the droplet bounce dynamics additionally include electrohydrodynamic effects on wettability and Cassie-Wenzel transition. This is qualitatively discussed in terms of coefficients of restitution and trends in contact time. This work was supported primarily by NASA Cooperative Agreement NNX12A047A.

Resistive spectroscopy coupled with non-contacting oscillator for detecting discontinuous-continuous transition of metallic films

NASA Astrophysics Data System (ADS)

Nakamura, N.; Ogi, H.

2017-09-01

In spectroscopic measurements, one measures responses of specimens to oscillating fields (including electric, magnetic, and stress fields) at different frequencies for characterizing the samples. In contrast, we develop spectroscopy where the response (loss) is measured by changing the electric resistance, named the resistive spectroscopy. In the resistive spectroscopy, an energy-loss peak appears when the resistance is changed. We here apply it for studying the morphological change of thin films. When a metallic material is deposited on a substrate, the morphological transition from discontinuous islands to the continuous film occurs. It accompanies a drastic change in the resistance of the deposited material because of the transition from an insulator to a conductor. We find that the energy-loss peak appears at the transition moment during deposition of Ag. The resistive spectroscopy we develop uses no electrodes; it adopts the electric field generated by a piezoelectric material vibrating at its resonant frequency beneath the substrate. It is observed that the full width at half maximum (FWHM) of the resonance shows the peak during the deposition for high resistance substrates. The FWHM peak fails to be found for low resistance substrates, but it appears when the resonance frequency is increased. We propose an electrical-circuit model for explaining these observations.

Magnetically-induced electric polarization in an organo-metallic magnet

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

Zapf, W S; Fabris, F W; Balakirev, F F

2009-01-01

The coupling between magnetic order and ferroelectricity has been under intense investigation in a wide range of transition metal oxides. The strongest coupling is obtained in so-called magnetically induced multiferroics where ferroelectricity arises directly from magnetic order that breaks inversion symmetry. However, it has been difficult to find non-oxide based materials in which these effects occur. Here we present a study of copper dimethyl sulfoxide dichloride (CDC), an organometallic quantum magnet containing S =1/1 Cu spins, in which a switchable electric polarization arises from field-tuned magnetic order. Fast magnetic field pulses allow us to perform sensitive measurements of the electricmore » polarization and demonstrate that the electric state is present only if the magnetic order is non-collinear. Furthermore, we show that the electric polarization can be switched in a stunning hysteretic fashion. Because the magnetic order in CDC is mediated by large organic molecules, our study shows that magnetoelectric interactions can exist in this important class of materials, opening the road to designing magnetoelectrics and multiferroics using large molecules as building blocks. Further, we demonstrate that CDC undergoes a magnetoelectric quantum phase transition -the first of its kind, where both ferroelectric and magnetic order emerge simultaneously as a function of magnetic field at very low temperatures.« less

A weak electric field-assisted ultrafast electrical switching dynamics in In3SbTe2 phase-change memory devices

NASA Astrophysics Data System (ADS)

Pandey, Shivendra Kumar; Manivannan, Anbarasu

2017-07-01

Prefixing a weak electric field (incubation) might enhance the crystallization speed via pre-structural ordering and thereby achieving faster programming of phase change memory (PCM) devices. We employed a weak electric field, equivalent to a constant small voltage (that is incubation voltage, Vi of 0.3 V) to the applied voltage pulse, VA (main pulse) for a systematic understanding of voltage-dependent rapid threshold switching characteristics and crystallization (set) process of In3SbTe2 (IST) PCM devices. Our experimental results on incubation-assisted switching elucidate strikingly one order faster threshold switching, with an extremely small delay time, td of 300 ps, as compared with no incubation voltage (Vi = 0 V) for the same VA. Also, the voltage dependent characteristics of incubation-assisted switching dynamics confirm that the initiation of threshold switching occurs at a lower voltage of 0.82 times of VA. Furthermore, we demonstrate an incubation assisted ultrafast set process of IST device for a low VA of 1.7 V (˜18 % lesser compared to without incubation) within a short pulse-width of 1.5 ns (full width half maximum, FWHM). These findings of ultrafast switching, yet low power set process would immensely be helpful towards designing high speed PCM devices with low power operation.

Investigation of the broadband ELF turbulence by observations of the FAST satellite

NASA Astrophysics Data System (ADS)

Golovchanskaya, I. V.; Kozelov, B. V.; Despirak, I. V.

2012-07-01

Scaling properties of variable electric fields in the topside ionosphere have been investigated on scales s from ˜30 m to 2 km by FAST electric field observations with sample rate of 512 s-1, in sixteen events of the broadband ELF turbulence. It is shown that down to scales of a few hundred meters, the power of turbulent electric fluctuations is a power law, ˜ s α. Scaling index α derived from the slope of logarithmic diagrams (LD) constructed by the discrete wavelet transform of data can be estimated as α = 2.2 ± 0.3, which is close to α estimate earlier reported for scales 1-30 km by electric field observations of the Dynamics Explorer 2 satellite. The behavior of α index is analyzed near the scale of the order of electron inertial length λe = c/ω0 (ω0 being the electron plasma frequency). At altitudes considered (700-2500 km), λe makes 100-900 m. We demonstrate that at scales ≤λe, a decrease of LD slope and deviation from the power law are typically observed. As pointed out in the discussion, this feature cannot be identified as a transition to the diffusion range, where dissipation of the turbulence occurs.

Tripolar electric field Structure in guide field magnetic reconnection

NASA Astrophysics Data System (ADS)

Fu, Song; Huang, Shiyong; Zhou, Meng; Ni, Binbin; Deng, Xiaohua

2018-03-01

It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

Calculation of surface potentials at the silica–water interface using molecular dynamics: Challenges and opportunities

NASA Astrophysics Data System (ADS)

Lowe, Benjamin M.; Skylaris, Chris-Kriton; Green, Nicolas G.; Shibuta, Yasushi; Sakata, Toshiya

2018-04-01

Continuum-based methods are important in calculating electrostatic properties of interfacial systems such as the electric field and surface potential but are incapable of providing sufficient insight into a range of fundamentally and technologically important phenomena which occur at atomistic length-scales. In this work a molecular dynamics methodology is presented for interfacial electric field and potential calculations. The silica–water interface was chosen as an example system, which is highly relevant for understanding the response of field-effect transistors sensors (FET sensors). Detailed validation work is presented, followed by the simulated surface charge/surface potential relationship. This showed good agreement with experiment at low surface charge density but at high surface charge density the results highlighted challenges presented by an atomistic definition of the surface potential. This methodology will be used to investigate the effect of surface morphology and biomolecule addition; both factors which are challenging using conventional continuum models.

Numerical analysis of real gas MHD flow on two-dimensional self-field MPD thrusters

NASA Astrophysics Data System (ADS)

Xisto, Carlos M.; Páscoa, José C.; Oliveira, Paulo J.

2015-07-01

A self-field magnetoplasmadynamic (MPD) thruster is a low-thrust electric propulsion space-system that enables the usage of magnetohydrodynamic (MHD) principles for accelerating a plasma flow towards high speed exhaust velocities. It can produce an high specific impulse, making it suitable for long duration interplanetary space missions. In this paper numerical results obtained with a new code, which is being developed at C-MAST (Centre for Mechanical and Aerospace Technologies), for a two-dimensional self-field MPD thruster are presented. The numerical model is based on the macroscopic MHD equations for compressible and electrically resistive flow and is able to predict the two most important thrust mechanisms that are associated with this kind of propulsion system, namely the thermal thrust and the electromagnetic thrust. Moreover, due to the range of very high temperatures that could occur during the operation of the MPD, it also includes a real gas model for argon.

Magnetosphere-ionosphere coupling during substorm onset

NASA Technical Reports Server (NTRS)

Maynard, N. C.; Burke, W. J.; Erickson, G. M.; Basinka, E. M.; Yahnin, A. G.

1996-01-01

Through the analysis of a combination of CRRES satellite measurements and ground-based measurements, an empirical scenario was developed for the onset of substorms. The process develops from ripples at the inner edge of the plasma sheet associated with dusk to dawn excursions of the electric field, prior to the beginning of dipolarization. The importance of Poynting flux is considered. Substorms develop when significant amounts of energy flow in both directions with the second cycle stronger than the initial cycle. Pseudobreakups occur when the energy flowing in both directions is weak or out of phase. The observations indicate that the dusk to dawn excursions of the cross-tail electric field correlate with changes in currents and particle energies observed by CRRES, and with ultra low frequency wave activity observed on the ground. Magnetic signatures of field aligned current filaments, associated with the substorm current wedge were observed to be initiated by the process.

Parametric electroconvection in a weakly conducting fluid in a horizontal parallel-plate capacitor

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

Kartavykh, N. N.; Smorodin, B. L., E-mail: bsmorodin@yandex.ru; Il’in, V. A.

2015-07-15

We study the flows of a nonuniformly heated weakly conducting fluid in an ac electric field of a horizontal parallel-plate capacitor. Analysis is carried out for fluids in which the charge formation is governed by electroconductive mechanism associated with the temperature dependence of the electrical conductivity of the medium. Periodic and chaotic regimes of fluid flow are investigated in the limiting case of instantaneous charge relaxation and for a finite relaxation time. Bifurcation diagrams and electroconvective regimes charts are constructed. The regions where fluid oscillations synchronize with the frequency of the external field are determined. Hysteretic transitions between electroconvection regimesmore » are studied. The scenarios of transition to chaotic oscillations are analyzed. Depending on the natural frequency of electroconvective system and the external field frequency, the transition from periodic to chaotic oscillations can occur via quasiperiodicity, a subharmonic cascade, or intermittence.« less

Negative ion source

DOEpatents

Delmore, James E.

1987-01-01

A method and apparatus for providing a negative ion source accelerates electrons away from a hot filament electron emitter into a region of crossed electric and magnetic fields arranged in a magnetron configuration. During a portion of the resulting cycloidal path, the electron velocity is reduced below its initial value. The electron accelerates as it leaves the surface at a rate of only slightly less than if there were no magnetic field, thereby preventing a charge buildup at the surface of the emitter. As the electron traverses the cycloid, it is decelerated during the second, third, and fourth quadrants, then reeccelerated as it approaches the end of the fourth quadrant to regain its original velocity. The minimum velocity occurs during the fourth quadrant, and corresponds to an electron temperature of 200.degree. to 500.degree. for the electric and magnetic fields commonly encountered in the ion sources of magnetic sector mass spectrometers. An ion source using the above-described thermalized electrons is also disclosed.

Variational electric fields at low latitudes and their relation to spread F and plasma irregularities

NASA Technical Reports Server (NTRS)

Holtet, J. A.; Maynard, N. C.; Heppner, J. P.

1976-01-01

Recordings from OGO 6 show that electric field irregularities are frequently present between + or - 35 deg geomagnetic latitude in the 2000 - 0600 local time sector. The signatures are very clear, and are easily distinguished from the normal AC background noise, and whistler and emission activity. The spectral appearance of the fields makes it meaningful to distinguish between 3 different types of irregularities: strong irregularities, weak irregularities, and weak irregularities with a rising spectrum. Strong irregularities seem most likely to occur in regions where gradients in ionization are present. Changes in plasma composition, resulting in an increase in the mean ion mass, are also often observed in the irregularity regions. Comparison with ground based ionosondes indicates a connection between strong irregularities and low latitude spread F. A good correlation is also present between strong fields and small scale fluctuations in ionization, delta N/N 1 percent. From the data it appears as if a gradient driven instability is the most likely source of the strong irregularities.

Computing by physical interaction in neurons.

PubMed

Aur, Dorian; Jog, Mandar; Poznanski, Roman R

2011-12-01

The electrodynamics of action potentials represents the fundamental level where information is integrated and processed in neurons. The Hodgkin-Huxley model cannot explain the non-stereotyped spatial charge density dynamics that occur during action potential propagation. Revealed in experiments as spike directivity, the non-uniform charge density dynamics within neurons carry meaningful information and suggest that fragments of information regarding our memories are endogenously stored in structural patterns at a molecular level and are revealed only during spiking activity. The main conceptual idea is that under the influence of electric fields, efficient computation by interaction occurs between charge densities embedded within molecular structures and the transient developed flow of electrical charges. This process of computation underlying electrical interactions and molecular mechanisms at the subcellular level is dissimilar from spiking neuron models that are completely devoid of physical interactions. Computation by interaction describes a more powerful continuous model of computation than the one that consists of discrete steps as represented in Turing machines.

Mapping and energization in the magnetotail. II - Particle acceleration

NASA Technical Reports Server (NTRS)

Kaufmann, Richard L.; Larson, Douglas J.; Lu, Chen

1993-01-01

Mapping with the Tsyganenko (1989) or T89 magnetosphere model has been examined previously. In the present work, an attempt is made to evaluate quantitatively what the selection of T89 implies for steady-state particle energization. The Heppner and Maynard (1987) or HM87 electric field model is mapped from the ionosphere to the equatorial plane, and the electric currents associated with T89 are evaluated. Consideration is also given to the nature of the acceleration that occurs when cross-tail current is suddenly diverted to the ionosphere.

Mass spectrometric characterization of a high-field asymmetric waveform ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Purves, Randy W.; Guevremont, Roger; Day, Stephen; Pipich, Charles W.; Matyjaszczyk, Matthew S.

1998-12-01

Ion mobility spectrometry (IMS) has become an important method for the detection of many compounds because of its high sensitivity and amenability to miniaturization for field-portable monitoring; applications include detection of narcotics, explosives, and chemical warfare agents. High-field asymmetric waveform ion mobility spectrometry (FAIMS) differs from IMS in that the electric fields are applied using a high-frequency periodic asymmetric waveform, rather than a dc voltage. Furthermore, in FAIMS the compounds are separated by the difference in the mobility of ions at high electric field relative to low field, rather than by compound to compound differences in mobility at low electric field (IMS). We report here the first cylindrical-geometry-FAIMS interface with mass spectrometry (FAIMS-MS) and the MS identification of the peaks observed in a FAIMS compensation voltage (CV) spectrum. Using both an electrometer-based-FAIMS (FAIMS-E) and FAIMS-MS, several variables that affect the sensitivity of ion detection were examined for two (polarity reversed) asymmetric waveforms (modes 1 and 2) each of which yields a unique spectrum. An increase in the dispersion voltage (DV) was found to improve the sensitivity and separation observed in the FAIMS CV spectrum. This increase in sensitivity and the unexpected dissimilarity in modes 1 and 2 suggest that atmospheric pressure ion focusing is occurring in the FAIMS analyzer. The sensitivity and peak locations in the CV spectra were affected by temperature, gas flow rates, operating pressure, and analyte concentration.

Latitude-dependent delay in the responses of the equatorial electrojet and Sq currents to X-class solar flares

NASA Astrophysics Data System (ADS)

Nogueira, Paulo A. B.; Abdu, Mangalathayil A.; Souza, Jonas R.; Denardini, Clezio M.; Barbosa Neto, Paulo F.; Serra de Souza da Costa, João P.; Silva, Ana P. M.

2018-01-01

We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field.

Atmosphere-Ionosphere Electrodynamic Coupling

NASA Astrophysics Data System (ADS)

Sorokin, V. M.; Chmyrev, V. M.

Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the formation of plasma density inhomogeneities, the excitation of gamma ray bursts and atmospheric emissions in different spectral bands, the generation of ULF/ELF/VLF electromagnetic waves and plasma turbulence in the ionosphere, the stimulation of radiation belt electron precipitations and the acceleration of ions in the upper ionosphere. The most interesting results of experimental and theoretical studies of these phenomena are discussed below. The ionosphere is subject to the action of the conductive electric current flowing in the atmosphere-ionosphere circuit. We present a physical model of DC electric field and current formation in this circuit. The key element of this model is an external current, which is formed with the occurrence of convective upward transport of charged aerosols and their gravitational sedimentation in the atmosphere. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization and change of electrical conductivity. Variation of conductivity and external current in the lower atmosphere leads to perturbation of the electric current flowing in the global atmosphere-ionosphere circuit and to the associated DC electric field perturbation both on the Earth's surface and in the ionosphere. Description of these processes and some results of the electric field and current calculations are presented below. The seismic-induced electric field perturbations produce noticeable effects in the ionosphere by generating the electromagnetic field and plasma disturbances. We describe the generation mechanisms of such experimentally observed effects as excitation of plasma density inhomogeneities, field-aligned currents, and ULF/ELF emissions and the modification of electron and ion altitude profiles in the upper ionosphere. The electrodynamic model of the ionosphere modification under the influence of some natural and man-made processes in the atmosphere is also discussed. The model is based on the satellite and ground measurements of electromagnetic field and plasma perturbations and on the data on atmospheric radioactivity and soil gas injection into the atmosphere.

The magnetic evolution of AR 6555 which lead to two impulsive, readily compact, X-type flares

NASA Technical Reports Server (NTRS)

Ambastha, A.; Fontenla, J. M.; Kalman, B.; Csepura, GY.

1995-01-01

We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 23-26 Mar. 1991. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first, but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity, and have very similar characteristics (soft X-ray light curves, energies, etc.). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares. (1) The flares occurred near regions of large magnetic 'shear,' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares, and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenla and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available data we suggest that these changes made the flaring possible, and we develop a scenario that can explain the origin of the magnetic free energy that was released in these flares.

The Magnetic Evolution of AR 6555 which led to Two Impulsive, Relatively Compact, X-Type Flares

NASA Technical Reports Server (NTRS)

Fontenla, J. M.; Ambastha, A.; Kalman, B.; Csepura, Gy.

1995-01-01

We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 1991 March 23-26. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity and have very similar characteristics (soft X-ray light curves, energies, etc,). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares: (1) The flares occurred near regions of large magnetic 'shear' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenia and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available data we suggest that these changes made the flaring possible, and we develop a scenario that can explain the origin of the magnetic free-energy that was released in these flares.

Vertical motion of a charged colloidal particle near an AC polarized electrode with a nonuniform potential distribution: theory and experimental evidence.

