High dynamic range electric field sensor for electromagnetic pulse detection.

PubMed

Lin, Che-Yun; Wang, Alan X; Lee, Beom Suk; Zhang, Xingyu; Chen, Ray T

2011-08-29

We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.

Probing the plasma near high power wave launchers in fusion devices for static and dynamic electric fields

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

Klepper, C Christopher; Martin, Elijah H; Isler, Ralph C

2014-01-01

An exploratory study was carried out in the long-pulse tokamak Tore Supra, to determine if electric fields in the plasma around high-power, RF wave launchers could be measured with non-intrusive, passive, optical emission spectroscopy. The focus was in particular on the use of the external electric field Stark effect. The feasibility was found to be strongly dependent on the spatial extent of the electric fields and overlap between regions of strong (> 1 kV/cm) electric fields and regions of plasma particle recycling and plasma-induced, spectral line emission. Most amenable to the measurement was the RF electric field in edge plasma,more » in front of a lower hybrid heating and current drive launcher. Electric field strengths and direction, derived from fitting the acquired spectra to a model including time-dependent Stark effect and the tokamak-range magnetic field Zeeman-effect, were found to be in good agreement with full-wave modeling of the observed launcher.« less

Probing the plasma near high power wave launchers in fusion devices for static and dynamic electric fields (invited)

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

Klepper, C. C., E-mail: kleppercc@ornl.gov; Isler, R. C.; Biewer, T. M.

2014-11-15

An exploratory study was carried out in the long-pulse tokamak Tore Supra, to determine if electric fields in the plasma around high-power, RF wave launchers could be measured with non-intrusive, passive, optical emission spectroscopy. The focus was in particular on the use of the external electric field Stark effect. The feasibility was found to be strongly dependent on the spatial extent of the electric fields and overlap between regions of strong (>∼1 kV/cm) electric fields and regions of plasma particle recycling and plasma-induced, spectral line emission. Most amenable to the measurement was the RF electric field in edge plasma, inmore » front of a lower hybrid heating and current drive launcher. Electric field strengths and direction, derived from fitting the acquired spectra to a model including time-dependent Stark effect and the tokamak-range magnetic field Zeeman-effect, were found to be in good agreement with full-wave modeling of the observed launcher.« less

Probing the plasma near high power wave launchers in fusion devices for static and dynamic electric fields (invited).

PubMed

Klepper, C C; Martin, E H; Isler, R C; Colas, L; Goniche, M; Hillairet, J; Panayotis, S; Pegourié, B; Jacquot, J; Lotte, Ph; Colledani, G; Biewer, T M; Caughman, J B; Ekedahl, A; Green, D L; Harris, J H; Hillis, D L; Shannon, S C; Litaudon, X

2014-11-01

An exploratory study was carried out in the long-pulse tokamak Tore Supra, to determine if electric fields in the plasma around high-power, RF wave launchers could be measured with non-intrusive, passive, optical emission spectroscopy. The focus was in particular on the use of the external electric field Stark effect. The feasibility was found to be strongly dependent on the spatial extent of the electric fields and overlap between regions of strong (>∼1 kV/cm) electric fields and regions of plasma particle recycling and plasma-induced, spectral line emission. Most amenable to the measurement was the RF electric field in edge plasma, in front of a lower hybrid heating and current drive launcher. Electric field strengths and direction, derived from fitting the acquired spectra to a model including time-dependent Stark effect and the tokamak-range magnetic field Zeeman-effect, were found to be in good agreement with full-wave modeling of the observed launcher.

Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

PubMed

Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

2015-06-03

On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

Novel high power impulse magnetron sputtering enhanced by an auxiliary electrical field

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

Li, Chunwei, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com; State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001; Tian, Xiubo, E-mail: lcwnefu@126.com, E-mail: xiubotian@163.com

2016-08-15

The high power impulse magnetron sputtering (HIPIMS) technique is a novel highly ionized physical vapor deposition method with a high application potential. However, the electron utilization efficiency during sputtering is rather low and the metal particle ionization rate needs to be considerably improved to allow for a large-scale industrial application. Therefore, we enhanced the HIPIMS technique by simultaneously applying an electric field (EF-HIPIMS). The effect of the electric field on the discharge process was studied using a current sensor and an optical emission spectrometer. Furthermore, the spatial distribution of the electric potential and electric field during the EF-HIPIMS process wasmore » simulated using the ANSYS software. The results indicate that a higher electron utilization efficiency and a higher particle ionization rate could be achieved. The auxiliary anode obviously changed the distribution of the electric potential and the electric field in the discharge region, which increased the plasma density and enhanced the degree of ionization of the vanadium and argon gas. Vanadium films were deposited to further compare both techniques, and the morphology of the prepared films was investigated by scanning electron microscopy. The films showed a smaller crystal grain size and a denser growth structure when the electric field was applied during the discharge process.« less

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array.

PubMed

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao; Luo, Hang

2018-02-01

Polymer-based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400-600 kV mm -1 , which may bring more challenges relating to the failure probability. Here, a simple two-step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm -3 is achieved at low electric fields, i.e., 143 kV mm -1 , which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm -2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis.

Giant Electric Field Enhancement in Split Ring Resonators Featuring Nanometer-Sized Gaps

NASA Astrophysics Data System (ADS)

Bagiante, S.; Enderli, F.; Fabiańska, J.; Sigg, H.; Feurer, T.

2015-01-01

Today's pulsed THz sources enable us to excite, probe, and coherently control the vibrational or rotational dynamics of organic and inorganic materials on ultrafast time scales. Driven by standard laser sources THz electric field strengths of up to several MVm-1 have been reported and in order to reach even higher electric field strengths the use of dedicated electric field enhancement structures has been proposed. Here, we demonstrate resonant electric field enhancement structures, which concentrate the incident electric field in sub-diffraction size volumes and show an electric field enhancement as high as ~14,000 at 50 GHz. These values have been confirmed through a combination of near-field imaging experiments and electromagnetic simulations.

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

Exposure to electromagnetic fields aboard high-speed electric multiple unit trains.

PubMed

Niu, D; Zhu, F; Qiu, R; Niu, Q

2016-01-01

High-speed electric multiple unit (EMU) trains generate high-frequency electric fields, low-frequency magnetic fields, and high-frequency wideband electromagnetic emissions when running. Potential human health concerns arise because the electromagnetic disturbances are transmitted mainly into the car body from windows, and from there to passengers and train staff. The transmission amount and amplitude distribution characteristics that dominate electromagnetic field emission need to be studied, and the exposure level of electromagnetic field emission to humans should be measured. We conducted a series of tests of the on board electromagnetic field distribution on several high-speed railway lines. While results showed that exposure was within permitted levels, the possibility of long-term health effects should be investigated.

Design of portable electric and magnetic field generators

NASA Astrophysics Data System (ADS)

Stewart, M. G.; Siew, W. H.; Campbell, L. C.; Stewart, M. G.; Siew, W. H.

2000-11-01

Electric and magnetic field generators capable of producing high-amplitude output are not readily available. This presents difficulties for electromagnetic compatibility testing of new measurement systems where these systems are intended to operate in a particularly hostile electromagnetic environment. A portable electric and a portable magnetic field generator having high pulsed field output are described in this paper. The output of these generators were determined using an electromagnetic-compatible measurement system. These generators allow immunity testing in the laboratory of electronic systems to very high electrical fields, as well as for functional verification of the electronic systems on site. In the longer term, the basic design of the magnetic field generator may be developed as the generator to provide the damped sinusoid magnetic field specified in IEC 61000-4-10, which is adopted in BS EN 61000-4-10.

Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

NASA Astrophysics Data System (ADS)

Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

2013-11-01

High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

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.

Magnetospheric electric fields and currents

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

Electric-field-induced structural changes in multilayer piezoelectric actuators during electrical and mechanical loading

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

Esteves, Giovanni; Fancher, Chris M.; Röhrig, Sören

The effects of electrical and mechanical loading on the behavior of domains and phases in Multilayer Piezoelectric Actuators (MAs) is studied using in situ high-energy X-ray diffraction (XRD) and macroscopic property measurements. Rietveld refinement is carried out on measured diffraction patterns using a two-phase tetragonal (P4mm) and rhombohedral (R3m) model. Applying an electric field promotes the rhombohedral phase, while increasing compressive uniaxial pre-stress prior to electric field application favors the tetragonal phase. The competition between electrical and mechanical energy leads to a maximal difference between electric-field-induced phase fractions at 70 MPa pre-stress. Additionally, the available volume fraction of non-180° domainmore » reorientation that can be accessed during electric field application increases with compressive pre-stress up to 70 MPa. The origin for enhanced strain and polarization with applied pre-stress is attributed to a combination of enhanced non-180° domain reorientation and electric-field-induced phase transitions. The suppression of both the electric-field-induced phase transitions and domain reorientation at high pre-stresses (>70 MPa) is attributed to a large mechanical energy barrier, and alludes to the competition of the electrical and mechanical energy within the MA during applied stimuli.« less

Electric-field-induced structural changes in multilayer piezoelectric actuators during electrical and mechanical loading

DOE PAGES

Esteves, Giovanni; Fancher, Chris M.; Röhrig, Sören; ...

2017-04-08

The effects of electrical and mechanical loading on the behavior of domains and phases in Multilayer Piezoelectric Actuators (MAs) is studied using in situ high-energy X-ray diffraction (XRD) and macroscopic property measurements. Rietveld refinement is carried out on measured diffraction patterns using a two-phase tetragonal (P4mm) and rhombohedral (R3m) model. Applying an electric field promotes the rhombohedral phase, while increasing compressive uniaxial pre-stress prior to electric field application favors the tetragonal phase. The competition between electrical and mechanical energy leads to a maximal difference between electric-field-induced phase fractions at 70 MPa pre-stress. Additionally, the available volume fraction of non-180° domainmore » reorientation that can be accessed during electric field application increases with compressive pre-stress up to 70 MPa. The origin for enhanced strain and polarization with applied pre-stress is attributed to a combination of enhanced non-180° domain reorientation and electric-field-induced phase transitions. The suppression of both the electric-field-induced phase transitions and domain reorientation at high pre-stresses (>70 MPa) is attributed to a large mechanical energy barrier, and alludes to the competition of the electrical and mechanical energy within the MA during applied stimuli.« less

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array

PubMed Central

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao

2017-01-01

Abstract Polymer‐based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400–600 kV mm−1, which may bring more challenges relating to the failure probability. Here, a simple two‐step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm−3 is achieved at low electric fields, i.e., 143 kV mm−1, which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm−2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis. PMID:29610724

Cryosurgery with Pulsed Electric Fields

PubMed Central

Daniels, Charlotte S.; Rubinsky, Boris

2011-01-01

This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to ablate cells in the high subzero freezing region of a cryosurgical lesion. PMID:22087224

Exposure assessment of extremely low frequency electric fields in Tehran, Iran, 2010.

PubMed

Nassiri, Parvin; Esmaeilpour, Mohammad Reza Monazzam; Gharachahi, Ehsan; Haghighat, Gholamali; Yunesian, Masoud; Zaredar, Narges

2013-01-01

Extremely Low-Frequency (ELF) electric and magnetic fields belonging to the nonionizing electromagnetic radiation spectrum have a frequency of 50 - 60 Hz. All people are exposed to a complex set of electric and magnetic fields that spread throughout the environment. The current study was carried out to assess people's exposure to an ELF electric field in the Tehran metropolitan area in 2010. The measurement of the electronic fields was performed using an HI-3604 power frequency field strength measurement device. A total number of 2,753 measurements were performed. Afterward, the data obtained were transferred to the base map using Arc View Version 3.2 and Arc Map Version 9.3. Finally, an interpolation method was applied to expand the intensity of the electric field to the entire city. Based on the results obtained, the electric field was divided into three parts with various intensities including 0-5 V m, 5-15 V m, and >15 V m. It should be noted that the status of high voltage transmission lines, electric substations, and specific points including schools and hospitals were also marked on the map. Minimum and maximum electric field intensities were measured tantamount to 0.31 V m and 19.80 V m, respectively. In all measurements, the electric field was much less than the amount provided in the ICNIRP Guide. The results revealed that 141 hospitals and 6,905 schools are situated in an area with electric field intensity equal to 0-5 V m, while 15 hospitals and 95 schools are located in zones of 5-15 V m and more than 15 V m. Examining high voltage transmission lines and electric substations in Tehran and its suburbs suggested that the impact of the lines on the background electric field of the city was low. Accordingly, 0.97 km of Tehran located on the city border adjacent to the high voltage transmission lines have an electric field in the range of 5 to 15 V m. The noted range is much lower than the available standards. In summary, it can be concluded that the public is not exposed to a risky background electric field in metropolitan Tehran. The result of comparing sensitive recipients showed that the schools have a more desirable status than the hospitals. Nonetheless, epidemiologic studies can lead to more understanding of the impact on public health.

Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

NASA Technical Reports Server (NTRS)

Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

1992-01-01

The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

Magneto-electric Nanoparticles to Enable Field-controlled High-Specificity Drug Delivery to Eradicate Ovarian Cancer Cells

PubMed Central

Guduru, Rakesh; Liang, Ping; Runowicz, Carolyn; Nair, Madhavan; Atluri, Venkata; Khizroev, Sakhrat

2013-01-01

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe2O4@BaTiO3 MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells. PMID:24129652

Magneto-electric nanoparticles to enable field-controlled high-specificity drug delivery to eradicate ovarian cancer cells.

PubMed

Guduru, Rakesh; Liang, Ping; Runowicz, Carolyn; Nair, Madhavan; Atluri, Venkata; Khizroev, Sakhrat

2013-10-16

The nanotechnology capable of high-specificity targeted delivery of anti-neoplastic drugs would be a significant breakthrough in Cancer in general and Ovarian Cancer in particular. We addressed this challenge through a new physical concept that exploited (i) the difference in the membrane electric properties between the tumor and healthy cells and (ii) the capability of magneto-electric nanoparticles (MENs) to serve as nanosized converters of remote magnetic field energy into the MENs' intrinsic electric field energy. This capability allows to remotely control the membrane electric fields and consequently trigger high-specificity drug uptake through creation of localized nano-electroporation sites. In in-vitro studies on human ovarian carcinoma cell (SKOV-3) and healthy cell (HOMEC) lines, we applied a 30-Oe d.c. field to trigger high-specificity uptake of paclitaxel loaded on 30-nm CoFe₂O₄ @BaTiO₃ MENs. The drug penetrated through the membrane and completely eradicated the tumor within 24 hours without affecting the normal cells.

High school students' representations and understandings of electric fields

NASA Astrophysics Data System (ADS)

Cao, Ying; Brizuela, Bárbara M.

2016-12-01

This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields postinstruction as indicated by students' performance on textbook-style questions. It has, however, inadequately captured student ideas expressed in other situations yet informative to educational research. In this study, we explore students' ideas of electric fields preinstruction as shown by students' representations produced in open-ended activities. 92 participant students completed a worksheet that involved drawing comic strips about electric charges as characters of a cartoon series. Three students who had spontaneously produced arrow diagrams were interviewed individually after class. We identified nine ideas related to electric fields that these three students spontaneously leveraged in the comic strip activity. In this paper, we describe in detail each idea and its situated context. As most research in the literature has understood students as having relatively fixed conceptions and mostly identified divergences in those conceptions from canonical targets, this study shows students' reasoning to be more variable in particular moments, and that variability includes common sense resources that can be productive for learning about electric fields.

Analysis of electric field distribution in GaAs metal-semiconductor field effect transistor with a field-modulating plate

NASA Astrophysics Data System (ADS)

Hori, Yasuko; Kuzuhara, Masaaki; Ando, Yuji; Mizuta, Masashi

2000-04-01

Electric field distribution in the channel of a field effect transistor (FET) with a field-modulating plate (FP) has been theoretically investigated using a two-dimensional ensemble Monte Carlo simulation. This analysis revealed that the introduction of FP is effective in canceling the influence of surface traps under forward bias conditions and in reducing the electric field intensity at the drain side of the gate edge under pinch-off bias conditions. This study also found that a partial overlap of the high-field region under the gate and that at the FP electrode is important for reducing the electric field intensity. The optimized metal-semiconductor FET with FP (FPFET) (LGF˜0.2 μm) exhibited a much lower peak electric field intensity than a conventional metal-semiconductor FET. Based on these numerically calculated results, we have proposed a design procedure to optimize the power FPFET structure with extremely high breakdown voltages while maintaining reasonable gain performance.

Effects of high voltage transmission lines on honeybees: a feasibility study. Final report

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

Greenberg, B.

1977-07-01

Methodology is described for the investigation of the effects of electric fields generated by high-tension power lines on honeybees (Apis mellifera L.). The parameters to be measured include colony population, honey stores, amount of acoustical noise generated by the bees, in-hive temperature, incidence of queen cell production, and tendency to swarm. Accompanying dosimetric support includes in-hive electric field measurements, development of shielding to eliminate the electric field from selected colonies, analysis of the acoustical data, and periodic checks on the ambient electric field present under the line and at the control site.

The Electric Field of a Weakly Electric Fish

NASA Astrophysics Data System (ADS)

Rasnow, Brian K.

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

Electric field control of deterministic current-induced magnetization switching in a hybrid ferromagnetic/ferroelectric structure

NASA Astrophysics Data System (ADS)

Cai, Kaiming; Yang, Meiyin; Ju, Hailang; Wang, Sumei; Ji, Yang; Li, Baohe; Edmonds, Kevin William; Sheng, Yu; Zhang, Bao; Zhang, Nan; Liu, Shuai; Zheng, Houzhi; Wang, Kaiyou

2017-07-01

All-electrical and programmable manipulations of ferromagnetic bits are highly pursued for the aim of high integration and low energy consumption in modern information technology. Methods based on the spin-orbit torque switching in heavy metal/ferromagnet structures have been proposed with magnetic field, and are heading toward deterministic switching without external magnetic field. Here we demonstrate that an in-plane effective magnetic field can be induced by an electric field without breaking the symmetry of the structure of the thin film, and realize the deterministic magnetization switching in a hybrid ferromagnetic/ferroelectric structure with Pt/Co/Ni/Co/Pt layers on PMN-PT substrate. The effective magnetic field can be reversed by changing the direction of the applied electric field on the PMN-PT substrate, which fully replaces the controllability function of the external magnetic field. The electric field is found to generate an additional spin-orbit torque on the CoNiCo magnets, which is confirmed by macrospin calculations and micromagnetic simulations.

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.

ROCSAT and HF Doppler sounder observations of the DP2-type electric field during the global Pc5 magnetic pulsation event

NASA Astrophysics Data System (ADS)

Hashimoto, K. K.; Kikuchi, T.; Nagatsuma, T.; Tomizawa, I.

2016-12-01

During the stormtime Pc5 magnetic pulsations on 31 October 2003, we detected large amplitude oscillations in the ionospheric electric field with the HF Doppler sounders at midlatitude for 10 hours from 11 to 21 LT. Similar oscillations were recorded on the magnetometer data at high-to-equatorial latitudes with significant amplitude enhancement at the dayside equator. We deduced the equatorial electrojet (EEJ) by subtracting the low latitude Pc5 from the equatorial Pc5 and found that the midlatitude electric field (EF) is well correlated with the EEJ with correlation coefficients (0.80-0.95) and that the EEJ to EF ratio reached maximum at 11 LT and dramatically decreased until 18 LT in a function of cos0.6(solar zenith angle). With these observations, we suggest that the midlatitude electric field (EF) is associated with the DP2 type ionospheric currents transmitted from high latitude to the equator. It is to be noted that the EF is well correlated with the EEJ during the night after 18 LT, indicating that the Pc5 electric field is so strong as to drive equatorial electrojet in the nighttime ionosphere. Using the electric field measured by ROCSAT-1/IPEI, we confirmed that the Pc5 electric field in the mid- and low-latitude ionosphere is comparable to or even stronger than those observed by the HF Doppler sounders. High correlations between the ground- and satellite-based observations over 15 minutes indicate that the Pc5 electric field distribute uniform over 6500 km along the ROCSAT orbit which is consistent with the large-scale DP2 electric field.

Short perturbations of cosmic ray intensity and electric field in atmosphere

NASA Technical Reports Server (NTRS)

Alexeyenko, V. V.; Chudakov, A. E.; Sborshikov, V. G.; Tizengauzen, V. A.

1985-01-01

Short perturbations of cosmic ray intensity were found to be a common phenomenon. Its meteorological origin and correlation with electric field is established. The phenomenon can be explained by the electric field if the strength of this field at high altitudes is much bigger than the measured one at surface.

A study of temporal dynamics and spatial variability of power frequency electromagnetic fields in Saint-Petersburg

NASA Astrophysics Data System (ADS)

Sturman, V. I.

2018-01-01

This paper studies spatial distribution and temporal dynamics of power frequency electric and magnetic fields in Saint-Petersburg. It was determined that sanitary-protection and exclusion zones of the standard size high-voltage transmission lines (HVTL) do not always ensure maximum allowable limits of the electrical field depression. A dependence of the electric field strength on meteorological factors was defined. A series of sources create a city-wide background for magnetic fields. That said, the heavier the man-caused load is, the higher the mean values of magnetic induction are. Abnormally high values of magnetic induction are explained by the influence of underground electric cables.

Changes in the superconducting properties of high-T(sub c) ceramics produced by applied electric fields

NASA Technical Reports Server (NTRS)

Smirnov, B. I.; Orlova, T. S.; Kaufmann, H.-J.

1995-01-01

Effect of an electrostatic field in the electrode-insulator-superconductor system on the current-voltage characteristics of high-T(sub c) ceramics with various composition and different preparation technology has been studied at 77 K. Ceramics of Y-Ba-Cu-O (123) and Bi-Pb-Sr-Ca-Cu-O (2223) systems and also ones doped by Ag have been used. Electric field strength has been up to 140 MV/m. It has been shown that there are reversible changes in the critical current I(sub c) and in the conductivity in electric field at the currents somewhat more than I(sub c) at T is less than T(sub c), while at T is greater than T(sub c) the noticeable electric field effect has not been found. These effects are qualitatively similar in both ceramic systems. High negative and positive gate voltages result in an increase of the conductivity. The electric field effect is modified by magnetic field H. The field effect decreases with increasing magnetic field and disappears at H is greater than 30 Oe. In Y-Ba-Cu-O/Ag (10 wt. percent) ceramics the field effect is practically absent. It may be supposed that in the ceramics the field-induced effect is consistent with weak links at grain boundaries.

Nonlinear conductivity in silicon nitride

NASA Astrophysics Data System (ADS)

Tuncer, Enis

2017-08-01

To better comprehend electrical silicon-package interaction in high voltage applications requires full characterization of the electrical properties of dielectric materials employed in wafer and package level design. Not only the packaging but wafer level dielectrics, i.e. passivation layers, would experience high electric fields generated by the voltage applied pads. In addition the interface between the passivation layer and a mold compound might develop space charge because of the mismatch in electrical properties of the materials. In this contribution electrical properties of a thin silicon nitride (Si3N4) dielectric is reported as a function of temperature and electric field. The measured values later analyzed using different temperature dependent exponential expressions and found that the Mott variable range hopping conduction model was successful to express the data. A full temperature/electric field dependency of conductivity is generated. It was found that the conduction in Si3N4 could be expressed like a field ionization or Fowler-Nordheim mechanism.

Cell Fragmentation and Permeabilization by a 1 ns Pulse Driven Triple-Point Electrode

PubMed Central

Li, Joy; Cho, Michael

2018-01-01

Ultrashort electric pulses (ns-ps) are useful in gaining understanding as to how pulsed electric fields act upon biological cells, but the electric field intensity to induce biological responses is typically higher than longer pulses and therefore a high voltage ultrashort pulse generator is required. To deliver 1 ns pulses with sufficient electric field but at a relatively low voltage, we used a glass-encapsulated tungsten wire triple-point electrode (TPE) at the interface among glass, tungsten wire, and water when it is immersed in water. A high electric field (2 MV/cm) can be created when pulses are applied. However, such a high electric field was found to cause bubble emission and temperature rise in the water near the electrode. They can be attributed to Joule heating near the electrode. Adherent cells on a cover slip treated by the combination of these stimuli showed two major effects: (1) cells in a crater (<100 μm from electrode) were fragmented and the debris was blown away. The principal mechanism for the damage is presumed to be shear forces due to bubble collapse; and (2) cells in the periphery of the crater were permeabilized, which was due to the combination of bubble movement and microstreaming as well as pulsed electric fields. These results show that ultrashort electric fields assisted by microbubbles can cause significant cell response and therefore a triple-point electrode is a useful ablation tool for applications that require submillimeter precision. PMID:29744357

The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas.

PubMed

Janssen, Arno M; Oostendorp, Thom F; Stegeman, Dick F

2015-05-17

The effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject's head. This implies that the direction of the induced electric field has a large effect on the efficiency of TMS. To improve future protocols, knowledge about the relationship between the coil orientation and the direction of the induced electric field on the one hand, and the head and brain anatomy on the other hand, seems crucial. Therefore, the induced electric field in the cortex as a function of the coil orientation has been examined in this study. The effect of changing the coil orientation on the induced electric field was evaluated for fourteen cortical targets. We used a finite element model to calculate the induced electric fields for thirty-six coil orientations (10 degrees resolution) per target location. The effects on the electric field due to coil rotation, in combination with target site anatomy, have been quantified. The results confirm that the electric field perpendicular to the anterior sulcal wall of the central sulcus is highly susceptible to coil orientation changes and has to be maximized for an optimal stimulation effect of the motor cortex. In order to obtain maximum stimulation effect in areas other than the motor cortex, the electric field perpendicular to the cortical surface in those areas has to be maximized as well. Small orientation changes (10 degrees) do not alter the induced electric field drastically. The results suggest that for all cortical targets, maximizing the strength of the electric field perpendicular to the targeted cortical surface area (and inward directed) optimizes the effect of TMS. Orienting the TMS coil based on anatomical information (anatomical magnetic resonance imaging data) about the targeted brain area can improve future results. The standard coil orientations, used in cognitive and clinical neuroscience, induce (near) optimal electric fields in the subject-specific head model in most cases.

Electric emissions from electrical appliances.

PubMed

Leitgeb, N; Cech, R; Schröttner, J

2008-01-01

Electric emissions from electric appliances are frequently considered negligible, and standards consider electric appliances to comply without testing. By investigating 122 household devices of 63 different categories, it could be shown that emitted electric field levels do not justify general disregard. Electric reference values can be exceeded up to 11-fold. By numerical dosimetry with homogeneous human models, induced intracorporal electric current densities were determined and factors calculated to elevate reference levels to accounting for reduced induction efficiency of inhomogeneous fields. These factors were found not high enough to allow generally concluding on compliance with basic restrictions without testing. Electric appliances usually simultaneously emit both electric and magnetic fields exposing almost the same body region. Since the sum of induced current densities is limited, one field component reduces the available margin for the other. Therefore, superposition of electric current densities induced by either field would merit consideration.

Influence of Electric Fields and Conductivity on Pollen Tube Growth assessed via Electrical Lab-on-Chip

PubMed Central

Agudelo, Carlos; Packirisamy, Muthukumaran; Geitmann, Anja

2016-01-01

Pollen tubes are polarly growing plant cells that are able to rapidly respond to a combination of chemical, mechanical, and electrical cues. This behavioural feature allows them to invade the flower pistil and deliver the sperm cells in highly targeted manner to receptive ovules in order to accomplish fertilization. How signals are perceived and processed in the pollen tube is still poorly understood. Evidence for electrical guidance in particular is vague and highly contradictory. To generate reproducible experimental conditions for the investigation of the effect of electric fields on pollen tube growth we developed an Electrical Lab-on-Chip (ELoC). Pollen from the species Camellia displayed differential sensitivity to electric fields depending on whether the entire cell or only its growing tip was exposed. The response to DC fields was dramatically higher than that to AC fields of the same strength. However, AC fields were found to restore and even promote pollen growth. Surprisingly, the pollen tube response correlated with the conductivity of the growth medium under different AC frequencies—consistent with the notion that the effect of the field on pollen tube growth may be mediated via its effect on the motion of ions. PMID:26804186

Field-aligned currents and large-scale magnetospheric electric fields

NASA Technical Reports Server (NTRS)

Dangelo, N.

1979-01-01

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

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.

Electric-field assisted switching of magnetization in perpendicularly magnetized (Ga,Mn)As films at high temperatures

NASA Astrophysics Data System (ADS)

Wang, Hailong; Ma, Jialin; Yu, Xueze; Yu, Zhifeng; Zhao, Jianhua

2017-01-01

The electric-field effects on the magnetism in perpendicularly magnetized (Ga,Mn)As films at high temperatures have been investigated. An electric-field as high as 0.6 V nm-1 is applied by utilizing a solid-state dielectric Al2O3 film as a gate insulator. The coercive field, saturation magnetization and magnetic anisotropy have been clearly changed by the gate electric-field, which are detected via the anomalous Hall effect. In terms of the Curie temperature, a variation of about 3 K is observed as determined by the temperature derivative of the sheet resistance. In addition, electrical switching of the magnetization assisted by a fixed external magnetic field at 120 K is demonstrated, employing the gate-controlled coercive field. The above experimental results have been attributed to the gate voltage modulation of the hole density in (Ga,Mn)As films, since the ferromagnetism in (Ga,Mn)As is carrier-mediated. The limited modulation magnitude of magnetism is found to result from the strong charge screening effect introduced by the high hole concentration up to 1.10  ×  1021 cm-3, while the variation of the hole density is only about 1.16  ×  1020 cm-3.

Electric toothbrushes induce electric current in fixed dental appliances by creating magnetic fields.

PubMed

Kameda, Takashi; Ohkuma, Kazuo; Ishii, Nozomu; Sano, Natsuki; Ogura, Hideo; Terada, Kazuto

2012-01-01

Magnetic fields can represent a health problem, especially low frequency electromagnetic fields sometimes induced by electric current in metallic objects worn or used in or on the body (as opposed to high frequency electromagnetic fields that produce heat). Electric toothbrushes are widely used because of their convenience, but the electric motors that power them may produce electromagnetic waves. In this study, we showed that electric toothbrushes generate low frequency (1-2000 Hz) magnetic fields and induce electric current in dental appliances (e. g. orthodontic and prosthetic appliances and dental implants). Current induced by electric toothbrushes might be dependent on the quantity and types of metals used, and the shape of the appliances. Furthermore, these induced currents in dental appliances could impact upon human oral health, producing pain and discomfort.

Reception and learning of electric fields in bees

PubMed Central

Greggers, Uwe; Koch, Gesche; Schmidt, Viola; Dürr, Aron; Floriou-Servou, Amalia; Piepenbrock, David; Göpfert, Martin C.; Menzel, Randolf

2013-01-01

Honeybees, like other insects, accumulate electric charge in flight, and when their body parts are moved or rubbed together. We report that bees emit constant and modulated electric fields when flying, landing, walking and during the waggle dance. The electric fields emitted by dancing bees consist of low- and high-frequency components. Both components induce passive antennal movements in stationary bees according to Coulomb's law. Bees learn both the constant and the modulated electric field components in the context of appetitive proboscis extension response conditioning. Using this paradigm, we identify mechanoreceptors in both joints of the antennae as sensors. Other mechanoreceptors on the bee body are potentially involved but are less sensitive. Using laser vibrometry, we show that the electrically charged flagellum is moved by constant and modulated electric fields and more strongly so if sound and electric fields interact. Recordings from axons of the Johnston organ document its sensitivity to electric field stimuli. Our analyses identify electric fields emanating from the surface charge of bees as stimuli for mechanoreceptors, and as biologically relevant stimuli, which may play a role in social communication. PMID:23536603

Reception and learning of electric fields in bees.

PubMed

Greggers, Uwe; Koch, Gesche; Schmidt, Viola; Dürr, Aron; Floriou-Servou, Amalia; Piepenbrock, David; Göpfert, Martin C; Menzel, Randolf

2013-05-22

Honeybees, like other insects, accumulate electric charge in flight, and when their body parts are moved or rubbed together. We report that bees emit constant and modulated electric fields when flying, landing, walking and during the waggle dance. The electric fields emitted by dancing bees consist of low- and high-frequency components. Both components induce passive antennal movements in stationary bees according to Coulomb's law. Bees learn both the constant and the modulated electric field components in the context of appetitive proboscis extension response conditioning. Using this paradigm, we identify mechanoreceptors in both joints of the antennae as sensors. Other mechanoreceptors on the bee body are potentially involved but are less sensitive. Using laser vibrometry, we show that the electrically charged flagellum is moved by constant and modulated electric fields and more strongly so if sound and electric fields interact. Recordings from axons of the Johnston organ document its sensitivity to electric field stimuli. Our analyses identify electric fields emanating from the surface charge of bees as stimuli for mechanoreceptors, and as biologically relevant stimuli, which may play a role in social communication.

Circuit modification in electrical field flow fractionation systems generating higher resolution separation of nanoparticles.

PubMed

Tasci, Tonguc O; Johnson, William P; Fernandez, Diego P; Manangon, Eliana; Gale, Bruce K

2014-10-24

Compared to other sub-techniques of field flow fractionation (FFF), cyclical electrical field flow fractionation (CyElFFF) is a relatively new method with many opportunities remaining for improvement. One of the most important limitations of this method is the separation of particles smaller than 100nm. For such small particles, the diffusion rate becomes very high, resulting in severe reductions in the CyElFFF separation efficiency. To address this limitation, we modified the electrical circuitry of the ElFFF system. In all earlier ElFFF reports, electrical power sources have been directly connected to the ElFFF channel electrodes, and no alteration has been made in the electrical circuitry of the system. In this work, by using discrete electrical components, such as resistors and diodes, we improved the effective electric field in the system to allow high resolution separations. By modifying the electrical circuitry of the ElFFF system, high resolution separations of 15 and 40nm gold nanoparticles were achieved. The effects of applying different frequencies, amplitudes and voltage shapes have been investigated and analyzed through experiments. Copyright © 2014 Elsevier B.V. All rights reserved.

Laboratory studies of aerosol electrification and experimental evidence for electrical breakdown at different scales.

NASA Astrophysics Data System (ADS)

Alois, Stefano; Merrison, Jonathan; Iversen, Jens Jacob; Sesterhenn, Joern

2017-04-01

Contact electrification between different particles size/material can lead to electric field generation high enough to produce electrical breakdown. Experimental studies of solid aerosol contact electrification (Alois et al., 2016) has shown various electrical breakdown phenomena; these range from field emission at the contact site (nm-scale) limiting particle surface charge concentration, to visible electrical discharges (cm-scale) observed both with the use of an electrometer and high-speed camera. In these experiments micron-size particles are injected into a low-pressure chamber, where they are deviated by an applied electric field. A laser Doppler velocimeter allows the simultaneous determination of particle size and charge of single grains. Results have shown an almost constant surface charge concentration, which is likely to be due to charge limitation by field emission at the contact site between particle and injector. In a second measurement technique, the electrically isolated injector tube (i.e. a Faraday cage) is connected to an oscilloscope and synchronised to a high speed camera filming the injection. Here the electrification of a large cloud of particles can be quantified and discharging effects studied. This study advances our understanding on the physical processes leading to electrification and electrical breakdown mechanisms.

Dynamical Generation of Quasi-Stationary Alfvenic Double Layers and Charge Holes and Unified Theory of Quasi-Static and Alfvenic Auroral Arc Formation

NASA Astrophysics Data System (ADS)

Song, Y.; Lysak, R. L.

2015-12-01

Parallel E-fields play a crucial role for the acceleration of charged particles, creating discrete aurorae. However, once the parallel electric fields are produced, they will disappear right away, unless the electric fields can be continuously generated and sustained for a fairly long time. Thus, the crucial question in auroral physics is how to generate such a powerful and self-sustained parallel electric fields which can effectively accelerate charge particles to high energy during a fairly long time. We propose that nonlinear interaction of incident and reflected Alfven wave packets in inhomogeneous auroral acceleration region can produce quasi-stationary non-propagating electromagnetic plasma structures, such as Alfvenic double layers (DLs) and Charge Holes. Such Alfvenic quasi-static structures often constitute powerful high energy particle accelerators. The Alfvenic DL consists of localized self-sustained powerful electrostatic electric fields nested in a low density cavity and surrounded by enhanced magnetic and mechanical stresses. The enhanced magnetic and velocity fields carrying the free energy serve as a local dynamo, which continuously create the electrostatic parallel electric field for a fairly long time. The generated parallel electric fields will deepen the seed low density cavity, which then further quickly boosts the stronger parallel electric fields creating both Alfvenic and quasi-static discrete aurorae. The parallel electrostatic electric field can also cause ion outflow, perpendicular ion acceleration and heating, and may excite Auroral Kilometric Radiation.

Underwater electric field detection system based on weakly electric fish

NASA Astrophysics Data System (ADS)

Xue, Wei; Wang, Tianyu; Wang, Qi

2018-04-01

Weakly electric fish sense their surroundings in complete darkness by their active electric field detection system. However, due to the insufficient detection capacity of the electric field, the detection distance is not enough, and the detection accuracy is not high. In this paper, a method of underwater detection based on rotating current field theory is proposed to improve the performance of underwater electric field detection system. First of all, we built underwater detection system based on the theory of the spin current field mathematical model with the help of the results of previous researchers. Then we completed the principle prototype and finished the metal objects in the water environment detection experiments, laid the foundation for the further experiments.

Multipactor susceptibility on a dielectric with a bias dc electric field and a background gas

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

Zhang Peng; Lau, Y. Y.; Franzi, Matthew

2011-05-15

We use Monte Carlo simulations and analytical calculations to derive the condition for the onset of multipactor discharge on a dielectric surface at various combinations of the bias dc electric field, rf electric field, and background pressures of noble gases, such as Argon. It is found that the presence of a tangential bias dc electric field on the dielectric surface lowers the magnitude of rf electric field threshold to initiate multipactor, therefore plausibly offering robust protection against high power microwaves. The presence of low pressure gases may lead to a lower multipactor saturation level, however. The combined effects of tangentialmore » dc electric field and external gases on multipactor susceptibility are presented.« less

Magnetic field controlled electronic state and electric field controlled magnetic state in α-Fe1.6Ga0.4O3 oxide

NASA Astrophysics Data System (ADS)

Lone, Abdul Gaffar; Bhowmik, R. N.

2018-04-01

We have prepared α-Fe1.6Ga0.4O3 (Ga doped α-Fe2O3) system in rhombohedral phase. The material has shown room temperature ferroelectric and ferromagnetic properties. The existence of magneto-electric coupling at room temperature has been confirmed by the experimental observation of magnetic field controlled electric properties and electric field controlled magnetization. The current-voltage characteristics were controlled by external magnetic field. The magnetic state switching and exchange bias effect are highly sensitive to the polarity and ON and OFF modes of external electric field. Such materials can find novel applications in magneto-electronic devices, especially in the field of electric field controlled spintronics devices and energy storage devices which need low power consumption.

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.

Plasma rotation by electric and magnetic fields in a discharge cylinder

NASA Technical Reports Server (NTRS)

Wilhelm, H. E.; Hong, S. H.

1977-01-01

A theoretical model for an electric discharge consisting of a spatially diverging plasma sustained electrically between a small ring cathode and a larger ring anode in a cylindrical chamber with an axial magnetic field is developed to study the rotation of the discharge plasma in the crossed electric and magnetic fields. The associated boundary-value problem for the coupled partial differential equations which describe the electric potential and the plasma velocity fields is solved in closed form. The electric field, current density, and velocity distributions are discussed in terms of the Hartmann number and the Hall coefficient. As a result of Lorentz forces, the plasma rotates with speeds as high as 1 million cm/sec around its axis of symmetry at typical conditions. As an application, it is noted that rotating discharges of this type could be used to develop a high-density plasma-ultracentrifuge driven by j x B forces, in which the lighter (heavier) ion and atom components would be enriched in (off) the center of the discharge cylinder.

Electric field imaging of single atoms

PubMed Central

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

2017-01-01

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

Electron drift velocity and mobility in graphene

NASA Astrophysics Data System (ADS)

Dong, Hai-Ming; Duan, Yi-Feng; Huang, Fei; Liu, Jin-Long

2018-04-01

We present a theoretical study of the electric transport properties of graphene-substrate systems. The drift velocity, mobility, and temperature of the electrons are self-consistently determined using the Boltzmann equilibrium equations. It is revealed that the electronic transport exhibits a distinctly nonlinear behavior. A very high mobility is achieved with the increase of the electric fields increase. The electron velocity is not completely saturated with the increase of the electric field. The temperature of the hot electrons depends quasi-linearly on the electric field. In addition, we show that the electron velocity, mobility, and electron temperature are sensitive to the electron density. These findings could be employed for the application of graphene for high-field nano-electronic devices.

Imaging electric field dynamics with graphene optoelectronics.

PubMed

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

2016-12-16

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

Effects of an electric field on the electronic and optical properties of zigzag boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh

2011-02-01

We have investigated the electro-optical properties of zigzag BNNTs, under an external electric field, using the tight binding approximation. It is found that an electric field modifies the band structure and splits the band degeneracy. Also the large electric strength leads to coupling the neighbor subbands which these effects reflect in the DOS and JDOS spectrum. It has been shown that, unlike CNTs, the band gap of BNNTs can be reduced linearly by applying a transverse external electric field. Also we show that the larger diameter tubes are more sensitive than small ones. The semiconducting metallic transition can be achieved through increasing the applied fields. The number and position of peaks in the JDOS spectrum are dependent on electric field strength. It is found that at a high electric field, the two lowest subbands are oscillatory with multiple nodes at the Fermi level.

A rocket borne instrument to measure electric fields inside electrified clouds

NASA Technical Reports Server (NTRS)

Ruhnke, L. H.

1971-01-01

The development of a rocket borne instrument to measure electric fields in thunderstorms is described. Corona currents from a sharp needle atop a small rocket are used to sense the electric field. A high ohm resistor in series with the corona needle linearizes the relationship between corona current and electric field. The corona current feeds a relaxation oscillator, whose pulses trigger a transmitter which operates in the 395 to 410 MHz meteorological band. The instrument senses fields between 5 kV/m and 100 kV/m.

CRIT II electric, magnetic, and density measurements within an ionizing neutral stream

NASA Technical Reports Server (NTRS)

Swenson, C. M.; Kelley, M. C.; Primdahl, F.; Baker, K. D.

1990-01-01

Measurements from rocket-borne sensors inside a high-velocity neutral barium beam show a-factor-of-six increase in plasma density in a moving ionizing front. This region was colocated with intense fluctuating electric fields at frequencies well under the lower hybrid frequency for a barium plasma. Large quasi-dc electric and magnetic field fluctuations were also detected with a large component of the current and the electric field parallel to B(0). An Alfven wave with a finite electric field component parallel to the geomagnetic field was observed to propagate along B(0), where it was detected by an instrumented subpayload.

Electric field driven evolution of topological domain structure in hexagonal manganites

NASA Astrophysics Data System (ADS)

Yang, K. L.; Zhang, Y.; Zheng, S. H.; Lin, L.; Yan, Z. B.; Liu, J.-M.; Cheong, S.-W.

2017-10-01

Controlling and manipulating the topological state represents an important topic in condensed matters for both fundamental researches and applications. In this work, we focus on the evolution of a real-space topological domain structure in hexagonal manganites driven by electric field, using the analytical and numerical calculations based on the Ginzburg-Landau theory. It is revealed that the electric field drives a transition of the topological domain structure from the type-I pattern to the type-II one. In particular, it is identified that a high electric field can enforce the two antiphase-plus-ferroelectric (AP +FE ) domain walls with Δ Φ =π /3 to approach each other and to merge into one domain wall with Δ Φ = 2 π /3 eventually if the electric field is sufficiently high, where Δ Φ is the difference in the trimerization phase between two neighboring domains. Our simulations also reveal that the vortex cores of the topological structure can be disabled at a sufficiently high critical electric field by suppressing the structural trimerization therein, beyond which the vortex core region is replaced by a single ferroelectric domain without structural trimerization (Q = 0 ). Our results provide a stimulating reference for understanding the manipulation of real-space topological domain structure in hexagonal manganites.

Trirotron: triode rotating beam radio frequency amplifier

DOEpatents

Lebacqz, Jean V.

1980-01-01

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

High-Altitude Aircraft-Based Electric-Field Measurements above Thunderstorms

NASA Technical Reports Server (NTRS)

Bateman, M. G.; Blakeslee, R. J.; Bailey, J. C.; Stewart, M. F.; Blair, A. K.

1999-01-01

We have developed a new set of eight electric field mills that were flown on a NASA ER-2 high-altitude aircraft. During the Third Convection And Moisture EXperiment (CAMEX- 3; Fall, 1998), measurements of electric field, storm dynamics, and ice microphysics were made over several hurricanes. Concurrently, the TExas-FLorida UNderflights (TEFLUN) program was being conducted to make the same measurements over Gulf Coast thunderstorms. Sample measurements will be shown. Our new mills have an internal 16-bit A/D, with a resolution of 0.25 V/m per bit at high gain, with a noise level less than the least significant bit. A second, lower gain channel gives us the ability to measure fields as high as 150 kV/m.

Permanent magnetic field, direct electric field, and infrared to reduce blood glucose level and hepatic function in mus musculus with diabetic mellitus

NASA Astrophysics Data System (ADS)

Suhariningsih; Basuki Notobroto, Hari; Winarni, Dwi; Achmad Hussein, Saikhu; Anggono Prijo, Tri

2017-05-01

Blood contains several electrolytes with positive (cation) and negative (anion) ion load. Both electrolytes deliver impulse synergistically adjusting body needs. Those electrolytes give specific effect to external disturbance such as electric, magnetic, even infrared field. A study has been conducted to reduce blood glucose level and liver function, in type 2 Diabetes Mellitus patients, using Biophysics concept which uses combination therapy of permanent magnetic field, electric field, and infrared. This study used 48 healthy mice (mus musculus), male, age 3-4 weeks, with approximately 25-30 g in weight. Mice was fed with lard as high fat diet orally, before Streptozotocin (STZ) induction become diabetic mice. Therapy was conducted by putting mice in a chamber that emits the combination of permanent magnetic field, electric field, and infrared, every day for 1 hour for 28 days. There were 4 combinations of therapy/treatment, namely: (1) permanent magnetic field, direct electric field, and infrared; (2) permanent magnetic field, direct electric field, without infrared; (3) permanent magnetic field, alternating electric field, and infrared; and (4) permanent magnetic field, alternating electric field, without infrared. The results of therapy show that every combination is able to reduce blood glucose level, AST, and ALT. However, the best result is by using combination of permanent magnetic field, direct electric field, and infrared.

High field gradient particle accelerator

DOEpatents

Nation, John A.; Greenwald, Shlomo

1989-01-01

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.

Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

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

Ahn, S. K.; Chang, H. Y.

To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90 MHz with argon pressures of 50 and 400 mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with themore » theories of electromagnetic effects in large area and/or high frequency capacitive discharges.« less

PLASMA DEVICE

DOEpatents

Baker, W.R.; Brathenahl, A.; Furth, H.P.

1962-04-10

A device for producing a confined high temperature plasma is described. In the device the concave inner surface of an outer annular electrode is disposed concentrically about and facing the convex outer face of an inner annular electrode across which electrodes a high potential is applied to produce an electric field there between. Means is provided to create a magnetic field perpendicular to the electric field and a gas is supplied at reduced pressure in the area therebetween. Upon application of the high potential, the gas between the electrodes is ionized, heated, and under the influence of the electric and magnetic fields there is produced a rotating annular plasma disk. The ionized plasma has high dielectric constant properties. The device is useful as a fast discharge rate capacitor, in controlled thermonuclear research, and other high temperature gas applications. (AEC)

Vector electric field measurement via position-modulated Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Dwyer, Ryan P.; Smieska, Louisa M.; Tirmzi, Ali Moeed; Marohn, John A.

2017-10-01

High-quality spatially resolved measurements of electric fields are critical to understanding charge injection, charge transport, and charge trapping in semiconducting materials. Here, we report a variation of frequency-modulated Kelvin probe force microscopy that enables spatially resolved measurements of the electric field. We measure electric field components along multiple directions simultaneously by employing position modulation and lock-in detection in addition to numeric differentiation of the surface potential. We demonstrate the technique by recording linescans of the in-plane electric field vector in the vicinity of a patch of trapped charge in a 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT) organic field-effect transistor. This technique is simple to implement and should be especially useful for studying electric fields in spatially inhomogeneous samples like organic transistors and photovoltaic blends.

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.

A corotation electric field model of the Earth derived from Swarm satellite magnetic field measurements

NASA Astrophysics Data System (ADS)

Maus, Stefan

2017-08-01

Rotation of the Earth in its own geomagnetic field sets up a primary corotation electric field, compensated by a secondary electric field of induced electrical charges. For the geomagnetic field measured by the Swarm constellation of satellites, a derivation of the global corotation electric field inside and outside of the corotation region is provided here, in both inertial and corotating reference frames. The Earth is assumed an electrical conductor, the lower atmosphere an insulator, followed by the corotating ionospheric E region again as a conductor. Outside of the Earth's core, the induced charge is immediately accessible from the spherical harmonic Gauss coefficients of the geomagnetic field. The charge density is positive at high northern and southern latitudes, negative at midlatitudes, and increases strongly toward the Earth's center. Small vertical electric fields of about 0.3 mV/m in the insulating atmospheric gap are caused by the corotation charges located in the ionosphere above and the Earth below. The corotation charges also flow outward into the region of closed magnetic field lines, forcing the plasmasphere to corotate. The electric field of the corotation charges further extends outside of the corotating regions, contributing radial outward electric fields of about 10 mV/m in the northern and southern polar caps. Depending on how the magnetosphere responds to these fields, the Earth may carry a net electric charge.

In situ emulsification using a non-uniform alternating electric field

NASA Astrophysics Data System (ADS)

Choi, Suhwan; Saveliev, Alexei V.

2014-08-01

We report an electric field based method for in situ emulsification of water droplets immersed in a continuous oil phase. High density water-in-oil emulsions are generated using non-uniform ac electric fields applied between needle and plate electrodes. An initial water droplet is entrained in the area of high electric field near the needle electrode where it is dispersed under the influence of high electric stresses. Breakup mechanisms responsible for a gradual dispersion of the water droplets are investigated. Identified mechanisms involve drop elongation to a cylindrical shape followed by a capillary breakup, ac electrospraying from individual water droplets, and formation and breakup of bead-like structures comprised by the water droplets interconnected by thin water bridges. Water droplets with diameters close to 1 μm and a narrow size distribution are formed at long processing times. The generated emulsion has a well-defined boundary and is confined near the needle electrode in a shape resembling a pendant drop.

Safety of High Speed Guided Ground Transportation Systems. Broadband Magnetic Fields : Their Possible Role in EMF Associated Bioeffects

DOT National Transportation Integrated Search

1993-08-01

This report reviews electric and magnetic field (EMF) exposures from electrical transportation systems, including : electrically powered rail and magnetic levitation (maglev). Material also covered includes research concerning : biological effects of...

Design of high breakdown voltage vertical GaN p-n diodes with high-K/low-K compound dielectric structure for power electronics applications

NASA Astrophysics Data System (ADS)

Du, Jiangfeng; Li, Zhenchao; Liu, Dong; Bai, Zhiyuan; Liu, Yang; Yu, Qi

2017-11-01

In this work, a vertical GaN p-n diode with a high-K/low-K compound dielectric structure (GaN CD-VGD) is proposed and designed to achieve a record high breakdown voltage (BV) with a low specific on-resistance (Ron,sp). By introducing compound dielectric structure, the electric field near the p-n junction interface is suppressed due to the effects of high-K passivation layer, and a new electric field peak is induced into the n-type drift region, because of a discontinuity of electrical field at the interface of high-K and low-K layer. Therefore the distribution of electric field in GaN p-n diode becomes more uniform and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN CD-VGD with a BV of 10650 V and a Ron,sp of 14.3 mΩ cm2, resulting in a record high figure-of-merit of 8 GW/cm2.

Electrically tunable hole g factor of an optically active quantum dot for fast spin rotations

NASA Astrophysics Data System (ADS)

Prechtel, Jonathan H.; Maier, Franziska; Houel, Julien; Kuhlmann, Andreas V.; Ludwig, Arne; Wieck, Andreas D.; Loss, Daniel; Warburton, Richard J.

2015-04-01

We report a large g factor tunability of a single hole spin in an InGaAs quantum dot via an electric field. The magnetic field lies in the in-plane direction x , the direction required for a coherent hole spin. The electrical field lies along the growth direction z and is changed over a large range, 100 kV/cm. Both electron and hole g factors are determined by high resolution laser spectroscopy with resonance fluorescence detection. This, along with the low electrical-noise environment, gives very high quality experimental results. The hole g factor ghx depends linearly on the electric field Fz,d ghx/d Fz=(8.3 ±1.2 ) ×10-4 cm/kV, whereas the electron g factor gex is independent of electric field d gex/d Fz=(0.1 ±0.3 ) ×10-4 cm/kV (results averaged over a number of quantum dots). The dependence of ghx on Fz is well reproduced by a 4 ×4 k .p model demonstrating that the electric field sensitivity arises from a combination of soft hole confining potential, an In concentration gradient, and a strong dependence of material parameters on In concentration. The electric field sensitivity of the hole spin can be exploited for electrically driven hole spin rotations via the g tensor modulation technique and based on these results, a hole spin coupling as large as ˜1 GHz can be envisaged.

Experimental investigation into the coupling effects of magnetic field, temperature and pressure on electrical resistivity of non-oriented silicon steel sheet

NASA Astrophysics Data System (ADS)

Xiao, Lijun; Yu, Guodong; Zou, Jibin; Xu, Yongxiang

2018-05-01

In order to analyze the performance of magnetic device which operate at high temperature and high pressure, such as submersible motor, oil well transformer, the electrical resistivity of non-oriented silicon steel sheets is necessary for precise analysis. But the reports of the examination of the measuring method suitable for high temperature up to 180 °C and high pressure up to 140 MPa are few. In this paper, a measurement system based on four-probe method and Archimedes spiral shape measurement specimens is proposed. The measurement system is suitable for measuring the electrical resistivity of unconventional specimens under high temperature and high pressure and can simultaneously consider the influence of the magnetic field on the electrical resistivity. It can be seen that the electrical resistivity of the non-oriented silicon steel sheets will fluctuate instantaneously when the magnetic field perpendicular to the conductive path of the specimens is loaded or removed. The amplitude and direction of the fluctuation are not constant. Without considering the effects of fluctuations, the electrical resistivity of the non-oriented silicon steel sheets is the same when the magnetic field is loaded or removed. And the influence of temperature on the electrical resistivity of the non-oriented silicon steel sheet is still the greatest even though the temperature and the pressure are coupled together. The measurement results also show that the electrical resistivity varies linearly with temperature, so the temperature coefficient of resistivity is given in the paper.