PubMed

Fagan, Jeffrey A; Sides, Paul J; Prieve, Dennis C

2004-06-08

Electroosmotic flow in the vicinity of a colloidal particle suspended over an electrode accounts for observed changes in the average height of the particle when the electrode passes alternating current at 100 Hz. The main findings are (1) electroosmotic flow provides sufficient force to move the particle and (2) a phase shift between the purely electrical force on the particle and the particle's motion provides evidence of an E2 force acting on the particle. The electroosmotic force in this case arises from the boundary condition applied when faradaic reactions occur on the electrode. The presence of a potential-dependent electrode reaction moves the likely distribution of electrical current at the electrode surface toward uniform current density around the particle. In the presence of a particle the uniform current density is associated with a nonuniform potential; thus, the electric field around the particle has a nonzero radial component along the electrode surface, which interacts with unbalanced charge in the diffuse double layer on the electrode to create a flow pattern and impose an electroosmotic-flow-based force on the particle. Numerical solutions are presented for these additional height-dependent forces on the particle as a function of the current distribution on the electrode and for the time-dependent probability density of a charged colloidal particle near a planar electrode with a nonuniform electrical potential boundary condition. The electrical potential distribution on the electrode, combined with a phase difference between the electric field in solution and the electrode potential, can account for the experimentally observed motion of particles in ac electric fields in the frequency range from approximately 10 to 200 Hz.

Ionospheric modification using relativistic electron beams

NASA Technical Reports Server (NTRS)

Banks, Peter M.; Fraser-Smith, Anthony C.; Gilchrist, B. E.

1990-01-01

The recent development of comparatively small electron linear accelerators (linacs) now makes possible a new class of ionospheric modification experiments using beams of relativistic electrons. These experiments can potentially provide much new information about the interactions of natural relativistic electrons with other particles in the upper atmosphere, and it may also make possible new forms of ionization structures extending down from the lower ionosphere into the largely un-ionized upper atmosphere. The consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere are investigated. If a small pitch angle with respect to the ambient geomagnetic field is selected, the beam produces a narrow column of substantial ionization extending down from the source altitude to altitudes of approximately 40 to 45 km. This column is immediately polarized by the natural middle atmosphere fair weather electric field and an increasingly large potential difference is established between the column and the surrounding atmosphere. In the regions between 40 to 60 km, this potential can amount to many tens of kilovolts and the associated electric field can be greater than the field required for breakdown and discharge. Under these conditions, it may be possible to initiate lightning discharges along the initial ionization channel. Filamentation may also occur at the lower end to drive further currents in the partially ionized gases of the stratosphere. Such discharges would derive their energy from the earth-ionosphere electrical system and would be sustained until plasma depletion and/or electric field reduction brought the discharge under control. It is likely that this artificially-triggered lightning would produce measurable low-frequency radiation.

The generation of post noon F3 layers over the dip equatorial location of Thiruvananthapuram- A new perspective

NASA Astrophysics Data System (ADS)

Mridula, N.; Pant, Tarun Kumar

2018-05-01

In the present paper, occurrence of post noon F3 layers over Thiruvananthapuram (8.5°N; 77°E; dip latitude ∼ 1.5 °N), a dip equatorial station in India have been investigated. F3 layers that occur beyond 13 IST and as observed using ground based ionosonde, for the years 2004-2008 have been studied. Our analysis shows that post noon F3 layers occur mostly on CEJ days around 16 IST to 18 IST. It is found that the time of the ionospheric E-region electric field reversal as inferred from collocated ground based magnetometer observations plays a crucial role in the generation of post noon F3 layers. In fact an early reversal of electric field emerged to be the necessary condition for the formation of post noon F3 layers. A time delay of three to 4 h is observed between the electric field reversal and the formation of F3 layer. It is proposed that this early reversal causes enhanced ionization over dip equatorial region, providing an additional ion drag to the flow of thermospheric zonal wind. This leads to accumulation of more ionization and neutrals culminating in the generation of post noon F3 layers as in the case of pre noon F3 layers. These results reveal that the generation of post noon F3 layers over the dip equatorial region is a natural consequence of the variability associated with the spatio-temporal evolution of EIA and prevailing thermospheric and ionospheric dynamics, and adds a new perspective to the present understanding.

Electrical Rectification in Betaine Derivatives

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

Sumpter, Bobby G; Meunier, Vincent; Filho, Antonio G. Souza

2008-01-01

We theoretically investigate the electric rectification in an organic two terminal push-pull molecular device using a combination of ab initio techniques. Our main finding is that the electric rectification is extremely sensitive to the length of the chain, undergoing a complete switching after a specific chain length. This unique process occurs for betainelike donor- bridge-acceptor systems and is directly associated with a conjugated bridge in the presence of an external electric field. The conjugated bridge between the donor and acceptor groups is composed of oligoethylene with sizes ranging from zero to ten C=C units. The appearance of electric rectification occursmore » when the bridge size is equal to 5 units and is complete for those larger than 6 units (i.e. full inversion). This new electronic effect is advantageous for the design of large hybrid organic/inorganic circuits with anincreased majority carrier flow that is necessary for the emerging needs of nanotechnology.« less

Residual stress evaluation by Barkhausen signals with a magnetic field sensor for high efficiency electrical motors

NASA Astrophysics Data System (ADS)

Tsuchida, Yuji; Enokizono, Masato

2018-04-01

The iron loss of industrial motors increases by residual stress during manufacturing processes. It is very important to make clear the distribution of the residual stress in the motor cores to reduce the iron loss in the motors. Barkhausen signals which occur on electrical steel sheets can be used for the evaluation of the residual stress because they are very sensitive to the material properties. Generally, a B-sensor is used to measure Barkhausen signals, however, we developed a new H-sensor to measure them and applied it into the stress evaluation. It is supposed that the Barkhausen signals by using a H-sensor can be much effective to the residual stress on the electrical steel sheets by referring our results regarding to the stress evaluations. We evaluated the tensile stress of the electrical steel sheets by measuring Barkhausen signals by using our developed H-sensor for high efficiency electrical motors.

Archaeological Graves Revealing By Means of Seismic-electric Effect

NASA Astrophysics Data System (ADS)

Boulytchov, A.

[a4paper,12pt]article english Seismic-electric effect was applied in field to forecast subsurface archaeological cul- tural objects. A source of seismic waves were repeated blows of a heavy hammer or powerful signals of magnetostrictive installation. Main frequency used was 500 Hz. Passed a soil layer and reached a second boundary between upper clayey-sand sedi- ments and archaeological object, the seismic wave caused electromagnetic fields on the both boundaries what in general is due to dipole charge separation owe to an im- balance of streaming currents induced by the seismic wave on opposite sides of a boundary interface. According to theoretical works of Pride the electromagnetic field appears on a boundary between two layers with different physical properties in the time of seismic wave propagation. Electric responses of electromagnetic fields were measured on a surface by pair of grounded dipole antennas or by one pivot and a long wire antenna acting as a capacitive pickup. The arrival times of first series of responses correspond to the time of seismic wave propagation from a source to a boundary between soil and clayey-sand layers. The arrival times of second row of responses correspond to the time of seismic wave way from a source to a boundary of clayey-sand layer with the archaeological object. The method depths successfully investigated were between 0.5-10 m. Similar electromagnetic field on another type of geological structure was also revealed by Mikhailov et al., Massachusetts, but their signals registered from two frontiers were too faint and not evident in comparing with ours ones that occurred to be perfect and clear. Seismic-electric method field experi- ments were successfully provided for the first time on archaeological objects.

[Electromagnetic pollution (electrosmog)--potential hazards of our electromagnetic future].

PubMed

Nowak, D; Radon, K

2004-02-26

The term electromagnetic environment encompasses the totality of all electric, magnetic and electromagnetic fields generated by natural and technical sources. A differentiation is made between low- and high-frequency electromagnetic fields. Typical sources of the former are domestic electricity Exposure to the latter is, for example, associated with the sue of mobile telephones. Studies on the health-related effects of electromagnetic fields are available in particular for the low-frequency range, based on an appropriate estimation of exposure. A number of these studies reveal an association between exposure to this type of electromagnetic fields and the occurrence of infantile leukemia in the highest exposure category. For high-frequency electromagnetic fields the number of epidemiological studies is limited. An increased risk of an accident occurring through the use of a cellular phone while driving has consistently been shown. Against the background of our limited knowledge about possible adverse effects of exposure to mobile phone transmitters, and the inability of the public to influence such exposure, transparency in the communication of the risks involved is of great importance.

Geomagnetic Field Distortion by a Solar Stream as a Mechanism for the Production of Polar Aurora and Electrojets

NASA Technical Reports Server (NTRS)

Kern, J. W.

1961-01-01

This paper describes a mechanism for charge separation in the geomagnetically trapped radiation which may account for some observed phenomena associated with the polar aurora and the electrojet current systems. The following development is proposed: given that there exist eastward or westward longitudinal gradients in the geomagnetic field resulting from distortion of the geomagnetic field by solar streams, if the trapped radiation is adiabatic in character, radial drift separation of positive and negative charged particles must occur. It follows that, for bounded or irregular distributions of plasma number density in such an adiabatic - drift region, electric fields will arise. The origin of such electric fields will not arrest the drift separation of the charged particles, but will contribute to exponential growth of irregularities in the trapped plasma density. An adiabatic acceleration mechanism is described, which is based on incorporating the electrostatic energy of the particle in the energy function for the particle. Direct consequences of polarization of the geomagnetically trapped radiation will be the polar electrojet current systems and the polar aurora.

Numerical Investigation of Two-Phase Flows With Charged Droplets in Electrostatic Field

NASA Technical Reports Server (NTRS)

Kim, Sang-Wook

1996-01-01

A numerical method to solve two-phase turbulent flows with charged droplets in an electrostatic field is presented. The ensemble-averaged Navier-Stokes equations and the electrostatic potential equation are solved using a finite volume method. The transitional turbulence field is described using multiple-time-scale turbulence equations. The equations of motion of droplets are solved using a Lagrangian particle tracking scheme, and the inter-phase momentum exchange is described by the Particle-In-Cell scheme. The electrostatic force caused by an applied electrical potential is calculated using the electrostatic field obtained by solving a Laplacian equation and the force exerted by charged droplets is calculated using the Coulombic force equation. The method is applied to solve electro-hydrodynamic sprays. The calculated droplet velocity distributions for droplet dispersions occurring in a stagnant surrounding are in good agreement with the measured data. For droplet dispersions occurring in a two-phase flow, the droplet trajectories are influenced by aerodynamic forces, the Coulombic force, and the applied electrostatic potential field.

Signatures of moderate (M-class) and low (C and B class) intensity solar flares on the equatorial electrojet current: Case studies

NASA Astrophysics Data System (ADS)

Chakrabarty, D.; Bagiya, Mala S.; Thampi, Smitha V.; Pathan, B. M.; Sekar, R.

2013-12-01

The present investigation brings out, in contrast to the earlier works, the changes in the equatorial electrojet (EEJ) current in response to a few moderate (M-class) and low (C and B class) intensity solar flares during 2005-2010. Special care is taken to pick these flare events in the absence of prompt electric field perturbations associated with geomagnetic storms and substorms that also affect the electrojet current. Interestingly, only the normalized (with respect to the pre-flare level) deviations of daytime EEJ (and not the deviations alone) change linearly with the increases in the EUV and X-ray fluxes. These linear relationships break down during local morning hours when the E-region electric field approaches zero before reversal of polarity. This elicits that the response of EEJ strength corresponding to less-intense flares can be appropriately gauged only when the local time variation of the quiet time E-region zonal electric field is taken into account. The flare events enhanced the EEJ strength irrespective of normal or counter electrojet (CEJ) conditions that shows that solar flares change the E-region ionization density and not the electric field. In addition, the enhancements in the X-ray and EUV fluxes, for these flares occurring during this solar minimum period, are found to be significantly correlated as opposed to the solar maximum period, indicating the differences in the solar processes in different solar epochs.

The possible consequences for cognitive functions of external electric fields at power line frequency on hippocampal CA1 pyramidal neurons.

PubMed

Migliore, Rosanna; De Simone, Giada; Leinekugel, Xavier; Migliore, Michele

2017-04-01

The possible effects on cognitive processes of external electric fields, such as those generated by power line pillars and household appliances are of increasing public concern. They are difficult to study experimentally, and the relatively scarce and contradictory evidence make it difficult to clearly assess these effects. In this study, we investigate how, why and to what extent external perturbations of the intrinsic neuronal activity, such as those that can be caused by generation, transmission and use of electrical energy can affect neuronal activity during cognitive processes. For this purpose, we used a morphologically and biophysically realistic three-dimensional model of CA1 pyramidal neurons. The simulation findings suggest that an electric field oscillating at power lines frequency, and environmentally measured strength, can significantly alter both the average firing rate and temporal spike distribution properties of a hippocampal CA1 pyramidal neuron. This effect strongly depends on the specific and instantaneous relative spatial location of the neuron with respect to the field, and on the synaptic input properties. The model makes experimentally testable predictions on the possible functional consequences for normal hippocampal functions such as object recognition and spatial navigation. The results suggest that, although EF effects on cognitive processes may be difficult to occur in everyday life, their functional consequences deserve some consideration, especially when they constitute a systematic presence in living environments. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Lightning Mapping Observations of Volume-Filling Small Discharges in Thunderstorms

NASA Astrophysics Data System (ADS)

Rison, W.; Krehbiel, P. R.; Thomas, R. J.; Rodeheffer, D.

2013-12-01

Lightning is usually considered to be a large-scale electrical discharge in the atmosphere. For example, the American Meteorological Society's Glossary of Meteorology defines lightning as "a transient, high-current electric discharge with pathlengths measured in kilometers" (http://glossary.ametsoc.org/wiki/Lightning). There have been several reported examples of short-duration discharges in thunderstorms, which have a duration of a few microseconds to less than a millisecond, and have a small spatial extent These short-duration discharges were located at high altitudes (> 14 km), altitudes consistent with being located between the upper positive charge and the negative screening layer. At these altitudes, the electric field needed to initiate an electrical discharge is much lower than it is at the altitudes of initiation for IC (~8 km) or CG (~5 km) flashes. We have recently reported on short-duration "precursor" discharges with durations of a few microseconds to a few milliseconds, which occur in the high-fields between the mid-level negative and upper positive charge regions. These "precursor" discharges are discrete in both time and space, being separated in time by hundreds of milliseconds to several seconds, and localized in space, usually very close to the initiation location of a subsequent IC discharge. We have recently observed nearly continuous, volume filling short-duration discharges in several thunderstorms. These discharges have durations of much less than a millisecond, spatial extents of less than a few hundred meters, and occur randomly in the volume between the mid-level negative and upper positive charge regions. During an active period, these discharges occur every few milliseconds. The rates of these discharges decreases dramatically to a few per second following an IC discharge, then increases to several hundred per second until the next discharge. In a storm just off the Florida coast, one cell was producing a large number of these small discharges, while a contemporaneous cell a few kilometers west produced no detectable small discharges. Short-duration discharges occur at altitudes between 10 km and 14 km in the intervals between lightning discharges. The rates of short-duration discharges decreases dramatically after a lightning discharge.

Direct simulation of phase delay effects on induced-charge electro-osmosis under large ac electric fields

NASA Astrophysics Data System (ADS)

Sugioka, Hideyuki

2016-08-01

The standard theory of induced-charge electro-osmosis (ICEO) often overpredicts experimental values of ICEO velocities. Using a nonsteady direct multiphysics simulation technique based on the coupled Poisson-Nernst-Planck and Stokes equations for an electrolyte around a conductive cylinder subject to an ac electric field, we find that a phase delay effect concerning an ion response provides a fundamental mechanism for electrokinetic suppression. A surprising aspect of our findings is that the phase delay effect occurs even at much lower frequencies (e.g., 50 Hz) than the generally believed charging frequency of an electric double layer (typically, 1 kHz) and it can decrease the electrokinetic velocities in one to several orders. In addition, we find that the phase delay effect may also cause a change in the electrokinetic flow directions (i.e., flow reversal) depending on the geometrical conditions. We believe that our findings move toward a more complete understanding of complex experimental nonlinear electrokinetic phenomena.

Apparatus for sensing patterns of electrical field variations across a surface

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

Warren, William L.; Devine, Roderick A. B.

An array of nonvolatile field effect transistors used to sense electric potential variations. The transistors owe their nonvolatility to the movement of protons within the oxide layer that occurs only in response to an externally applied electric potential between the gate on one side of the oxide and the source/drain on the other side. The position of the protons within the oxide layer either creates or destroys a conducting channel in the adjacent source/channel/drain layer below it, the current in the channel being measured as the state of the nonvolatile memory. The protons can also be moved by potentials createdmore » by other instrumentalities, such as charges on fingerprints or styluses above the gates, pressure on a piezoelectric layer above the gates, light shining upon a photoconductive layer above the gates. The invention allows sensing of fingerprints, handwriting, and optical images, which are converted into digitized images thereof in a nonvolatile format.« less

Explorer 45 wave observations during the large magnetic storm of August 4-5, 1972

NASA Technical Reports Server (NTRS)

Taylor, W. W. L.; Anderson, R. G.

1977-01-01

The magnetospheric compression associated with the very large magnetic storm of August 4-5, 1972, provided an opportunity for Explorer 45 to observe plasma waves in the magnetosphere and the magnetosheath during extremely disturbed conditions. Electrostatic noise bursts were observed near the plasmapause in electric-field channels from 35 Hz to 5.62 kHz. In the outer magnetosphere, electric-field noise bands apparently harmonically related to the electron gyrofrequency with components as low as 3 kHz and as high as 50 kHz were observed. The electric field of the fundamental was perpendicular to the magnetic-field vector. A mechanism including the electron cyclotron instability may generate the noise band. Hiss of 100-1000 Hz was observed in the outer magnetosphere. The electromagnetic hiss was generally weak and was observed in the magnetic wide-band data only when it was strong. In the magnetosheath broad band, incoherent noise (hiss) was observed from 1 Hz to 100 kHz. This magnetosheath hiss was the strongest phenomenon observed by the plasma-wave detectors during the lifetime of Explorer 45. The highest intensities of magnetosheath hiss occurred at the magnetopause. Its broad-band nature suggests that magnetosheath hiss was generated locally. Broad-band noise bursts and short bursts of chorus were also observed in the magnetosheath.