Controlling turbulent drag across electrolytes using electric fields.

PubMed

Ostilla-Mónico, Rodolfo; Lee, Alpha A

2017-07-01

Reversible in operando control of friction is an unsolved challenge that is crucial to industrial tribology. Recent studies show that at low sliding velocities, this control can be achieved by applying an electric field across electrolyte lubricants. However, the phenomenology at high sliding velocities is yet unknown. In this paper, we investigate the hydrodynamic friction across electrolytes under shear beyond the transition to turbulence. We develop a novel, highly parallelised numerical method for solving the coupled Navier-Stokes Poisson-Nernst-Planck equation. Our results show that turbulent drag cannot be controlled across dilute electrolytes using static electric fields alone. The limitations of the Poisson-Nernst-Planck formalism hint at ways in which turbulent drag could be controlled using electric fields.

Electric field controlled emulsion phase contactor

DOEpatents

Scott, Timothy C.

1995-01-01

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

Method of using an electric field controlled emulsion phase contactor

DOEpatents

Scott, Timothy C.

1993-01-01

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

Electric field controlled emulsion phase contactor

DOEpatents

Scott, T.C.

1995-01-31

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

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.

Magnetic and electric field meters developed for the US Department of Energy

NASA Technical Reports Server (NTRS)

Kirkham, H.; Johnson, A.

1988-01-01

This report describes work done at the Jet Propulsion Laboratory for the Office of Energy Storage and Distribution of DOE on the measurement of power line fields. A magnetic field meter is discussed that uses fiber optics to couple a small measuring probe to a remote readout device. The use of fiber optics minimizes electric field perturbation due to the presence of the probe and provides electric isolation for the probe, so that it could be used in a high field or high voltage environment. Power to operate the sensor electronics is transferred via an optical fiber, and converted to electrical form by a small photodiode array. The fundamental, the second and third harmonics of the field are filtered and separately measured, as well as the broadband rms level of the field. The design of the meter is described in detail and data from laboratory tests are presented. The report also describes work done to improve the performance of a DC bushing in a Swedish factory, using the improved meter. The DC electric fields are measured with synchronous detection to provide field magnitude data in two component directions.

Measurements of Electric Field in a Nanosecond Pulse Discharge by 4-WAVE Mixing

NASA Astrophysics Data System (ADS)

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

2017-06-01

Picosecond four-wave mixing is used to measure temporally and Picosecond four-wave mixing is used to measure temporally and spatially resolved electric field in a nanosecond pulse dielectric discharge sustained in room air and in an atmospheric pressure hydrogen diffusion flame. Measurements of the electric field, and more precisely the reduced electric field (E/N) in the plasma is critical for determination rate coefficients of electron impact processes in the plasma, as well as for quantifying energy partition in the electric discharge among different molecular energy modes. The four-wave mixing measurements are performed using a collinear phase matching geometry, with nitrogen used as the probe species, at temporal resolution of about 2 ns . Absolute calibration is performed by measurement of a known electrostatic electric field. In the present experiments, the discharge is sustained between two stainless steel plate electrodes, each placed in a quartz sleeve, which greatly improves plasma uniformity. Our previous measurements of electric field in a nanosecond pulse dielectric barrier discharge by picosecond 4-wave mixing have been done in air at room temperature, in a discharge sustained between a razor edge high-voltage electrode and a plane grounded electrode (a quartz plate or a layer of distilled water). Electric field measurements in a flame, which is a high-temperature environment, are more challenging because the four-wave mixing signal is proportional to the to square root of the difference betwen the populations of N2 ground vibrational level (v=0) and first excited vibrational level (v=1). At high temperatures, the total number density is reduced, thus reducing absolute vibrational level populations of N2. Also, the signal is reduced further due to a wider distribution of N2 molecules over multiple rotational levels at higher temperatures, while the present four-wave mixing diagnostics is using spectrally narrow output of a ps laser and a high-pressure Raman cell, providing access only to a few N2 rotational levels. Because of this, the four-wave mixing signal in the flame is lower by more than an order of magnitude compared to the signal generated in room temperature air plasma. Preliminary experiments demonstrated four-wave mixing signal generated by the electric field in the flame, following ns pulse discharge breakdown. The electric field in the flame is estimated using four-wave mixing signal calibration vs. temperature in electrostatic electric field generated in heated air. Further measurements in the flame are underway.

[INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

NASA Astrophysics Data System (ADS)

Gamaly, Eugene G.; Rode, Andrei V.

2016-08-01

Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval's axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

Asymptotic expansion of pair production probability in a time-dependent electric field

NASA Astrophysics Data System (ADS)

Arai, Takashi

2015-12-01

We study particle creation in a single pulse of an electric field in scalar quantum electrodynamics. We investigate the parameter condition for the case where the dynamical pair creation and Schwinger mechanism respectively dominate. Then, an asymptotic expansion for the particle distribution in terms of the time interval of the applied electric field is derived. We compare our result with particle creation in a constant electric field with a finite-time interval. These results coincide in an extremely strong field, however they differ in general field strength. We interpret the reason of this difference as a nonperturbative effect of high-frequency photons in external electric fields. Moreover, we find that the next-to-leading-order term in our asymptotic expansion coincides with the derivative expansion of the effective action.

Measuring the vertical electrical field above an oceanic convection system using a meteorological sounding balloon

NASA Astrophysics Data System (ADS)

Chen, A. B.; Chiu, C.; Lai, S.; Chen, C.; Kuo, C.; Su, H.; Hsu, R.

2012-12-01

The vertical electric field above thundercloud plays an important role in the generation and modeling of transient luminous events. For example, Pasko [1995] proposed that the high quasi-static E-field following the positive cloud-to-ground lightning could accelerate and input energy to ambient electrons; as they collide and excite nitrogen and oxygen molecules in upper atmosphere, sprites may be induced. A series of balloon experiments led by Holzworth have investigated the temporal and spatial fluctuations of the electric field and conductivity in the upper atmosphere at different sites [Holzworth 2005, and references in]. But the strength and variation of the vertical electric field above thundercloud, especially oceanic ones, are not well documented so far. A lightweight, low-cost measurement system including an electric field meter and the associated aviation electronics are developed to carry out the in-situ measurement of the vertical electric field and the inter-cloud charge distribution. Our measuring system was first deployed using a meteorological sounding balloon from Taitung, Taiwan in May 2012. The measured electric field below 3km height shows an exponential decay and it is consistent with the expected potential gradient variation between ionosphere and the Earth surface. But the background strength of the measured E-field grows up exponentially and a violent fluctuations is also observed when the balloon flew over a developing oceanic convection cell. The preliminary results from this flight will be reported and discussed. This low-cost electric field meter is developed within one year. In the coming months, more flights will be performed with the aim to measure the rapid variation of the electric field above thundercloud as well as the E-field that may induce transient luminous events. Our ground campaigns show that the occurrence rates of blue and gigantic jet are relatively high in the vicinity of Taiwan. Our experiment can be used to diagnose the dynamics of the E-field associated with blue and gigantic jets.

Measuring of the pitch variation of cholesteric liquid crystals under electric field using wavelength-swept laser

NASA Astrophysics Data System (ADS)

Ko, Myeong Ock; Kim, Sung-Jo; Kim, Jong-Hyun; Jeon, Min Yong

2017-04-01

We measure the pitch variation of cholesteric liquid crystals (CLCs) according to the applied electric field using a wavelength-swept laser. While the electric field is applied to the CLC, the pitch of the CLC is elongated normal to the direction of electric field. Therefore, the reflection band is shifted to the longer wavelength. When the applied electric field to the CLC cell was over 1.52 V/μm, the reflection band was changed to the longer wavelength of about 75.1 nm. We believe that the dynamic behavior of the CLC can be analyzed if a high-speed wavelength-swept laser is used as an optical source.

Stripe formation in an immiscible polymer blend under electric and shear-flow fields

NASA Astrophysics Data System (ADS)

Na, Yang-Ho; Shibuya, Tetsunori; Ujiie, Seiji; Nagaya, Tomoyuki; Orihara, Hiroshi

2008-04-01

We found a stripe formation in an emulsion of a liquid crystalline polymer (LCP) and a machine oil (OIL) in electric and shear fields. Through the simultaneous measurement with a confocal scanning laser microscope and a rheometer, it was clearly shown that the formation of stripes, which are periodically arrayed, leads to the increase of the shear stress. The droplets, which are one component of the emulsion, start to be connected at low electric fields and then change into the stripes with the increase of electric field. Finally, a three-dimensional network is formed at high electric fields. The period and fluctuation of the stripe structure were also investigated in detail.

High-sensitivity visualization of localized electric fields using low-energy electron beam deflection

NASA Astrophysics Data System (ADS)

Jeong, Samuel; Ito, Yoshikazu; Edwards, Gary; Fujita, Jun-ichi

2018-06-01

The visualization of localized electronic charges on nanocatalysts is expected to yield fundamental information about catalytic reaction mechanisms. We have developed a high-sensitivity detection technique for the visualization of localized charges on a catalyst and their corresponding electric field distribution, using a low-energy beam of 1 to 5 keV electrons and a high-sensitivity scanning transmission electron microscope (STEM) detector. The highest sensitivity for visualizing a localized electric field was ∼0.08 V/µm at a distance of ∼17 µm from a localized charge at 1 keV of the primary electron energy, and a weak local electric field produced by 200 electrons accumulated on the carbon nanotube (CNT) apex can be visualized. We also observed that Au nanoparticles distributed on a CNT forest tended to accumulate a certain amount of charges, about 150 electrons, at a ‑2 V bias.

Effect of Electric Field Gradient on Sub-nanometer Spatial Resolution of Tip-enhanced Raman Spectroscopy

PubMed Central

Meng, Lingyan; Yang, Zhilin; Chen, Jianing; Sun, Mengtao

2015-01-01

Tip-enhanced Raman spectroscopy (TERS) with sub-nanometer spatial resolution has been recently demonstrated experimentally. However, the physical mechanism underlying is still under discussion. Here we theoretically investigate the electric field gradient of a coupled tip-substrate system. Our calculations suggest that the ultra-high spatial resolution of TERS can be partially attributed to the electric field gradient effect owning to its tighter spatial confinement and sensitivity to the infrared (IR)-active of molecules. Particularly, in the case of TERS of flat-lying H2TBPP molecules,we find the electric field gradient enhancement is the dominating factor for the high spatial resolution, which qualitatively coincides with previous experimental report. Our theoretical study offers a new paradigm for understanding the mechanisms of the ultra-high spatial resolution demonstrated in tip-enhanced spectroscopy which is of importance but neglected. PMID:25784161

High-Altitude Aircraft-Based Electric-Field Measurements Above Thunderstorms

NASA Technical Reports Server (NTRS)

Bateman, M. G.; Blakeslee, R. J.; Bailey, J. C.; Stewart, M. F.; Blair, A. K.

1999-01-01

We have developed a new set of eight electric field mills that were flown on a NASA ER-2 high-altitude aircraft. During the Third Convection And Moisture EXperiment (CAMEX-3; Fall, 1998), measurements of electric field, storm dynamics, and ice microphysics were made over several hurricanes. Concurrently, the TExas-FLorida UNderflights (TEFLUN) program was being conducted to make the same measurements over Gulf Coast thunderstorms. Sample measurements are shown: typical flight altitude is 20km. Our new mills have an internal 16-bit A/D, with a resolution of 0.25V/m per bit at high gain, with a noise level less than the least significant bit. A second, lower gain channel gives us the ability to measure fields as high as 150 kV/m.

Dynamic Stark spectroscopic measurements of microwave electric fields inside the plasma near a high-power antenna.

PubMed

Klepper, C C; Isler, R C; Hillairet, J; Martin, E H; Colas, L; Ekedahl, A; Goniche, M; Harris, J H; Hillis, D L; Panayotis, S; Pegourié, B; Lotte, Ph; Colledani, G; Martin, V

2013-05-24

Fully dynamic Stark effect visible spectroscopy was used for the first time to directly measure the local rf electric field in the boundary plasma near a high-power antenna in high-performance, magnetically confined, fusion energy experiment. The measurement was performed in the superconducting tokamak Tore Supra, in the near field of a 1–3 MW, lower-hybrid, 3.7 GHz wave-launch antenna, and combined with modeling of neutral atom transport to estimate the local rf electric field amplitude (as low as 1–2 kV/cm) and direction in this region. The measurement was then shown to be consistent with the predicted values from a 2D full-wave propagation model. Notably the measurement confirmed that the electric field direction deviates substantially from the direction in which it is launched by the waveguides as it penetrates only a few cm radially inward into the plasma from the waveguides, consistent with the model.

Method for improving performance of highly stressed electrical insulating structures

DOEpatents

Wilson, Michael J.; Goerz, David A.

2002-01-01

Removing the electrical field from the internal volume of high-voltage structures; e.g., bushings, connectors, capacitors, and cables. The electrical field is removed from inherently weak regions of the interconnect, such as between the center conductor and the solid dielectric, and places it in the primary insulation. This is accomplished by providing a conductive surface on the inside surface of the principal solid dielectric insulator surrounding the center conductor and connects the center conductor to this conductive surface. The advantage of removing the electric fields from the weaker dielectric region to a stronger area improves reliability, increases component life and operating levels, reduces noise and losses, and allows for a smaller compact design. This electric field control approach is currently possible on many existing products at a modest cost. Several techniques are available to provide the level of electric field control needed. Choosing the optimum technique depends on material, size, and surface accessibility. The simplest deposition method uses a standard electroless plating technique, but other metalization techniques include vapor and energetic deposition, plasma spraying, conductive painting, and other controlled coating methods.

Wetting and motion behaviors of water droplet on graphene under thermal-electric coupling field

NASA Astrophysics Data System (ADS)

Zhang, Zhong-Qiang; Dong, Xin; Ye, Hong-Fei; Cheng, Guang-Gui; Ding, Jian-Ning; Ling, Zhi-Yong

2015-02-01

Wetting dynamics and motion behaviors of a water droplet on graphene are characterized under the electric-thermal coupling field using classical molecular dynamics simulation method. The water droplet on graphene can be driven by the temperature gradient, while the moving direction is dependent on the electric field intensity. Concretely, the water droplet on graphene moves from the low temperature region to the high temperature region for the relatively weak electric field intensity. The motion acceleration increases with the electric field intensity on graphene, whereas the moving direction switches when the electric field intensity increases up to a threshold. The essence is the change from hydrophilic to hydrophobic for the water droplet on graphene at a threshold of the electric field intensity. Moreover, the driven force of the water droplet caused by the overall oscillation of graphene has important influence on the motion behaviors. The results are helpful to control the wettability of graphene and further develop the graphene-based fluidic nanodevices.

Imaging electric field dynamics with graphene optoelectronics

DOE PAGES

Horng, Jason; Balch, Halleh B.; McGuire, Allister F.; ...

2016-12-16

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

Imaging electric field dynamics with graphene optoelectronics

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

Horng, Jason; Balch, Halleh B.; McGuire, Allister F.

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

High field gradient particle accelerator

DOEpatents

Nation, J.A.; Greenwald, S.

1989-05-30

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

First Results on the Variability of Mid- and High-Latitude Ionospheric Electric Fields at 1- Second Time Scales

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.; Greenwald, R. A.; Oksavik, K.; Baker, J. B.

2007-12-01

The electric fields at high latitudes are often modeled as a static pattern in the absence of variation in solar wind parameters or geomagnetic disturbance. However, temporal variability in the local electric fields on time scales of minutes for stable conditions has been reported and characterized statistically as an intrinsic property amounting to turbulence. We describe the results of applying a new technique to SuperDARN HF radar observations of ionospheric plasma convection at middle and high latitudes that gives views of the variability of the electric fields at sub-second time scales. We address the question of whether there is a limit to the temporal scale of the electric field variability and consider whether the turbulence on minute time scales is due to organized but unresolved behavior. The basis of the measurements is the ability to record raw samples from the individual multipulse sequences that are transmitted during the standard 3 or 6-second SuperDARN integration period; a backscattering volume is then effectively sampled at a cadence of 200 ms. The returns from the individual sequences are often sufficiently well-ordered to permit a sequence-by-sequence characterization of the electric field and backscattered power. We attempt a statistical characterization of the variability at these heretofore inaccessible time scales and consider how variability is influenced by solar wind and magentospheric factors.

Softened Mechanical Properties of Graphene Induced by Electric Field.

PubMed

Huang, Peng; Guo, Dan; Xie, Guoxin; Li, Jian

2017-10-11

The understanding on the mechanical properties of graphene under the applications of physical fields is highly relevant to the reliability and lifetime of graphene-based nanodevices. In this work, we demonstrate that the application of electric field could soften the mechanical properties of graphene dramatically on the basis of the conductive AFM nanoindentation method. It has been found that the Young's modulus and fracture strength of graphene nanosheets suspended on the holes almost stay the same initially and then exhibit a sharp drop when the normalized electric field strength increases to be 0.18 ± 0.03 V/nm. The threshold voltage of graphene nanosheets before the onset of fracture under the fixed applied load increases with the thickness. Supported graphene nanosheets can sustain larger electric field under the same applied load than the suspended ones. The excessively regional Joule heating caused by the high electric current under the applied load is responsible for the electromechanical failure of graphene. These findings can provide a beneficial guideline for the electromechanical applications of graphene-based nanodevices.

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

Fukao, Shinji; Nakanishi, Yoshikazu; Mizoguchi, Tadahiro

X-rays are radiated due to the bremsstrahlung caused by the collision of electrons with a metal target placed opposite the negative electric surface of a crystal by changing the temperature of a LiNbO{sub 3} single crystal uniaxially polarized in the c-axis direction. It is suggested that both electric field intensity and electron density determine the intensity of X-ray radiation. Electrons are supplied by the ionization of residual gas in space, field emission from a case inside which a crystal is located, considered to be due to the high electric-field intensity formed by the surface charges on the crystal, and anmore » external electron source, such as a thermionic source. In a high vacuum, it was found that the electrons supplied by electric-field emission mainly contribute to the radiation of X-rays. It was found that the integrated intensity of X-rays can be maximized by supplying electrons both external and by electric-field emission. Furthermore, the integrated intensity of the X-rays is stable for many repeated temperature changes.« less

Electric-field-controlled ferromagnetism in high-Curie-temperature Mn0.05Ge0.95 quantum dots.

PubMed

Xiu, Faxian; Wang, Yong; Kim, Jiyoung; Hong, Augustin; Tang, Jianshi; Jacob, Ajey P; Zou, Jin; Wang, Kang L

2010-04-01

Electric-field manipulation of ferromagnetism has the potential for developing a new generation of electric devices to resolve the power consumption and variability issues in today's microelectronics industry. Among various dilute magnetic semiconductors (DMSs), group IV elements such as Si and Ge are the ideal material candidates because of their excellent compatibility with the conventional complementary metal-oxide-semiconductor (MOS) technology. Here we report, for the first time, the successful synthesis of self-assembled dilute magnetic Mn(0.05)Ge(0.95) quantum dots with ferromagnetic order above room temperature, and the demonstration of electric-field control of ferromagnetism in MOS ferromagnetic capacitors up to 100 K. We found that by applying electric fields to a MOS gate structure, the ferromagnetism of the channel layer can be effectively modulated through the change of hole concentration inside the quantum dots. Our results are fundamentally important in the understanding and to the realization of high-efficiency Ge-based spin field-effect transistors.

Electric Field Detection in Sawfish and Shovelnose Rays

PubMed Central

Wueringer, Barbara E.; Jnr, Lyle Squire; Kajiura, Stephen M.; Tibbetts, Ian R.; Hart, Nathan S.; Collin, Shaun P.

2012-01-01

In the aquatic environment, living organisms emit weak dipole electric fields, which spread in the surrounding water. Elasmobranchs detect these dipole electric fields with their highly sensitive electroreceptors, the ampullae of Lorenzini. Freshwater sawfish, Pristis microdon, and two species of shovelnose rays, Glaucostegus typus and Aptychotrema rostrata were tested for their reactions towards weak artificial electric dipole fields. The comparison of sawfishes and shovelnose rays sheds light on the evolution and function of the elongated rostrum (‘saw’) of sawfish, as both groups evolved from a shovelnose ray-like ancestor. Electric stimuli were presented both on the substrate (to mimic benthic prey) and suspended in the water column (to mimic free-swimming prey). Analysis of around 480 behavioural sequences shows that all three species are highly sensitive towards weak electric dipole fields, and initiate behavioural responses at median field strengths between 5.15 and 79.6 nVcm−1. The response behaviours used by sawfish and shovelnose rays depended on the location of the dipoles. The elongation of the sawfish’s rostrum clearly expanded their electroreceptive search area into the water column and enables them to target free-swimming prey. PMID:22848543

The mechanism of high-T(sub c) superconductivity due to bound hole mediators: Relationship to ferroelectricity

NASA Technical Reports Server (NTRS)

Vezzoli, G. C.; Stanley, William

1990-01-01

The mediation by bound holes creating Cooper pairing in high T(sub c) superconductors has its origin in charge transfer excitations on the multivalence cation (virtual excitions) and in bound excitions or polarizations associated with the oxygen 2p electrons. These phenomena are produced and/or enhanced by a high internal electric field which is itself created by virtue of the unique crystal structures and polyhedral building blocks of high T(sub c) materials. The polarizations which can create oxygen holes (in addition to excitions) may be due to simply the internal electric field or to polaronic and electron-deficient bond behavior. This gives rise to two energy-dependent oxygen bands near the Fermi level. The magnitude and direction of the internal electric fields were calculated for Y1Ba2Cu3O(7-delta) (1-2-3) and show strong z-direction fields at the Cu(2), O2, and O3 sites and an even stronger -z direction field at the O4 site. The field calculations also show why electrical conductivity in the 1-2-3 material is essentially in the base plane of the CuO5 pyramid (the CuO2 plane).

Transient features in nanosecond pulsed electric fields differentially modulate mitochondria and viability.

PubMed

Beebe, Stephen J; Chen, Yeong-Jer; Sain, Nova M; Schoenbach, Karl H; Xiao, Shu

2012-01-01

It is hypothesized that high frequency components of nanosecond pulsed electric fields (nsPEFs), determined by transient pulse features, are important for maximizing electric field interactions with intracellular structures. For monopolar square wave pulses, these transient features are determined by the rapid rise and fall of the pulsed electric fields. To determine effects on mitochondria membranes and plasma membranes, N1-S1 hepatocellular carcinoma cells were exposed to single 600 ns pulses with varying electric fields (0-80 kV/cm) and short (15 ns) or long (150 ns) rise and fall times. Plasma membrane effects were evaluated using Fluo-4 to determine calcium influx, the only measurable source of increases in intracellular calcium. Mitochondria membrane effects were evaluated using tetramethylrhodamine ethyl ester (TMRE) to determine mitochondria membrane potentials (ΔΨm). Single pulses with short rise and fall times caused electric field-dependent increases in calcium influx, dissipation of ΔΨm and cell death. Pulses with long rise and fall times exhibited electric field-dependent increases in calcium influx, but diminished effects on dissipation of ΔΨm and viability. Results indicate that high frequency components have significant differential impact on mitochondria membranes, which determines cell death, but lesser variances on plasma membranes, which allows calcium influxes, a primary determinant for dissipation of ΔΨm and cell death.

High pressure xenon ionization detector

DOEpatents

Markey, J.K.

1989-11-14

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

High pressure xenon ionization detector

DOEpatents

Markey, John K.

1989-01-01

A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

Formation of Organized Protein Thin Films with External Electric Field.

PubMed

Ferreira, Cecília Fabiana da G; Camargo, Paulo C; Benelli, Elaine M

2015-10-01

The effect of an external electric field on the formation of protein GlnB-Hs films and on its buffer solution on siliconized glass slides has been analyzed by current versus electric field curves and atomic force microscopy (AFM). The Herbaspirillum seropedicae GlnB protein (GlnB-Hs) is a globular, soluble homotrimer (36 kDa) with its 3-D structure previously determined. Concentrations of 10 nM native denatured GlnB-Hs protein were deposited on siliconized glass slides under ambient conditions. Immediately after solution deposition a maximum electric field of 30 kV/m was applied with rates of 3 V/s. The measured currents were surface currents and were analyzed as transport current. Electric current started to flow only after a minimum electric field (critical value) for the systems analyzed. The AFM images showed films with a high degree of directional organization only when the proteins were present in the solution. These results showed that the applied electric field favored directional organization of the protein GlnB-Hs films and may contribute to understand the formation of protein films under applied electric fields.

Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

2015-12-01

A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

Method of using an electric field controlled emulsion phase contactor

DOEpatents

Scott, T.C.

1993-11-16

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

Relationships between field-aligned currents, electric fields, and particle precipitation as observed by Dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1984-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

Relationships between field-aligned currents, electric fields and particle precipitation as observed by dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1983-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

Modeling of the coupled magnetospheric and neutral wind dynamos

NASA Technical Reports Server (NTRS)

Thayer, Jeff P.

1993-01-01

The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet to be quantitatively evaluated. In this program, we are evaluating the coupled magnetospheric and neutral wind dynamos at high latitudes under various conditions. In addition to examining the impact of seasonal variations, we are investigating the consequences of the separate dynamos having pure current-source or voltage-source behaviors.

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.

A study of the glow discharge plasma jet of the novel Hamburger-electrode

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

Liu, Wenzheng, E-mail: wzhliu@bjtu.edu.cn; Ma, Chuanlong, E-mail: 15121452@bjtu.edu.cn; Yang, Xiao

2016-08-15

To generate atmospheric pressure glow discharge plasma jets (APGDPJs), a novel Hamburger-electrode was proposed. Through the study on electric field distributions, flow field distributions, and characteristics of the discharge and jet, we found that adopting the mode of dielectric barrier discharge with non-uniform thickness of dielectric, it was easy to form the strong electric field areas which were conducive to generate discharge and electric field distributions with large electric field intensity in the narrow gap and weak electric field intensity in the wide gap that were not inclined to form a filament discharge. Using the structure of evenly distributed innermore » electrodes, it was easy to weaken the pressure of strong electric field areas and form flow field distributions which is beneficial for taking out the high density charged particles and generating APGDPJs. Stable APGDPJs in nitrogen with 3.5 mm in diameter and 9 mm in length were formed by using the novel Hamburger-electrode.« less

Theoretical evaluation of maximum electric field approximation of direct band-to-band tunneling Kane model for low bandgap semiconductors

NASA Astrophysics Data System (ADS)

Dang Chien, Nguyen; Shih, Chun-Hsing; Hoa, Phu Chi; Minh, Nguyen Hong; Thi Thanh Hien, Duong; Nhung, Le Hong

2016-06-01

The two-band Kane model has been popularly used to calculate the band-to-band tunneling (BTBT) current in tunnel field-effect transistor (TFET) which is currently considered as a promising candidate for low power applications. This study theoretically clarifies the maximum electric field approximation (MEFA) of direct BTBT Kane model and evaluates its appropriateness for low bandgap semiconductors. By analysing the physical origin of each electric field term in the Kane model, it has been elucidated in the MEFA that the local electric field term must be remained while the nonlocal electric field terms are assigned by the maximum value of electric field at the tunnel junction. Mathematical investigations have showed that the MEFA is more appropriate for low bandgap semiconductors compared to high bandgap materials because of enhanced tunneling probability in low field regions. The appropriateness of the MEFA is very useful for practical uses in quickly estimating the direct BTBT current in low bandgap TFET devices.