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

Peng, Yong; Yao, Manwen, E-mail: yaomw@tongji.edu.cn; Chen, Jianwen

The electrical characteristics of SrTiO{sub 3}/Al{sub 2}O{sub 3} (160 nm up/90 nm down) laminated film capacitors using the sol-gel process have been investigated. SrTiO{sub 3} is a promising and extensively studied high-K dielectric material, but its leakage current property is poor. SrTiO{sub 3}/Al{sub 2}O{sub 3} laminated films can effectively suppress the demerits of pure SrTiO{sub 3} films under low electric field, but the leakage current value reaches to 0.1 A/cm{sup 2} at higher electric field (>160 MV/m). In this study, a new approach was applied to reduce the leakage current and improve the dielectric strength of SrTiO{sub 3}/Al{sub 2}O{sub 3} laminated films. Compared tomore » laminated films with Au top electrodes, dielectric strength of laminated films with Al top electrodes improves from 205 MV/m to 322 MV/m, simultaneously the leakage current maintains the same order of magnitude (10{sup −4} A/cm{sup 2}) until the breakdown occurs. The above electrical characteristics are attributed to the anodic oxidation reaction in origin, which can repair the defects of laminated films at higher electric field. The anodic oxidation reactions have been confirmed by the corresponding XPS measurement and the cross sectional HRTEM analysis. This work provides a new approach to fabricate dielectrics with high dielectric strength and low leakage current.« less

Coordination nano-space as stage of hydrogen ortho-para conversion.

PubMed

Kosone, Takashi; Hori, Akihiro; Nishibori, Eiji; Kubota, Yoshiki; Mishima, Akio; Ohba, Masaaki; Tanaka, Hiroshi; Kato, Kenichi; Kim, Jungeun; Real, José Antonio; Kitagawa, Susumu; Takata, Masaki

2015-07-01

The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)-para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o-p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o-p conversion.

Modelling in conventional electroporation for model cell with organelles using COMSOL Multiphysics

NASA Astrophysics Data System (ADS)

Sulaeman, M. Y.; Widita, R.

2016-03-01

Conventional electroporation is a formation of pores in the membrane cell due to the external electric field applied to the cell. The purpose of creating pores in the cell using conventional electroporation are to increase the effectiveness of chemotherapy (electrochemotherapy) and to kill cancer tissue using irreversible electroporation. Modeling of electroporation phenomenon on a model cell had been done by using software COMSOL Multiphysics 4.3b with the applied external electric field with intensity at 1.1 kV/cm to find transmembrane voltage and pore density. It can be concluded from the results of potential distribution and transmembrane voltage, it show that pores formation only occurs in the membrane cells and it could not penetrate into inside the model cell so there is not pores formation in its organells.

Structure of conducting channel of lightning

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

Alanakyan, Yu. R.

2013-08-15

The spatial distribution of the plasma density in a lightning channel is studied theoretically. It is shown that the electric-field double layer is formed at the channel boundary. In this case, the electron temperature changes abruptly and ions are accelerated by the electric field of the double layer. The ion momentum flux density is close to the surrounding gas pressure. Cleaning of the channel from heavy particles occurs in particle-exchange processes between the plasma channel and the surrounding air. Hydrogen ions are accumulated inside the expanding channel from the surrounding air, which is enriched by hydrogen-contained molecules. In this case,more » the plasma channel is unstable and splits to a chain of equidistant bunches of plasma. The hydrogen-enrich bunches burn diffusely after recombination exhibiting the bead lightning behavior.« less

Wireless Electrical Device Using Open-Circuit Elements Having No Electrical Connections

NASA Technical Reports Server (NTRS)

Taylor, Bryant Douglas (Inventor); Woodard, Stanley E. (Inventor)

2012-01-01

A wireless electrical device includes an electrically unconnected electrical conductor and at least one electrically unconnected electrode spaced apart from the electrical conductor. The electrical conductor is shaped for storage of an electric field and a magnetic field. In the presence of a time-varying magnetic field, the electrical conductor so-shaped resonates to generate harmonic electric and magnetic field responses. Each electrode is at a location lying within the magnetic field response so-generated and is constructed such that a linear movement of electric charges is generated in each electrode due to the magnetic field response so-generated.

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.

Ionosonde observations of the effects of the major magnetic storm of September 22-26, 1999 at equatorial station in west Africa

NASA Astrophysics Data System (ADS)

Coulibaly, I. S.; Adohi, B. J.-P.; Tanoh, K. S.

2018-05-01

A new approach to study the mechanisms of storm-time variations in the F-layer height and critical frequency at dip-equator is proposed. The latitudinal variations in the magnetic disturbance index DP were combined with h'F and foF2 data from an IPS 42-type ionosonde at Korkogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, to investigate the nighttime ionospheric effects of the geomagnetic storm of September 22-26, 1999 in the West-African sector. A clear equatorward penetration of magnetic disturbances from high latitudes regions was observed. At dip-equator, the DP magnetic disturbance pattern showed up to four distinct regimes of disturbance electric fields, each associated with a specific phase of the storm. A regime of westward transient electric fields followed by a regime of eastward transient electric fields occurred during the main phase of the storm. This was preceded by a period of quasi-absence of disturbance during the compression phase, the whole followed by a regime of westward persistent disturbance electric fields during the recovery phase. From the latitudinal variations and the shapes of these perturbations, we could associate the regime of westward (resp. eastward) disturbance electric fields with prompt penetration (resp. overshielding) occasioned by magnetospheric convections and the persistent one with a cumulative effect of storm-time winds and magnetospheric convections from high latitudes regions. The h'F variations were found to be strongly correlated with the DP ones, clearly providing evidence for the prevalence of these electric fields on the observed F-layer motions. Additionally, the foF2 variations showed two periods of depleted electron density, one in the evening during the compression phase of the storm and the other near midnight. We discussed the mechanisms of these ionospheric negative storms in the light of earlier investigations of storm-time ionospheric disturbances and validated our method by comparison of the above results with those based on criteria by other authors.

The physical foundation of the reconnection electric field

NASA Astrophysics Data System (ADS)

Hesse, M.; Liu, Y.-H.; Chen, L.-J.; Bessho, N.; Wang, S.; Burch, J. L.; Moretto, T.; Norgren, C.; Genestreti, K. J.; Phan, T. D.; Tenfjord, P.

2018-03-01

Magnetic reconnection is a key charged particle transport and energy conversion process in environments ranging from astrophysical systems to laboratory plasmas [Yamada et al., Rev. Mod. Phys. 82, 603-664 (2010)]. Magnetic reconnection facilitates plasma transport by establishing new connections of magnetic flux tubes, and it converts, often explosively, energy stored in the magnetic field to kinetic energy of charged particles [J. L. Burch and J. F. Drake, Am. Sci. 97, 392-299 (2009)]. The intensity of the magnetic reconnection process is measured by the reconnection electric field, which regulates the rate of flux tube connectivity changes. The change of magnetic connectivity occurs in the current layer of the diffusion zone, where the plasma transport is decoupled from the transport of magnetic flux. Here we report on computer simulations and analytic theory to provide a self-consistent understanding of the role of the reconnection electric field, which extends substantially beyond the simple change of magnetic connections. Rather, we find that the reconnection electric field is essential to maintain the current density in the diffusion region, which would otherwise be dissipated by a set of processes. Natural candidates for current dissipation are the average convection of current carriers away from the reconnection region by the outflow of accelerated particles, or the average rotation of the current density by the magnetic field reversal in the vicinity. Instead, we show here that the current dissipation is the result of thermal effects, underlying the statistical interaction of current-carrying particles with the adjacent magnetic field. We find that this interaction serves to redirect the directed acceleration of the reconnection electric field to thermal motion. This thermalization manifests itself in form of quasi-viscous terms in the thermal energy balance of the current layer. This collisionless viscosity, found in the pressure evolution equation, dominates near the x-line. These quasi-viscous terms act to increase the average thermal energy. Our predictions regarding current and thermal energy balance are readily amenable to exploration in the laboratory or by satellite missions, in particular, by NASA's Magnetospheric Multiscale mission.

Large-eddy simulation, atmospheric measurement and inverse modeling of greenhouse gas emissions at local spatial scales

NASA Astrophysics Data System (ADS)

Nottrott, Anders Andelman

Multiferroic materials and devices have attracted intensified interests due to the demonstrated strong magnetoelectric coupling in new multiferroic materials, artificial multiferroic heterostructures and devices with unique functionalities and superior performance characteristics. This offers great opportunities for achieving compact, fast, energy-efficient and voltage tunable spintronic devices. In traditional magnetic materials based magnetic random access memories (MRAM) devices, the binary information is stored as magnetization. The high coercivity of the ferromagnetic media requires large magnetic fields for switching the magnetic states thus consuming large amount of energy. In modern MRAM information writing process, spin-torque technique is utilized for minimizing the large energy for generating magnetic field by passing through a spin-polarized current directly to the magnets. However, both methods still need large current/current density to toggle the magnetic bits which consume large amount of energy. With the presence of multiferroic or magnetoelectric materials, spin is controlled by electric field which opens new opportunities for power-efficient voltage control of magnetization in spintronic devices leading to magnetoelectric random access memories (MERAM) with ultra-low energy consumption. However, state of the art multiferroic materials still have difficulty of realizing nonvolatile 180° magnetization reversal, which is desired in realizing MERAM. In a strain-mediated multiferroic system, the typical modification of the magnetism of ferromagnetic phase as a function of bipolar electric field shows a "butterfly" like behavior. This is due to the linear piezoelectricity of ferroelectric phase which has a "butterfly" like piezostrain as a function of electric field curve resulting from ferroelectric domain wall switching. In this case, the magnetization state is volatile because of the vanishing of the piezostrain at zero electric field. However, the non-volatile switching of magnetization would be more promising for information storage or MERAM devices with lower energy consumption and the magnetic state can be further controlled by voltage impulse. In this work, we first study the equivalent of direct and converse magnetoelectric effects. The resonant direct and converse magnetoelectric (ME) effects have been investigated experimentally and theoretically in FeGa/PZT/FeGa sandwich laminate composites. The frequency responses of direct and converse magnetoelectric effects were measured under the same electric and magnetic bias conditions. The resonant direct ME effect (DME) occurs at an antiresonance frequency, while resonant converse ME effect (CME) occurs at a resonance frequency. The antiresonance and resonance frequencies have close but different values under identical bias conditions. The magnitudes of resonant effective ME coefficients for direct and converse ME effects are also not equal. Based on different sets of constitutive equations of the materials for DME and CME, a new model was developed to describe the frequency response of DME and CME in laminate composite, which was in good agreement with the experimental results. Inequivalence of resonant ME effects is ascribed to the different mechanical and electrical boundary conditions for DME and CME. On the other hand, similar bias E and H field dependence was observed for both DME and CME resonance frequencies and resonant coefficients, indicating consistency between DME and CME effects. In the study of the frequency response of DME and CME, the linear piezoelectric effect is used. However, this linear piezoelectric effect in converse magnetoelectric coupling would lead to "butter-fly" like magnetization vs. electric field curve which leads to a "volatile" behavior in magnetic memory system. In the presented study, a unique ferroelastic switching pathway in ferroelectric substrates is utilized to produce two distinct, reversible and stable lattice strain states which leads to the establish of two stable magnetization states of the ferromagnetic thin film. In this process, instead of complete 180° ferromagnetic domain switching, 71°/109° ferroelastic domain wall switching is involved, where the electric polarization is switching between in-plane and out-of-plane direction. A voltage impulse induced reversible bistable magnetization switching in FeGaB/lead zirconate titanate (PZT) multiferroic heterostructures at room temperature is first demonstrated. Two reversible and stable voltage-impulse induced mechanical strain states were obtained in the PZT by applying an electric field impulse with its amplitude smaller than the electric coercive field, which led to reversible voltage impulse induced bistable magnetization switching. Direct and converse magnetoelectric effects are carefully quantified.

EHD Approach to Tornadic Thunderstorms and Methods of Their Destruction

NASA Astrophysics Data System (ADS)

Kikuchi, H.

2005-05-01

In many cases, tornadoes are accompanied or involved by lightning discharges and are thought to be com- posed of uncharged and charged components different from each other in terms of velocity, vorticity, heli- city, and appearance (shape and luminosity). Their visible dark portion may correspond to uncharged tor- nadoes, while luminous or bright part may involve charged tornadoes with return strokes. Usually, un- charged tornadoes have been considered to be ascending hot streams of thermohydrodynamic origin. This is the conventional theory of tornadoes, based on hydrodynamics (HD) or thermohydrodynamics (THD) but does not consider electrical effects that are really significant in tornadic thunderstorms..It has been shown, however, that a new electrohydrodynamics (EHD) established and developed over the last more than a decade is applicable to tornadic thunderstorms with lightning. This paper summarizes such an EHD approach and proposes the methods of tornado destruction based on EHD. Space charge and electric field configurations in tornadic thunderstorms are considered to be quadrupole-like, taking into account the cloud-charge images onto the ground. Accordingly, dynamics of particles and EHD flows in an electric quadrupole forming an electric cusp and mirror can straightly apply to those circumstances. When the gas pressure is below the breakdown threshold, there occur helical motion of particles, not only charged but also even uncharged, and/or vortex generation. While for gases whose pressure is beyond the breakdown threshold, the following basic processes succeed one after another. When the grain is uncharged, a dis- charge channel is formed towards each pole as a result of X-type reconnection. For a negatively or posi- tively charged grain, I-type reconnection occurs between the grain and positive or negative poles, respect- ively. For uncharged two grains, O-type reconnection between both grains could be involved in addition to X-type between each pole, while for oppositely charged two grains, F-type reconnection could be in- volved between grains in addition to I-type between each grain and a pole with opposite polarity. Thus one can say that the uncharged component of tornadic thunderstorms is composed of conventional ascending hot streams of thermohydrodynamic origin and particle flows of new EHD origin produced by a quadru- pole-like cloud-base, funnel-top charge distributions, while the charged component is a bunch of return strokes including charged flows due to dust-related electric reconnection and EHD vortices in large-scale generated by EHD helical turbulence where there may occur self-organization to coalescence of fluid vor- tex and electric displacement field lines at least in an initial stage of return stroke (rise time of some ms), since earth's magnetic field could be ignored. This also indicates that fluid vortex breakdown points also tend to merge electric cusps, X-type and O-type. Then the principle of dust-related electric reconnection could be replaced by dust cluster injection into electric cusps (X-type and O-type) in several ways just mentioned above. Thus a variety of such dust cluster injection could cause additional cloud-to-dust cluster discharges, expending electrostatic energy accumulated in thunderclouds considerably and destructing tornadoes consequently.

IShTAR ICRF antenna field characterization in vacuum and plasma by using probe diagnostic

NASA Astrophysics Data System (ADS)

Usoltceva, Mariia; Ochoukov, Roman; D'Inca, Rodolphe; Jacquot, Jonathan; Crombé, Kristel; Kostic, Ana; Heuraux, Stéphane; Faudot, Eric; Noterdaeme, Jean-Marie

2017-10-01

RF sheath physics is one of the key topics relevant for improvements of ICRF heating systems, which are present on nearly all modern magnetic fusion machines. This paper introduces developement and validation of a new approach to understanding general RF sheath physics. The presumed reason of enhanced plasma-antenna interactions, parallel electric field, is not measured directly, but proposed to be obtained from simulations in COMSOL Multiphysics® Modeling Software. Measurements of RF magnetic field components with B-dot probes are done on a linear device IShTAR (Ion cyclotron Sheath Test ARrangement) and then compared to simulations. Good resulting accordance is suggested to be the criterion for trustworthiness of parallel electric field estimation as a component of electromagnetic field in modeling. A comparison between simulation and experiment for one magnetic field component in vacuum has demonstrated a close match. An additional complication to this ICRF antenna field characterization study is imposed by the helicon antenna which is used as a plasma ignition tool in the test arrangement. The plasma case, in contrast to the vacuum case, must be approached carefully, since the overlapping of ICRF antenna and helicon antenna fields occurs. Distinguishing of the two fields is done by an analysis of correlation between measurements with both antennas together and with each one separately.

Nanosecond electric modification of order parameters

NASA Astrophysics Data System (ADS)

Borshch, Volodymyr

In this Dissertation, we study a nanosecond electro-optic response of a nematic liquid crystal in a geometry where an applied electric field E modifies the tensor order parameter but does not change the orientation of the optic axis (director N̂). We use nematics with negative dielectric anisotropy with the electric field applied perpendicularly to N̂. The field changes the dielectric tensor at optical frequencies (optic tensor), due to the following mechanisms: (a) nanosecond creation of biaxial orientational order; (b) uniaxial modification of the orientational order that occurs over the timescales of tens of nanoseconds, and (c) quenching of director fluctuations with a wide range of characteristic times up to milliseconds. We develop a model to describe the dynamics of all three mechanisms. We design the experimental conditions to selectively suppress the contributions from the quenching of director fluctuations (c) and from the biaxial order effect (a) and thus, separate the contributions of the three mechanisms in the electro-optic response. As a result, the experimental data can be well fitted with the model parameters. The analysis provides a rather detailed physical picture of how the liquid crystal responds to a strong electric field, E ˜ 108 V/m, on a timescale of nanoseconds. This work provides a useful guide in the current search of the biaxial nematic phase. Namely, the temperature dependence of the biaxial susceptibility allows one to estimate the temperature of the potential uniaxial-to-biaxial phase transition. An analysis of the quenching of director fluctuations indicates that on a timescale of nanoseconds, the classic model with constant viscoelastic material parameters might reach its limit of validity. The effect of nanosecond electric modification of the order parameter (NEMOP) can be used in applications in which one needs to achieve ultrafast (nanosecond) changes of optical characteristics, such as birefringence.

Electrokinetic framework of dielectrophoretic deposition devices

NASA Astrophysics Data System (ADS)

Burg, Brian R.; Bianco, Vincenzo; Schneider, Julian; Poulikakos, Dimos

2010-06-01

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant aspect for limiting process effects during device fabrication, all while increasing dielectrophoretic deposition efficiency in nanostructured networks.

The mechanism of the appearance of luminescence and electrification in liquid flows through narrow channels

NASA Astrophysics Data System (ADS)

Margulis, M. A.; Pil'Gunov, V. N.