Influence and Correction from the Human Body on the Measurement of a Power-Frequency Electric Field Sensor

PubMed Central

Xiao, Dongping; Liu, Huaitong; Zhou, Qiang; Xie, Yutong; Ma, Qichao

2016-01-01

According to the operating specifications of existing electric field measuring instruments, measuring technicians must be located far from the instruments to eliminate the influence of the human body occupancy on a spatial electric field. Nevertheless, in order to develop a portable safety protection instrument with an effective electric field warning function for working staff in a high-voltage environment, it is necessary to study the influence of an approaching human body on the measurement of an electric field and to correct the measurement results. A single-shaft electric field measuring instrument called the Type LP-2000, which was developed by our research team, is used as the research object in this study. First, we explain the principle of electric field measurement and describe the capacitance effect produced by the human body. Through a theoretical analysis, we show that the measured electric field value decreases as a human body approaches. Their relationship is linearly proportional. Then, the ratio is identified as a correction coefficient to correct for the influence of human body proximity. The conclusion drawn from the theoretical analysis is proved via simulation. The correction coefficient kb = 1.8010 is obtained on the basis of the linear fitting of simulated data. Finally, a physical experiment is performed. When no human is present, we compare the results from the Type LP-2000 measured with Narda EFA-300 and the simulated value to verify the accuracy of the Type LP-2000. For the case of an approaching human body, the correction coefficient kb* = 1.9094 is obtained by comparing the data measured with the Type LP-2000 to the simulated value. The correction coefficient obtained from the experiment (i.e., kb*) is highly consistent with that obtained from the simulation (i.e., kb). Two experimental programs are set; under these programs, the excitation voltages and distance measuring points are regulated to produce different electric field intensities. Using kb = 1.9094, the corrected measurement of electric field intensity can accurately reflect the original environmental electric field intensity, and the maximal error is less than 6% in all the data comparisons. These results verify the effectiveness of our proposed method. PMID:27294936

Transmission of the electric fields to the low latitude ionosphere in the magnetosphere-ionosphere current circuit

NASA Astrophysics Data System (ADS)

Kikuchi, Takashi; Hashimoto, Kumiko K.

2016-12-01

The solar wind energy is transmitted to low latitude ionosphere in a current circuit from a dynamo in the magnetosphere to the equatorial ionosphere via the polar ionosphere. During the substorm growth phase and storm main phase, the dawn-to-dusk convection electric field is intensified by the southward interplanetary magnetic field (IMF), driving the ionospheric DP2 currents composed of two-cell Hall current vortices in high latitudes and Pedersen currents amplified at the dayside equator (EEJ). The EEJ-Region-1 field-aligned current (R1 FAC) circuit is completed via the Pedersen currents in midlatitude. On the other hand, the shielding electric field and the Region-2 FACs develop in the inner magnetosphere, tending to cancel the convection electric field at the mid-equatorial latitudes. The shielding often causes overshielding when the convection electric field reduces substantially and the EEJ is overcome by the counter electrojet (CEJ), leading to that even the quasi-periodic DP2 fluctuations are contributed by the overshielding as being composed of the EEJ and CEJ. The overshielding develop significantly during substorms and storms, leading to that the mid and low latitude ionosphere is under strong influence of the overshielding as well as the convection electric fields. The electric fields on the day- and night sides are in opposite direction to each other, but the electric fields in the evening are anomalously enhanced in the same direction as in the day. The evening anomaly is a unique feature of the electric potential distribution in the global ionosphere. DP2-type electric field and currents develop during the transient/short-term geomagnetic disturbances like the geomagnetic sudden commencements (SC), which appear simultaneously at high latitude and equator within the temporal resolution of 10 s. Using the SC, we can confirm that the electric potential and currents are transmitted near-instantaneously to low latitude ionosphere on both day- and night sides, which is explained by means of the light speed propagation of the TM0 mode waves in the Earth-ionosphere waveguide.

Transmission of the Magnetospheric Electric Fields to the Low Latitude Ionosphere during Storm and Substorms

NASA Astrophysics Data System (ADS)

Kikuchi, T.; Hashimoto, K. K.; Ebihara, Y.; Tanaka, T.; Tomizawa, I.; Nagatsuma, T.

2016-12-01

The solar wind energy is transmitted to the low latitude ionosphere in a current circuit from a dynamo in the magnetosphere to the equatorial ionosphere via the polar ionosphere. During the substorm growth phase and storm main phase, the dawn-to-dusk convection electric field is intensified by the southward interplanetary magnetic field (IMF), driving the ionospheric DP2 currents composed of two-cell Hall current vortices in high latitudes and Pedersen currents amplified at the dayside equator (EEJ). The EEJ-Region-1 field-aligned current (R1 FAC) circuit is completed via the Pedersen currents in midlatitude. On the other hand, the shielding electric field and the Region-2 FACs develop in the inner magnetosphere, tending to cancel the convection electric field at the mid-equatorial latitudes. The shielding often causes overshielding when the convection electric field reduces substantially and the EEJ is overcome by the counter-electrojet (CEJ), leading to that even the quasi-periodic DP2 fluctuations are contributed by the overshielding. The overshielding develop significantly during substorms and storms, leading to that the mid and low latitude ionosphere is under strong influence of the overshielding as well as the convection electric fields. The electric fields on the day- and night-sides are in opposite direction to each other, but the electric fields in the evening are anomalously enhanced in the same direction as in the day. The evening anomaly is a unique feature of the electric potential distribution in the global ionosphere. DP2-type electric field and currents also develop during the transient/short-term geomagnetic disturbances like the geomagnetic sudden commencements (SC) and ULF pulsations, which appear simultaneously at high latitude and equator within the temporal resolution of 10 sec. Using the SC, we can confirm that the electric potential and currents are transmitted near-instantaneously to low latitude ionosphere on both the day- and night-sides, which is explained by means of the light speed propagation of the TM0 mode waves in the Earth-ionosphere waveguide.

Influence and Correction from the Human Body on the Measurement of a Power-Frequency Electric Field Sensor.

PubMed

Xiao, Dongping; Liu, Huaitong; Zhou, Qiang; Xie, Yutong; Ma, Qichao

2016-06-10

According to the operating specifications of existing electric field measuring instruments, measuring technicians must be located far from the instruments to eliminate the influence of the human body occupancy on a spatial electric field. Nevertheless, in order to develop a portable safety protection instrument with an effective electric field warning function for working staff in a high-voltage environment, it is necessary to study the influence of an approaching human body on the measurement of an electric field and to correct the measurement results. A single-shaft electric field measuring instrument called the Type LP-2000, which was developed by our research team, is used as the research object in this study. First, we explain the principle of electric field measurement and describe the capacitance effect produced by the human body. Through a theoretical analysis, we show that the measured electric field value decreases as a human body approaches. Their relationship is linearly proportional. Then, the ratio is identified as a correction coefficient to correct for the influence of human body proximity. The conclusion drawn from the theoretical analysis is proved via simulation. The correction coefficient kb = 1.8010 is obtained on the basis of the linear fitting of simulated data. Finally, a physical experiment is performed. When no human is present, we compare the results from the Type LP-2000 measured with Narda EFA-300 and the simulated value to verify the accuracy of the Type LP-2000. For the case of an approaching human body, the correction coefficient kb* = 1.9094 is obtained by comparing the data measured with the Type LP-2000 to the simulated value. The correction coefficient obtained from the experiment (i.e., kb*) is highly consistent with that obtained from the simulation (i.e., kb). Two experimental programs are set; under these programs, the excitation voltages and distance measuring points are regulated to produce different electric field intensities. Using kb = 1.9094, the corrected measurement of electric field intensity can accurately reflect the original environmental electric field intensity, and the maximal error is less than 6% in all the data comparisons. These results verify the effectiveness of our proposed method.

On the role of electric field direction in the formation of sporadic E-layers in the southern polar cap ionosphere

NASA Astrophysics Data System (ADS)

Parkinson, M. L.; Dyson, P. L.; Monselesan, D. P.; Morris, R. J.

1998-03-01

Measurements of the occurrence of sporadic E (Es)-layers and F-region electric fields were obtained with a modern, HF digital ionosonde located at Casey, Antarctica (66.3°S, 110.5°E, 81°S CGM latitude) during the late austral summer of 1995/96. The occurrence of Es-layers was inferred from the presence of appropriate traces in normal swept-frequency ionograms, and the electric fields were inferred from F-region ``drift-mode'' velocities assuming that the plasma convection velocities given by E × B/B2 were measured, on average, by the interferometer. The theory of formation of high-latitude Es-layers predicts that electric fields directed toward the south west (SW) should be particularly effective at producing thin layers in the southern hemisphere. Our measurements made at a true polar cap station are consistent with this expectation, and are contrasted with observations made by incoherent scatter radars in the northern hemisphere, which also show the importance of SW electric fields, whereas the same theory predicts that NW electric fields should be important at northern latitudes. We reconcile the interhemispheric differences with simple calculations of ion convergence driven by the electric fields specified by the IZMIRAN electrodynamic model (IZMEM) in both hemispheres. The importance of the interplanetary magnetic field in the control of high-latitude Es formation is emphasised as an important adjunct to space weather modelling and forecasting.

Surface electric fields for North America during historical geomagnetic storms

USGS Publications Warehouse

Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

2013-01-01

To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

Principle of radial transport in low temperature annular plasmas

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

Zhang, Yunchao, E-mail: yunchao.zhang@anu.edu.au; Charles, Christine; Boswell, Rod

2015-07-15

Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electricmore » field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number.« less

Electric-field-induced phase transformation at a lead-free morphotropic phase boundary: Case study in a 93%(Bi0.5Na0.5)TiO3-7% BaTiO3 piezoelectric ceramic

NASA Astrophysics Data System (ADS)

Daniels, John E.; Jo, Wook; Rödel, Jürgen; Jones, Jacob L.

2009-07-01

The electric-field-induced strain in 93%(Bi0.5Na0.5)TiO3-7%BaTiO3 polycrystalline ceramic is shown to be the result of an electric-field-induced phase transformation from a pseudocubic to tetragonal symmetry. High-energy x-ray diffraction is used to illustrate the microstructural nature of the transformation. A combination of induced unit cell volumetric changes, domain texture, and anisotropic lattice strains are responsible for the observed macroscopic strain. This strain mechanism is not analogous to the high electric-field-induced strains observed in lead-based morphotropic phase boundary systems. Thus, systems which appear cubic under zero field should not be excluded from the search for lead-free piezoelectric compositions.

Stretching magnetism with an electric field in a nitride semiconductor

PubMed Central

Sztenkiel, D.; Foltyn, M.; Mazur, G. P.; Adhikari, R.; Kosiel, K.; Gas, K.; Zgirski, M.; Kruszka, R.; Jakiela, R.; Li, Tian; Piotrowska, A.; Bonanni, A.; Sawicki, M.; Dietl, T.

2016-01-01

The significant inversion symmetry breaking specific to wurtzite semiconductors, and the associated spontaneous electrical polarization, lead to outstanding features such as high density of carriers at the GaN/(Al,Ga)N interface—exploited in high-power/high-frequency electronics—and piezoelectric capabilities serving for nanodrives, sensors and energy harvesting devices. Here we show that the multifunctionality of nitride semiconductors encompasses also a magnetoelectric effect allowing to control the magnetization by an electric field. We first demonstrate that doping of GaN by Mn results in a semi-insulating material apt to sustain electric fields as high as 5 MV cm−1. Having such a material we find experimentally that the inverse piezoelectric effect controls the magnitude of the single-ion magnetic anisotropy specific to Mn3+ ions in GaN. The corresponding changes in the magnetization can be quantitatively described by a theory developed here. PMID:27782126

Electric field generated by longitudinal axial microtubule vibration modes with high spatial resolution microtubule model

NASA Astrophysics Data System (ADS)

Cifra, M.; Havelka, D.; Deriu, M. A.

2011-12-01

Microtubules are electrically polar structures fulfilling prerequisites for generation of oscillatory electric field in the kHz to GHz region. Energy supply for excitation of elasto-electrical vibrations in microtubules may be provided from GTP-hydrolysis; motor protein-microtubule interactions; and energy efflux from mitochondria. It recently was determined from anisotropic elastic network modeling of entire microtubules that the frequencies of microtubule longitudinal axial eigenmodes lie in the region of tens of GHz for the physiologically common microtubule lengths. We calculated electric field generated by axial longitudinal vibration modes of microtubule, which model is based on subnanometer precision of charge distribution. Due to elastoelectric nature of the vibrations, the vibration wavelength is million-fold shorter than that of the electromagnetic field in free space and the electric field around the microtubule manifests rich spatial structure with multiple minima. The dielectrophoretic force exerted by electric field on the surrounding molecules will influence the kinetics of reactions via change in the probability of the transport of charge and mass particles. The electric field generated by vibrations of electrically polar cellular structures is expected to play a role in biological self-organization.

Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage

DTIC Science & Technology

2015-10-01

AWARD NUMBER: W81XWH-14-1-0591 TITLE: Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage PRINCIPAL...DATES COVERED 30 Sep 2014 – 29 Sep 2015 4. TITLE AND SUBTITLE Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage...instability, among other traumatic affections of joints, and occupations or sports that subject joints to high levels of impact and torsional loading

A comparison of in situ measurements of vector-E and - vector-V x vector-B from Dynamics Explorer 2

NASA Technical Reports Server (NTRS)

Hanson, W. B.; Coley, W. R.; Heelis, R. A.; Maynard, N. C.; Aggson, T. L.

1993-01-01

Dynamics Explorer-2 provided the first opportunity to make a direct comparison of in situ measurements of the high-latitude convection electric field by two distinctly different techniques. The vector electric field instrument (VEFI) used antennae to measure the intrinsic electric fields and the ion drift meter (IDM) and retarding potential analyzer (RPA) measured the ion drift velocity vector, from which the convection electric field can be deduced. The data from three orbits having large electric fields at high latitude are presented, one at high, one at medium, and one at low altitudes. The general agreement between the two measurements of electric field is very good, with typical differences at high latitudes of the order of a few millivolts per meter, but there are some regions where the particle fluxes are extremely large (e.g., the cusp) and the disagreement is worse, probably because of IDM difficulties. The auroral zone potential patterns derived from the two devices are in excellent agreement for two of the cases, but not in the third, where bad attitude data may be the problem. At low latitudes there are persistent differences in the measurements of a few millivolts per meter, though these differences are quite constant from orbit to orbit. This problem seems to arise from some shortcoming in the VEFI measurments. Overall, however, these measurements confirm the concept of `frozen-in' plasma that drifts with velocity vector-E x vector-B/B(exp 2) within the measurement errors of the two techniques.

Electric field measurements in a near atmospheric pressure nanosecond pulse discharge with picosecond electric field induced second harmonic generation

NASA Astrophysics Data System (ADS)

Goldberg, Benjamin M.; Chng, Tat Loon; Dogariu, Arthur; Miles, Richard B.

2018-02-01

We present an optical electric field measurement method for use in high pressure plasma discharges. The method is based upon the field induced second harmonic generation technique and can be used for localized electric field measurements with sub-nanosecond resolution in any gaseous species. When an external electric field is present, a dipole is induced in the typically centrosymmetric medium, allowing for second harmonic generation with signal intensities which scale by the square of the electric field. Calibrations have been carried out in 100 Torr room air, and a minimum sensitivity of 450 V/cm is demonstrated. Measurements were performed with nanosecond or faster temporal resolution in a 100 Torr room air environment both with and without a plasma present. It was shown that with no plasma present, the field follows the applied voltage to gap ratio, as measured using the back current shunt method. When the electric field is strong enough to exceed the breakdown threshold, the measured field was shown to exceed the anticipated voltage to gap ratio which is taken as an indication of the ionization wave front as it sweeps through the plasma volume.

Electroporation of the photosynthetic membrane: structural changes in protein and lipid-protein domains.

PubMed Central

Rosemberg, Y; Rotenberg, M; Korenstein, R

1994-01-01

A biological membrane undergoes a reversible permeability increase through structural changes in the lipid domain when exposed to high external electric fields. The present study shows the occurrence of electric field-induced changes in the conductance of the proton channel of the H(+)-ATPase as well as electric field-induced structural changes in the lipid-protein domain of photosystem (PS) II in the photosynthetic membrane. The study was carried out by analyzing the electric field-stimulated delayed luminescence (EPL), which originates from charge recombination in the protein complexes of PS I and II of photosynthetic vesicles. We established that a small fraction of the total electric field-induced conductance change was abolished by N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of the H(+)-ATPase. This reversible electric field-induced conductance change has characteristics of a small channel and possesses a lifetime < or = 1 ms. To detect electric field-induced changes in the lipid-protein domains of PS II, we examined the effects of phospholipase A2 (PLA2) on EPL. Higher values of EPL were observed from vesicles that were exposed in the presence of PLA2 to an electroporating electric field than to a nonelectroporating electric field. The effect of the electroporating field was a long-lived one, lasting for a period > or = 2 min. This effect was attributed to long-lived electric field-induced structural changes in the lipid-protein domains of PS II. PMID:7811916

Aligned Single Wall Carbon Nanotube Polymer Composites Using an Electric Field

NASA Technical Reports Server (NTRS)

Park, Cheol; Wiklinson, John; Banda, Sumanth; Ounaies, Zoubeida; Wise, Kristopher E.; Sauti, Godfrey; Lillehei, Peter T.; Harrison, Joycelyn S.

2005-01-01

While high shear alignment has been shown to improve the mechanical properties of single wall carbon nanotubes (SWNT)-polymer composites, it is difficult to control and often results in degradation of the electrical and dielectric properties of the composite. Here, we report a novel method to actively align SWNTs in a polymer matrix, which allows for control over the degree of alignment of SWNTs without the side effects of shear alignment. In this process, SWNTs are aligned via field-induced dipolar interactions among the nanotubes under an AC electric field in a liquid matrix followed by immobilization by photopolymerization while maintaining the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy and the morphology of the aligned nanocomposites was investigated by high resolution scanning electron microscopy. The structure of the field induced aligned SWNTs is intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties in addition to improving the mechanical properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field conditions.

Effect of high-hydrostatic pressure and moderate-intensity pulsed electric field on plum.

PubMed

García-Parra, J; González-Cebrino, F; Delgado-Adámez, J; Cava, R; Martín-Belloso, O; Élez-Martínez, P; Ramírez, R

2018-03-01

Moderate intensity pulse electric fields were applied in plum with the aim to increase bioactive compounds content of the fruit, while high-hydrostatic pressure was applied to preserve the purées. High-hydrostatic pressure treatment was compared with an equivalent thermal treatment. The addition of ascorbic acid during purée manufacture was also evaluated. The main objective of this study was to assess the effects on microorganisms, polyphenoloxidase, color and bioactive compounds of high-hydrostatic pressure, or thermal-processed plum purées made of moderate intensity pulse electric field-treated or no-moderate intensity pulse electric field-treated plums, after processing during storage. The application of moderate intensity pulse electric field to plums slightly increased the levels of anthocyanins and the antioxidant activity of purées. The application of Hydrostatic-high pressure (HHP) increased the levels of bioactive compounds in purées, while the thermal treatment preserved better the color during storage. The addition of ascorbic acid during the manufacture of plum purée was an important factor for the final quality of purées. The color and the bioactive compounds content were better preserved in purées with ascorbic acid. The no inactivation of polyphenoloxidase enzyme with treatments applied in this study affected the stability purées. Probably more intense treatments conditions (high-hydrostatic pressure and thermal treatment) would be necessary to reach better quality and shelf life during storage.

Influence of direct and alternating current electric fields on efficiency promotion and leaching risk alleviation of chelator assisted phytoremediation.

PubMed

Luo, Jie; Cai, Limei; Qi, Shihua; Wu, Jian; Sophie Gu, Xiaowen

2018-03-01

Direct and alternating current electric fields with various voltages were used to improve the decontamination efficiency of chelator assisted phytoremediation for multi-metal polluted soil. The alleviation effect of electric field on leaching risk caused by chelator application during phytoremediation process was also evaluated. Biomass yield, pollutant uptake and metal leaching retardation under alternating current (AC) and direct current (DC) electric fields were compared. The biomass yield of Eucalyptus globulus under AC fields with various voltages (2, 4 and 10 V) were 3.91, 4.16 and 3.67kg, respectively, significantly higher than the chelator treatment without electric field (2.71kg). Besides growth stimulation, AC fields increased the metal concentrations of plant tissues especially in aerial parts manifested by the raised translocation factor of different metals. Direct current electric fields with low and moderate voltages increased the biomass production of the species to 3.45 and 3.12kg, respectively, while high voltage on the contrary suppressed the growth of the plants (2.66kg). Under DC fields, metal concentrations elevated obviously with increasing voltages and the metal translocation factors were similar under all voltages. Metal extraction per plant achieved the maximum value under moderate voltage due to the greatest biomass production. DC field with high voltage (10V) decreased the volume of leachate from the chelator treatment without electric field from 1224 to 56mL, while the leachate gathered from AC field treatments raised from 512 to 670mL. DC field can retard the downward movement of metals caused by chelator application more effectively relative to AC field due to the constant water flow and electroosmosis direction. Alternating current field had more promotive effect on chelator assisted phytoremediation efficiency than DC field illustrated by more metal accumulation in the species. However, with the consideration of leaching risk, DC field with moderate voltage was the optimal supplementary technique for phytoremediation. Copyright © 2017 Elsevier Inc. All rights reserved.

Microscopic study of crystal growth in cryopreservation agent solutions and water.

PubMed

Tao, Le-Ren; Hua, Tse-Chao

2002-10-01

Ice formation inside or outside cells during cryopreservation is evidently the main factor of cryoinjury to cells. In the study described here a high voltage DC electric field and a cryomicroscopic stage were used to test DMSO and NaCl solutions under electric field strengths ranging from 83 kV/m to 320 kV/m. Dendritic ice crystals became asymmetric when the electric field was activated. This change in the ice crystal shape was more pronounced in the ionic NaCl solution. In addition, ice growth of distilled water without an electric field was tested under different cooling rates.

Bioelectromagnetics 2005

DTIC Science & Technology

2006-08-14

fields in wound healing and nerve regeneration; 2) ultrashort high voltage pulses for tumor treatment; 3) therapeutic uses of magnetic fields; 4...7 Session 3: Role Of Electric Fields In Wound Healing And Nerve Regeneration (Continued)..........26 Session 4: Exposure...8 Bioelectromagnetics 2005, Dublin, Ireland Session 1: Role Of Electric Fields In Wound Healing And Nerve Regeneration Chairs: Richard

Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving

NASA Astrophysics Data System (ADS)

Ye, Hongfei; Zheng, Yonggang; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen

2016-08-01

Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units.

Electric field control in DC cable test termination by nano silicone rubber composite

NASA Astrophysics Data System (ADS)

Song, Shu-Wei; Li, Zhongyuan; Zhao, Hong; Zhang, Peihong; Han, Baozhong; Fu, Mingli; Hou, Shuai

2017-07-01

The electric field distributions in high voltage direct current cable termination are investigated with silicone rubber nanocomposite being the electric stress control insulator. The nanocomposite is composed of silicone rubber, nanoscale carbon black and graphitic carbon. The experimental results show that the physical parameters of the nanocomposite, such as thermal activation energy and nonlinearity-relevant coefficient, can be manipulated by varying the proportion of the nanoscale fillers. The numerical simulation shows that safe electric field distribution calls for certain parametric region of the thermal activation energy and nonlinearity-relevant coefficient. Outside the safe parametric region, local maximum of electric field strength around the stress cone appears in the termination insulator, enhancing the breakdown of the cable termination. In the presence of the temperature gradient, thermal activation energy and nonlinearity-relevant coefficient work as complementary factors to produce a reasonable electric field distribution. The field maximum in the termination insulator show complicate variation in the transient processes. The stationary field distribution favors the increase of the nonlinearity-relevant coefficient; for the transient field distribution in the process of negative lighting impulse, however, an optimized value of the nonlinearity-relevant coefficient is necessary to equalize the electric field in the termination.

Optical Remote Sensing of Electric Fields Above Thunderstorms

NASA Astrophysics Data System (ADS)

Burns, B. M.; Carlson, B. E.; Lauben, D.; Cohen, M.; Smith, D.; Inan, U. S.

2010-12-01

Measurement of thunderstorm electric fields typically require balloon-borne measurements in the region of interest. Such measurements are cumbersome and provide limited information at a single point. Remote sensing of electric fields by Kerr-effect induced optical polarization changes of background skylight circumvents many of these difficulties and can in principle provide a high-speed movie of electric field behavior. Above-thundercloud 100 kV/m quasi-static electric fields are predicted to produce polarization changes at above the part in one million level that should be detectable at a ground instrument featuring 1 cm2sr geometric factor and 1 kHz bandwidth (though more sensitivity is nonetheless desired). Currently available optical and electronic components may meet these requirements. We review the principles of this measurement and discuss the current status of a field-ready prototype instrument currently in construction.

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

Lin, Meng-Lin; Peng, J. S.; Lee, Sanboh, E-mail: sblee@mx.nthu.edu.tw

We studied the digestive ripening of thiol-capped gold nanoparticles under simultaneous action of electric field and reflux heating in a silicone oil bath at 130 °C, using transmission electron microscopy. Observation revealed that a polydispersed gold nanoparticle system reached the state of nearly monodispersity under the action of an electric field and the thiol-capped gold nanoparticles carried negative charges. The electric field caused the increase of the particle size for the nearly monodispersed gold nanoparticle system. The self-assembly of the nearly monodisperse gold nanoparticles under the action of an electric field of a high field intensity was observed. The gold nanoparticlesmore » tended to form self-assembled nanostructures of six-fold symmetry. This study provides a new route for system engineering to control the particle size of metallic nanoparticles by electric field and digestive ripening.« less

Multi-barrier field-emission behavior in PBTTT thin films at low temperatures

PubMed Central

Kang, Evan S. H.; Kim, Eunseong

2015-01-01

We investigated the low-temperature transport mechanism for poly[2,5-bis(3-alkylthiophen-2-yl)thieno(3,2-b)thiophene] (PBTTT). The temperature-dependent transport behavior was studied by varying the drain–source electric field and gate bias. The results suggest that low-temperature charge transport is dominated by direct tunneling at low electric fields, while field emission is prevailing for high electric fields with high carrier densities. However, the obtained barrier heights are remarkably greater than expected in a conventional field emission. We propose a simplified model of field emission through quasi-one-dimensional path with multiple barriers which shows good agreement with the results more clearly. Field emission across the domain boundaries may assist in overcoming the transport barriers induced by the interchain disorder, which results in the weak temperature dependence of conductivities and nonlinear current–voltage relation at low temperatures. PMID:25670532

Prebreakdown characteristics of weakly ionized liquid and gaseous media in the strongly nonuniform electric field

NASA Astrophysics Data System (ADS)

Apfelbaum, M. S.; Syrovatka, R. A.; Vladimirov, V. I.