2009-10-01

The mechanism of the effects observed in hydrodynamic unit throttles was studied. These effects included luminescence in the visible range localized in a microscopic toroidal volume and electric pulses when a dielectric liquid flew through a narrow passage orifice. Equations for charging and conduction currents were obtained. The stationary electric charge, potential, and field strength on the internal surface of a passage orifice were calculated. It was shown theoretically that the appearance of luminescence most probably occurred in electrical breakdowns in cavitation bubbles in the initial flow section inside the passage orifice. Electric charge formed not only during hydrodynamic cavitation but also in a laminar throttle in the absence of cavitation in the liquid; the electrokinetic mechanism applied to this phenomenon too. It was shown experimentally that electric charges appeared not only in plastic but also in metallic throttles. The suggested mechanism of light emission and electric charge appearance was in agreement with the experimental results.

Missile launch detection electric field perturbation experiment. Final report

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

Kane, R.J.; Rynne, T.M.

1993-04-28

The Lawrence Livermore National Laboratory and SARA Inc. participated in the ATMD missile launch activities that occurred at WSMR during January 1993. LLNL and SARA deployed sensors for monitoring of basic phenomena. An attempt was made to measure perturbations of the earth geo-potential during the launch of a Lance missile. The occurrence of the perturbation is expected from the conducting body of the missile and the exhaust plume. A set of voltage-probe antennas were used to monitor the local electric field perturbation from the launch at ranges of approximately 1 km. Examination of the data acquired during the launch periodmore » failed to show identifiable correlation of the field variations with the launch event. Three reasons are ascribed to this lack of event data: (1) The electric field potential variations have a limited spatial correlation length - the fields measured in one region have little correlation to measurements made at distances of a kilometer away. The potential variations are related to localized atmospheric disturbances and are generally unpredictable. A value for the spatial correlation length is also not known. (2) The conductivity of the plume and missile body are not adequate to produce a field perturbation of adequate magnitude. Phenomena related to the exhaust plume and missile may exist and be outside of the collection range of the equipment employed for these measurements. (3) The presence of 60 Hz power line noise was of sufficient magnitude to irreversibly contaminate measurements.« less

Natural Electrotransformation of Lightning-Competent Pseudomonas sp. Strain N3 in Artificial Soil Microcosms

PubMed Central

Cérémonie, Hélène; Buret, François; Simonet, Pascal; Vogel, Timothy M.

2006-01-01

The lightning-competent Pseudomonas sp. strain N3, recently isolated from soil, has been used to study the extent of natural electrotransformation (NET) or lightning transformation as a horizontal gene transfer mechanism in soil. The variation of electrical fields applied to the soil with a laboratory-scale lightning system provides an estimate of the volume of soil affected by NET. Based on the range of the electric field that induces NET of Pseudomonas strain N3, the volume of soil, where NET could occur, ranges from 2 to 950 m3 per lightning strike. The influence of DNA parameters (amount, size, and purity) and DNA soil residence time were also investigated. NET frequencies (electrotransformants/recipient cells) ranged from 10−8 for cell lysate after 1 day of residence in soil to 4 × 10−7 with a purified plasmid added immediately before the lightning. The electrical field gradient (in kilovolts per cm) also played a role as NET frequencies ranging from 1 × 10−5 at 2.3 kV/cm to 1.7 × 10−4 at 6.5 kV/cm. PMID:16597934

Quantifying pulsed electric field-induced membrane nanoporation in single cells.

PubMed

Moen, Erick K; Ibey, Bennett L; Beier, Hope T; Armani, Andrea M

2016-11-01

Plasma membrane disruption can trigger a host of cellular activities. One commonly observed type of disruption is pore formation. Molecular dynamic (MD) simulations of simplified lipid membrane structures predict that controllably disrupting the membrane via nano-scale poration may be possible with nanosecond pulsed electric fields (nsPEF). Until recently, researchers hoping to verify this hypothesis experimentally have been limited to measuring the relatively slow process of fluorescent markers diffusing across the membrane, which is indirect evidence of nanoporation that could be channel-mediated. Leveraging recent advances in nonlinear optical microscopy, we elucidate the role of pulse parameters in nsPEF-induced membrane permeabilization in live cells. Unlike previous techniques, it is able to directly observe loss of membrane order at the onset of the pulse. We also develop a complementary theoretical model that relates increasing membrane permeabilization to membrane pore density. Due to the significantly improved spatial and temporal resolution possible with our imaging method, we are able to directly compare our experimental and theoretical results. Their agreement provides substantial evidence that nanoporation does occur and that its development is dictated by the electric field distribution. Copyright © 2016 Elsevier B.V. All rights reserved.

Characteristics of electroluminescence phenomenon in virgin and thermally aged LDPE

NASA Astrophysics Data System (ADS)

Bani, N. A.; Abdul-Malek, Z.; Ahmad, H.; Muhammad-Sukki, F.; Mas'ud, A. A.

2015-08-01

High voltage cable requires a good insulating material such as low density polyethylene (LDPE) to be able to operate efficiently in high voltage stresses and high temperature environment. However, any polymeric material will experience degradation after prolonged application of high electrical stresses or other extreme conditions. The continuous degradation will shorten the life of a cable therefore further understanding on the behaviour of the aged high voltage cable needs to be undertaken. This may be observed through electroluminescence (EL) measurement. EL occurs when a solid-state material is subjected to a high electrical field stress and associated with the generation of charge carriers within the polymeric material and that these charges can be produced by injection, de-trapping and field-dissociation at the metal-polymer interface. The behaviour of EL emission can be affected by applied field, applied frequency, ageing time, ageing temperature and types of materials, among others. This paper focuses on the measurement of EL emission of additive-free LDPE thermally aged at different temperature subjected to varying electric stresses at 50Hz. It can be observed that EL emission increases as voltage applied is increased. However, EL emission decreases as ageing temperature is increased for varying applied voltage.

Theoretical simulation of the multipole seismoelectric logging while drilling

NASA Astrophysics Data System (ADS)

Guan, Wei; Hu, Hengshan; Zheng, Xiaobo

2013-11-01

Acoustic logging-while-drilling (LWD) technology has been commercially used in the petroleum industry. However it remains a rather difficult task to invert formation compressional and shear velocities from acoustic LWD signals due to the unwanted strong collar wave, which covers or interferes with signals from the formation. In this paper, seismoelectric LWD is investigated for solving that problem. The seismoelectric field is calculated by solving a modified Poisson's equation, whose source term is the electric disturbance induced electrokinetically by the travelling seismic wave. The seismic wavefield itself is obtained by solving Biot's equations for poroelastic waves. From the simulated waveforms and the semblance plots for monopole, dipole and quadrupole sources, it is found that the electric field accompanies the collar wave as well as other wave groups of the acoustic pressure, despite the fact that seismoelectric conversion occurs only in porous formations. The collar wave in the electric field, however, is significantly weakened compared with that in the acoustic pressure, in terms of its amplitude relative to the other wave groups in the full waveforms. Thus less and shallower grooves are required to damp the collar wave if the seismoelectric LWD signals are recorded for extracting formation compressional and shear velocities.

Subfemtosecond directional control of chemical processes in molecules

NASA Astrophysics Data System (ADS)

Alnaser, Ali S.; Litvinyuk, Igor V.

2017-02-01

Laser pulses with a waveform-controlled electric field and broken inversion symmetry establish the opportunity to achieve directional control of molecular processes on a subfemtosecond timescale. Several techniques could be used to break the inversion symmetry of an electric field. The most common ones include combining a fundamental laser frequency with its second harmonic or with higher -frequency pulses (or pulse trains) as well as using few-cycle pulses with known carrier-envelope phase (CEP). In the case of CEP, control over chemical transformations, typically occurring on a timescale of many femtoseconds, is driven by much faster sub-cycle processes of subfemtosecond to few-femtosecond duration. This is possible because electrons are much lighter than nuclei and fast electron motion is coupled to the much slower nuclear motion. The control originates from populating coherent superpositions of different electronic or vibrational states with relative phases that are dependent on the CEP or phase offset between components of a two-color pulse. In this paper, we review the recent progress made in the directional control over chemical processes, driven by intense few-cycle laser pulses a of waveform-tailored electric field, in different molecules.

Venus - Dead or alive?

NASA Technical Reports Server (NTRS)

Taylor, Harry A., Jr.; Cloutier, Paul A.

1986-01-01

In situ nightside electric field observations from the Pioneer Venus Orbiter have been interpreted as evidence of extensive lightning in the lower atmosphere of Venus. The scenario, including proposed evidence of clustering of lightning over surface highland regions, has encouraged the acceptance of currently active volcanic output as part of several investigations of the dynamics and chemistry of the atmosphere and the geology of the planet. However, the correlation between the 100-hertz electric field events attributed to lightning and nightside ionization troughs resulting from the interaction of the solar wind with the ionosphere indicates that the noise results from locally generated plasma instabilities and not from any behavior of the lower atmosphere. Furthemore, analysis of the spatial distribution of the noise shows that it is not clustered over highland topography, but rather occurs at random throughout the latitude and longitude regions sampled by the orbiter during the first 5 years of operation, from 1978 to 1984. Thus the electric field observations do not identify lightning and do not provide a basis for inferring the presence of currently active volcanic output. In the absence of known evidence to the contrary, it appears that Venus is no longer active.

LSA field test

NASA Technical Reports Server (NTRS)

Jaffe, P.

1979-01-01

Degradation tests indicate that electrical degradation is not a slow monotonically increasing phenomenon as originally thought but occurs abruptly as the result of some traumatic event. This finding has led to a change in the test philosophy. A discussion of this change is presented along with a summary of degradation and failure data from all the sites and results from a variety of special tests. New instrumentation for in-field measurements are described. Field testing activity was expanded by the addition of twelve remote sites located as far away as Alaska and the Canal Zone. Descriptions of the new sites are included.

Magneto-tunable relaxor ferroelectric properties in tricolor superlattices

NASA Astrophysics Data System (ADS)

Lee, Dongwook; Ah Qune, L. F. N.; Seo, Ji Won

2018-05-01

An artificial structure composed of antiferroelectric NdMnO3, SrMnO3, and LaMnO3 layers exhibits high dielectric permittivity. It also shows ferromagnetic behavior despite that the layers are all antiferromagnetic. The structure displays frequency-dependent relaxor behavior under AC electric field and the permittivity increased up to 70% by an external magnetic field. Inhomogeneous polar nano-regions occur at the interfaces inside the structure and it originates from Mn3+/Mn4+, which induces ferroelectric/ferromagnetic properties in the structure and causes ferroelectric relaxor as well as magnetic-field induced behavior.

Theory of Dielectric Breakdown in Randomly Inhomogeneous Materials

NASA Astrophysics Data System (ADS)

Gyure, Mark Franklin

1990-01-01

Two models of dielectric breakdown in disordered metal-insulator composites have been developed in an attempt to explain in detail the greatly reduced breakdown electric field observed in these materials. The first model is a two dimensional model in which the composite is treated as a random array of conducting cylinders embedded in an otherwise uniform dielectric background. The two dimensional samples are generated by the Monte Carlo method and a discretized version of the integral form of Laplace's equation is solved to determine the electric field in each sample. Breakdown is modeled as a quasi-static process by which one breakdown at a time occurs at the point of maximum electric field in the system. A cascade of these local breakdowns leads to complete dielectric failure of the system after which the breakdown field can be determined. A second model is developed that is similar to the first in terms of breakdown dynamics, but uses coupled multipole expansions of the electrostatic potential centered at each particle to obtain a more computationally accurate and faster solution to the problem of determining the electric field at an arbitrary point in a random medium. This new algorithm allows extension of the model to three dimensions and treats conducting spherical inclusions as well as cylinders. Successful implementation of this algorithm relies on the use of analytical forms for off-centered expansions of cylindrical and spherical harmonics. Scaling arguments similar to those used in theories of phase transitions are developed for the breakdown field and these arguments are discussed in context with other theories that have been developed to explain the break-down behavior of random resistor and fuse networks. Finally, one of the scaling arguments is used to predict the breakdown field for some samples of solid fuel rocket propellant tested at the China Lake Naval Weapons Center and is found to compare quite well with the experimentally measured breakdown fields.

Modeling of electric and heat processes in spot resistance welding of cross-wire steel bars

NASA Astrophysics Data System (ADS)

Iatcheva, Ilona; Darzhanova, Denitsa; Manilova, Marina

2018-03-01

The aim of this work is the modeling of coupled electric and heat processes in a system for spot resistance welding of cross-wire reinforced steel bars. The real system geometry, dependences of material properties on the temperature, and changes of contact resistance and released power during the welding process have been taken into account in the study. The 3D analysis of the coupled AC electric and transient thermal field distributions is carried out using the finite element method. The novel feature is that the processes are modeled for several successive time stages, corresponding to the change of contact area, related contact resistance, and reduction of the released power, occurring simultaneously with the creation of contact between the workpieces. The values of contact resistance and power changes have been determined on the basis of preliminary experimental and theoretical investigations. The obtained results present the electric and temperature field distributions in the system. Special attention has been paid to the temperature evolution at specified observation points and lines in the contact area. The obtained information could be useful for clarification of the complicated nature of interrelated electric, thermal, mechanical, and physicochemical welding processes. Adequate modeling is also an opportunity for proper control and improvement of the system.

Positron Lifetime Modulation by Electric Field Induced Positronium Formation on a Gold Surface

DTIC Science & Technology

2012-03-22

Angular Momentum (3) ......................................................................... 11 Stopping Power (4...isotope from which it was born, diffused into the material before annihilation occurred. 6 The radioisotope used in this experiment is Na-22 which...that positrons may be useful in studying the internal structure of a wide variety of materials. The radioisotope positron source used in this

Electric Field Sensor for Lightning Early Warning System

NASA Astrophysics Data System (ADS)

Premlet, B.; Mohammed, R.; Sabu, S.; Joby, N. E.

2017-12-01

Electric field mills are used popularly for atmospheric electric field measurements. Atmospheric Electric Field variation is the primary signature for Lightning Early Warning systems. There is a characteristic change in the atmospheric electric field before lightning during a thundercloud formation.A voltage controlled variable capacitance is being proposed as a method for non-contacting measurement of electric fields. A varactor based mini electric field measurement system is developed, to detect any change in the atmospheric electric field and to issue lightning early warning system. Since this is a low-cost device, this can be used for developing countries which are facing adversities. A network of these devices can help in forming a spatial map of electric field variations over a region, and this can be used for more improved atmospheric electricity studies in developing countries.

Effects of E × B drift on electron transport across the magnetic field in a miniature microwave discharge neutralizer

NASA Astrophysics Data System (ADS)

Hiramoto, Kenta; Nakagawa, Yuichi; Koizumi, Hiroyuki; Takao, Yoshinori

2017-06-01

Using a three-dimensional particle-in-cell model, electron transport across a magnetic field has been investigated by obtaining the time-varying electric field and plasma parameters in a miniature microwave discharge neutralizer. The size of the neutralizer is 20 × 20 × 4 mm3. Ring-shaped antenna producing 4.2 GHz microwaves and permanent magnets for xenon plasma discharges are present inside. There are four orifices for electron extraction. The simulation area consists of both the discharge chamber and the vacuum region for the extraction. The numerical results show that radial striped patterns occur where the peak electron density is obtained, and the patterns seem to rotate in the azimuthal direction. This characteristic structure is very similar to recent results obtained in Hall thrusters and is probably due to the electron drift instability. Owing to the plasma structure, the azimuthal electric field is generated, which results in the E × B drift velocity in the axial direction with the radial magnetic field of the permanent magnets. This E × B drift velocity is a key factor in the electron transport across the magnetic field, leading to the electron extraction from the discharge chamber.

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.

Rotational magnetization: Problems in experimental and theoretical studies of electrical steels and amorphous magnetic materials

NASA Astrophysics Data System (ADS)

Moses, A. J.

1994-03-01

Flux rotating in the plane of laminations of amorphous materials or electrical steels can cause additional losses in electrical machines. To make full use of laboratory rotational magnetization studies, a better understanding of the nature of rotational flux in machine cores is needed. This paper highlights the need for careful laboratory simulation of the conditions which occur in actual machines. Single specimen tests must produce uniform flux over a given measuring region and output from field and flux sensors need careful analysis. Differences between thermal and flux sensing methods are shown as well as anomalies caused when the magnetisation direction is reversed in an anistropic specimen. Methods of overcoming these problems are proposed.

[Preclinical treatment of severe burn trauma due to an electric arc on an overhead railway cable].

PubMed

Spelten, O; Wetsch, W A; Hinkelbein, J

2013-09-01

Severe burns due to electrical accidents occur rarely in Germany but represent a challenge for emergency physicians and their team. Apart from extensive burns cardiac arrhythmia, neurological damage caused by electric current and osseous injury corresponding to the trauma mechanism are also common. It is important to perform a survey of the pattern of injuries and treat acute life-threatening conditions immediately in the field. Furthermore, specific conditions related to burns must be considered, e.g. fluid resuscitation, thermal management and analgesia. In addition, a correct strategy for further medical care in an appropriate hospital is essential. Exemplified by this case guidelines for the treatment of severe burns and typical pitfalls are presented.

Synergistic effect of electrical and chemical factors on endocytosis in micro-discharge plasma gene transfection

NASA Astrophysics Data System (ADS)

Jinno, M.; Ikeda, Y.; Motomura, H.; Isozaki, Y.; Kido, Y.; Satoh, S.

2017-06-01

We have developed a new micro-discharge plasma (MDP)-based gene transfection method, which transfers genes into cells with high efficiency and low cytotoxicity; however, the mechanism underlying the method is still unknown. Studies revealed that the N-acetylcysteine-mediated inhibition of reactive oxygen species (ROS) activity completely abolished gene transfer. In this study, we used laser-produced plasma to demonstrate that gene transfer does not occur in the absence of electrical factors. Our results show that both electrical and chemical factors are necessary for gene transfer inside cells by microplasma irradiation. This indicates that plasma-mediated gene transfection utilizes the synergy between electrical and chemical factors. The electric field threshold required for transfection was approximately 1 kV m-1 in our MDP system. This indicates that MDP irradiation supplies sufficient concentrations of ROS, and the stimulation intensity of the electric field determines the transfection efficiency in our system. Gene transfer by plasma irradiation depends mainly on endocytosis, which accounts for at least 80% of the transfer, and clathrin-mediated endocytosis is a dominant endocytosis. In plasma-mediated gene transfection, alterations in electrical and chemical factors can independently regulate plasmid DNA adhesion and triggering of endocytosis, respectively. This implies that plasma characteristics can be adjusted according to target cell requirements, and the transfection process can be optimized with minimum damage to cells and maximum efficiency. This may explain how MDP simultaneously achieves high transfection efficiency with minimal cell damage.