2018-01-01

A theoretical model of electrohydrodynamic prebreakdown phenomena in slightly ionized (weakly conductive) media is proposed. The electric high voltage conduction of weakly conductive liquids and slightly ionized gases in intense electric fields using this model is considered. The formula for the calculations of volt-ampere characteristics under high voltage spherical capacitor field is analytically obtained. The experimental corona discharge volt-ampere characteristics of air are presented. It was found that the size of the ionization region in the case of corona discharge in air increases monotonically with increasing discharge voltage.

Decomposition of Composite Electric Field in a Three-Phase D-Dot Voltage Transducer Measuring System

PubMed Central

Hu, Xueqi; Wang, Jingang; Wei, Gang; Deng, Xudong

2016-01-01

In line with the wider application of non-contact voltage transducers in the engineering field, transducers are required to have better performance for different measuring environments. In the present study, the D-dot voltage transducer is further improved based on previous research in order to meet the requirements for long-distance measurement of electric transmission lines. When measuring three-phase electric transmission lines, problems such as synchronous data collection and composite electric field need to be resolved. A decomposition method is proposed with respect to the superimposed electric field generated between neighboring phases. The charge simulation method is utilized to deduce the decomposition equation of the composite electric field and the validity of the proposed method is verified by simulation calculation software. With the deduced equation as the algorithm foundation, this paper improves hardware circuits, establishes a measuring system and constructs an experimental platform for examination. Under experimental conditions, a 10 kV electric transmission line was tested for steady-state errors, and the measuring results of the transducer and the high-voltage detection head were compared. Ansoft Maxwell Stimulation Software was adopted to obtain the electric field intensity in different positions under transmission lines; its values and the measuring values of the transducer were also compared. Experimental results show that the three-phase transducer is characterized by a relatively good synchronization for data measurement, measuring results with high precision, and an error ratio within a prescribed limit. Therefore, the proposed three-phase transducer can be broadly applied and popularized in the engineering field. PMID:27754340

Phenomenological Considerations of the Electric Field Induced Transitions in Improper Ferroelectrics and Ferroelastics. III. Application to Gd2(MoO4)3

NASA Astrophysics Data System (ADS)

Suzuki, Ikuo; Ishibashi, Yoshihiro

1987-02-01

The electric field induced phase transitions are discussed in the improper ferroelectrics and ferroelastics, where the high symmetry phase is assumed to be piezoelectric as in the gadolinium molybdate (GMO). The dependence on the electric field of the polarization is discussed, and the D-E hysteresis loops are compared with the one experimentally observed in GMO.

Generation of Alfvenic Double Layers, Formation of Auroral Arcs, and Their Impact on Energy and Momentum Transfer in M-I Coupling System

NASA Astrophysics Data System (ADS)

Song, Y.; Lysak, R. L.

2017-12-01

Parallel electrostatic electric fields provide a powerful mechanism to accelerate auroral particles to high energy in the auroral acceleration region (AAR), creating both quasi-static and Alfvenic discrete aurorae. The total field-aligned current can be written as J||total=J||+J||D, where the displacement current is denoted as J||D=(1/4π)(∂E||/∂t), which describes the E||-generation (Song and Lysak, 2006). The generation of the total field-aligned current is related to spatial gradients of the parallel vorticity caused by the axial torque acting on field-aligned flux tubes in M-I coupling system. It should be noticed that parallel electric fields are not produced by the field-aligned current. In fact, the E||-generation is caused by Alfvenic interaction in the M-I coupling system, and is favored by a low plasma density and the enhanced localized azimuthal magnetic flux. We suggest that the nonlinear interaction of incident and reflected Alfven wave packets in the AAR can create reactive stress concentration, and therefore can generate the parallel electrostatic electric fields together with a seed low density cavity. The generated electric fields will quickly deepen the seed low density cavity, which can effectively create even stronger electrostatic electric fields. The electrostatic electric fields nested in a low density cavity and surrounded by enhanced azimuthal magnetic flux constitute Alfvenic electromagnetic plasma structures, such as Alfvenic Double Layers (DLs). The Poynting flux carried by Alfven waves can continuously supply energy from the generator region to the auroral acceleration region, supporting and sustaining Alfvenic DLs with long-lasting electrostatic electric fields which accelerate auroral particles to high energy. The generation of parallel electric fields and the formation of auroral arcs can redistribute perpendicular mechanical and magnetic stresses in auroral flux tubes, decoupling the magnetosphere from ionosphere drag locally. This may enhance the magnetotail earthward shear flows and rapidly buildup stronger parallel electric fields in the auroral acceleration region, leading to a sudden and violent tail energy release, if there is accumulated free magnetic energy in the tail.

Externally applied electric fields up to 1.6 × 10(5) V/m do not affect the homogeneous nucleation of ice in supercooled water.

PubMed

Stan, Claudiu A; Tang, Sindy K Y; Bishop, Kyle J M; Whitesides, George M

2011-02-10

The freezing of water can initiate at electrically conducting electrodes kept at a high electric potential or at charged electrically insulating surfaces. The microscopic mechanisms of these phenomena are unknown, but they must involve interactions between water molecules and electric fields. This paper investigates the effect of uniform electric fields on the homogeneous nucleation of ice in supercooled water. Electric fields were applied across drops of water immersed in a perfluorinated liquid using a parallel-plate capacitor; the drops traveled in a microchannel and were supercooled until they froze due to the homogeneous nucleation of ice. The distribution of freezing temperatures of drops depended on the rate of nucleation of ice, and the sensitivity of measurements allowed detection of changes by a factor of 1.5 in the rate of nucleation. Sinusoidal alternation of the electric field at frequencies from 3 to 100 kHz prevented free ions present in water from screening the electric field in the bulk of drops. Uniform electric fields in water with amplitudes up to (1.6 ± 0.4) × 10(5) V/m neither enhanced nor suppressed the homogeneous nucleation of ice. Estimations based on thermodynamic models suggest that fields in the range of 10(7)-10(8) V/m might cause an observable increase in the rate of nucleation.

Measurements of Ozone, Lightning, and Electric Fields within Thunderstorms over Langmuir Laboratory, New Mexico

NASA Astrophysics Data System (ADS)

Eack, K. B.; Winn, W. P.; Rust, W. D.; Minschwaner, K.; Fredrickson, S.; Kennedy, D.; Edens, H. E.; Kalnajs, L. E.; Rabin, R. M.; Lu, G. P.; Bonin, D.

2008-12-01

A field project was conducted at the Langmuir Laboratory for Atmospheric Research during the summer of 2008 in an effort to better understand the direct production of ozone within electrically active storms. Five balloon flights were successfully launched into thunderstorms during this project. In situ measurements from the balloon instrument package included ozone mixing ratio, electric field strength, meteorological variables, and GPS location and timing. Lightning discharges were identified within each storm using a ground based lightning mapping array. The data show that the instruments ascended through regions of high electric fields within the sampled storms, and in some cases the balloon was in very close proximity to lightning. Relationships between electric field, lightning, and ozone observed during these flights will be discussed.

Radiation of X-Rays Using Uniaxially Polarized LiNbO3 Single Crystal

NASA Astrophysics Data System (ADS)

Fukao, Shinji; Nakanishi, Yoshikazu; Mizoguchi, Tadahiro; Ito, Yoshiaki; Nakamura, Toru; Yoshikado, Shinzo

2009-03-01

X-rays are radiated due to the bremsstrahlung caused by the collision of electrons with a metal target placed opposite the negative electric surface of a crystal by changing the temperature of a LiNbO3 single crystal uniaxially polarized in the c-axis direction. It is suggested that both electric field intensity and electron density determine the intensity of X-ray radiation. Electrons are supplied by the ionization of residual gas in space, field emission from a case inside which a crystal is located, considered to be due to the high electric-field intensity formed by the surface charges on the crystal, and an external electron source, such as a thermionic source. In a high vacuum, it was found that the electrons supplied by electric-field emission mainly contribute to the radiation of X-rays. It was found that the integrated intensity of X-rays can be maximized by supplying electrons both external and by electric-field emission. Furthermore, the integrated intensity of the X-rays is stable for many repeated temperature changes.

Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

NASA Technical Reports Server (NTRS)

Bojarevics, V.; Easter, S.; Pericleous, K.

2012-01-01

Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

Bubble Formation and Detachment in Reduced Gravity Under the Influence of Electric Fields

NASA Technical Reports Server (NTRS)

Herman, Cila; Iacona, Estelle; Chang, Shinan

2002-01-01

The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Both uniform and nonuniform electric field configurations were considered. Bubble formation and detachment were recorded and visualized in reduced gravity (corresponding to gravity levels on Mars, on the Moon as well as microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

Strain-engineered inverse charge-funnelling in layered semiconductors.

PubMed

De Sanctis, Adolfo; Amit, Iddo; Hepplestone, Steven P; Craciun, Monica F; Russo, Saverio

2018-04-25

The control of charges in a circuit due to an external electric field is ubiquitous to the exchange, storage and manipulation of information in a wide range of applications. Conversely, the ability to grow clean interfaces between materials has been a stepping stone for engineering built-in electric fields largely exploited in modern photovoltaics and opto-electronics. The emergence of atomically thin semiconductors is now enabling new ways to attain electric fields and unveil novel charge transport mechanisms. Here, we report the first direct electrical observation of the inverse charge-funnel effect enabled by deterministic and spatially resolved strain-induced electric fields in a thin sheet of HfS 2 . We demonstrate that charges driven by these spatially varying electric fields in the channel of a phototransistor lead to a 350% enhancement in the responsivity. These findings could enable the informed design of highly efficient photovoltaic cells.

Exposure to residential electric and magnetic fields and risk of childhood leukemia.

PubMed

London, S J; Thomas, D C; Bowman, J D; Sobel, E; Cheng, T C; Peters, J M

1991-11-01

The relation between exposure to electric and magnetic fields in the home, as assessed by measurements, wiring configuration, and self-reported appliance use, and risk of leukemia was investigated in a case-control study among children from birth to age 10 years in Los Angeles County, California. Cases were ascertained through a population-based tumor registry from 1980 to 1987. Controls were drawn from friends and by random digit dialing. Interviews were obtained from 232 cases and 232 controls. Available for analysis were measurements of the magnetic field in the child's bedroom over 24 hours or longer (164 cases and 144 controls), spot measurements of magnetic and electric fields (140 cases and 109 controls), and wiring configuration (219 cases and 207 controls). No clear associations between leukemia risk and measured magnetic or electric fields were seen. An association between the Denver Wertheimer-Leeper wiring configuration and childhood leukemia risk was observed (odds ratio for very high relative to very low current and underground configuration combined = 2.15, 95% confidence interval 1.08-4.28; p for trend = 0.008) and was not substantially altered by adjustment for potential confounding factors. Cases were more likely than controls to report use of several appliances that produce high electric and magnetic fields. Our results support an association between childhood leukemia risk and wiring configuration, but not direct measurements of electric and magnetic fields.

Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

NASA Technical Reports Server (NTRS)

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

1979-01-01

Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

An investigation into the induced electric fields from transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Hadimani, Ravi; Lee, Erik; Duffy, Walter; Waris, Mohammed; Siddiqui, Waquar; Islam, Faisal; Rajamani, Mahesh; Nathan, Ryan; Jiles, David; David C Jiles Team; Walter Duffy Collaboration

Transcranial magnetic stimulation (TMS) is a promising tool for noninvasive brain stimulation that has been approved by the FDA for the treatment of major depressive disorder. To stimulate the brain, TMS uses large, transient pulses of magnetic field to induce an electric field in the head. This transient magnetic field is large enough to cause the depolarization of cortical neurons and initiate a synaptic signal transmission. For this study, 50 unique head models were created from MRI images. Previous simulation studies have primarily used a single head model, and thus give a limited image of the induced electric field from TMS. This study uses finite element analysis simulations on 50 unique, heterogeneous head models to better investigate the relationship between TMS and the electric field induced in brain tissues. Results showed a significant variation in the strength of the induced electric field in the brain, which can be reasonably predicted by the distance from the TMS coil to the stimulated brain. Further, it was seen that some models had high electric field intensities in over five times as much brain volume as other models.

An all-organic composite actuator material with a high dielectric constant.

PubMed

Zhang, Q M; Li, Hengfeng; Poh, Martin; Xia, Feng; Cheng, Z-Y; Xu, Haisheng; Huang, Cheng

2002-09-19

Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields--referred to here as field-type EAPs--include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70 V micro m(-1)) to generate such high elastic energy densities (>0.1 J cm(-3); refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V micro m(-1). The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery.

Silicon Photomultiplier Performance in High ELectric Field

NASA Astrophysics Data System (ADS)

Montoya, J.; Morad, J.

2016-12-01

Roughly 27% of the universe is thought to be composed of dark matter. The Large Underground Xenon (LUX) relies on the emission of light from xenon atoms after a collision with a dark matter particle. After a particle interaction in the detector, two things can happen: the xenon will emit light and charge. The charge (electrons), in the liquid xenon needs to be pulled into the gas section so that it can interact with gas and emit light. This allows LUX to convert a single electron into many photons. This is done by applying a high voltage across the liquid and gas regions, effectively ripping electrons out of the liquid xenon and into the gas. The current device used to detect photons is the photomultiplier tube (PMT). These devices are large and costly. In recent years, a new technology that is capable of detecting single photons has emerged, the silicon photomultiplier (SiPM). These devices are cheaper and smaller than PMTs. Their performance in a high electric fields, such as those found in LUX, are unknown. It is possible that a large electric field could introduce noise on the SiPM signal, drowning the single photon detection capability. My hypothesis is that SiPMs will not observe a significant increase is noise at an electric field of roughly 10kV/cm (an electric field within the range used in detectors like LUX). I plan to test this hypothesis by first rotating the SiPMs with no applied electric field between two metal plates roughly 2 cm apart, providing a control data set. Then using the same angles test the dark counts with the constant electric field applied. Possibly the most important aspect of LUX, is the photon detector because it's what detects the signals. Dark matter is detected in the experiment by looking at the ratio of photons to electrons emitted for a given interaction in the detector. Interactions with a low electron to photon ratio are more like to be dark matter events than those with a high electron to photon ratio. The ability to distinguish these ratios relies on the high sensitivity to single photons. To achieve a similar sensitivity to dark matter interactions as LUX, the new SiPM devices need to operate in the same conditions without any loss in sensitivity to single photons. Knowing that this new type of technology operates in high electric field without issues, could save hundreds of thousands of dollars and valuable space.

Comparison of flow cytometry, fluorescence microscopy and spectrofluorometry for analysis of gene electrotransfer efficiency.

PubMed

Marjanovič, Igor; Kandušer, Maša; Miklavčič, Damijan; Keber, Mateja Manček; Pavlin, Mojca

2014-12-01

In this study, we compared three different methods used for quantification of gene electrotransfer efficiency: fluorescence microscopy, flow cytometry and spectrofluorometry. We used CHO and B16 cells in a suspension and plasmid coding for GFP. The aim of this study was to compare and analyse the results obtained by fluorescence microscopy, flow cytometry and spectrofluorometry and in addition to analyse the applicability of spectrofluorometry for quantifying gene electrotransfer on cells in a suspension. Our results show that all the three methods detected similar critical electric field strength, around 0.55 kV/cm for both cell lines. Moreover, results obtained on CHO cells showed that the total fluorescence intensity and percentage of transfection exhibit similar increase in response to increase electric field strength for all the three methods. For B16 cells, there was a good correlation at low electric field strengths, but at high field strengths, flow cytometer results deviated from results obtained by fluorescence microscope and spectrofluorometer. Our study showed that all the three methods detected similar critical electric field strengths and high correlations of results were obtained except for B16 cells at high electric field strengths. The results also demonstrated that flow cytometry measures higher values of percentage transfection compared to microscopy. Furthermore, we have demonstrated that spectrofluorometry can be used as a simple and consistent method to determine gene electrotransfer efficiency on cells in a suspension.

Electric field effect in superconductor-ferroelectric structures

NASA Technical Reports Server (NTRS)

Lemanov, V. V.

1995-01-01

Electric field effect (the E-effect) in superconductors has been studied since 1960 when Glover and Sherill published their results on a shift of the critical temperature T(sub c) about 0.1 mK in Sn and In thin films under the action Off the field E=300 kV/cm. Stadler was the first to study the effect or spontaneous polarization of ferroelectric substrate on the electric properties of superconductors. He observed that the reversal of polarization of TGS substrate under action of external electric field in Sn-TGS structures induced the T(sub c) shift in Sn about 1.3 mK. Since in this case the effect is determined not by the electric field but by the spontaneous polarization, we may call this effect the P-effect. High-T(sub c) superconductors opened the new possibilities to study the E- and P-effects due to low charge carrier density, as compared to conventional superconductors, and to anomalously small coherence length. Experiments in this field began in many laboratories but a breakthrough was made where a shift in T(sub c) by 50 mK was observed in YBCO thin films. Much higher effects were observed in subsequent studies. The first experiments on the P-effect in high-T(sub c) superconductors were reported elsewhere. In this report we shall give a short description of study on the P-effect in high-T(sub c) superconductors.

Interplanetary magnetic field effects on high latitude ionospheric convection

NASA Technical Reports Server (NTRS)

Heelis, R. A.

1985-01-01

Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

AC Application of HTS Conductors in Highly Dynamic Electric Motors

NASA Astrophysics Data System (ADS)

Oswald, B.; Best, K.-J.; Setzer, M.; Duffner, E.; Soell, M.; Gawalek, W.; Kovalev, L. K.

2006-06-01

Based on recent investigations we design highly dynamic electric motors up to 400 kW and linear motors up to 120 kN linear force using HTS bulk material and HTS tapes. The introduction of HTS tapes into AC applications in electric motors needs fundamental studies on double pancake coils under transversal magnetic fields. First theoretical and experimental results on AC field distributions in double-pancake-coils and corresponding AC losses will be presented. Based on these results the simulation of the motor performance confirms extremely high power density and efficiency of both types of electric motors. Improved characteristics of rare earth permanent magnets used in our motors at low temperatures give an additional technological benefit.

Nanosecond pulsed electric fields (nsPEFs) low cost generator design using power MOSFET and Cockcroft-Walton multiplier circuit as high voltage DC source

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

Sulaeman, M. Y.; Widita, R.

2014-09-30

Purpose: Non-ionizing radiation therapy for cancer using pulsed electric field with high intensity field has become an interesting field new research topic. A new method using nanosecond pulsed electric fields (nsPEFs) offers a novel means to treat cancer. Not like the conventional electroporation, nsPEFs able to create nanopores in all membranes of the cell, including membrane in cell organelles, like mitochondria and nucleus. NsPEFs will promote cell death in several cell types, including cancer cell by apoptosis mechanism. NsPEFs will use pulse with intensity of electric field higher than conventional electroporation, between 20–100 kV/cm and with shorter duration of pulsemore » than conventional electroporation. NsPEFs requires a generator to produce high voltage pulse and to achieve high intensity electric field with proper pulse width. However, manufacturing cost for creating generator that generates a high voltage with short duration for nsPEFs purposes is highly expensive. Hence, the aim of this research is to obtain the low cost generator design that is able to produce a high voltage pulse with nanosecond width and will be used for nsPEFs purposes. Method: Cockcroft-Walton multiplier circuit will boost the input of 220 volt AC into high voltage DC around 1500 volt and it will be combined by a series of power MOSFET as a fast switch to obtain a high voltage with nanosecond pulse width. The motivation using Cockcroft-Walton multiplier is to acquire a low-cost high voltage DC generator; it will use capacitors and diodes arranged like a step. Power MOSFET connected in series is used as voltage divider to share the high voltage in order not to damage them. Results: This design is expected to acquire a low-cost generator that can achieve the high voltage pulse in amount of −1.5 kV with falltime 3 ns and risetime 15 ns into a 50Ω load that will be used for nsPEFs purposes. Further detailed on the circuit design will be explained at presentation.« less

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, James L.

1996-01-01

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/.mu.c-Si) solar cells which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell.

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, J.L.

1996-07-23

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/{micro}c-Si) solar cells are disclosed which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell. 4 figs.

Giant Permittivity in Epitaxial Ferroelectric Heterostructures

NASA Astrophysics Data System (ADS)

Erbil, A.; Kim, Y.; Gerhardt, R. A.

1996-08-01

A giant permittivity associated with the motion of domain walls is reported in epitaxial hetero- structures having alternating layers of ferroelectric and nonferroelectric oxides. At low frequencies, permittivities as high as 420 000 are found. Real and imaginary parts of the dielectric constant show large dispersion at high frequencies. In dc measurements, a nonlinear resistance is observed with a well-defined threshold field correlated with the dc bias-field dependence of ac permittivities. We interpret the observations as a result of the motion of a pinned domain wall lattice at low electric fields and sliding-mode motion at high electric fields.

Limiting electric fields of HVDC overhead power lines.

PubMed

Leitgeb, N

2014-05-01

As a consequence of the increased use of renewable energy and the now long distances between energy generation and consumption, in Europe, electric power transfer by high-voltage (HV) direct current (DC) overhead power lines gains increasing importance. Thousands of kilometers of them are going to be built within the next years. However, existing guidelines and regulations do not yet contain recommendations to limit static electric fields, which are one of the most important criteria for HVDC overhead power lines in terms of tower design, span width and ground clearance. Based on theoretical and experimental data, in this article, static electric fields associated with adverse health effects are analysed and various criteria are derived for limiting static electric field strengths.

Intense transient electric field sensor based on the electro-optic effect of LiNbO{sub 3}

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

Yang, Qing, E-mail: yangqing@cqu.edu.cn; Sun, Shangpeng; Han, Rui

2015-10-15

Intense transient electric field measurements are widely applied in various research areas. An optical intense E-field sensor for time-domain measurements, based on the electro-optic effect of lithium niobate, has been studied in detail. Principles and key issues in the design of the sensor are presented. The sensor is insulated, small in size (65 mm × 15 mm × 15 mm), and suitable for high-intensity (<801 kV/m) electric field measurements over a wide frequency band (10 Hz–10 MHz). The input/output characteristics of the sensor were obtained and the sensor calibrated. Finally, an application using this sensor in testing laboratory lightning impulsesmore » and in measuring transient electric fields during switch-on of a disconnector confirmed that the sensor is expected to find widespread use in transient intense electric field measurement applications.« less

Intense transient electric field sensor based on the electro-optic effect of LiNbO3

NASA Astrophysics Data System (ADS)

Yang, Qing; Sun, Shangpeng; Han, Rui; Sima, Wenxia; Liu, Tong

2015-10-01

Intense transient electric field measurements are widely applied in various research areas. An optical intense E-field sensor for time-domain measurements, based on the electro-optic effect of lithium niobate, has been studied in detail. Principles and key issues in the design of the sensor are presented. The sensor is insulated, small in size (65 mm × 15 mm × 15 mm), and suitable for high-intensity (<801 kV/m) electric field measurements over a wide frequency band (10 Hz-10 MHz). The input/output characteristics of the sensor were obtained and the sensor calibrated. Finally, an application using this sensor in testing laboratory lightning impulses and in measuring transient electric fields during switch-on of a disconnector confirmed that the sensor is expected to find widespread use in transient intense electric field measurement applications.

Electric Field Effects in Self-Propagating High-Temperature Synthesis under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Unuvar, C.; Frederick, D. M.; Shaw, B. D.; Munir, Z. A.

2003-01-01

Self-propagating high-temperature synthesis (SHS) has been used to form many materials. SHS generally involves mixing reactants together (e.g., metal powders) and igniting the mixture such that a combustion (deflagration) wave passes though the mixture. The imposition of an electric field (AC or DC) across SHS reactants has been shown to have a marked effect on the dynamics of wave propagation and on the nature, composition, and homogeneity of the product . The use of an electric field with SHS has been termed "field-assisted SHS". Combustion wave velocities and temperatures are directly affected by the field, which is typically perpendicular to the average wave velocity. The degree of activation by the field (e.g., combustion rate) is related to the current density distribution within the sample, and is therefore related to the temperature-dependent spatial distribution of the effective electrical conductivity of reactants and products. Furthermore, the field can influence other important SHS-related phenomena including capillary flow, mass-transport in porous media, and Marangoni flows. These phenomena are influenced by gravity in conventional SHS processes (i.e., without electric fields). As a result the influence of the field on SHS under reduced gravity is expected to be different than under normal gravity. It is also known that heat loss rates from samples, which can depend significantly on gravity, can influence final products in SHS. This research program is focused on studying field-assisted SHS under reduced gravity conditions. The broad objective of this research program is to understand the role of an electric field in SHS reactions under conditions where gravity-related effects are suppressed. The research will allow increased understanding of fundamental aspects of field-assisted SHS processes as well as synthesis of materials that cannot be formed in normal gravity.

High resolution separations of charge variants and disulfide isomers of monoclonal antibodies and antibody drug conjugates using ultra-high voltage capillary electrophoresis with high electric field strength.

PubMed

Henley, W Hampton; He, Yan; Mellors, J Scott; Batz, Nicholas G; Ramsey, J Michael; Jorgenson, James W

2017-11-10

Ultra-high voltage capillary electrophoresis with high electric field strength has been applied to the separation of the charge variants, drug conjugates, and disulfide isomers of monoclonal antibodies. Samples composed of many closely related species are difficult to resolve and quantify using traditional analytical instrumentation. High performance instrumentation can often save considerable time and effort otherwise spent on extensive method development. Ideally, the resolution obtained for a given CE buffer system scales with the square root of the applied voltage. Currently available commercial CE instrumentation is limited to an applied voltage of approximately 30kV and a maximum electric field strength of 1kV/cm due to design limitations. The instrumentation described here is capable of safely applying potentials of at least 120kV with electric field strengths over 2000V/cm, potentially doubling the resolution of the best conventional CE buffer/capillary systems while decreasing analysis time in some applications. Separations of these complex mixtures using this new instrumentation demonstrate the potential of ultra-high voltage CE to identify the presence of previously unresolved components and to reduce analysis time for complex mixtures of antibody variants and drug conjugates. Copyright © 2017 Elsevier B.V. All rights reserved.

Electric fields and field-aligned currents in polar regions of the solar corona: 3-D MHD consideration

NASA Technical Reports Server (NTRS)

Pisanko, Yu. V.

1995-01-01

The calculation of the solar rotation electro-dynamical effects in the near-the-Sun solar wind seems more convenient from the non-inertial corotating reference frame. This implies some modification of the 3-D MHD equations generally on the base of the General Theory of Relativity. The paper deals with the search of stationary (in corotating non-inertial reference frame) solutions of the modified 3-D MHD equations for the in near-the-Sun high latitude sub-alfvenic solar wind. The solution is obtained requiring electric fields and field-aligned electric currents in the high latitude near-the-Sun solar wind. Various scenario are explored self-consistently via a number of numerical experiments. The analogy with the high latitude Earth's magnetosphere is used for the interpretation of the results. Possible observational manifestations are discussed.