Increased electrical conductivity of peptides through annealing process

NASA Astrophysics Data System (ADS)

Namgung, Seok Daniel; Lee, Jaehun; Choe, Ik Rang; Sung, Taehoon; Kim, Young-O.; Lee, Yoon-Sik; Nam, Ki Tae; Kwon, Jang-Yeon

2017-08-01

Biocompatible biologically occurring polymer is suggested as a component of human implantable devices since conventional inorganic materials are apt to trigger inflammation and toxicity problem within human body. Peptides consisting of aromatic amino acid, tyrosine, are chosen, and enhancement on electrical conductivity is studied. Annealing process gives rise to the decrease on resistivity of the peptide films and the growth of the carrier concentration is a plausible reason for such a decrease on resistivity. The annealed peptides are further applied to an active layer of field effect transistor, in which low on/off current ratio (˜10) is obtained.

Electrostatically Induced Carbon Nanotube Alignment for Polymer Composite Applications

NASA Astrophysics Data System (ADS)

Chapkin, Wesley Aaron

We have developed a non-invasive technique utilizing polarized Raman spectroscopy to measure changes in carbon nanotube (CNT) alignment in situ and in real time in a polymer matrix. With this technique, we have confirmed the prediction of faster alignment for CNTs in higher electric fields. Real-time polarized Raman spectroscopy also allows us to demonstrate the loss of CNT alignment that occurs after the electric field is removed, which reveals the need for fast polymerization steps or the continued application of the aligning force during polymerization to lock in CNT alignment. Through a study on the effect of polymer viscosity on the rate of CNT alignment, we have determined that shear viscosity serves as the controlling mechanism for CNT rotation. This finding matches literature modeling of rigid rod mobility in a polymer melt and demonstrates that the rotational mobility of CNTs can be explained by a continuum model even though the diameters of single-walled CNTs are 1-2 nm. The viscosity dependence indicates that the manipulation of temperature (and indirectly viscosity) will have a direct effect on the rate of CNT alignment, which could prove useful in expediting the manufacturing of CNT-reinforced composites cured at elevated temperatures. Using real-time polarized Raman spectroscopy, we also demonstrate that electric fields of various strengths lead not only to different speeds of CNT rotation but also to different degrees of alignment. We hypothesize that this difference in achievable alignment results from discrete populations of nanotubes based on their length. The results are then explained by balancing the alignment energy for a given electric field strength with the randomizing thermal energy of the system. By studying the alignment dynamics of different CNT length distributions, we show that different degrees of alignment achieved as a function of the applied electric field strength are directly related to the square of the nanotube length. This finding matches an electrostatic potential energy model for CNT rotation. Lastly, we investigate the effects of conductive carbon fibers on electrostatically induced alignment of CNTs within carbon fiber composites. The relative electric field strength throughout the composite is modeled using COMSOL Multiphysics. We show the ability to generate enhanced electric field gradients within the gaps between carbon fibers for various fiber orientations. Using polarized Raman spectroscopy, increased levels of CNT alignment are observed between carbon fiber tows, which is consistent with the modeled higher electric field strengths in these regions. These findings could potentially lead to the development of carbon fiber composites with CNT additions that selectively enhance the composite properties outside the carbon fiber interphase in the neat epoxy.

Recent developments in the understanding of equatorial ionization anomaly: A review

NASA Astrophysics Data System (ADS)

Balan, N.; Souza, J.; Bailey, G. J.

2018-06-01

A brief review of the recent developments in the understanding of the equatorial plasma fountain (EPF) and equatorial ionization anomaly (EIA) under quiet and active conditions is presented. It is clarified that (1) the EPF is not upward ExB plasma drift at the equator followed by downward plasma diffusion, but it is field perpendicular ExB plasma drift and field-aligned plasma diffusion acting together all along the field lines at all altitudes and plasma flowing in the direction of the resultant. (2) The EIA is formed not from the accumulation of plasma at the crests but mainly from the removal of plasma from around the equator by the upward ExB drift with small accumulations when the crests are within approximately ±20° magnetic latitude. The accumulations reduce with increasing latitude and become zero by approximately ±25°. (3) An asymmetric neutral wind makes EPF and EIA asymmetric with stronger fountain and stronger crest usually occurring in opposite hemispheres especially at equinoxes when winter anomaly is absent. (4) During the early stages of daytime main phase of major geomagnetic storms, the plasma fountain becomes a super fountain and the EIA becomes strong not due to the eastward prompt penetration electric field (PPEF) alone but due to the combined effect of eastward PPEF and storm-time equatorward winds (SEW). (5) During the later stages of the storms when EIA gets inhibited a peak sometimes occurs around the equator not due to westward electric fields but mainly due to the convergence of plasma from both hemispheres due to SEW.

Microphysical and Kinematic Characteristics of Regions of Flash Initiation in a Supercell Storm and a Multicell Storm Observed During the DC3 Field Program

NASA Astrophysics Data System (ADS)

DiGangi, E.; MacGorman, D. R.; Ziegler, C.; Betten, D.; Biggerstaff, M. I.

2017-12-01

Lightning initiation in thunderstorms requires that the local electric field magnitude exceed breakdown values somewhere, and this tends to occur between regions of positive and negative charge, where the largest electric field magnitudes tend to occur. Past studies have demonstrated that, near updrafts, storms with very strong updrafts tend to elevate regions of charge and of flash initiations higher, as well as to have more flashes initiated by small pockets of charge, than in storms with much weaker updrafts. In all thunderstorms, the source of these charge regions is generally thought to be microscopic charge separation via the relative growth rate noninductive mechanism, followed by macroscopic charge separation via sedimentation, although other charge generation mechanisms can contribute to charge in some regions. Charge generation and lightning initiation are therefore inherently dependent on the microphysical and kinematic characteristics of a given storm. This study compares the results of a hydrometeor classification algorithm applied to C-band mobile radar data with mixing ratios calculated by a diabatic Lagrangian analysis retrieval from the dual-Doppler wind fields for two storms, the 29-30 May 2012 supercell storm and the 21 June 2012 multicell storm, observed during the Deep Convective Clouds and Chemistry experiment. Using these data, we then compare the inferred microphysical and kinematic characteristics of regions in which the Oklahoma Lightning Mapping Array indicated that flashes were initiated in these two very different storms.

Monitoring and Characterizing Crop Root Systems Using Electrical Impedance Tomography (EIT)

NASA Astrophysics Data System (ADS)

Weigand, M.; Kemna, A.

2016-12-01

A better understanding of root-soil interactions and associated processes is essential to achieve progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. Such methods are still lacking, in particular for characterizing root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which provides images of the low-frequency electrical conduction and polarization properties and thus can be used to investigate polarization processes occurring within and in the direct vicinity of roots under the influence of an external alternating electric field. This approach takes advantage of the well-known polarization properties associated with electrical double layers forming at membranes of cells and cell clusters. However, upscaling these processes to the scale of an impedance, or complex conductivity, spectrum of the whole root system is not trivial given the lack of electrical root models, the complexity of root systems, and the occurrence of additional larger-scale, ion-selective, and therefore polarizable, structures such as the Casparian strip. We here present results from several EIT laboratory studies on rhizotrons with crop root systems in aqueous solutions. Based on optimized experimental and data analysis procedures, enabling the imaging of the weak signals encountered in our studies, we found systematic spatial and temporal changes of both the magnitude and the shape of the spectral polarization signatures during nutrient deprivation and in response to the decapitation of plants. Consistent, but relatively weak, spectral impedance changes were also observed over diurnal cycles. Our results provide evidence for the capability of EIT to non-invasively image and monitor root systems at the rhizotron scale. They further suggest that EIT is a promising tool for imaging, characterizing, and monitoring crop roots at the field scale.

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.

Sources of anomalous transient electric signals (ATESs) in the ULF band in the Lamia region (central Greece): electrochemical mechanisms for their generation

NASA Astrophysics Data System (ADS)

Pham, V.-N.; Boyer, D.; Chouliaras, G.; Savvaidis, A.; Stavrakakis, G.; Le Mouël, J.-L.

2002-04-01

Anomalous transient electric signals (ATESs) in the ultra low frequency (ULF) band have been often observed during magnetotelluric (MT) investigations [Nature 319 (1986) 310; Phys. Earth Planet. Int. 114 (1999) 141; Geophys. J. Int. 142 (2000) 948], but their origin was unknown until now. They have the same characteristics as the so-called seismic electric signals (SES) claimed to be earthquake precursors by the VAN group (e.g. [Tectonophysics 110 (1984) 73] and later works by this group). Our analysis suggests that the so-called SES could be of anthropic origin. Following the devastating 7 September 1999 Athens earthquake, the VAN group claimed that a SES had been recorded at LAM station (Lamia, central Greece) some days prior to the main shock and that a second SES, which might correspond to an impending even larger earthquake, had been observed after the main shock. In the 2 years after the Athens main shock, no subsequent large earthquakes have occurred near Athens. We conducted a campaign of measurement in the Lamia region in May and June 2001. The results show that ATESs, which look like SES, have several different sources: pump-stations for ground-water, high power electric lines, and factories located to the SE of Lamia city. The ATESs can be generated by two electrochemical mechanisms of metallic electrode polarization: the "galvanic cell" and the "ac electrolytic cell" which are studied by simulated field experiments and discussed in detail in Appendix A. These two mechanisms can occur over a wide range of length scales in the field. Any isolation failure in buried metallic conductors, such as electrical and telecommunication networks, oil, water and gas pipes, railways, high power electric lines, factories and so on, can produce a galvanic cell or an ac electrolytic cell, or both, which could generate, under some circumstances, an "overvoltage", the ATES. Finally, the absence of a magnetic signal has been observed during ATES and does not constitute a firm criterion for SES [Acta Geophys. Pol. 44 (1996b) 301]. Thus, great care must be taken when claiming the existence of electric precursors of seismic or volcanic events.

Fluctuations in Student Understanding of Newton's 3rd Law

NASA Astrophysics Data System (ADS)

Clark, Jessica W.; Sayre, Eleanor C.; Franklin, Scott V.

2010-10-01

We present data from a between-student study on student response to questions on Newton's Third Law given throughout the academic year. The study, conducted at Rochester Institute of Technology, involved students from the first and third of a three-quarter sequence. Construction of a response curve reveals subtle dynamics in student learning not captured by simple pre/post testing. We find a a significant positive effect from direct instruction, peaking at the end of instruction on forces, that diminishes by the end of the quarter. Two quarters later, in physics III, a significant dip in correct response occurs when instruction changes from the vector quantities of electric forces and fields to the scalar quantity of electric potential. Student response rebounds to its initial values, however, once instruction returns to the vector-based topics involving magnetic fields.

Coordination nano-space as stage of hydrogen ortho–para conversion

PubMed Central

Kosone, Takashi; Hori, Akihiro; Nishibori, Eiji; Kubota, Yoshiki; Mishima, Akio; Ohba, Masaaki; Tanaka, Hiroshi; Kato, Kenichi; Kim, Jungeun; Real, José Antonio; Kitagawa, Susumu; Takata, Masaki

2015-01-01

The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)–para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o–p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o–p conversion. PMID:26587262

Turbulent inward pinch of plasma confined by a levitated dipole magnet

NASA Astrophysics Data System (ADS)

Boxer, A. C.; Bergmann, R.; Ellsworth, J. L.; Garnier, D. T.; Kesner, J.; Mauel, M. E.; Woskov, P.

2010-03-01

The rearrangement of plasma as a result of turbulence is among the most important processes that occur in planetary magnetospheres and in experiments used for fusion energy research. Remarkably, fluctuations that occur in active magnetospheres drive particles inward and create centrally peaked profiles. Until now, the strong peaking seen in space has been undetectable in the laboratory because the loss of particles along the magnetic field is faster than the net driven flow across the magnetic field. Here, we report the first laboratory measurements in which a strong superconducting magnet is levitated and used to confine high-temperature plasma in a configuration that resembles planetary magnetospheres. Levitation eliminates field-aligned particle loss, and the central plasma density increases markedly. The build-up of density characterizes a sustained turbulent pinch and is equal to the rate predicted from measured electric-field fluctuations. Our observations show that dynamic principles describing magnetospheric plasma are relevant to plasma confined by a levitated dipole.

[National system of protection against electromagnetic fields 0 Hz-300 GHz in the light of current legal regulations].

PubMed

Aniołczyk, Halina

2006-01-01

Exposure to electromagnetic fields (EMF) occurs when man is exposed to the effect of electric, magnetic and electromagnetic fields and contact currents different from those resulting from physiological processes in the organism or other natural phenomena. In Poland, the system of protection against EMF has been functioning for over 35 years. In 2001, when the Minister of Labor and Social Policy issued the regulation introducing the maximum admissible intensities (MAI) for electromagnetic fields and radiation within the range of 0 Hz-300 GHz, the system was directed mainly towards evaluation of exposure to EMF occurring in the occupational environment. The system is linked via MAI values with human protection in the natural environment. In this paper, the background, principles and the range of the national system of protection against EMF and its monitoring are presented. The project of implementation of EU directives, following Poland's accession to the European Union is also discussed.

Magnetic field of the Earth

NASA Astrophysics Data System (ADS)

Popov, Aleksey

2013-04-01

The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws of electromagnetism. According to a rule of the left hand: if the magnetic field in a kernel is directed to drawing, electric current are directed to an axis of rotation of the Earth, - a action of force clockwise (to West). Definition of the force causing drift a kernel according to the law of Ampere F = IBlsin. Powerful force 3,5 × 1012 Nyton, what makes drift of the central part of a kernel of the Earth on 0,2 the longitude in year to West, and also it is engine of the mechanism of movement of slabs together with continents. Movement of a core of the Earth carry out around of a terrestrial axis one circulation in the western direction in 2000 of years. Linear speed of rotation of a kernel concerning a mantle on border the mantle a kernel: V = × 3,471 × 10 = 3,818 × 10 m/s = 33 m/day = 12 km/years. Considering greater viscosity of a mantle, the powerful energy at rotation of a kernel seize a mantle and lithospheric slabs and makes their collisions as a result of which there are earthquakes and volcano. Continents Northern and Southern America every year separate from the Europe and Africa on several centimeters. Atlantic ocean as a result of movement of these slabs with such speed was formed for 200 million years, that in comparison with the age of the Earth - several billions years, not so long time. Drift of a kernel in the western direction is a principal cause of delay of speed of rotation of the Earth. Flow of radial electric currents allot according to the law of Joule - Lenz, the quantity of warmth : Q = I2Rt = IUt, of thermal energy 6,92 × 1017 calories/year. This defines heating of a kernel and the Earth as a whole. In the valley of the median-Atlantic ridge having numerous volcanos, the lava flow constantly thus warm up waters of Atlantic ocean. It is a fact the warm current Gulf Stream. Thawing of a permafrost and ices of Arctic ocean, of glaciers of Greenland and Antarctica is acknowledgement: the warmth of earth defines character of thawing of glaciers and a permafrost. This is a global warming. The version of the author: the periods of inversion of a magnetic field of the Earth determine cycles of the Ice Age. At inversions of a magnetic field when B=0, radial electric currents are small or are absent, excretion of thermal energy minimally or an equal to zero,it is the beginning of the cooling the Earth and offensive of the Ice Age. Disappearance warm current Gulf Stream warming the north of the Europe and Canada. Drift of a magnetic dipole of the Earth in a rotation the opposite to rotation of the Earth, is acknowledgement of drift of a kernel of the Earth in a rotation the opposite to rotation of the Earth and is acknowledgement of the theory « the Magnetic field of the Earth ». The author continues to develop the theory « the Magnetic field of the Earth » and invites geophysicists to accept in it participation in it.

Analysis of the processes occurring in a submicrosecond discharge with a linear current density of up to 3 MA/cm through a thick-wall stainless-steel electrode

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

Branitsky, A. V.; Grabovski, E. V.; Dzhangobegov, V. V.

The state of conductors carrying a megampere current from the generator to the load is studied experimentally. It is found that the plasma produced from cylindrical stainless-steel tubes during the passage of a submicrosecond current pulse with a linear density of 3 MA/cm expands with a velocity of 5.5 km/s. Numerical results on the diffusion of the magnetic field induced by a current with a linear density of 1–3MA/cm into metal electrodes agree with the experimental data on the penetration time of the magnetic field. For a linear current density of 3.1 MA/cm, the experimentally determined electric field strength onmore » the inner surface of the tube is 4 kV/cm. The calculated electric field strength on the inner surface of the tube turns out to be two times higher, which can be explained by plasma production on the outer and inner surfaces of the electrode.« less

Dephasing effects on ac-driven triple quantum dot systems

NASA Astrophysics Data System (ADS)

Maldonado, I.; Villavicencio, J.; Contreras-Pulido, L. D.; Cota, E.; Maytorena, J. A.

2018-05-01

We analyze the effect of environmental dephasing on the electrical current in an ac-driven triple quantum dot system in a symmetric Λ configuration. The current is explored by solving the time evolution equation of the density matrix as a function of the frequency and amplitude of the driving field. Two characteristic spectra are observed depending on the field amplitude. At the resonance condition, when the frequency matches the interdot energy difference, one spectrum shows a distinctive Fano-type peak, while the other, occurring at larger values of the field amplitude, exhibits a strong current suppression due to dynamic localization. In the former case we observe that the current maximum is reduced due to dephasing, while in the latter it is shown that dephasing partially alleviates the localization. In both cases, away from resonance, we observe current oscillations which are dephasing-enhanced for a wide range of frequencies. These effects are also discussed using Floquet theory, and analytical expressions for the electrical current are obtained within the rotating wave approximation.

Giant Stark effect in double-stranded porphyrin ladder polymers

NASA Astrophysics Data System (ADS)

Pramanik, Anup; Kang, Hong Seok

2011-03-01

Using the first-principles calculations, we have investigated the stability and the electronic structure of two types of recently synthesized one-dimensional nanoribbons, i.e., double-stranded zinc(II) porphyrin ladder polymer (LADDER) arrays. First, electronic structure calculations were used to show that the LADDER is a semiconductor. Most importantly, the application of a transverse electric field significantly reduces the band gap of the LADDER, ultimately converting the LADDER to a metal at a field strength of 0.1 V/Å. The giant Stark effect in this case is almost as strong as that in boron nitride nanotubes and nanoribbons. In the presence of an electric field, hole conduction and electronic conduction will occur entirely through spatially separated strands, rendering these materials useful for nanoelectronic devices. Second, the substitution of hydrogen atoms in the porphyrin units or that of zinc ions with other kinds of chemical species is found to increase the binding strength of the LADDER and reduce the band gap.

Quantum transport in new two-dimensional heterostructures: Thin films of topological insulators, phosphorene

NASA Astrophysics Data System (ADS)

Majidi, Leyla; Zare, Moslem; Asgari, Reza

2018-06-01

The unusual features of the charge and spin transport characteristics are investigated in new two-dimensional heterostructures. Intraband specular Andreev reflection is realized in a topological insulator thin film normal/superconducting junction in the presence of a gate electric field. Perfect specular electron-hole conversion is shown for different excitation energy values in a wide experimentally available range of the electric field and also for all angles of incidence when the excitation energy has a particular value. It is further demonstrated that the transmission probabilities of the incoming electrons from different spin subbands to the monolayer phosphorene ferromagnetic/normal/ferromagnetic (F/N/F) hybrid structure have different behavior with the angle of incidence and perfect transmission occurs at defined angles of incidence to the proposed structure with different length of the N region, and different alignments of magnetization vectors. Moreover, the sign change of the spin-current density is demonstrated by tuning the chemical potential and exchange field of the F region.

Ion-Scale Structure in Mercury's Magnetopause Reconnection Diffusion Region

NASA Technical Reports Server (NTRS)

Gershman, Daniel J.; Dorelli, John C.; DiBraccio, Gina A.; Raines, Jim M.; Slavin, James A.; Poh, Gangkai; Zurbuchen, Thomas H.

2016-01-01

The strength and time dependence of the electric field in a magnetopause diffusion region relate to the rate of magnetic reconnection between the solar wind and a planetary magnetic field. Here we use approximately 150 milliseconds measurements of energetic electrons from the Mercury Surface, Space Environment, GEochemistry, and Ranging (MESSENGER) spacecraft observed over Mercury's dayside polar cap boundary (PCB) to infer such small-scale changes in magnetic topology and reconnection rates. We provide the first direct measurement of open magnetic topology in flux transfer events at Mercury, structures thought to account for a significant portion of the open magnetic flux transport throughout the magnetosphere. In addition, variations in PCB latitude likely correspond to intermittent bursts of approximately 0.3 to 3 millivolts per meter reconnection electric fields separated by approximately 5 to10 seconds, resulting in average and peak normalized dayside reconnection rates of approximately 0.02 and approximately 0.2, respectively. These data demonstrate that structure in the magnetopause diffusion region at Mercury occurs at the smallest ion scales relevant to reconnection physics.

Improved negative ion source

DOEpatents

Delmore, J.E.

1984-05-01

A method and apparatus for providing a negative ion source accelerates electrons away from a hot filament electron emitter into a region of crossed electric and magnetic fields arranged in a magnetron configuration. During a portion of the resulting cycloidal path, the electron velocity is reduced below its initial value. The electron accelerates as it leaves the surface at a rate of only slightly less than if there were no magnetic field, thereby preventing a charge buildup at the surface of the emitter. As the electron traverses the cycloid, it is decelerated during the second, third, and fourth quadrants, then reaccelerated as it approaches the end of the fourth quadrant to regain its original velocity. The minimum velocity occurs during the fourth quadrant, and corresponds to an electron temperature of 200 to 500/sup 0/C for the electric and magnetic fields commonly encountered in the ion sources of magnetic sector mass spectrometers. An ion source using the above-described thermalized electrons is also disclosed.

Influence of Electric Fields on Biofouling of Carbonaceous Electrodes.

PubMed

Pandit, Soumya; Shanbhag, Sneha; Mauter, Meagan; Oren, Yoram; Herzberg, Moshe

2017-09-05

Biofouling commonly occurs on carbonaceous capacitive deionization electrodes in the process of treating natural waters. Although previous work reported the effect of electric fields on bacterial mortality for a variety of medical and engineered applications, the effect of electrode surface properties and the magnitude and polarity of applied electric fields on biofilm development has not been comprehensively investigated. This paper studies the formation of a Pseudomonas aeruginosa biofilm on a Papyex graphite (PA) and a carbon aerogel (CA) in the presence and the absence of an electric field. The experiments were conducted using a two-electrode flow cell with a voltage window of ±0.9 V. The CA was less susceptible to biofilm formation compared to the PA due to its lower surface roughness, lower hydrophobicity, and significant antimicrobial properties. For both positive and negative applied potentials, we observed an inverse relationship between biofilm formation and the magnitude of the applied potential. The effect is particularly strong for the CA electrodes and may be a result of cumulative effects between material toxicity and the stress experienced by cells at high applied potentials. Under the applied potentials for both electrodes, high production of endogenous reactive oxygen species (ROS) was indicative of bacterial stress. For both electrodes, the elevated specific ROS activity was lowest for the open circuit potential condition, elevated when cathodically and anodically polarized, and highest for the ±0.9 V cases. These high applied potentials are believed to affect the redox potential across the cell membrane and disrupt redox homeostasis, thereby inhibiting bacterial growth.

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

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

Cheng, Li-Hong; Xue, Ju-Kui, E-mail: xuejk@nwnu.edu.cn; Liu, Jie, E-mail: liu-jie@iapcm.ac.cn

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 lasermore » 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.« less

Seismomagnetic effects from the long-awaited 28 September 2004 M 6.0 parkfield earthquake

USGS Publications Warehouse

Johnston, M.J.S.; Sasai, Y.; Egbert, G.D.; Mueller, R.J.

2006-01-01

Precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked-to-creeping transition region of the San Andreas fault at Parkfield, California, since 1976. The M 6.0 Parkfield earthquake on 28 September 2004, occurred within this array and generated coseismic magnetic field changes of between 0.2 and 0.5 nT at five sites in the network. No preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month, week, and days before the earthquake (or expected in light of the absence of measurable precursive deformation, seismicity, or pore pressure changes). Observations of electric and magnetic fields from 0.01 to 20 Hz are also made at one site near the end of the earthquake rupture and corrected for common-mode signals from the ionosphere/magnetosphere using a second site some 115 km to the northwest along the fault. These magnetic data show no indications of unusual noise before the earthquake in the ULF band (0.01-20 Hz) as suggested may have preceded the 1989 ML 7.1 Loma Prieta earthquake. Nor do we see electric field changes similar to those suggested to occur before earthquakes of this magnitude from data in Greece. Uniform and variable slip piezomagnetic models of the earthquake, derived from strain, displacement, and seismic data, generate magnetic field perturbations that are consistent with those observed by the magnetometer array. A higher rate of longer-term magnetic field change, consistent with increased loading in the region, is apparent since 1993. This accompanied an increased rate of secular shear strain observed on a two-color EDM network and a small network of borehole tensor strainmeters and increased seismicity dominated by three M 4.5-5 earthquakes roughly a year apart in 1992, 1993, and 1994. Models incorporating all of these data indicate increased slip at depth in the region, and this may have played a role in the final occurrence of the 28 September 2004 M 6.0 Parkfield earthquake. The absence of electric and magnetic field precursors for this, and other earthquakes with M 5-7.3 elsewhere in the San Andreas fault system, indicates useful prediction of damaging earthquakes seems unlikely using these electromagnetic data.

Transmembrane potential measurements on plant cells using the voltage-sensitive dye ANNINE-6.

PubMed

Flickinger, Bianca; Berghöfer, Thomas; Hohenberger, Petra; Eing, Christian; Frey, Wolfgang

2010-11-01

The charging of the plasma membrane is a necessary condition for the generation of an electric-field-induced permeability increase of the plasmalemma, which is usually explained by the creation and the growth of aqueous pores. For cells suspended in physiological buffers, the time domain of membrane charging is in the submicrosecond range. Systematic measurements using Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) protoplasts stained with the fast voltage-sensitive fluorescence dye ANNINE-6 have been performed using a pulsed laser fluorescence microscopy setup with a time resolution of 5 ns. A clear saturation of the membrane voltage could be measured, caused by a strong membrane permeability increase, commonly explained by enhanced pore formation, which prevents further membrane charging by external electric field exposure. The field strength dependence of the protoplast's transmembrane potential V (M) shows strong asymmetric saturation characteristics due to the high resting potential of the plants plasmalemma. At the pole of the hyperpolarized hemisphere of the cell, saturation starts at an external field strength of 0.3 kV/cm, resulting in a measured transmembrane voltage shift of ∆V(M) = -150 mV, while on the cathodic (depolarized) cell pole, the threshold for enhanced pore formation is reached at a field strength of approximately 1.0 kV/cm and ∆V(M) = 450 mV, respectively. From this asymmetry of the measured maximum membrane voltage shifts, the resting potential of BY-2 protoplasts at the given experimental conditions can be determined to V(R) = -150 mV. Consequently, a strong membrane permeability increase occurs when the membrane voltage diverges |V(M)| = 300 mV from the resting potential of the protoplast. The largest membrane voltage change at a given external electric field occurs at the cell poles. The azimuthal dependence of the transmembrane potential, measured in angular intervals of 10° along the circumference of the cell, shows a flattening and a slight decrease at higher fields at the pole region due to enhanced pore formation. Additionally, at the hyperpolarized cell pole, a polarization reversal could be observed at an external field range around 1.0 kV/cm. This behavior might be attributed to a fast charge transfer through the membrane at the hyperpolarized pole, e.g., by voltage-gated channels.

Mathematical Modeling of Electrodynamics Near the Surface of Earth and Planetary Water Worlds

NASA Technical Reports Server (NTRS)

Tyler, Robert H.

2017-01-01

An interesting feature of planetary bodies with hydrospheres is the presence of an electrically conducting shell near the global surface. This conducting shell may typically lie between relatively insulating rock, ice, or atmosphere, creating a strong constraint on the flow of large-scale electric currents. All or parts of the shell may be in fluid motion relative to main components of the rotating planetary magnetic field (as well as the magnetic fields due to external bodies), creating motionally-induced electric currents that would not otherwise be present. As such, one may expect distinguishing features in the types of electrodynamic processes that occur, as well as an opportunity for imposing specialized mathematical methods that efficiently address this class of application. The purpose of this paper is to present and discuss such specialized methods. Specifically, thin-shell approximations for both the electrodynamics and fluid dynamics are combined to derive simplified mathematical formulations describing the behavior of these electric currents as well as their associated electric and magnetic fields. These simplified formulae allow analytical solutions featuring distinct aspects of the thin-shell electrodynamics in idealized cases. A highly efficient numerical method is also presented that is useful for calculations under inhomogeneous parameter distributions. Finally, the advantages as well as limitations in using this mathematical approach are evaluated. This evaluation is presented primarily for the generic case of bodies with water worlds or other thin spherical conducting shells. More specific discussion is given for the case of Earth, but also Europa and other satellites with suspected oceans.

Electromagnetic compatibility and the all-electric airplane

NASA Technical Reports Server (NTRS)

Christman, Al

1995-01-01

NASA is studying the feasibility of installing 'all-electric' controls in future commercial aircraft, replacing the current hydraulic and pneumatic systems. Planes utilizing such equipment should weigh less and be cheaper to maintain, but might also be susceptible to interference from undesired external electromagnetic fields. Possible sources of these extraneous signals include radio and television broadcasters, two-way communications stations, and radar installations of all kinds. One way to reduce the hazard would be to use fiber-optic cables to carry signals from the cockpit to the various points of use, a concept known as 'fly-by-light' or FBL. However, electrical circuits (PBW, or 'power-by-wire') would still be required at both ends of the cables to perform control functions, so the possibility of harmful interference would remain. Computer models for two different antennas were created in order to find the magnitude of the electric fields which would be generated in the airspace around them while in the transmit mode. The first antenna was a horizontal 'rhombic' used by the Voice of America (VOA) for long-distance short-wave broadcasting. The second antenna was a multi-element 'log-periodic dipole array' (LPDA) of a type often used for two-way radio communications. For each case, a specified amount of power was applied in the computer model, and the resulting electric field intensity was predicted at a variety of locations surrounding the antenna. This information will then be used to calculate the levels of interference which could occur inside an airplane flying in the vicinity of these radiation emitters.

Cable Bacteria in Freshwater Sediments

PubMed Central

Kristiansen, Michael; Frederiksen, Rasmus B.; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

2015-01-01

In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage. PMID:26116678

Auroral zone electric fields from DE 1 and 2 at magnetic conjunctions

NASA Technical Reports Server (NTRS)

Weimer, D. R.; Goertz, C. K.; Gurnett, D. A.; Maynard, N. C.; Burch, J. L.

1985-01-01

Nearly simultaneous measurements of auroral zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4,500 km during magnetic conjunctions. The measured electric fields are usually perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function which accounts for the convergence of the magnetic field lines. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by both DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes, as expected. Superimposed on the large-scale fields, however, are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the auroral zone the electric field spectrums are nearly identical. But within the auroral zone the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1.

Multipoint Spacecraft Observations of Long-Lasting Poloidal Pc4 Pulsations in the Dayside Magnetosphere on 1-2 May 2014

NASA Technical Reports Server (NTRS)

Korotova, Galina; Sibeck, David; Engebretson, Mark; Wygant, John; Thaller, Scott; Spence, Harlan; Kletzing, Craig; Angelopoulos, Vassilis; Redmon, Robert

2016-01-01

We use magnetic field and plasma observations from the Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geostationary Operational Environmental Satellite system (GOES) spacecraft to study the spatial and temporal characteristics of long-lasting poloidal Pc4 pulsations in the dayside magnetosphere. The pulsations were observed after the main phase of a moderate storm during low geomagnetic activity. The pulsations occurred during various interplanetary conditions and the solar wind parameters do not seem to control the occurrence of the pulsations. The most striking feature of the Pc4 magnetic field pulsations was their occurrence at similar locations during three of four successive orbits. We used this information to study the latitudinal nodal structure of the pulsations and demonstrated that the latitudinal extent of the magnetic field pulsations did not exceed 2 Earth radii (R(sub E)). A phase shift between the azimuthal and radial components of the electric and magnetic fields was observed from Z(sub SM) = 0.30 R(sub E) to Z(sub SM) = -0.16 R(sub E). We used magnetic and electric field data from Van Allen Probes to determine the structure of ULF waves. We showed that the Pc4 magnetic field pulsations were radially polarized and are the second-mode harmonic waves. We suggest that the spacecraft were near a magnetic field null during the second orbit when they failed to observe the magnetic field pulsations at the local times where pulsations were observed on previous and successive orbits. We investigated the spectral structure of the Pc4 pulsations. Each spacecraft observed a decrease of the dominant period as it moved to a smaller L shell (stronger magnetic field strength). We demonstrated that higher frequencies occurred at times and locations where Alfven velocities were greater, i.e., on Orbit 1. There is some evidence that the periods of the pulsations increased during the plasmasphere refilling following the storm.

Binding and release of brain calcium by low-level electromagnetic fields: A review

NASA Astrophysics Data System (ADS)

Adey, W. R.; Bawin, S. M.

Evidence has accumulated that sensitivity of brain tissue to specific weak oscillating electromagnetic fields occurs in the absence of significant tissue heating (less than 0.1°C). This review focuses on the ‘windowed’ character of sensitivities of calcium binding and electrical activity in brain tissue to low-frequency modulation and intensity characteristics of impressed RF fields. ELF fields decrease calcium efflux from isolated chick and cat cerebral tissue by about 15% only in narrow amplitude and frequency ‘windows,’ between 6 and 20 Hz and between 10 and 100 V/m (approximate tissue gradient, 10-7 V/cm). VHF (147 MHz) and UHF (450 MHz) fields increase calcium efflux from isolated chick brain by about 15% when amplitude modulated between 6 and 20 Hz, but only for incident fields in the vicinity of 1.0 mW/cm2. We have now shown that this increased efflux in response to 16-Hz amplitude-modulated 450-MHz, 0.75-mW/cm2 field exposure is insensitive to variations in calcium concentration from 0 to 4.16 mM in the testing solution but is enhanced by addition of hydrogen ions (0.108 mM 0.1 N HCl) and inhibited in the absence of normal bicarbonate ion levels (2.4 mM). In the presence of lanthanum ions (2.0 mM), which block transmembrane movement of calcium, exposure to these EM fields decreases the 45Ca2 + efflux. Low-frequency gradients may be transduced in a specific class of extracellular binding sites, normally occupied by calcium ions and susceptible to competitive hydrogen ion binding. Transductive coupling may involve coherent charge states between anionic sites on membrane surface glycoproteins, with longrange cooperative interactions triggered by weak extracellular electric fields. Proton ‘tunneling’ may occur at boundaries between coherent and noncoherent charge zones.

Particle Dynamics at and near the Electron and Ion Diffusion Regions as a Function of Guide Field

NASA Astrophysics Data System (ADS)

Giles, Barbara; Burch, James; Phan, Tai; Webster, James; Avanov, Levon; Torbert, Roy; Chen, Li-Jen; Chandler, Michael; Dorelli, John; Ergun, Robert; Fuselier, Stephen; Gershman, Daniel; Lavraud, Benoit; Moore, Thomas; Paterson, William; Pollock, Craig; Russell, Christopher; Saito, Yoshifumi; Strangeway, Robert; Wang, Shan

2017-04-01

At the dayside magnetopause, magnetic reconnection often occurs in thin sheets of plasma carrying electrical currents and rotating magnetic fields. Charged particles interact strongly with the magnetic field and simultaneously their motions modify the fields. Researchers are able to simulate the macroscopic interactions between the two plasma domains on both sides of the magnetopause and, for precise results, include individual particle motions to better describe the microscopic scales. Here, observed ion and electron distributions are compared for asymmetric reconnection events with weak-, moderate-, and strong-guide fields. Several of the structures noted have been demonstrated in simulations and others have not been predicted or explained to date. We report on these observations and their persistence. In particular, we highlight counterstreaming low-energy ion distributions that are seen to persist regardless of increasing guide-field. Distributions of this type were first published by Burch and Phan [GRL, 2016] for an 8 Dec 2015 event and by Wang et al. [GRL, 2016] for a 16 Oct 2015 event. Wang et al. showed the distributions were produced by the reflection of magnetosheath ions by the normal electric field at the magnetopause. This report presents further results on the relationship between the counterstreaming ions with electron distributions, which show the ions traversing the magnetosheath, X-line, and in one case the electron stagnation point. We suggest the counterstreaming ions become the source of D-shaped distributions at points where the field line opening is indicated by the electron distributions. In addition, we suggest they become the source of ion crescent distributions that result from acceleration of ions by the reconnection electric field. Burch, J. L., and T. D. Phan (2016), Magnetic reconnection at the dayside magnetopause: Advances with MMS, Geophys. Res. Lett., 43, 8327-8338, doi:10.1002/2016GL069787. Wang, S., et al. (2016), Two-scale ion meandering caused by the polarization electric field during asymmetric reconnection, Geophys. Res. Lett., 43, 7831-7839, doi:10.1002/2016GL069842.