Science Notes.

ERIC Educational Resources Information Center

Murray, A. J. S.; And Others

1988-01-01

Presents 31 science activities for use with high school or college science classes. Topics included are: chromatography, ecology, invertebrates, enzymes, genetics, botany, creep, crystals, diffusion, computer interfaces, acid rain, teaching techniques, chemical reactions, waves, electric fields, rainbows, electricity, magnetic fields, and a Pitot…

A novel high-performance high-frequency SOI MESFET by the damped electric field

NASA Astrophysics Data System (ADS)

Orouji, Ali A.; Khayatian, Ahmad; Keshavarzi, Parviz

2016-06-01

In this paper, we introduce a novel silicon-on-insulator (SOI) metal-semiconductor field-effect-transistor (MESFET) using the damped electric field (DEF). The proposed structure is geometrically symmetric and compatible with common SOI CMOS fabrication processes. It has two additional oxide regions under the side gates in order to improve DC and RF characteristics of the DEF structure due to changes in the electrical potential, the electrical field distributions, and rearrangement of the charge carriers. Improvement of device performance is investigated by two-dimensional and two-carrier simulation of fundamental parameters such as breakdown voltage (VBR), drain current (ID), output power density (Pmax), transconductance (gm), gate-drain and gate-source capacitances, cut-off frequency (fT), unilateral power gain (U), current gain (h21), maximum available gain (MAG), and minimum noise figure (Fmin). The results show that proposed structure operates with higher performances in comparison with the similar conventional SOI structure.

Modelling and assessment of the electric field strength caused by mobile phone to the human head.

PubMed

Buckus, Raimondas; Strukcinskiene, Birute; Raistenskis, Juozas; Stukas, Rimantas

2016-06-01

Electromagnetic field exposure is the one of the most important physical agents that actively affects live organisms and environment. Active use of mobile phones influences the increase of electromagnetic field radiation. The aim of the study was to measure and assess the electric field strength caused by mobile phones to the human head. In this paper the software "COMSOL Multiphysics" was used to establish the electric field strength created by mobile phones around the head. The second generation (2G) Global System for Mobile (GSM) phones that operate in the frequency band of 900 MHz and reach the power of 2 W have a stronger electric field than (2G) GSM mobile phones that operate in the higher frequency band of 1,800 MHz and reach the power up to 1 W during conversation. The third generation of (3G) UMTS smart phones that effectively use high (2,100 MHz) radio frequency band emit the smallest electric field strength values during conversation. The highest electric field strength created by mobile phones is around the ear, i.e. the mobile phone location. The strength of mobile phone electric field on the phantom head decreases exponentially while moving sidewards from the center of the effect zone (the ear), and constitutes 1-12% of the artificial head's surface. The highest electric field strength values of mobile phones are associated with their higher power, bigger specific energy absorption rate (SAR) and lower frequency of mobile phone. The stronger electric field emitted by the more powerful mobile phones takes a higher percentage of the head surface. The highest electric field strength created by mobile phones is distributed over the user's ear.

Effects of retarded electrical fields on observables sensitive to the high-density behavior of the nuclear symmetry energy in heavy-ion collisions at intermediate energies

NASA Astrophysics Data System (ADS)

Wei, Gao-Feng; Li, Bao-An; Yong, Gao-Chan; Ou, Li; Cao, Xin-Wei; Liu, Xu-Yang

2018-03-01

Within the isospin- and momentum-dependent transport model IBUU11, we examine the relativistic retardation effects of electrical fields on the π-/π+ ratio and neutron-proton differential transverse flow in heavy-ion collisions at intermediate energies. Compared to the static Coulomb fields, the retarded electric fields of fast-moving charges are known to be anisotropic and the associated relativistic corrections can be significant. They are found to increase the number of energetic protons in the participant region at the maximum compression by as much as 25% but that of energetic neutrons by less than 10% in 197Au+197Au reactions at a beam energy of 400 MeV/nucleon. Consequently, more π+ and relatively fewer π- mesons are produced, leading to an appreciable reduction of the π-/π+ ratio compared to calculations with the static Coulomb fields. Also, the neutron-proton differential transverse flow, as another sensitive probe of high-density symmetry energy, is also decreased appreciably due to the stronger retarded electrical fields in directions perpendicular to the velocities of fast-moving charges compared to calculations using the isotropic static electrical fields. Moreover, the retardation effects on these observables are found to be approximately independent of the reaction impact parameter.

Direct observation of trapped charges under field-plate in p-GaN gate AlGaN/GaN high electron mobility transistors by electric field-induced optical second-harmonic generation

NASA Astrophysics Data System (ADS)

Katsuno, Takashi; Manaka, Takaaki; Soejima, Narumasa; Iwamoto, Mitsumasa

2017-02-01

Trapped charges underneath the field-plate (FP) in a p-gallium nitride (GaN) gate AlGaN/ GaN high electron mobility transistor device were visualized by using electric field-induced optical second-harmonic generation imaging. Second-harmonic (SH) signals in the off-state of the device with FP indicated that the electric field decreased at the p-GaN gate edge and concentrated at the FP edge. Nevertheless, SH signals originating from trapped charges were slightly observed at the p-GaN gate edge and were not observed at the FP edge in the on-state. Compared with the device without FP, reduction of trapped charges at the p-GaN gate edge of the device with FP is attributed to attenuation of the electric field with the aid of the FP. Negligible trapped charges at the FP edge is owing to lower trap density of the SiO2/AlGaN interface at the FP edge compared with that of the SiO2/p-GaN sidewall interface at the p-GaN gate edge and attenuated electric field by the thickness of the SiO2 passivation layer on the AlGaN surface.

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Hadimani, R. L.; Kanthasamy, A. G.; Jiles, D. C.

2014-05-01

Transcranial magnetic stimulation (TMS) offers the possibility of non-invasive treatment of brain disorders in humans. Studies on animals can allow rapid progress of the research including exploring a variety of different treatment conditions. Numerical calculations using animal models are needed to help design suitable TMS coils for use in animal experiments, in particular, to estimate the electric field induced in animal brains. In this paper, we have implemented a high-resolution anatomical MRI-derived mouse model consisting of 50 tissue types to accurately calculate induced electric field in the mouse brain. Magnetic field measurements have been performed on the surface of the coil and compared with the calculations in order to validate the calculated magnetic and induced electric fields in the brain. Results show how the induced electric field is distributed in a mouse brain and allow investigation of how this could be improved for TMS studies using mice. The findings have important implications in further preclinical development of TMS for treatment of human diseases.

Electric field-based technologies for valorization of bioresources.

PubMed

Rocha, Cristina M R; Genisheva, Zlatina; Ferreira-Santos, Pedro; Rodrigues, Rui; Vicente, António A; Teixeira, José A; Pereira, Ricardo N

2018-04-01

This review provides an overview of recent research on electrotechnologies applied to the valorization of bioresources. Following a comprehensive summary of the current status of the application of well-known electric-based processing technologies, such as pulsed electric fields (PEF) and high voltage electrical discharges (HVED), the application of moderate electric fields (MEF) as an extraction or valorization technology will be considered in detail. MEF, known by its improved energy efficiency and claimed electroporation effects (allowing enhanced extraction yields), may also originate high heating rates - ohmic heating (OH) effect - allowing thermal stabilization of waste stream for other added-value applications. MEF is a simple technology that mostly makes use of green solvents (mainly water) and that can be used on functionalization of compounds of biological origin broadening their application range. The substantial increase of MEF-based plants installed in industries worldwide suggests its straightforward application for waste recovery. Copyright © 2018 Elsevier Ltd. All rights reserved.

Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

NASA Technical Reports Server (NTRS)

Malaspina, David; Horanyi, M.; Zaslavsky, A.; Goetz, K.; Wilson, L. B., III; Kersten, K.

2014-01-01

Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

K-shell spectroscopy of silicon ions as diagnostic for high electric fields

NASA Astrophysics Data System (ADS)

Loetzsch, R.; Jäckel, O.; Höfer, S.; Kämpfer, T.; Polz, J.; Uschmann, I.; Kaluza, M. C.; Förster, E.; Stambulchik, E.; Kroupp, E.; Maron, Y.

2012-11-01

We developed a detection scheme, capable of measuring X-ray line shape of tracer ions in μm thick layers at the rear side of a target foil irradiated by ultra intense laser pulses. We performed simulations of the effect of strong electric fields on the K-shell emission of silicon and developed a spectrometer dedicated to record this emission. The combination of a cylindrically bent crystal in von Hámos geometry and a CCD camera with its single photon counting capability allows for a high dynamic range of the instrument and background free spectra. This approach will be used in future experiments to study electric fields of the order of TV/m at high density plasmas close to solid density.

Electric field and space charge distribution measurement in transformer oil struck by impulsive high voltage

NASA Astrophysics Data System (ADS)

Sima, Wenxia; Guo, Hongda; Yang, Qing; Song, He; Yang, Ming; Yu, Fei

2015-08-01

Transformer oil is widely used in power systems because of its excellent insulation properties. The accurate measurement of electric field and space charge distribution in transformer oil under high voltage impulse has important theoretical and practical significance, but still remains challenging to date because of its low Kerr constant. In this study, the continuous electric field and space charge distribution over time between parallel-plate electrodes in high-voltage pulsed transformer oil based on the Kerr effect is directly measured using a linear array photoelectrical detector. Experimental results demonstrate the applicability and reliability of this method. This study provides a feasible approach to further study the space charge effects and breakdown mechanisms in transformer oil.

Pair-Wise, Deformable Mirror, Image Plane-Based Diversity Electric Field Estimation for High Contrast Coronagraphy

NASA Technical Reports Server (NTRS)

Give'on, Amir; Kern, Brian D.; Shaklan, Stuart

2011-01-01

In this paper we describe the complex electric field reconstruction from image plane intensity measurements for high contrast coronagraphic imaging. A deformable mirror (DM) surface is modied with pairs of complementary shapes to create diversity in the image plane of the science camera where the intensity of the light is measured. Along with the Electric Field Conjugation correction algorithm, this estimation method has been used in various high contrast imaging testbeds to achieve the best contrasts to date both in narrow and in broad band light. We present the basic methodology of estimation in easy to follow list of steps, present results from HCIT and raise several open quations we are confronted with using this method.

Relationship Between the Global Electric Circuit and Electrified Cloud Parameters at Diurnal, Seasonal and Interannual Timescales

NASA Astrophysics Data System (ADS)

Lavigne, Thomas

In the early 1900's, J.W. Whipple began validating C.R. Wilson's Global Electric Circuit (GEC) hypothesis by correlating diurnal variations of global thunder days with diurnal variations of the fair weather electric field. This study applies 16+ years of Precipitation Feature (PF) data from the Tropical Rainfall Measuring Mission (TRMM), including lightning data from the Lightning Imaging Sensor (LIS), alongside 12-years of electric field measurements from Vostok, Antarctica to further examine this relationship. Joint diurnal-seasonal variations of the electric field are compared with PF parameters that are potentially related to the GEC. The flash rate and volume of 30 dBZ between -5°C and -35°C variables are shown to have the best direct relationship to the electric field, with r2 values of 0.67 and 0.62, respectively. However, the Coefficient of Variation (COV) of the flash rate (28%) and the electric field (12%), display relatively large differences in the spread of the variables. The volume of 30 dBZ between -5°C and -35°C shows a closer amplitude agreement to the variance of the electric field (COV=17%). Furthermore, these relationships are analyzed during two different phases of the El Nino Southern Oscillation (ENSO). Results show different seasonal-diurnal variations of the electric field during ENSO phases, with enhancements in the electric field between January through April at 16-24 UTC in La Nina years. In all, similar variations have been found in the fair weather electric field, and the variation of properties of global PFs with high potential of electrification at diurnal, seasonal, and interannual timescales. These confirm the dominant role of the global thunderclouds and electrified clouds in the global electric circuit.

Nanomaterial-Enabled Neural Stimulation

PubMed Central

Wang, Yongchen; Guo, Liang

2016-01-01

Neural stimulation is a critical technique in treating neurological diseases and investigating brain functions. Traditional electrical stimulation uses electrodes to directly create intervening electric fields in the immediate vicinity of neural tissues. Second-generation stimulation techniques directly use light, magnetic fields or ultrasound in a non-contact manner. An emerging generation of non- or minimally invasive neural stimulation techniques is enabled by nanotechnology to achieve a high spatial resolution and cell-type specificity. In these techniques, a nanomaterial converts a remotely transmitted primary stimulus such as a light, magnetic or ultrasonic signal to a localized secondary stimulus such as an electric field or heat to stimulate neurons. The ease of surface modification and bio-conjugation of nanomaterials facilitates cell-type-specific targeting, designated placement and highly localized membrane activation. This review focuses on nanomaterial-enabled neural stimulation techniques primarily involving opto-electric, opto-thermal, magneto-electric, magneto-thermal and acousto-electric transduction mechanisms. Stimulation techniques based on other possible transduction schemes and general consideration for these emerging neurotechnologies are also discussed. PMID:27013938

Comparison of pulsed corona plasma and pulsed electric fields for the decontamination of water containing Legionella pneumophila as model organism.

PubMed

Banaschik, Robert; Burchhardt, Gerhard; Zocher, Katja; Hammerschmidt, Sven; Kolb, Juergen F; Weltmann, Klaus-Dieter

2016-12-01

Pulsed corona plasma and pulsed electric fields were assessed for their capacity to kill Legionella pneumophila in water. Electrical parameters such as in particular dissipated energy were equal for both treatments. This was accomplished by changing the polarity of the applied high voltage pulses in a coaxial electrode geometry resulting in the generation of corona plasma or an electric field. For corona plasma, generated by high voltage pulses with peak voltages of +80kV, Legionella were completely killed, corresponding to a log-reduction of 5.4 (CFU/ml) after a treatment time of 12.5min. For the application of pulsed electric fields from peak voltages of -80kV a survival of log 2.54 (CFU/ml) was still detectable after this treatment time. Scanning electron microscopy images of L. pneumophila showed rupture of cells after plasma treatment. In contrast, the morphology of bacteria seems to be intact after application of pulsed electric fields. The more efficient killing for the same energy input observed for pulsed corona plasma is likely due to induced chemical processes and the generation of reactive species as indicated by the evolution of hydrogen peroxide. This suggests that the higher efficacy and efficiency of pulsed corona plasma is primarily associated with the combined effect of the applied electric fields and the promoted reaction chemistry. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental Measurements of the Dynamic Electric Field Topology Associated with Magnetized RF Sheaths

NASA Astrophysics Data System (ADS)

Martin, E. H.; Caughman, J. B. O.; Shannon, S. C.; Klepper, C. C.; Isler, R. C.

2013-10-01

A major challenge facing magnetic fusion devices and the success of ITER is the design and implementation of reliable ICRH systems. The primary issue facing ICRH is the parasitic near-field which leads to an increased heat flux, sputtering, and arcing of the antenna/faraday screen. In order to aid the theoretical development of near-field physics and thus propel the design process experimental measurements are highly desired. In this work we have developed a diagnostic based on passive emission spectroscopy capable of measuring time periodic electric fields utilizing a generalized dynamic Stark effect model and a novel spectral line profile fitting package. The diagnostic was implemented on a small scale laboratory experiment designed to simulate the edge environment associated with ICRF antenna/faraday screen. The spatially and temporally resolved electric field associated with magnetized RF sheaths will be presented for two field configurations: magnetic field parallel to electric field and magnetic field perpendicular to electric field, both hydrogen and helium discharges where investigated. ORNL is managed by UT-Battelle, LCC, for the US DOE under Contract No. DE-AC05-00OR22725.

On The Design and Implementation of a New Electric-Field Meter with Reciprocating Shutter and Field-Change-Antenna Option

NASA Astrophysics Data System (ADS)

Swenson, J.; Byerley, L. G.; Bogoev, I.; Hinckley, A.; Beasley, W. H.

2003-12-01

The atmospheric electric field is a unique indicator of locally disturbed weather, local thunderstorms and local atmospheric electrical hazards. Yet, surprisingly, routine observations of ambient electric field have never been included in the canonical suite of measured meteorological variables. This notable omission may be a result of the historically high costs to acquire, install, and maintain conventional electric-field mills. To reduce costs and overcome limitations of traditional field meters, Campbell Scientific, Inc. has developed an electric-field meter (patent pending) with a reciprocating shutter that eliminates the problem of making electrical contact with a rotating shaft. The reciprocating action is under microprocessor control, so the sample rate can be varied in response to measured conditions. Between samples of electric field, the shutter can even be left open indefinitely, allowing the instrument to function as a field-change antenna. Since the shutter is closed before and after each measurement in field-meter mode, it is relatively easy to account for drift and offsets automatically, so that measurements can be made even if the electrode insulator becomes degraded by conductive deposits of the types likely to be encountered in severe outdoor environments. Because the motor is energized for only a small fraction of each measurement cycle, average power consumption is exceptionally low, making the new field meter especially suitable for solar-powered applications such as automated remote meteorological stations. Some preliminary observations demonstrate the capabilities of the instrument.

Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

NASA Technical Reports Server (NTRS)

Dye, J. E.; Bateman, M. G.; Christian, H. J.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.; Willett, J. C.;

Influence of the pulsating electric field on the ECR heating in a nonuniform magnetic field

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

Balmashnov, A. A., E-mail: abalmashnov@sci.pfu.edu.ru; Umnov, A. M.

2011-12-15

According to a computer simulation, the randomized pulsating electric field can strongly influence the ECR plasma heating in a nonuniform magnetic field. It has been found out that the electron energy spectrum is shifted to the high energy region. The obtained effect is intended to be used in the ECR sources for effective X-ray generation.

Radio frequency self-resonant coil for contactless AC-conductivity in 100 T class ultra-strong pulse magnetic fields

NASA Astrophysics Data System (ADS)

Nakamura, D.; Altarawneh, M. M.; Takeyama, S.

2018-03-01

A contactless measurement system of electrical conductivity was developed for application under pulsed high magnetic fields over 100 T by using a self-resonant-type, high-frequency circuit. Electromagnetic fields in the circuit were numerically analysed by the finite element method, to show how the resonant power spectra of the circuit depends on the electrical conductivity of a sample set on the probe-coil. The performance was examined using a high-temperature cuprate superconductor, La2-x Sr x CuO4, in magnetic fields up to 102 T with a high frequency of close to 800 MHz. As a result, the upper critical field could be determined with a good signal-to-noise ratio.

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''.

Electrohydrodynamics in nanochannels coated by mixed polymer brushes: effects of electric field strength and solvent quality

NASA Astrophysics Data System (ADS)

Cao, Qianqian; Tian, Xiu; You, Hao

2018-04-01

We examine the electrohydrodynamics in mixed polymer brush-coated nanochannels and the conformational dynamics of grafted polymers using molecular dynamics simulations. Charged (A) and neutral polymers (B) are alternately grafted on the channel surfaces. The effects of the electric field strength and solvent quality are addressed in detail. The dependence of electroosmotic flow characteristics and polymer conformational behavior on the solvent quality is influenced due to the change of the electric field strength. The enhanced electric field induces a collapse of the neutral polymer chains which adopt a highly extended conformation along the flow direction. However, the thickness of the charged polymer layer is affected weakly by the electric field, and even a slight swelling is identified for the A-B attraction case, implying the conformational coupling between two polymer species. Furthermore, the charged polymer chains incline entirely towards the electric field direction oppositely to the flow direction. More importantly, unlike the neutral polymer chains, the shape factor of the charged polymer chains, which is used to describe the overall shape of polymer chains, is reduced significantly with increasing the electric field strength, corresponding to a more coiled structure.

Self-assembled tunable networks of sticky colloidal particles

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

Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim

Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part I: Design and model evaluation

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

Wang, Jian; Pikridas, Michael; Spielman, Steven R.

This study discusses, a fast integrated mobility spectrometer (FIMS) was previously developed to characterize submicron aerosol size distributions at a frequency of 1 Hz and with high size resolution and counting statistics. However, the dynamic size range of the FIMS was limited to one decade in particle electrical mobility. It was proposed that the FIMS dynamic size range can be greatly increased by using a spatially varying electric field. This electric field creates regions with drastically different field strengths in the separator, such that particles of a wide diameter range can be simultaneously classified and subsequently measured. A FIMS incorporatingmore » this spatially varying electric field is developed. This paper describes the theoretical frame work and numerical simulations of the FIMS with extended dynamic size range, including the spatially varying electric field, particle trajectories, activation of separated particles in the condenser, and the transfer function, transmission efficiency, and mobility resolution. The influences of the particle Brownian motion on FIMS transfer function and mobility resolution are examined. The simulation results indicate that the FIMS incorporating the spatially varying electric field is capable of measuring aerosol size distribution from 8 to 600 nm with high time resolution. As a result, the experimental characterization of the FIMS is presented in an accompanying paper.« less

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part I: Design and model evaluation

DOE PAGES

Wang, Jian; Pikridas, Michael; Spielman, Steven R.; ...

2017-06-01

This study discusses, a fast integrated mobility spectrometer (FIMS) was previously developed to characterize submicron aerosol size distributions at a frequency of 1 Hz and with high size resolution and counting statistics. However, the dynamic size range of the FIMS was limited to one decade in particle electrical mobility. It was proposed that the FIMS dynamic size range can be greatly increased by using a spatially varying electric field. This electric field creates regions with drastically different field strengths in the separator, such that particles of a wide diameter range can be simultaneously classified and subsequently measured. A FIMS incorporatingmore » this spatially varying electric field is developed. This paper describes the theoretical frame work and numerical simulations of the FIMS with extended dynamic size range, including the spatially varying electric field, particle trajectories, activation of separated particles in the condenser, and the transfer function, transmission efficiency, and mobility resolution. The influences of the particle Brownian motion on FIMS transfer function and mobility resolution are examined. The simulation results indicate that the FIMS incorporating the spatially varying electric field is capable of measuring aerosol size distribution from 8 to 600 nm with high time resolution. As a result, the experimental characterization of the FIMS is presented in an accompanying paper.« less

Simulation of Space Charge Dynamic in Polyethylene Under DC Continuous Electrical Stress

NASA Astrophysics Data System (ADS)

Boukhari, Hamed; Rogti, Fatiha

2016-10-01

The space charge dynamic plays a very important role in the aging and breakdown of polymeric insulation materials under high voltage. This is due to the intensification of the local electric field and the attendant chemical-mechanical effects in the vicinity around the trapped charge. In this paper, we have investigated the space charge dynamic in low-density polyethylene under high direct-current voltage, which is evaluated by experimental conditions. The evaluation is on the basis of simulation using a bipolar charge transport model consisting of charge injection, transports, trapping, detrapping, and recombination phenomena. The theoretical formulation of the physical problem is based on the Poisson, the continuity, and the transport equations. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges (net charge density, mobile and trapped of electron density, mobile hole density), conduction and displacement current densities, and the external current. The result shows the appearance of the negative packet-like space charge with a large amount of the bulk under the dc electric field of 100 kV/mm, and the induced distortion of the electric field is largely near to the anode, about 39% higher than the initial electric field applied.

Effects of direct current electric-field using ITO plate on breast cancer cell migration.

PubMed

Kim, Min Sung; Lee, Mi Hee; Kwon, Byeong-Ju; Seo, Hyok Jin; Koo, Min-Ah; You, Kyung Eun; Kim, Dohyun; Park, Jong-Chul

2014-01-01

Cell migration is an essential activity of the cells in various biological phenomena. The evidence that electrotaxis plays important roles in many physiological phenomena is accumulating. In electrotaxis, cells move with a directional tendency toward the anode or cathode under direct-current electric fields. Indium tin oxide, commonly referred to as ITO has high luminous transmittance, high infrared reflectance, good electrical conductivity, excellent substrate adherence, hardness and chemical inertness and hence, have been widely and intensively studied for many years. Because of these properties of ITO films, the electrotaxis using ITO plate was evaluated. Under the 0 V/cm condition, MDA-MB-231 migrated randomly in all directions. When 1 V/cm of dc EF was applied, cells moved toward anode. The y forward migration index was -0.046 ± 0.357 under the 0 V/cm and was 0.273 ± 0.231 under direct-current electric field of 1 V/cm. However, the migration speed of breast cancer cell was not affected by direct-current electric field using ITO plate. In this study, we designed a new electrotaxis system using an ITO coated glass and observed the migration of MDA-MB-231 on direct current electric-field of the ITO glass.

Mercury monohalides: suitability for electron electric dipole moment searches.

PubMed

Prasannaa, V S; Vutha, A C; Abe, M; Das, B P

2015-05-08

Heavy polar diatomic molecules are the primary tools for searching for the T-violating permanent electric dipole moment of the electron (eEDM). Valence electrons in some molecules experience extremely large effective electric fields due to relativistic interactions. These large effective electric fields are crucial to the success of polar-molecule-based eEDM search experiments. Here we report on the results of relativistic ab initio calculations of the effective electric fields in a series of molecules that are highly sensitive to an eEDM, the mercury monohalides (HgF, HgCl, HgBr, and HgI). We study the influence of the halide anions on E_{eff}, and identify HgBr and HgI as attractive candidates for future electric dipole moment search experiments.

Electro-aerodynamic field aided needleless electrospinning.

PubMed

Yan, Guilong; Niu, Haitao; Zhou, Hua; Wang, Hongxia; Shao, Hao; Zhao, Xueting; Lin, Tong

2018-06-08

Auxiliary fields have been used to enhance the performance of needle electrospinning. However, much less has been reported on how auxiliary fields affect needleless electrospinning. Herein, we report a novel needleless electrospinning technique that consists of an aerodynamic field and a second electric field. The second electric field is generated by setting two grounded inductive electrodes near the spinneret. The two auxiliary fields have to be applied simultaneously to ensure working of the electrospinning process. A synergistic effect was observed between inductive electrode and airflow. The aerodynamic-electric auxiliary field was found to significantly increase fiber production rate (4.5 g h -1 ), by 350% in comparison to the setup without auxiliary field (1.0 g h -1 ), whereas it had little effect on fiber diameter. The auxiliary fields allow running needleless electrospinning at an applied voltage equivalent to that in needle electrospinning (e.g. 10-30 kV). The finite element analyses of electric field and airflow field verify that the inductive electrodes increase electric field strength near the spinneret, and the airflow assists in fiber deposition. This novel needleless electrospinning may be useful for development of high-efficiency, low energy-consumption nanofiber production systems.

Electro-aerodynamic field aided needleless electrospinning

NASA Astrophysics Data System (ADS)

Yan, Guilong; Niu, Haitao; Zhou, Hua; Wang, Hongxia; Shao, Hao; Zhao, Xueting; Lin, Tong

2018-06-01

Auxiliary fields have been used to enhance the performance of needle electrospinning. However, much less has been reported on how auxiliary fields affect needleless electrospinning. Herein, we report a novel needleless electrospinning technique that consists of an aerodynamic field and a second electric field. The second electric field is generated by setting two grounded inductive electrodes near the spinneret. The two auxiliary fields have to be applied simultaneously to ensure working of the electrospinning process. A synergistic effect was observed between inductive electrode and airflow. The aerodynamic-electric auxiliary field was found to significantly increase fiber production rate (4.5 g h‑1), by 350% in comparison to the setup without auxiliary field (1.0 g h‑1), whereas it had little effect on fiber diameter. The auxiliary fields allow running needleless electrospinning at an applied voltage equivalent to that in needle electrospinning (e.g. 10–30 kV). The finite element analyses of electric field and airflow field verify that the inductive electrodes increase electric field strength near the spinneret, and the airflow assists in fiber deposition. This novel needleless electrospinning may be useful for development of high-efficiency, low energy-consumption nanofiber production systems.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.

PubMed

Müller, Knut; Krause, Florian F; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-12-15

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction

NASA Astrophysics Data System (ADS)

Müller, Knut; Krause, Florian F.; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-12-01

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction

PubMed Central

Müller, Knut; Krause, Florian F.; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-01-01

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms. PMID:25501385

Electric shocks at work in Europe: development of a job exposure matrix.

PubMed

Huss, Anke; Vermeulen, Roel; Bowman, Joseph D; Kheifets, Leeka; Kromhout, Hans

2013-04-01

Electric shocks have been suggested as a potential risk factor for neurological disease, in particular for amyotrophic lateral sclerosis. While actual exposure to shocks is difficult to measure, occurrence and variation of electric injuries could serve as an exposure proxy. We assessed risk of electric injury, using occupational accident registries across Europe to develop an electric shock job-exposure-matrix (JEM). Injury data were obtained from five European countries, and the number of workers per occupation and country from EUROSTAT was compiled at a 3-digit International Standard Classification of Occupations 1988 level. We pooled accident rates across countries with a random effects model and categorised jobs into low, medium and high risk based on the 75th and 90th percentile. We next compared our JEM to a JEM that classified extremely low frequency magnetic field exposure of jobs into low, medium and high. Of 116 job codes, occupations with high potential for electric injury exposure were electrical and electronic equipment mechanics and fitters, building frame workers and finishers, machinery mechanics and fitters, metal moulders and welders, assemblers, mining and construction labourers, metal-products machine operators, ships' decks crews and power production and related plant operators. Agreement between the electrical injury and magnetic field JEM was 67.2%. Our JEM classifies occupational titles according to risk of electric injury as a proxy for occurrence of electric shocks. In addition to assessing risk potentially arising from electric shocks, this JEM might contribute to disentangling risks from electric injury from those of extremely low frequency magnetic field exposure.

On the electrostatic deceleration of argon atoms in high Rydberg states by time-dependent inhomogeneous electric fields

NASA Astrophysics Data System (ADS)

Vliegen, E.; Merkt, F.

2005-06-01

Argon atoms in a pulsed supersonic expansion are prepared in selected Stark components of Rydberg states with effective principal quantum number in the range n* = 15-25. When traversing regions of inhomogeneous electric fields, these atoms get accelerated or decelerated depending on whether the Stark states are low- or high-field seeking states. Using a compact electrode design, which enables the application of highly inhomogeneous and time-dependent electric fields, the Rydberg atoms experience kinetic energy changes of up to 1.2 × 10-21 J (i.e. 60 cm-1 in spectroscopic units) in a single acceleration/deceleration stage of 3 mm length. The resulting differences in the velocities of the low- and high-field seeking states are large enough that the corresponding distributions of times of flight to the Rydberg particle detector are fully separated. As a result, efficient spectral searches of the Rydberg states best suited for acceleration/deceleration experiments are possible. Numerical simulations of the particle trajectories are used to analyse the time-of-flight distributions and to optimize the time dependence of the inhomogeneous electric fields. The decay of the Rydberg states by fluorescence, collisions and transitions induced by black-body radiation takes place on a timescale long enough not to interfere significantly with the deceleration during the first ~5 µs.

Measurement of surface charges on the dielectric film based on field mills under the HVDC corona wire

NASA Astrophysics Data System (ADS)

Donglai, WANG; Tiebing, LU; Yuan, WANG; Bo, CHEN; Xuebao, LI

2018-05-01

The ion flow field on the ground is one of the significant parameters used to evaluate the electromagnetic environment of high voltage direct current (HVDC) power lines. HVDC lines may cross the greenhouses due to the restricted transmission corridors. Under the condition of ion flow field, the dielectric films on the greenhouses will be charged, and the electric fields in the greenhouses may exceed the limit value. Field mills are widely used to measure the ground-level direct current electric fields under the HVDC power lines. In this paper, the charge inversion method is applied to calculate the surface charges on the dielectric film according to the measured ground-level electric fields. The advantages of hiding the field mill probes in the ground are studied. The charge inversion algorithm is optimized in order to decrease the impact of measurement errors. Based on the experimental results, the surface charge distribution on a piece of quadrate dielectric film under a HVDC corona wire is studied. The enhanced effect of dielectric film on ground-level electric field is obviously weakened with the increase of film height. Compared with the total electric field strengths, the normal components of film-free electric fields at the corresponding film-placed positions have a higher effect on surface charge accumulation.

RichMol: A general variational approach for rovibrational molecular dynamics in external electric fields

NASA Astrophysics Data System (ADS)

Owens, Alec; Yachmenev, Andrey

2018-03-01

In this paper, a general variational approach for computing the rovibrational dynamics of polyatomic molecules in the presence of external electric fields is presented. Highly accurate, full-dimensional variational calculations provide a basis of field-free rovibrational states for evaluating the rovibrational matrix elements of high-rank Cartesian tensor operators and for solving the time-dependent Schrödinger equation. The effect of the external electric field is treated as a multipole moment expansion truncated at the second hyperpolarizability interaction term. Our fully numerical and computationally efficient method has been implemented in a new program, RichMol, which can simulate the effects of multiple external fields of arbitrary strength, polarization, pulse shape, and duration. Illustrative calculations of two-color orientation and rotational excitation with an optical centrifuge of NH3 are discussed.

Design and simulation of a novel E-mode GaN MIS-HEMT based on a cascode connection for suppression of electric field under gate and improvement of reliability

NASA Astrophysics Data System (ADS)

Li, Weiyi; Zhang, Zhili; Fu, Kai; Yu, Guohao; Zhang, Xiaodong; Sun, Shichuang; Song, Liang; Hao, Ronghui; Fan, Yaming; Cai, Yong; Zhang, Baoshun

2017-07-01

We proposed a novel AlGaN/GaN enhancement-mode (E-mode) high electron mobility transistor (HEMT) with a dual-gate structure and carried out the detailed numerical simulation of device operation using Silvaco Atlas. The dual-gate device is based on a cascode connection of an E-mode and a D-mode gate. The simulation results show that electric field under the gate is decreased by more than 70% compared to that of the conventional E-mode MIS-HEMTs (from 2.83 MV/cm decreased to 0.83 MV/cm). Thus, with the discussion of ionized trap density, the proposed dual-gate structure can highly improve electric field-related reliability, such as, threshold voltage stability. In addition, compared with HEMT with field plate structure, the proposed structure exhibits a simplified fabrication process and a more effective suppression of high electric field. Project supported by the Key Technologies Support Program of Jiangsu Province (No. BE2013002-2) and the National Key Scientific Instrument and Equipment Development Projects of China (No. 2013YQ470767).

Mechanisms of high-gradient microwave breakdown on metal surfaces in high power microwave source

NASA Astrophysics Data System (ADS)

Xie, Jialing; Chen, Changhua; Chang, Chao; Wu, Cheng; Huo, Yankun

2017-12-01

A breakdown cavity was designed to study the high-gradient microwave breakdown on a metal surface. The breakdown cavity can be distinguished into an electron emission boundary and a bombardment boundary as there is an evident difference in amplitude of the electric field between the two planes in the cavity. Breakdown tracks on the cavity were studied with an electron scanning microscope. The tracks on the electron emission boundary with the higher electric field were eroded; a component analysis indicates that these tracks contain an emission boundary material. On the bombardment boundary with a lower electric field, two kinds of tracks exist: an erosion track containing a bombardment boundary material and a sputtered track containing an emission boundary material. From these tracks, the mechanisms of high-gradient microwave breakdown on a metal surface have been analyzed.

Initial Characterization of Colombian High School Physics Teachers' Pedagogical Content Knowledge on Electric Fields

ERIC Educational Resources Information Center

Melo-Niño, Lina Viviana; Cañada, Florentina; Mellado, Vicente

2017-01-01

We explore the initial characterization of the pedagogical content knowledge of four, in-service, Colombian pre-university secondary education physics teachers on the concept of electric field. Two of them teach the content in English as a second language. The aim of the study was to obtain an image of the participants' teaching of electric field…

Mode jumping of split-ring resonator metamaterials controlled by high-permittivity BST and incident electric fields

PubMed Central

Fu, Xiaojian; Zeng, Xinxi; Cui, Tie Jun; Lan, Chuwen; Guo, Yunsheng; Zhang, Hao Chi; Zhang, Qian

2016-01-01

We investigate the resonant modes of split-ring resonator (SRR) metamaterials that contain high-permittivity BST block numerically and experimentally. We observe interesting mode-jumping phenomena from the BST-included SRR absorber structure as the excitation wave is incident perpendicularly to the SRR plane. Specifically, when the electric field is parallel to the SRR gap, the BST block in the gap will induce a mode jumping from the LC resonance to plasmonic resonance (horizontal electric-dipole mode), because the displacement current excited by the Mie resonance in the dielectric block acts as a current channel in the gap. When the electric field is perpendicular to the gap side, the plasmonic resonance mode (vertical electric-dipole mode) in SRR changes to two joint modes contributed simultaneously by the back layer, SRR and BST block, as a result of connected back layer and SRR layer by the displacement current in the BST dielectric block. Based on the mode jumping effect as well as temperature and electric-field dependent dielectric constant, the BST-included SRR metamaterials may have great potentials for the applications in electromagnetic switches and widely tunable metamaterial devices. PMID:27502844

Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas

PubMed Central

Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S.-I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

2016-01-01

Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt “radial” electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson’s equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude. PMID:27489128

Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss

NASA Astrophysics Data System (ADS)

Wu, Shan; Burlingame, Quinn; Lin, Minren; Zhang, Qiming

2013-03-01

There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density Ue while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high Ue, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (>1 GV/m) with a high Ue (~ 24 J/cm3) , which is very attractive for energy storage capacitors.

Modification of solid state CdZnTe (CZT) radiation detectors with high sensitivity or high resolution operation

DOEpatents

Washington, II, Aaron L; Duff, Martine C; Teague, Lucile C; Burger, Arnold; Groza, Michael

2014-11-11

An apparatus and process is provided to illustrate the manipulation of the internal electric field of CZT using multiple wavelength light illumination on the crystal surface at RT. The control of the internal electric field is shown through the polarization in the IR transmission image under illumination as a result of the Pockels effect.

Enhancing the lycopene in vitro bioaccessibility of tomato juice synergistically applying thermal and non-thermal processing technologies.

PubMed

Jayathunge, K G L R; Stratakos, Alexandros Ch; Cregenzán-Albertia, Oliver; Grant, Irene R; Lyng, James; Koidis, Anastasios

2017-04-15

The influence of moderate intensity pulsed electric field pre-processing on increasing the lycopene bioaccessibility of tomato fruit, and the combined effect of blanching, ultrasonic and high intensity pulsed electric field processing on further enhancement of the lycopene bioaccessibility after juicing were investigated. Maximum total lycopene bioaccessibility (9.6%) of the tomato fruit was achieved by a 4μs pre-processed treatment after 24h holding period and further processing results revealed that all treatments were effective to increase the total lycopene. Most of juice processing treatments decreased the release of lycopene from the tomato matrix during digestion. Only the treatment of blanching followed by high intensity pulsed electric field showed a significant release of trans-(4.01±0.48) and cis-(5.04±0.26μg/g) lycopene, achieving 15.6% total lycopene bioaccessibility. Thus, processing of pre-blanched juice using high intensity pulsed electric field, derived from pre-processed tomato was the best overall process to achieve the highest nutritive value. Copyright © 2016 Elsevier Ltd. All rights reserved.

Time-Varying Seismogenic Coulomb Electric Fields as a Probable Source for Pre-Earthquake Variation in the Ionospheric F2-Layer

NASA Astrophysics Data System (ADS)

Kim, Vitaly P.; Hegai, Valery V.; Liu, Jann Yenq; Ryu, Kwangsun; Chung, Jong-Kyun

2017-12-01

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a time- varying irregular vertical Coulomb field presumably produced on the Earth’s surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of 20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of 7×105 more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

A high-performance electric field detector for space missions

NASA Astrophysics Data System (ADS)

Badoni, D.; Ammendola, R.; Bertello, I.; Cipollone, P.; Conti, L.; De Santis, C.; Diego, P.; Masciantonio, G.; Picozza, P.; Sparvoli, R.; Ubertini, P.; Vannaroni, G.

2018-04-01

We present the prototype of an Electric Field Detector (EFD) for space applications, that has been developed in the framework of the Chinese-Italian collaboration on the CSES (China Seismo-Electromagnetic Satellite) forthcoming missions. In particular CSES-1 will be placed in orbit in the early 2018. The detector consists of spherical probes designed to be installed at the tips of four booms deployed from a 3-axes stabilized satellite. The instrument has been conceived for space-borne measurements of electromagnetic phenomena such as ionospheric waves, lithosphere-atmosphere-ionosphere-magnetosphere coupling and anthropogenic electromagnetic emissions. The detector allows to measure electric fields in a wide band of frequencies extending from quasi-DC up to about 4 MHz , with a sensitivity of the order of 1 μV / m in the ULF band. With these bandwidth and sensitivity, the described electric field detector represents a very performing and updated device for electric field measurements in space.

Dielectrophoretic systems without embedded electrodes

DOEpatents

Cummings, Eric B [Livermore, CA; Singh, Anup K [San Francisco, CA

2006-03-21

Method and apparatus for dielectrophoretic separation of particles in a fluid based using array of insulating structures arranged in a fluid flow channel. By utilizing an array of insulating structures, a spatially inhomogeneous electric field is created without the use of the embedded electrodes conventionally employed for dielectrophoretic separations. Moreover, by using these insulating structures a steady applied electric field has been shown to provide for dielectrophoresis in contrast to the conventional use of an alternating electric field. In a uniform array of posts, dielectrophoretic effects have been produced flows having significant pressure-driven and electrokinetic transport. Above a threshold applied electric field, filaments of concentrated and rarefied particles appear in the flow as a result of dielectrophoresis. Above a higher threshold applied voltage, dielectrophoresis produces zones of highly concentrated and immobilized particles. These patterns are strongly influenced by the angle of the array of insulating structures with respect to the mean applied electric field and the shape of the insulating structures.

Effects of 60-Heartz electric and magnetic fields on implanted cardiac pacemakers. Final report. [Hazards of power transmission line frequencies

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

Bridges, J.E.; Frazier, M.J.

1979-09-01

The effects of 60-Hz electric and magnetic fields of exta-high voltage (EHV) transmission lines on the performance of implanted cardiac pacemakers were studied by: (1) in vitro bench tests of a total of thirteen cardiac pacemakers; (2) in vivo tests of six implanted cardiac pacemakers in baboons; and (3) non-hazardous skin measurement tests on four humans. Analytical methods were developed to predict the thresholds of body current and electric fields capable of affecting normal pacemaker operation in humans. The field strengths calculated to alter implanted pacemaker performance were compared with the range of maximum electric and magnetic field strengths amore » human would normally encounter under transmission lines of various voltages. Results indicate that the electric field or body current necessary to alter the normal operation of pacemakers is highly dependent on the type of pacemaker and the location of the implanted electrodes. However, cardiologists have not so far detected harmful effects of pacemaker reversion to the asynchronous mode in current types of pacemakers and with present methods of implantation. Such interferences can be eliminated by using advanced pacemakers less sensitive to 60-Hz voltages or by using implantation lead arrangements less sensitive to body current.« less

Atmospheric Electrical Modeling in Support of the NASA F-106 Storm Hazards Project

NASA Technical Reports Server (NTRS)

Helsdon, John H., Jr.

1988-01-01

A recently developed storm electrification model (SEM) is used to investigate the operating environment of the F-106 airplane during the NASA Storm Hazards Project. The model is 2-D, time dependent and uses a bulkwater microphysical parameterization scheme. Electric charges and fields are included, and the model is fully coupled dynamically, microphysically and electrically. One flight showed that a high electric field was developed at the aircraft's operating altitude (28 kft) and that a strong electric field would also be found below 20 kft; however, this low-altitude, high-field region was associated with the presence of small hail, posing a hazard to the aircraft. An operational procedure to increase the frequency of low-altitude lightning strikes was suggested. To further the understanding of lightning within the cloud environment, a parameterization of the lightning process was included in the SEM. It accounted for the initiation, propagation, termination, and charge redistribution associated with an intracloud discharge. Finally, a randomized lightning propagation scheme was developed, and the effects of cloud particles on the initiation of lightning investigated.

Evaluation of a “Field Cage” for Electric Field Control in GaN-Based HEMTs That Extends the Scalability of Breakdown Into the kV Regime

DOE PAGES

Tierney, Brian D.; Choi, Sukwon; DasGupta, Sandeepan; ...

2017-08-16

A distributed impedance “field cage” structure is proposed and evaluated for electric field control in GaN-based, lateral high electron mobility transistors (HEMTs) operating as kilovolt-range power devices. In this structure, a resistive voltage divider is used to control the electric field throughout the active region. The structure complements earlier proposals utilizing floating field plates that did not employ resistively connected elements. Transient results, not previously reported for field plate schemes using either floating or resistively connected field plates, are presented for ramps of dV ds /dt = 100 V/ns. For both DC and transient results, the voltage between the gatemore » and drain is laterally distributed, ensuring the electric field profile between the gate and drain remains below the critical breakdown field as the source-to-drain voltage is increased. Our scheme indicates promise for achieving breakdown voltage scalability to a few kV.« less

Evaluation of a “Field Cage” for Electric Field Control in GaN-Based HEMTs That Extends the Scalability of Breakdown Into the kV Regime

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

Tierney, Brian D.; Choi, Sukwon; DasGupta, Sandeepan

A distributed impedance “field cage” structure is proposed and evaluated for electric field control in GaN-based, lateral high electron mobility transistors (HEMTs) operating as kilovolt-range power devices. In this structure, a resistive voltage divider is used to control the electric field throughout the active region. The structure complements earlier proposals utilizing floating field plates that did not employ resistively connected elements. Transient results, not previously reported for field plate schemes using either floating or resistively connected field plates, are presented for ramps of dV ds /dt = 100 V/ns. For both DC and transient results, the voltage between the gatemore » and drain is laterally distributed, ensuring the electric field profile between the gate and drain remains below the critical breakdown field as the source-to-drain voltage is increased. Our scheme indicates promise for achieving breakdown voltage scalability to a few kV.« less

Signal Cloaking by Electric Fish

PubMed Central

STODDARD, PHILIP K.; MARKHAM, MICHAEL R.

2010-01-01

Electric fish produce weak electric fields to image their world in darkness and to communicate with potential mates and rivals. Eavesdropping by electroreceptive predators exerts selective pressure on electric fish to shift their signals into less-detectable high-frequency spectral ranges. Hypopomid electric fish evolved a signal-cloaking strategy that reduces their detectability by predators in the lab (and thus presumably their risk of predation in the field). These fish produce broad-frequency electric fields close to the body, but the heterogeneous local fields merge over space to cancel the low-frequency spectrum at a distance. Mature males dynamically regulate this cloaking mechanism to enhance or suppress low-frequency energy. The mechanism underlying electric-field cloaking involves electrogenic cells that produce two independent action potentials. In a unique twist, these cells orient sodium and potassium currents in the same direction, potentially boosting their capabilities for current generation. Exploration of such evolutionary inventions could aid the design of biogenerators to power implantable medical devices, an ambition that would benefit from the complete genome sequence of a gymnotiform fish. PMID:20209064

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

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.

MMS Observations of Parallel Electric Fields During a Quasi-Perpendicular Bow Shock Crossing

NASA Astrophysics Data System (ADS)

Goodrich, K.; Schwartz, S. J.; Ergun, R.; Wilder, F. D.; Holmes, J.; Burch, J. L.; Gershman, D. J.; Giles, B. L.; Khotyaintsev, Y. V.; Le Contel, O.; Lindqvist, P. A.; Strangeway, R. J.; Russell, C.; Torbert, R. B.

2016-12-01

Previous observations of the terrestrial bow shock have frequently shown large-amplitude fluctuations in the parallel electric field. These parallel electric fields are seen as both nonlinear solitary structures, such as double layers and electron phase-space holes, and short-wavelength waves, which can reach amplitudes greater than 100 mV/m. The Magnetospheric Multi-Scale (MMS) Mission has crossed the Earth's bow shock more than 200 times. The parallel electric field signatures observed in these crossings are seen in very discrete packets and evolve over time scales of less than a second, indicating the presence of a wealth of kinetic-scale activity. The high time resolution of the Fast Particle Instrument (FPI) available on MMS offers greater detail of the kinetic-scale physics that occur at bow shocks than ever before, allowing greater insight into the overall effect of these observed electric fields. We present a characterization of these parallel electric fields found in a single bow shock event and how it reflects the kinetic-scale activity that can occur at the terrestrial bow shock.

The effect of a radial electric field on ripple-trapped ions observed by neutral particle fluxes

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

Heikkinen, J.A.; Herrmann, W.; Kurki-Suonio, T.

1997-10-01

The effect of a radial electric field on nonthermal ripple-trapped ions is investigated using toroidal Monte Carlo simulations for edge tokamak plasmas. The increase in the neutral particle flux from the ions trapped in local magnetic wells observed by the charge exchange (CX) detector at a low confinement to high confinement transition at ASDEX (Axially Symmetric Divertor Experiment). Upgrade tokamak [{ital Proceedings of the 20th European Conference on Controlled Fusion and Plasma Physics}, Lisbon (European Physical Society, Petit-Lancy, Switzerland, 1993), Vol. 17C, Part I, p. 267] is reproduced in the simulations by turning on a radial electric field near themore » plasma periphery. The poloidal and toroidal angles at which the CX detector signal is most sensitive to the radial electric field are determined. A fast response time of the signal in the range of 50{endash}100 {mu}s to the appearance of the electric field can be found in the simulations with a relatively large half-width of the negative electric field region. {copyright} {ital 1997 American Institute of Physics.}« less

Field-aligned currents and large scale magnetospheric electric fields

NASA Technical Reports Server (NTRS)

Dangelo, N.

1980-01-01

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

Electric Fields, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms

NASA Technical Reports Server (NTRS)

Dye, J. E.; Bateman, M. G.; Christian, H. J.; Defer, E.; Grainger, C. A.; Hall, W. D.; Krider, E. P.; Lewis, S. A.; Mach, D. M.; Merceret, F. J.;

HIGH ENERGY GASEOUS PLASMA CONTAINMENT DEVICE

DOEpatents

Josephson, V.; Hammel, J.E.

1959-01-13

An apparatus is presenied for producing neutrons as a result of collisions between ions in high temperature plasmas. The invention resides in the particular arrangement of ihe device whereby ihe magneiic and electric fields are made to cross at substantially right angles in several places along a torus shaped containment vessel. A plasma of deuterium gas is generated in the vessel under the electric fields and is "trapped" in any one of the "crossed field" regions to produce a release of energy.

Signal transduction on enzymes: the effect of electromagnetic field stimuli on superoxide dismutase (SOD).

PubMed

Marracino, P; Migliorati, M; Paffi, A; Liberti, M; Denzi, A; d'Inzeo, G; Apollonio, F

2012-01-01

Protein functions and characteristics can highly differ from physiological conditions in presence of chemical, mechanical or electromagnetic stimuli. In this work we provide a rigorous picture of electric field effects on proteins behavior investigating, at atomistic details, the possible ways in which an external signal can be transduced into biochemical effects. Results from molecular dynamics (MD) simulations of a single superoxidismutase (SOD) enzyme in presence of high exogenous alternate electric fields will be discussed.

Magnetic fields from electric toothbrushes promote corrosion in orthodontic stainless steel appliances but not in titanium appliances.

PubMed

Kameda, Takashi; Ohkuma, Kazuo; Oda, Hirotake; Sano, Natsuki; Batbayar, Nomintsetseg; Terashima, Yukari; Sato, Soh; Terada, Kazuto

2013-01-01

Electric toothbrushes are widely used, and their electric motors have been reported to produce low-frequency electromagnetic fields that induced electric currents in metallic objects worn by the users. In this study, we showed that electric toothbrushes generated low-frequency magnetic fields (MFs) and induced electric currents in orthodontic appliances in artificial saliva (AS), which accelerated corrosion in stainless steel (SUS) appliances, but not in titanium (Ti) appliances; the corrosion was evaluated by using an inductively coupled plasma-optical emission spectrometer and a three-dimensional laser confocal microscope. The pH of AS used for appliance immersion did not change during or after MF exposure. These results suggested that MF-induced currents from electric toothbrushes could erode SUS appliances, but not Ti appliances, because of their high corrosion potentials. Further studies are required to clarify the mechanisms of metallic corrosion by induced currents in dental fields, which may trigger metal allergies in patients.

Analysis of magnetically immersed electron guns with non-adiabatic fields

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

Pikin, Alexander; Alessi, James G.; Beebe, Edward N.

Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams withmore » high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field. By analyzing the electron trajectories angles and presenting the results in a gun performance map different geometries of magnetically immersed electron guns with non-adiabatic fields are compared with each other and with a more traditional adiabatic electron gun. Some advantages and limitations of guns with non-adiabatic fields are outlined. In conclusion, the tests results of non-adiabatic electron gun with modified magnetic field are presented.« less

Analysis of magnetically immersed electron guns with non-adiabatic fields

DOE PAGES

Pikin, Alexander; Alessi, James G.; Beebe, Edward N.; ...

2016-11-08

Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams withmore » high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field. By analyzing the electron trajectories angles and presenting the results in a gun performance map different geometries of magnetically immersed electron guns with non-adiabatic fields are compared with each other and with a more traditional adiabatic electron gun. Some advantages and limitations of guns with non-adiabatic fields are outlined. In conclusion, the tests results of non-adiabatic electron gun with modified magnetic field are presented.« less

Analysis of magnetically immersed electron guns with non-adiabatic fields.

PubMed

Pikin, Alexander; Alessi, James G; Beebe, Edward N; Raparia, Deepak; Ritter, John

2016-11-01

Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams with high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field. By analyzing the electron trajectories angles and presenting the results in a gun performance map, different geometries of magnetically immersed electron guns with non-adiabatic fields are compared with each other and with a more traditional adiabatic electron gun. Some advantages and limitations of guns with non-adiabatic fields are outlined. The tests' results of a non-adiabatic electron gun with modified magnetic field are presented.