Analysis of Surface Electric Field Measurements from an Array of Electric Field Mills

NASA Astrophysics Data System (ADS)

Lucas, G.; Thayer, J. P.; Deierling, W.

2016-12-01

Kennedy Space Center (KSC) has operated an distributed array of over 30 electric field mills over the past 18 years, providing a unique data set of surface electric field measurements over a very long timespan. In addition to the electric field instruments there are many meteorological towers around KSC that monitor the local meteorological conditions. Utilizing these datasets we have investigated and found unique spatial and temporal signatures in the electric field data that are attributed to local meteorological effects and the global electric circuit. The local and global scale influences on the atmospheric electric field will be discussed including the generation of space charge from the ocean surf, local cloud cover, and a local enhancement in the electric field that is seen at sunrise.

Photogeneration of Charge Carriers in Bilayer Assemblies of Conjugated Rigid-Rod Polymers

DTIC Science & Technology

1994-07-08

photoinduced electron transfer and exciplex formation at the bilayer interface. Thus photocarrier generation on photoexcitation of the conjugated rigid...rod polymers in the bilayer occurs by photoinduced electron transfer, forming intermolecular exciplexes which dissociate efficiently in electric field...photogeneration, conjugated rigid-rod polymers, is. MACI COD bilayer assemblies, electron transfer, exciplexes . 11. SEOJUTY CLASUICA 10. 51(11MIE CLASSIMIAVION

A Comparison of Inductive Sensors in the Characterization of Partial Discharges and Electrical Noise Using the Chromatic Technique.

PubMed

Ardila-Rey, Jorge Alfredo; Montaña, Johny; de Castro, Bruno Albuquerque; Schurch, Roger; Covolan Ulson, José Alfredo; Muhammad-Sukki, Firdaus; Bani, Nurul Aini

2018-03-29

Partial discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. PD detection is a standardized technique to qualify the state of the insulation in electric assets such as machines and power cables. Generally, the classical phase-resolved partial discharge (PRPD) patterns are used to perform the identification of the type of PD source when they are related to a specific degradation process and when the electrical noise level is low compared to the magnitudes of the PD signals. However, in practical applications such as measurements carried out in the field or in industrial environments, several PD sources and large noise signals are usually present simultaneously. In this study, three different inductive sensors have been used to evaluate and compare their performance in the detection and separation of multiple PD sources by applying the chromatic technique to each of the measured signals.

An experimental investigation of electric flashover across solid insulators in vacuum

NASA Technical Reports Server (NTRS)

Vonbaeyer, H. C.

1984-01-01

The insulation of high voltage conductors often employs solid insulators for many applications. In such applications, an unexpected electric flashover may occur along the insulator surface. Under conditions of high vacuum, the flashover voltage across the insulator is observed to be lower compared with that of the same electrode separation without an insulator. The reason for such an extreme reduction of flashover voltage is not well understood. Several models based on the secondary electron emission, were proposed to explain the onset of the surface flashover. The starting point and the developing velocity of the surface flashover were determined. An intensified image converter camera was used to observe the initial stage of electrical flashover along the insulator surface parallel to the electric field. Several different insulator materials were used as test pieces to determine the effect of the dielectric constant on the flashover voltage characteristics.

X-ray Production in a Laboratory Streamer Discharge

NASA Astrophysics Data System (ADS)

Lehtinen, N. G.; Kochkin, P.; Ostgaard, N.

2016-12-01

A 1D model of a 1-m scale laboratory discharge streamer system [Lehtinen et al, 2016, http://meetingorganizer.copernicus.org/EGU2016/EGU2016-6180.pdf] has reproduced the experimentally-observed [Kochkin et al, 2014, doi:10.1088/0022-3727/47/14/145203] detached streamer systems (pilots). The pilots grow in both directions and thus produce counter-streamers which collide with forward-moving streamers, a mechanism which was proposed to lead to the production of x-rays [Cooray, 2009, doi:10.1016/j.jastp.2009.07.010]. However, the 1D model is insufficient to analyse this process because in this model the electric field between the colliding streamers is averaged in the transverse direction and therefore the maximum fields are underestimated. In this presentation, we include the microscopic processes in the modeling of streamer propagation in order to calculate accurately the electric field enhancement between colliding streamers of opposite polarity. We evaluate the temporal and spatial characteristics of the enhanced electric field, which define the production of relativistic runaway electrons and x-rays. The x-ray output for the conditions occuring in a laboratory discharge is compared to the experimental data [Kochkin et al, 2012, doi:10.1088/0022-3727/45/42/425202; 2015, doi:10.1088/0022-3727/48/2/025205]. We note that the previous modeling of streamer collisions [Ihaddadene and Celestin, 2015, doi:10.1002/2015GL064623] obtained the field enhancements which are insufficient for the observed x-ray production.

Electrotropism of maize roots. Role of the root cap and relationship to gravitropism

NASA Technical Reports Server (NTRS)

Ishikawa, H.; Evans, M. L.

1990-01-01

We examined the kinetics of electrotropic curvature in solutions of low electrolyte concentration using primary roots of maize (Zea mays L., variety Merit). When submerged in oxygenated solution across which an electric field was applied, the roots curved rapidly and strongly toward the positive electrode (anode). The strength of the electrotropic response increased and the latent period decreased with increasing field strength. At a field strength of 7.5 volts per centimeter the latent period was 6.6 minutes and curvature reached 60 degrees in about 1 hour. For electric fields greater than 10 volts per centimeter the latent period was less than 1 minute. There was no response to electric fields less than 2.8 volts per centimeter. Both electrotropism and growth were inhibited when indoleacetic acid (10 micromolar) was included in the medium. The auxin transport inhibitor pyrenoylbenzoic acid strongly inhibited electrotropism without inhibiting growth. Electrotropism was enhanced by treatments that interfere with gravitropism, e.g. decapping the roots or pretreating them with ethyleneglycol-bis-[beta-ethylether]-N,N,N',N' -tetraacetic acid. Similarly, roots of agravitropic pea (Pisum sativum, variety Ageotropum) seedlings were more responsive to electrotropic stimulation than roots of normal (variety Alaska) seedlings. The data indicate that the early steps of gravitropism and electrotropism occur by independent mechanisms. However, the motor mechanisms of the two responses may have features in common since auxin and auxin transport inhibitors reduced both gravitropism and electrotropism.

Anatomical and morphogenetic analysis of seismoelectric conversion patterns at geological units

NASA Astrophysics Data System (ADS)

Kröger, B.; Kemna, A.

2012-04-01

Characterisation of the hydraulic properties of a reservoir, such as porosity and permeability, and their spatial distribution plays an important role in many subsurface geophysical investigations. A fully developed seismoelectric exploration method is very appealing since it would offer the potential to directly determine these parameters in field-scale applications. In fluid-saturated rocks, seismic waves can generate electromagnetic fields, due to electrokinetic coupling mechanisms at the fluid-mineral interface. Using numerical modelling, we investigated the spatio-temporal occurrence and evolution of the seismoelectric effects that occur in spatially confined lithological units. Such geometries may represent clay lenses embedded in an aquifer or petroleum deposits in a host rock. For the modelling, we use a simplified time-domain formulation of the coupled physical problem and its efficient implementation in a 2D finite-element framework. Two occurring seismoelectric phenomena are investigated: (1) the co-seismic field associated with the seismic displacement at each point and (2) the interface response generated at layer boundaries. To gain insight into the morphogenetic field behaviour of the seismoelectric effects, we run numerical simulations using several material parameter set-ups for various target geometries. Accordingly, we varied both the thickness of the confined units and the value of the electrical bulk conductivity in the considered media. The analysis of the seismoelectric effects revealed an important difference in the generation of the interface response at either electrically conductive or resistive units. We find that the contrast in the electrical bulk conductivity between the host rock and the target geological unit controls the shape and structure of the seismoelectric conversion patterns. Our results show that the seismoelectric interface response captures both the petrophysical and geometrical characteristics of the converting geological unit. The considered models indicate the general potential of using the seismoelectric interface response for reservoir characterisation in hydrogeological or hydrocarbon exploration studies.

Accumulation of electric currents driving jetting events in the solar atmosphere

NASA Astrophysics Data System (ADS)

Vargas Domínguez, S.; Guo, Y.; Demoulin, P.; Schmieder, B.; Ding, M.; Liu, Y.

2013-12-01

The solar atmosphere is populated with a wide variety of structures and phenomena at different spatial and temporal scales. Explosive phenomena are of particular interest due to their contribution to the atmosphere's energy budget and their implications, e.g. coronal heating. Recent instrumental developments have provided important observations and therefore new insights for tracking the dynamic evolution of the solar atmosphere. Jets of plasma are frequently observed in the solar corona and are thought to be a consequence of magnetic reconnection, however, the physics involved is not fully understood. Unprecedented observations (EUV and vector magnetic fields) are used to study solar jetting events, from which we derive the magnetic flux evolution, the photospheric velocity field, and the vertical electric current evolution. The evolution of magnetic parasitic polarities displaying diverging flows are detected to trigger recurrent jets in a solar regionon 17 September 2010. The interaction drive the build up of electric currents. Observed diverging flows are proposed to build continuously such currents. Magnetic reconnection is proposed to occur periodically, in the current layer created between the emerging bipole and the large scale active region field. SDO/AIA EUV composite images. Upper: SDO/AIA 171 Å image overlaid by the line-of-sight magnetic field observed at the same time as that of the 171 Å image. Lower: Map of photospheric transverse velocities derived from LCT analysis with the HMI magnetograms.

Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors.

PubMed

Lee, Hyeonju; Zhang, Xue; Hwang, Jaeeun; Park, Jaehoon

2016-10-19

We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites.

A pilot study with very low-intensity, intermediate-frequency electric fields in patients with locally advanced and/or metastatic solid tumors.

PubMed

Salzberg, Marc; Kirson, Eilon; Palti, Yoram; Rochlitz, Christoph

2008-07-01

The transmission of electric fields using insulated electrodes has demonstrated that very low-intensity, properly tuned, intermediate-frequency electric fields, termed tumor-treating fields (TTFields), selectively stunts tumor cell growth and is accompanied by a decrease in tumor angiogenesis. This open, prospective pilot study was designed to evaluate the safety, tolerability, and efficacy profile of TTFields treatment in patients with locally advanced and/or metastatic solid tumors using the NovoTTF100A(TM) device. All 6 patients were heavily pre-treated with several lines of therapy; no additional standard treatment option was available to them. TTFields treatment using continuous NovoTTF-100A lasted a minimum of 14 days and was very well tolerated. No related serious adverse events occurred. Outcomes showed 1 partial response of a treated skin metastasis from a primary breast cancer, 3 cases where tumor growth was arrested during treatment, and 1 case of disease progression. One mesothelioma patient experienced lesion regression near TTFields with simultaneous tumor stability or progression in distal areas. Although the number of patients in this study is small, the lack of therapy toxicity and the efficacy observed in data gathered to date indicate the potential of TTFields as a new treatment modality for solid tumors, definitely warranting further investigation. (c) 2008 S. Karger AG, Basel

Morphological Influence of Solution-Processed Zinc Oxide Films on Electrical Characteristics of Thin-Film Transistors

PubMed Central

Lee, Hyeonju; Zhang, Xue; Hwang, Jaeeun; Park, Jaehoon

2016-01-01

We report on the morphological influence of solution-processed zinc oxide (ZnO) semiconductor films on the electrical characteristics of ZnO thin-film transistors (TFTs). Different film morphologies were produced by controlling the spin-coating condition of a precursor solution, and the ZnO films were analyzed using atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and Hall measurement. It is shown that ZnO TFTs have a superior performance in terms of the threshold voltage and field-effect mobility, when ZnO crystallites are more densely packed in the film. This is attributed to lower electrical resistivity and higher Hall mobility in a densely packed ZnO film. In the results of consecutive TFT operations, a positive shift in the threshold voltage occurred irrespective of the film morphology, but the morphological influence on the variation in the field-effect mobility was evident. The field-effect mobility in TFTs having a densely packed ZnO film increased continuously during consecutive TFT operations, which is in contrast to the mobility decrease observed in the less packed case. An analysis of the field-effect conductivities ascribes these results to the difference in energetic traps, which originate from structural defects in the ZnO films. Consequently, the morphological influence of solution-processed ZnO films on the TFT performance can be understood through the packing property of ZnO crystallites. PMID:28773973

Preliminary Findings from the One-Year Electric Field Study in the North Slope of Alaska (OYES-NSA), Atmospheric Radiation Measurement (ARM) Field Campaign

NASA Astrophysics Data System (ADS)

Lavigne, T.; Liu, C.

2017-12-01

Previous studies focusing on the comparison of the measured electric field to the physical properties of global electrified clouds have been conducted almost exclusively in the Southern Hemisphere. The One-Year Electric Field Study-North Slope of Alaska (OYES-NSA) aims to establish a long-running collection of this valuable electric field data in the Northern Hemisphere. Presented here is the six-month preliminary data and results of the OYES-NSA Atmospheric Radiation Mission (ARM) field campaign. The local electric field measured in Barrow, Alaska using two CS110 reciprocating shutter field meters, has been compared to simultaneous measurements from the ARM Ka-Band zenith radar, to better understand the influence and contribution of different types of clouds on the local electric field. The fair-weather electric field measured in Barrow has also been analyzed and compared to the climatology of electric field at Vostok Station, Antarctica. The combination of the electric field dataset in the Northern Hemisphere, alongside the local Ka cloud radar, global Precipitation Feature (PF) database, and quasi-global lightning activity (55oN-55oS), allows for advances in the physical understanding of the local electric field, as well as the Global Electric Circuit (GEC).

Trigger, an active release experiment that stimulated auroral particle precipitation and wave emissions

NASA Technical Reports Server (NTRS)

Holmgren, G.; Bostroem, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Fahleson, U. V.; Bering, E. A.; Sheldon, W. R.

1979-01-01

The experiment design, including a description of the diagnostic and chemical release payload, and the general results are given for an auroral process simulation experiment. A drastic increase of the field aligned charged particle flux was observed over the approximate energy range 10 eV to more than 300 keV, starting about 150 ms after the release and lasting about one second. The is evidence of a second particle burst, starting one second after the release and lasting for tens of seconds, and evidence for a periodic train of particle bursts occurring with a 7.7 second period from 40 to 130 seconds after the release. A transient electric field pulse of 200 mv/m appeared just before the particle flux increase started. Electrostatic wave emissions around 2 kHz, as well as a delayed perturbation of the E-region below the plasma cloud were also observed. Some of the particle observations are interpreted in terms of field aligned electrostatic acceleration a few hundred kilometers above the injected plasma cloud. It is suggested that the acceleration electric field was created by an instability driven by field aligned currents originating in the plasma cloud.

Consideration of the effects of intense tissue heating on the RF electromagnetic fields during MRI: simulations for MRgFUS in the hip

NASA Astrophysics Data System (ADS)

Xuegang Xin, Sherman; Gu, Shiyong; Carluccio, Giuseppe; Collins, Christopher M.

2015-01-01

Due to the strong dependence of tissue electrical properties on temperature, it is important to consider the potential effects of intense tissue heating on the RF electromagnetic fields during MRI, as can occur in MR-guided focused ultrasound surgery. In principle, changes of the RF electromagnetic fields could affect both efficacy of RF pulses, and the MRI-induced RF heating (SAR) pattern. In this study, the equilibrium temperature distribution in a whole-body model with 2 mm resolution before and during intense tissue heating up to 60 °C at the target region was calculated. Temperature-dependent electric properties of tissues were assigned to the model to establish a temperature-dependent electromagnetic whole-body model in a 3T MRI system. The results showed maximum changes in conductivity, permittivity, ≤ft|\\mathbf{B}1+\\right|, and SAR of about 25%, 6%, 2%, and 20%, respectively. Though the B1 field and SAR distributions are both temperature-dependent, the potential harm to patients due to higher SARs is expected to be minimal and the effects on the B1 field distribution should have minimal effect on images from basic MRI sequences.

The dynamics of current carriers in standing Alfvén waves: Parallel electric fields in the auroral acceleration region

NASA Astrophysics Data System (ADS)

Wright, Andrew N.; Allan, W.; Ruderman, Michael S.; Elphic, R. C.

2002-07-01

The acceleration of current carriers in an Alfvén wave current system is considered. The model incorporates a dipole magnetic field geometry, and we present an analytical solution of the two-fluid equations by successive approximations. The leading solution corresponds to the familiar single-fluid toroidal oscillations. The next order describes the nonlinear dynamics of electrons responsible for carrying a few μAm-2 field aligned current into the ionosphere. The solution shows how most of the electron acceleration in the magnetosphere occurs within 1 RE of the ionosphere, and that a parallel electric field of the order of 1 mVm-1 is responsible for energising the electrons to 1 keV. The limitations of the electron fluid approximation are considered, and a qualitative solution including electron beams and a modified E∥ is developed in accord with observations. We find that the electron acceleration can be nonlinear, (ve∥∇∥)ve∥ > ωve∥, as a result of our nonuniform equilibrium field geometry even when ve∥ is less than the Alfvén speed. Our calculation also elucidates the processes through which E∥ is generated and supported.

Specific spacecraft evaluation: Special report. [charged particle transport from a mercury ion thruster to spacecraft surfaces

NASA Technical Reports Server (NTRS)

Sellen, J. M., Jr.

1978-01-01

Charged and neutral particle transport from an 8 cm mercury ion thruster to the surfaces of the P 80-1 spacecraft and to the Teal Ruby sensor and the ECOM-501 sensor of that spacecraft were investigated. Laboratory measurements and analyses were used to examine line-of-sight and nonline-of sight particle transport modes. The recirculation of Hg(+) ions in the magnetic field of the earth was analyzed for spacecraft velocity and Earth magnetic field vector configurations which are expected to occur in near Earth, circular, high inclination orbits. For these magnetic field and orbit conditions and for expected ion release distribution functions, in both angles and energies, the recirculation/re-interception of ions on spacecraft surfaces was evaluated. The refraction of weakly energetic ions in the electric fields of the thruster plasma plume and in the electric fields between this plasma plume and the material boundaries of the thruster, the thruster sputter shield, and the various spacecraft surfaces were examined. The neutral particle transport modes of interest were identified as sputtered metal atoms from the thruster beam shield. Results, conclusions, and future considerations are presented.

Rashba and Dresselhaus spin-orbit couplings effects on electromagnetically induced transparency of a lens-shaped quantum dot: External electric and magnetic fields

NASA Astrophysics Data System (ADS)

Zamani, A.; Setareh, F.; Azargoshasb, T.; Niknam, E.; Mohammadhosseini, E.

2017-06-01

In this article the spin of electron as well as simultaneous effects of Rashba and Dresselhaus spin-orbit interactions are considered for a lens-shaped GaAs quantum dot and the influences of applied electric field and Zeeman effect on the electromagnetically induced transparency (EIT) of this system are investigated. To do so, the absorption, refractive index as well as the group velocity of the probe light pulse are presented and discussed. Study of the absorption and refractive index reveals that, at a particular frequency of probe field, absorption diminishes, refractive index becomes unity and so the EIT occurs. Furthermore, the investigation of group velocity show that, around such frequency the probe propagation is sub-luminal, which shifts to super-luminal for higher and lower frequencies. Our results illustrate that the EIT frequency, transparency window and sub(super)-luminal frequency intervals are strongly sensitive to applied fields in the presence of spin-orbit couplings. It is found that, in comparison with the investigations with negligence of spin, the EIT behavior under the effects of applied fields are quite different.

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

Garimella, Sandilya V. B.; Ibrahim, Yehia M.; Tang, Keqi

A novel concept for ion spatial peak compression is described, and discussed primarily in the context of ion mobility spectrometry (IMS). Using theoretical and numerical methods, the effects of using non-constant (e.g., linearly varying) electric fields on ion distributions (e.g., an ion mobility peak) is evaluated both in the physical and temporal domains. The application of linearly decreasing electric field in conjunction with conventional drift field arrangements is shown to lead to a reduction in IMS physical peak width. When multiple ion packets in a selected mobility window are simultaneously subjected to such fields, there is ion packet compression, i.e.,more » a reduction in peak widths of all species. This peak compression occurs with a modest reduction of resolution, but which can be quickly recovered as ions drift in a constant field after the compression event. Compression also yields a significant increase in peak intensities. In addition, approaches for peak compression in traveling wave IMS are also discussed. Ion mobility peak compression can be particularly useful for mitigating diffusion driven peak spreading over very long path length separations (e.g., in cyclic multi-pass arrangements), and for achieving higher S/N and IMS resolution over a selected mobility range.« less

Inhomogeneity at the LaAlO3/SrTiO3 interface

NASA Astrophysics Data System (ADS)

Claeson, T.; Kalabukhov, A.; Gunnarsson, R.; Winkler, D.; Borjesson, J.; Ljustina, N.; Olsson, E.; Popok, V.; Boikov, Yu.; Serenkov, I.; Sakharov, V.

2010-03-01

High electrical conductivity has been reported for the interface between two wide-band gap insulators, LaAlO3 (LAO) and SrTiO3 (STO). It occurs above a critical thickness of LAO and can be tuned by an electric field. The conduction has been attributed to i) ``polar catastrophe'' , where the electrostatic charge at the interface is compensated by the transfer of half an electron per unit cell to the interface, ii) oxygen vacancies in the STO, and iii) cation intermixing, which may result in the formation of metallic La1-xSrxTiO3 layer. The relation between microstructure and electrical properties is crucial for understanding the origin of electrical conductivity. We have investigated the interface composition using medium-energy ion spectroscopy, high resolution electron microscopy, and Kelvin probe force microscopy. We find a correlation between cationic intermixing at the interface and electrical properties and inhomogeneities of the interface conductivity that may support a percolation model. Work supported by Swedish VR & KAW, Russian ISTC 3743, EC NANOXIDE

Streaming current magnetic fields in a charged nanopore.

PubMed

Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W

2016-11-11

Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques.

Streaming current magnetic fields in a charged nanopore

NASA Astrophysics Data System (ADS)

Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W.

2016-11-01

Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques.

Neuron matters: electric activation of neuronal tissue is dependent on the interaction between the neuron and the electric field.

PubMed

Ye, Hui; Steiger, Amanda

2015-08-12

In laboratory research and clinical practice, externally-applied electric fields have been widely used to control neuronal activity. It is generally accepted that neuronal excitability is controlled by electric current that depolarizes or hyperpolarizes the excitable cell membrane. What determines the amount of polarization? Research on the mechanisms of electric stimulation focus on the optimal control of the field properties (frequency, amplitude, and direction of the electric currents) to improve stimulation outcomes. Emerging evidence from modeling and experimental studies support the existence of interactions between the targeted neurons and the externally-applied electric fields. With cell-field interaction, we suggest a two-way process. When a neuron is positioned inside an electric field, the electric field will induce a change in the resting membrane potential by superimposing an electrically-induced transmembrane potential (ITP). At the same time, the electric field can be perturbed and re-distributed by the cell. This cell-field interaction may play a significant role in the overall effects of stimulation. The redistributed field can cause secondary effects to neighboring cells by altering their geometrical pattern and amount of membrane polarization. Neurons excited by the externally-applied electric field can also affect neighboring cells by ephaptic interaction. Both aspects of the cell-field interaction depend on the biophysical properties of the neuronal tissue, including geometric (i.e., size, shape, orientation to the field) and electric (i.e., conductivity and dielectricity) attributes of the cells. The biophysical basis of the cell-field interaction can be explained by the electromagnetism theory. Further experimental and simulation studies on electric stimulation of neuronal tissue should consider the prospect of a cell-field interaction, and a better understanding of tissue inhomogeneity and anisotropy is needed to fully appreciate the neural basis of cell-field interaction as well as the biological effects of electric stimulation.

Simple estimation of induced electric fields in nervous system tissues for human exposure to non-uniform electric fields at power frequency

NASA Astrophysics Data System (ADS)

Tarao, Hiroo; Miyamoto, Hironobu; Korpinen, Leena; Hayashi, Noriyuki; Isaka, Katsuo

2016-06-01

Most results regarding induced current in the human body related to electric field dosimetry have been calculated under uniform field conditions. We have found in previous work that a contact current is a more suitable way to evaluate induced electric fields, even in the case of exposure to non-uniform fields. If the relationship between induced currents and external non-uniform fields can be understood, induced electric fields in nervous system tissues may be able to be estimated from measurements of ambient non-uniform fields. In the present paper, we numerically calculated the induced electric fields and currents in a human model by considering non-uniform fields based on distortion by a cubic conductor under an unperturbed electric field of 1 kV m-1 at 60 Hz. We investigated the relationship between a non-uniform external electric field with no human present and the induced current through the neck, and the relationship between the current through the neck and the induced electric fields in nervous system tissues such as the brain, heart, and spinal cord. The results showed that the current through the neck can be formulated by means of an external electric field at the central position of the human head, and the distance between the conductor and the human model. As expected, there is a strong correlation between the current through the neck and the induced electric fields in the nervous system tissues. The combination of these relationships indicates that induced electric fields in these tissues can be estimated solely by measurements of the external field at a point and the distance from the conductor.

Spherical Ethylene/Air Diffusion Flames Subject to Concentric DC Electric Field in Microgravity

NASA Technical Reports Server (NTRS)

Yuan, Z. -G.; Hegde, U.; Faeth, G. M.

2001-01-01

It is well known that microgravity conditions, by eliminating buoyant flow, enable many combustion phenomena to be observed that are not possible to observe at normal gravity. One example is the spherical diffusion flame surrounding a porous spherical burner. The present paper demonstrates that by superimposing a spherical electrical field on such a flame, the flame remains spherical so that we can study the interaction between the electric field and flame in a one-dimensional fashion. Flames are susceptible to electric fields that are much weaker than the breakdown field of the flame gases owing to the presence of ions generated in the high temperature flame reaction zone. These ions and the electric current of the moving ions, in turn, significantly change the distribution of the electric field. Thus, to understand the interplay between the electric field and the flame is challenging. Numerous experimental studies of the effect of electric fields on flames have been reported. Unfortunately, they were all involved in complex geometries of both the flow field and the electric field, which hinders detailed study of the phenomena. In a one-dimensional domain, however, the electric field, the flow field, the thermal field and the chemical species field are all co-linear. Thus the problem is greatly simplified and becomes more tractable.

Miniature Ion-Mobility Spectrometer

NASA Technical Reports Server (NTRS)

Hartley, Frank T.

2006-01-01

The figure depicts a proposed miniature ion-mobility spectrometer that would be fabricated by micromachining. Unlike prior ion-mobility spectrometers, the proposed instrument would not be based on a time-of-flight principle and, consequently, would not have some of the disadvantageous characteristics of prior time-of-flight ion-mobility spectrometers. For example, one of these characteristics is the need for a bulky carrier-gas-feeding subsystem that includes a shutter gate to provide short pulses of gas in order to generate short pulses of ions. For another example, there is need for a complex device to generate pulses of ions from the pulses of gas and the device is capable of ionizing only a fraction of the incoming gas molecules; these characteristics preclude miniaturization. In contrast, the proposed instrument would not require a carrier-gas-feeding subsystem and would include a simple, highly compact device that would ionize all the molecules passing through it. The ionization device in the proposed instrument would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several megavolts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. Ionization (but not avalanche arcing) would occur because the distance between the ionizing electrodes would be less than the mean free path of gas molecules at the operating pressure of instrument. An accelerating grid would be located inside the instrument, downstream from the ionizing membrane. The electric potential applied to this grid would be negative relative to the potential on the inside electrode of the ionizing membrane and would be of a magnitude sufficient to generate a moderate electric field. Positive ions leaving the membrane holes would be accelerated in this electric field. The resulting flux of ions away from the ionization membrane would create a partial vacuum that would draw more of the gas medium through the membrane. The figure depicts a filter electrode and detector electrodes located along the sides of a drift tube downstream from the accelerator electrode. These electrodes would apply a transverse AC electric field superimposed on a ramped DC electric field. The AC field would effect differential transverse dispersal of ions. At a given instant of time, the trajectories of most of the ions would be bent toward the electrodes, causing most of the ions to collide with the electrodes and thereby become neutralized. The DC field would partly counteract the dispersive effect of the AC field, straightening the trajectories of a selected species of ions; the selection would vary with the magnitude of the applied DC field. The straightening of the trajectories of the selected ions would enable them to pass into the region between the detector electrodes. Depending on the polarity of the voltage applied to the detector electrodes, the electric field between the detector electrodes would draw the selected ions to one of these electrodes. Hence, the current collected by one of the detector electrodes would be a measure of the abundance of ions of the selected species. The ramping of the filter- electrode DC voltage would sweep the selection of ions through the spectrum of ionic species.

Landfill gas to electricity demonstration project

NASA Astrophysics Data System (ADS)

Giuliani, A. J.; Cagliostro, L. A.

1982-03-01

Medium Btu methane gas is a naturally occurring by product of anaerobic digestion of landfilled municipal solid waste. The energy potential of landfill gas in New York State is estimated to be 61 trillion Btu's per year or the equivalent of 10 percent of the natural gas used annually in the State. The 18-month Landfill Gas to Electricity Demonstration Project conducted at the Fresh Kills Landfill in Staten Island, New York conclusively demonstrated that landfill gas is an acceptable fuel for producing electricity using an internal combustion engine/generator set. Landfill gas proved to be a reliable and consistent fuel source during a six-month field test program. Engine exhaust emissions were determined to be comparable to that of natural gas and no unusually high corrosion rates on standard pipeline material were found.

The application of the electrodynamic separator in minerals beneficiation

NASA Astrophysics Data System (ADS)

Skowron, M.; Syrek, P.; Surowiak, A.

2017-05-01

The aim of presented paper is elaboration of methodology of upgrading natural minerals in example of chalcocite and bornite sample. The results were obtained by means of laboratory drum separator. This device operates in accordance to properties of materials, which in this case was electrical conductivity. The study contains the analysis of the forces occurring inside of electrodynamic separator chamber, that act on the particles of various electrical properties. Both, the potential and electric field strength distributions were calculated, with set of separators setpoints. Theoretical analysis influenced on separator parameters, and hence impacted the empirical results too. Next, the authors conducted empirical research on chalcocite and bornite beneficiation by means of electrodynamic separation. The results of this process were shown graphically in form of upgrading curves of chalcocite considering elementary copper and lead.

Solidification processing of alloys using an applied electric field

NASA Technical Reports Server (NTRS)

Mckannan, Eugene C. (Inventor); Schmidt, Deborah D. (Inventor); Ahmed, Shaffiq (Inventor); Bond, Robert W. (Inventor)

1990-01-01

A method is provided for obtaining an alloy having an ordered microstructure which comprises the steps of heating the central portion of the alloy under uniform temperature so that it enters a liquid phase while the outer portions remain solid, applying a constant electric current through the alloy during the heating step, and solidifying the liquid central portion of the alloy by subjecting it to a temperature-gradient zone so that cooling occurs in a directional manner and at a given rate of speed while maintaining the application of the constant electric current through the alloy. The method of the present invention produces an alloy having superior characteristics such as reduced segregation. After subsequent precipitation by heat-treatment, the alloys produced by the present invention will have excellent strength and high-temperature resistance.

A General Computational Approach for Magnetohydrodynamic Flows Using the CFX Code: Buoyant Flow Through a Vertical Square Channel

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

Di Piazza, Ivan; Buehler, Leo

2000-09-15

The buoyancy-driven magnetoconvection in the cross section of an infinitely long vertical square duct is investigated numerically using the CFX code package. The implementation of a magnetohydrodynamic (MHD) problem in CFX is discussed, with particular reference to the Lorentz forces and the electric potential boundary conditions for arbitrary electrical conductivity of the walls. The method proposed is general and applies to arbitrary geometries with an arbitrary orientation of the magnetic field. Results for fully developed flow under various thermal boundary conditions are compared with asymptotic analytical solutions. The comparison shows that the asymptotic analysis is confirmed for highly conducting wallsmore » as high velocity jets occur at the side walls. For weakly conducting walls, the side layers become more conducting than the side walls, and strong electric currents flow within these layers parallel to the magnetic field. As a consequence, the velocity jets are suppressed, and the core solution is only corrected by the viscous forces near the wall. The implementation of MHD in CFX is achieved.« less

Numerical simulations of electric potential field for alternating current potential drop associated with surface cracks in low-alloy steel nuclear material

NASA Astrophysics Data System (ADS)

Yeh, Chun-Ping; Huang, Jiunn-Yuan

2018-04-01

Low-alloy steels used as structural materials in nuclear power plants are subjected to cyclic stresses during power plant operations. As a result, cracks may develop and propagate through the material. The alternating current potential drop technique is used to measure the lengths of cracks in metallic components. The depth of the penetration of the alternating current is assumed to be small compared to the crack length. This assumption allows the adoption of the unfolding technique to simplify the problem to a surface Laplacian field. The numerical modelling of the electric potential and current density distribution prediction model for a compact tension specimen and the unfolded crack model are presented in this paper. The goal of this work is to conduct numerical simulations to reduce deviations occurring in the crack length measurements. Numerical simulations were conducted on AISI 4340 low-alloy steel with different crack lengths to evaluate the electric potential distribution. From the simulated results, an optimised position for voltage measurements in the crack region was proposed.

Electrostatics in the environment: How they may affect health and productivity

NASA Astrophysics Data System (ADS)

Jamieson, K. S.; Simon, H. M. Ap; Bell, J. N. B.

2008-12-01

Lifestyles and the built environment have changed considerably during the past century and have greatly influenced the electric field, small air ion and charged submicron aerosol regimes to which individuals are often exposed. In particular the use of electrical items, synthetic materials/finishes and low humidity levels that can lead to the generation of high electrostatic charges, along with inadequate grounding protocols and building techniques which create 'Faraday cage'-like conditions, have all greatly altered the electromagnetic nature of the microclimates many people occupy for prolonged periods of time. It is suggested that the type, polarity and strengths of electric fields individuals are exposed to may affect their likelihood of succumbing to ill-health through influencing biological functioning, oxygen-uptake and retention rates of inhaled submicron contaminants to a far greater degree than previously realised. These factors can also influence the degree of local surface contamination and adhesion that occurs. It is further suggested that both health and work productivity can be affected by such factors, and that improved 'best practice' electro-hygiene/productivity protocols should be adopted wherever practical.

Electrical resistivity tomography to delineate greenhouse soil variability

NASA Astrophysics Data System (ADS)

Rossi, R.; Amato, M.; Bitella, G.; Bochicchio, R.

2013-03-01

Appropriate management of soil spatial variability is an important tool for optimizing farming inputs, with the result of yield increase and reduction of the environmental impact in field crops. Under greenhouses, several factors such as non-uniform irrigation and localized soil compaction can severely affect yield and quality. Additionally, if soil spatial variability is not taken into account, yield deficiencies are often compensated by extra-volumes of crop inputs; as a result, over-irrigation and overfertilization in some parts of the field may occur. Technology for spatially sound management of greenhouse crops is therefore needed to increase yield and quality and to address sustainability. In this experiment, 2D-electrical resistivity tomography was used as an exploratory tool to characterize greenhouse soil variability and its relations to wild rocket yield. Soil resistivity well matched biomass variation (R2=0.70), and was linked to differences in soil bulk density (R2=0.90), and clay content (R2=0.77). Electrical resistivity tomography shows a great potential in horticulture where there is a growing demand of sustainability coupled with the necessity of stabilizing yield and product quality.