Electric field induced sheeting and breakup of dielectric liquid jets

NASA Astrophysics Data System (ADS)

Khoshnevis, Ahmad; Tsai, Scott S. H.; Esmaeilzadeh, Esmaeil

2014-01-01

We report experimental observations of the controlled deformation of a dielectric liquid jet subjected to a local high-voltage electrostatic field in the direction normal to the jet. The jet deforms to the shape of an elliptic cylinder upon application of a normal electrostatic field. As the applied electric field strength is increased, the elliptic cylindrical jet deforms permanently into a flat sheet, and eventually breaks-up into droplets. We interpret this observation—the stretch of the jet is in the normal direction to the applied electric field—qualitatively using the Taylor-Melcher leaky dielectric theory, and develop a simple scaling model that predicts the critical electric field strength for the jet-to-sheet transition. Our model shows a good agreement with experimental results, and has a form that is consistent with the classical drop deformation criterion in the Taylor-Melcher theory. Finally, we statistically analyze the resultant droplets from sheet breakup, and find that increasing the applied electric field strength improves droplet uniformity and reduces droplet size.

Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

PubMed

Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

2016-01-19

We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.

Calculations of low-frequency radio emission by cosmic-ray-induced particle showers

NASA Astrophysics Data System (ADS)

García-Fernández, Daniel; Revenu, Benoît; Charrier, Didier; Dallier, Richard; Escudie, Antony; Martin, Lilian

2018-05-01

The radio technique for the detection of high-energy cosmic rays consists in measuring the electric field created by the particle showers created inside a medium by the primary cosmic ray. The electric field is then used to infer the properties of the primary particle. Nowadays, the radio technique is a standard, well-established technique. While most current experiments measure the field at frequencies above 20 MHz, several experiments have reported a large emission at low frequencies, below 10 MHz. The EXTASIS experiment aims at measuring again and understanding this low-frequency electric field. Since at low frequencies the standard far-field approximation for the calculation of the electric field does not necessarily hold, in order to comprehend the low-frequency emission we need to go beyond the far-field approximation. We present in this work a formula for the electric field created by a particle track inside a dielectric medium that is valid for all frequencies. We then implement this formula in the SELFAS Monte Carlo code and calculate the low-frequency electric field of the extensive air shower (EAS). We also study the electric field of a special case of the transition radiation mechanism when the EAS particles cross the air-soil boundary. We introduce the sudden death pulse, the direct emission caused by the coherent deceleration of the shower front at the boundary, as a first approximation to the whole electric field for the air-soil transition, and study its properties. We show that at frequencies larger than 20 MHz and distances larger than 100 m, the standard far-field approximation for the horizontal polarizations of the field is always accurate at the 1% level.

Fish Geometry and Electric Organ Discharge Determine Functional Organization of the Electrosensory Epithelium

PubMed Central

Sanguinetti-Scheck, Juan Ignacio; Pedraja, Eduardo Federico; Cilleruelo, Esteban; Migliaro, Adriana; Aguilera, Pedro; Caputi, Angel Ariel; Budelli, Ruben

2011-01-01

Active electroreception in Gymnotus omarorum is a sensory modality that perceives the changes that nearby objects cause in a self generated electric field. The field is emitted as repetitive stereotyped pulses that stimulate skin electroreceptors. Differently from mormyriformes electric fish, gymnotiformes have an electric organ distributed along a large portion of the body, which fires sequentially. As a consequence shape and amplitude of both, the electric field generated and the image of objects, change during the electric pulse. To study how G. omarorum constructs a perceptual representation, we developed a computational model that allows the determination of the self-generated field and the electric image. We verify and use the model as a tool to explore image formation in diverse experimental circumstances. We show how the electric images of objects change in shape as a function of time and position, relative to the fish's body. We propose a theoretical framework about the organization of the different perceptive tasks made by electroreception: 1) At the head region, where the electrosensory mosaic presents an electric fovea, the field polarizing nearby objects is coherent and collimated. This favors the high resolution sampling of images of small objects and perception of electric color. Besides, the high sensitivity of the fovea allows the detection and tracking of large faraway objects in rostral regions. 2) In the trunk and tail region a multiplicity of sources illuminate different regions of the object, allowing the characterization of the shape and position of a large object. In this region, electroreceptors are of a unique type and capacitive detection should be based in the pattern of the afferents response. 3) Far from the fish, active electroreception is not possible but the collimated field is suitable to be used for electrocommunication and detection of large objects at the sides and caudally. PMID:22096578

COMSOL based Simulation on the Effect of Electric Field changes due to Lightning on Ground

NASA Astrophysics Data System (ADS)

Premlet, B.; Joby, N. E.; Sabu, S.

2017-12-01

The phenomenon of lightning is accompanied by localised changes in atmospheric electric fields. In cloud-to-ground strike locations, changes in atmospheric electric fields can even be observed at the ground a few minutes prior to a strike. A lot of research has been done already on the electrostatic changes prior to lightning in the region above ground. Through this work, we investigate into the effects of lightning electric fields on/under ground with the aid of simulations done in COMSOL Multiphysics. Horizontal and vertical profiles of voltage gradient, electric field, polarisation etc. are investigated. Simulation experiments were conducted using a general model of lightning electric fields formed using data recorded by the Electric Field Mills(EFMs) from three diverse parts of the world- Kennedy Space Centre (KSC),Florida (Using GHRC datasets),Sonnblick Observatory, Austria and National Centre for Earth Science Studies Trivandrum (NCESS),India. COMSOL models of the global electric circuit were developed using Sandstone as the base model for ground. Similar works in literature have only dealt with lightning electric fields above the ground. This work is the first step towards a high-level simulation on the effects of atmospheric electric field on/below ground. The results of this simulation work can aid lightning forecasting and preparedness by opening new doors for voltage based prediction methods at ground. It is also a tool to understand phenomena such as fulgurites, corona effect etc. It also helps in the design of buried cables and improved grounding systems. This work can also be a first step towards understanding localised potential variations at the ground during lightning.

Effect of the local electric field on the formation of an ordered structure in porous anodic alumina

NASA Astrophysics Data System (ADS)

Lazarouk, S. K.; Katsuba, P. S.; Leshok, A. A.; Vysotskii, V. B.

2015-09-01

Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90-250 V is calculated. It is found that the electric field in the layers with a porosity of 1-10% in growing alumina reaches 109-1010 V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.

Pair aligning improved motility of Quincke rollers.

PubMed

Lu, Shi Qing; Zhang, Bing Yue; Zhang, Zhi Chao; Shi, Yan; Zhang, Tian Hui

2018-06-06

Density-dependent speed is studied in a two-dimensional active colloid in which the colloidal particles are propelled by an external electric field via a Quincke rotation. Above the critcal electric field, dense dynamic clusters form spotaneously, in which the particles are highly aligned in velocity and move much faster than isolated units. Detailed observations on pair collision reveal that the alignment of velocity is induced by the long-ranged hydrodynamic interactions and the improvement of speed in the clusters arises from pair aligning in which two particles are closely paired and rotate synchronically. In the aligning state, the short-range in-plane dipole-dipole attraction enhances the rotation torque and gives rises to a larger rolling speed. The pair aligning becomes difficult and unstable at high electric field where the normal dipole-dipole repulsion becomes dominant. As a consequence, the dependence of speed on density becomes weak increasingly upon the increase of the electric field. This result offers an interpretation for the discrepancy between our and previous observations on Quincke rollers.

Fatigue response of a PZT multilayer actuator under high-field electric cycling with mechanical preload

NASA Astrophysics Data System (ADS)

Wang, Hong; Wereszczak, Andrew A.; Lin, Hua-Tay

2009-01-01

An electric fatigue test system was developed for evaluating the reliability of piezoelectric actuators with a mechanical loading capability. Fatigue responses of a lead zirconate titanate (PZT) multilayer actuator with a platethrough electrode configuration were studied under an electric field (1.7 times that of the coercive field of PZT material) and a concurrent mechanical preload (30.0 MPa). A total of 109 cycles was carried out. Variations in charge density and mechanical strain under the high electric field and constant mechanical loads were observed during the fatigue test. The dc and the first harmonic (at 10 Hz) dielectric and piezoelectric coefficients were subsequently characterized using fast Fourier transformation. Both the dielectric and the piezoelectric coefficients exhibited a monotonic decrease prior to 2.86×108 cycles under certain preloading conditions, and then fluctuated. Both the dielectric loss tangent and the piezoelectric loss tangent also fluctuated after a decrease. The results are interpreted and discussed with respect to domain wall activities, microdefects, and other anomalies.

Evaluation of the effects of electric fields on implanted cardiac pacemakers. Final report

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

Moss, A.J.; Carstensen, E.

1985-02-01

The effects of extra high voltage (EHV) transmission line electric fields on pacemaker function were evaluated in 11 patients with seven different implanted pacemaker models from four manufacturers. Alteration in pacemaker function was demonstrated in five unipolar units (three different models) from two manufacturers during exposure to electric fields ranging from 2 to 9 kV/m, with total body currents from 47 to 175 ..mu..A. These electric fields and body currents are representative of values that can be encountered by individuals standing beneath EHV transmission lines. Transient alterations in pacemaker function observed in this study included inappropriate triggered activity, inhibition ofmore » impulse generation, reduction in rate, and reversion from demand to asynchronous mode. Electromagnetic interference from high voltage transmission lines can induce alterations in pacemaker function in certain designs of these devices. However, pacemaker manufacturers can incorporate appropriate circuits in the pacemaker design to eliminate this problem. 8 references.« less

High resistance to sulfur poisoning of Ni with copper skin under electric field

NASA Astrophysics Data System (ADS)

Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

2017-02-01

The effects of sulfur poisoning on the (1 0 0), (1 1 0) and (1 1 1) surfaces of pure Ni and Cu/Ni alloy are studied in consideration of the effect of electric field. The effects of Cu dopants on the S poisoning characteristics are analyzed by the means of the density functional theory results in combination with thermodynamics data using the ab initio atomistic thermodynamic method. When the Cu concentration increases to 50% on the surface layer of the Cu/Ni alloy, the (1 1 0) surface becomes the most vulnerable to the sulfur poisoning. Ni with a copper skin can mostly decrease the sulfur poisoning effect. Especially under the electric field of 1.0 V/Å, the sulfur adsorption and phase transition temperature can be further reduced. We therefore propose that Ni surfaces with copper skin can be very effective to improve the resistance to sulfur poisoning of the Ni anode under high electric field.

Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles

PubMed Central

Walid Rezanoor, Md.; Dutta, Prashanta

2016-01-01

Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion. PMID:27014394

Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles.

PubMed

Walid Rezanoor, Md; Dutta, Prashanta

2016-03-01

Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion.

Numerical simulation of electromagnetic fields and impedance of CERN LINAC4 H(-) source taking into account the effect of the plasma.

PubMed

Grudiev, A; Lettry, J; Mattei, S; Paoluzzi, M; Scrivens, R

2014-02-01

Numerical simulation of the CERN LINAC4 H(-) source 2 MHz RF system has been performed taking into account a realistic geometry from 3D Computer Aided Design model using commercial FEM high frequency simulation code. The effect of the plasma has been added to the model by the approximation of a homogenous electrically conducting medium. Electric and magnetic fields, RF power losses, and impedance of the circuit have been calculated for different values of the plasma conductivity. Three different regimes have been found depending on the plasma conductivity: (1) Zero or low plasma conductivity results in RF electric field induced by the RF antenna being mainly capacitive and has axial direction; (2) Intermediate conductivity results in the expulsion of capacitive electric field from plasma and the RF power coupling, which is increasing linearly with the plasma conductivity, is mainly dominated by the inductive azimuthal electric field; (3) High conductivity results in the shielding of both the electric and magnetic fields from plasma due to the skin effect, which reduces RF power coupling to plasma. From these simulations and measurements of the RF power coupling on the CERN source, a value of the plasma conductivity has been derived. It agrees well with an analytical estimate calculated from the measured plasma parameters. In addition, the simulated and measured impedances with and without plasma show very good agreement as well demonstrating validity of the plasma model used in the RF simulations.

Generation of high-density biskyrmions by electric current

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

Peng, Licong; Zhang, Ying; He, Min

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Generation of high-density biskyrmions by electric current

DOE PAGES

Peng, Licong; Zhang, Ying; He, Min; ...

2017-06-16

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Electrical control of the anomalous valley Hall effect in antiferrovalley bilayers

NASA Astrophysics Data System (ADS)

Tong, Wen-Yi; Duan, Chun-Gang

2017-08-01

In analogy to all-electric spintronics, all-electric valleytronics, i.e., valley manipulation via electric means, becomes an exciting new frontier as it may bring revolutions in the field of data storage with ultra-high speed and ultra-low power consumption. The existence of the anomalous valley Hall effect in ferrovalley materials demonstrates the possibility of electrical detection for valley polarization. However, in previously proposed valley-polarized monolayers, the anomalous valley Hall effect is controlled by external magnetic fields. Here, through elaborate structural design, we propose the antiferrovally bilayer as an ideal candidate for realizing all-electric valleytronic devices. Using the minimal k.p model, we show that the energy degeneracy between valley indexes in such system can be lifted by electric approaches. Subsequently, the anomalous valley Hall effect strongly depends on the electric field as well. Taking the bilayer VSe2 as an example, all-electric tuning and detecting of anomalous valley Hall effect is confirmed by density-functional theory calculations, indicating that the valley information in such antiferrovalley bilayer can be reversed by an electric field perpendicular to the plane of the system and easily probed through the sign of the Hall voltage.

Microwave absorption in powders of small conducting particles for heating applications.

PubMed

Porch, Adrian; Slocombe, Daniel; Edwards, Peter P

2013-02-28

In microwave chemistry there is a common misconception that small, highly conducting particles heat profusely when placed in a large microwave electric field. However, this is not the case; with the simple physical explanation that the electric field (which drives the heating) within a highly conducting particle is highly screened. Instead, it is the magnetic absorption associated with induction that accounts for the large experimental heating rates observed for small metal particles. We present simple principles for the effective heating of particles in microwave fields from calculations of electric and magnetic dipole absorptions for a range of practical values of particle size and conductivity. For highly conducting particles, magnetic absorption dominates electric absorption over a wide range of particle radii, with an optimum absorption set by the ratio of mean particle radius a to the skin depth δ (specifically, by the condition a = 2.41δ). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately σ ≈ 3ωε(0) ≈ 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples.

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.

Experimental and theoretical investigation of temperature-dependent electrical fatigue studies on 1-3 type piezocomposites

NASA Astrophysics Data System (ADS)

Mohan, Y.; Arockiarajan, A.

2016-03-01

1-3 type piezocomposites are very attractive materials for transducers and biomedical application, due to its high electromechanical coupling effects. Reliability study on 1-3 piezocomposites subjected to cyclic loading condition in transducer application is one of the primary concern. Hence, this study focuses on 1-3 piezocomposites for various PZT5A1 fiber volume fraction subjected to electrical fatigue loading up-to 106 cycles and at various elevated temperature. Initially experiments are performed on 1-3 piezocomposites, in order to understand the degradation phenomena due to various range in amplitude of electric fields (unipolar & bipolar), frequency of applied electric field and for various ambient temperature. Performing experiments for high cycle fatigue and for different fiber volume fraction of PZT5A1 is a time consuming process. Hence, a simplified macroscopic uni-axial model based on physical mechanisms of domain switching and continuum damage mechanics has been developed to predict the non-linear fatigue behaviour of 1-3 piezocomposites for temperature dependent electrical fatigue loading conditions. In this model, damage effects namely domain pinning, frozen domains and micro cracks, are considered as a damage variable (ω). Remnant variables and material properties are considered as a function of internal damage variable and the growth of the damage is derived empirically based on the experimental observation to predict the macroscopic changes in the properties. The measured material properties and dielectric hysteresis (electric displacement vs. electric field) as well as butterfly curves (longitudinal strain vs. electric field) are compared with the simulated results. It is observed that variation in amplitude of bipolar electric field and temperature has a strong influence on the response of 1-3 piezocomposites.

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.

Inferring electric fields and currents from ground magnetometer data - A test with theoretically derived inputs

NASA Technical Reports Server (NTRS)

Wolf, R. A.; Kamide, Y.

1983-01-01

Advanced techniques considered by Kamide et al. (1981) seem to have the potential for providing observation-based high time resolution pictures of the global ionospheric current and electric field patterns for interesting events. However, a reliance on the proposed magnetogram-inversion schemes for the deduction of global ionospheric current and electric field patterns requires proof that reliable results are obtained. 'Theoretical' tests of the accuracy of the magnetogram inversion schemes have, therefore, been considered. The present investigation is concerned with a test, involving the developed KRM algorithm and the Rice Convection Model (RCM). The test was successful in the sense that there was overall agreement between electric fields and currents calculated by the RCM and KRM schemes.

Finite element method (FEM) model of the mechanical stress on phospholipid membranes from shock waves produced in nanosecond electric pulses (nsEP)

NASA Astrophysics Data System (ADS)

Barnes, Ronald; Roth, Caleb C.; Shadaram, Mehdi; Beier, Hope; Ibey, Bennett L.

2015-03-01

The underlying mechanism(s) responsible for nanoporation of phospholipid membranes by nanosecond pulsed electric fields (nsEP) remains unknown. The passage of a high electric field through a conductive medium creates two primary contributing factors that may induce poration: the electric field interaction at the membrane and the shockwave produced from electrostriction of a polar submersion medium exposed to an electric field. Previous work has focused on the electric field interaction at the cell membrane, through such models as the transport lattice method. Our objective is to model the shock wave cell membrane interaction induced from the density perturbation formed at the rising edge of a high voltage pulse in a polar liquid resulting in a shock wave propagating away from the electrode toward the cell membrane. Utilizing previous data from cell membrane mechanical parameters, and nsEP generated shockwave parameters, an acoustic shock wave model based on the Helmholtz equation for sound pressure was developed and coupled to a cell membrane model with finite-element modeling in COMSOL. The acoustic structure interaction model was developed to illustrate the harmonic membrane displacements and stresses resulting from shockwave and membrane interaction based on Hooke's law. Poration is predicted by utilizing membrane mechanical breakdown parameters including cortical stress limits and hydrostatic pressure gradients.

Nano-electro-mechanical pump: Giant pumping of water in carbon nanotubes

PubMed Central

Farimani, Amir Barati; Heiranian, Mohammad; Aluru, Narayana R.

2016-01-01

A fully controllable nano-electro-mechanical device that can pump fluids at nanoscale is proposed. Using molecular dynamics simulations, we show that an applied electric field to an ion@C60 inside a water-filled carbon nanotube can pump water with excellent efficiency. The key physical mechanism governing the fluid pumping is the conversion of electrical energy into hydrodynamic flow with efficiencies as high as 64%. Our results show that water can be compressed up to 7% higher than its bulk value by applying electric fields. High flux of water (up to 13,000 molecules/ns) is obtained by the electro-mechanical, piston-cylinder-like moving mechanism of the ion@C60 in the CNT. This large flux results from the piston-like mechanism, compressibility of water (increase in density of water due to molecular ordering), orienting dipole along the electric field and efficient electrical to mechanical energy conversion. Our findings can pave the way towards efficient energy conversion, pumping of fluids at nanoscale, and drug delivery. PMID:27193507

Nano-electro-mechanical pump: Giant pumping of water in carbon nanotubes

NASA Astrophysics Data System (ADS)

Farimani, Amir Barati; Heiranian, Mohammad; Aluru, Narayana R.

2016-05-01

A fully controllable nano-electro-mechanical device that can pump fluids at nanoscale is proposed. Using molecular dynamics simulations, we show that an applied electric field to an ion@C60 inside a water-filled carbon nanotube can pump water with excellent efficiency. The key physical mechanism governing the fluid pumping is the conversion of electrical energy into hydrodynamic flow with efficiencies as high as 64%. Our results show that water can be compressed up to 7% higher than its bulk value by applying electric fields. High flux of water (up to 13,000 molecules/ns) is obtained by the electro-mechanical, piston-cylinder-like moving mechanism of the ion@C60 in the CNT. This large flux results from the piston-like mechanism, compressibility of water (increase in density of water due to molecular ordering), orienting dipole along the electric field and efficient electrical to mechanical energy conversion. Our findings can pave the way towards efficient energy conversion, pumping of fluids at nanoscale, and drug delivery.

Nano-electro-mechanical pump: Giant pumping of water in carbon nanotubes.

PubMed

Farimani, Amir Barati; Heiranian, Mohammad; Aluru, Narayana R

2016-05-19

A fully controllable nano-electro-mechanical device that can pump fluids at nanoscale is proposed. Using molecular dynamics simulations, we show that an applied electric field to an ion@C60 inside a water-filled carbon nanotube can pump water with excellent efficiency. The key physical mechanism governing the fluid pumping is the conversion of electrical energy into hydrodynamic flow with efficiencies as high as 64%. Our results show that water can be compressed up to 7% higher than its bulk value by applying electric fields. High flux of water (up to 13,000 molecules/ns) is obtained by the electro-mechanical, piston-cylinder-like moving mechanism of the ion@C60 in the CNT. This large flux results from the piston-like mechanism, compressibility of water (increase in density of water due to molecular ordering), orienting dipole along the electric field and efficient electrical to mechanical energy conversion. Our findings can pave the way towards efficient energy conversion, pumping of fluids at nanoscale, and drug delivery.

Solar-terrestrial coupling through atmospheric electricity

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

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.

Speed, Acceleration, and Velocity: Level II, Unit 9, Lesson 1; Force, Mass, and Distance: Lesson 2; Types of Motion and Rest: Lesson 3; Electricity and Magnetism: Lesson 4; Electrical, Magnetic, and Gravitational Fields: Lesson 5; The Conservation and Conversion of Matter and Energy: Lesson 6; Simple Machines and Work: Lesson 7; Gas Laws: Lesson 8; Principles of Heat Engines: Lesson 9; Sound and Sound Waves: Lesson 10; Light Waves and Particles: Lesson 11; Program. A High.....

ERIC Educational Resources Information Center

Manpower Administration (DOL), Washington, DC. Job Corps.

This self-study program for high-school level contains lessons on: Speed, Acceleration, and Velocity; Force, Mass, and Distance; Types of Motion and Rest; Electricity and Magnetism; Electrical, Magnetic, and Gravitational Fields; The Conservation and Conversion of Matter and Energy; Simple Machines and Work; Gas Laws; Principles of Heat Engines;…

A high-order relativistic two-fluid electrodynamic scheme with consistent reconstruction of electromagnetic fields and a multidimensional Riemann solver for electromagnetism

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

Balsara, Dinshaw S., E-mail: dbalsara@nd.edu; Amano, Takanobu, E-mail: amano@eps.s.u-tokyo.ac.jp; Garain, Sudip, E-mail: sgarain@nd.edu

In various astrophysics settings it is common to have a two-fluid relativistic plasma that interacts with the electromagnetic field. While it is common to ignore the displacement current in the ideal, classical magnetohydrodynamic limit, when the flows become relativistic this approximation is less than absolutely well-justified. In such a situation, it is more natural to consider a positively charged fluid made up of positrons or protons interacting with a negatively charged fluid made up of electrons. The two fluids interact collectively with the full set of Maxwell's equations. As a result, a solution strategy for that coupled system of equationsmore » is sought and found here. Our strategy extends to higher orders, providing increasing accuracy. The primary variables in the Maxwell solver are taken to be the facially-collocated components of the electric and magnetic fields. Consistent with such a collocation, three important innovations are reported here. The first two pertain to the Maxwell solver. In our first innovation, the magnetic field within each zone is reconstructed in a divergence-free fashion while the electric field within each zone is reconstructed in a form that is consistent with Gauss' law. In our second innovation, a multidimensionally upwinded strategy is presented which ensures that the magnetic field can be updated via a discrete interpretation of Faraday's law and the electric field can be updated via a discrete interpretation of the generalized Ampere's law. This multidimensional upwinding is achieved via a multidimensional Riemann solver. The multidimensional Riemann solver automatically provides edge-centered electric field components for the Stokes law-based update of the magnetic field. It also provides edge-centered magnetic field components for the Stokes law-based update of the electric field. The update strategy ensures that the electric field is always consistent with Gauss' law and the magnetic field is always divergence-free. This collocation also ensures that electromagnetic radiation that is propagating in a vacuum has both electric and magnetic fields that are exactly divergence-free. Coupled relativistic fluid dynamic equations are solved for the positively and negatively charged fluids. The fluids' numerical fluxes also provide a self-consistent current density for the update of the electric field. Our reconstruction strategy ensures that fluid velocities always remain sub-luminal. Our third innovation consists of an efficient design for several popular IMEX schemes so that they provide strong coupling between the finite-volume-based fluid solver and the electromagnetic fields at high order. This innovation makes it possible to efficiently utilize high order IMEX time update methods for stiff source terms in the update of high order finite-volume methods for hyperbolic conservation laws. We also show that this very general innovation should extend seamlessly to Runge–Kutta discontinuous Galerkin methods. The IMEX schemes enable us to use large CFL numbers even in the presence of stiff source terms. Several accuracy analyses are presented showing that our method meets its design accuracy in the MHD limit as well as in the limit of electromagnetic wave propagation. Several stringent test problems are also presented. We also present a relativistic version of the GEM problem, which shows that our algorithm can successfully adapt to challenging problems in high energy astrophysics.« less

A high-order relativistic two-fluid electrodynamic scheme with consistent reconstruction of electromagnetic fields and a multidimensional Riemann solver for electromagnetism

NASA Astrophysics Data System (ADS)

Balsara, Dinshaw S.; Amano, Takanobu; Garain, Sudip; Kim, Jinho

2016-08-01

In various astrophysics settings it is common to have a two-fluid relativistic plasma that interacts with the electromagnetic field. While it is common to ignore the displacement current in the ideal, classical magnetohydrodynamic limit, when the flows become relativistic this approximation is less than absolutely well-justified. In such a situation, it is more natural to consider a positively charged fluid made up of positrons or protons interacting with a negatively charged fluid made up of electrons. The two fluids interact collectively with the full set of Maxwell's equations. As a result, a solution strategy for that coupled system of equations is sought and found here. Our strategy extends to higher orders, providing increasing accuracy. The primary variables in the Maxwell solver are taken to be the facially-collocated components of the electric and magnetic fields. Consistent with such a collocation, three important innovations are reported here. The first two pertain to the Maxwell solver. In our first innovation, the magnetic field within each zone is reconstructed in a divergence-free fashion while the electric field within each zone is reconstructed in a form that is consistent with Gauss' law. In our second innovation, a multidimensionally upwinded strategy is presented which ensures that the magnetic field can be updated via a discrete interpretation of Faraday's law and the electric field can be updated via a discrete interpretation of the generalized Ampere's law. This multidimensional upwinding is achieved via a multidimensional Riemann solver. The multidimensional Riemann solver automatically provides edge-centered electric field components for the Stokes law-based update of the magnetic field. It also provides edge-centered magnetic field components for the Stokes law-based update of the electric field. The update strategy ensures that the electric field is always consistent with Gauss' law and the magnetic field is always divergence-free. This collocation also ensures that electromagnetic radiation that is propagating in a vacuum has both electric and magnetic fields that are exactly divergence-free. Coupled relativistic fluid dynamic equations are solved for the positively and negatively charged fluids. The fluids' numerical fluxes also provide a self-consistent current density for the update of the electric field. Our reconstruction strategy ensures that fluid velocities always remain sub-luminal. Our third innovation consists of an efficient design for several popular IMEX schemes so that they provide strong coupling between the finite-volume-based fluid solver and the electromagnetic fields at high order. This innovation makes it possible to efficiently utilize high order IMEX time update methods for stiff source terms in the update of high order finite-volume methods for hyperbolic conservation laws. We also show that this very general innovation should extend seamlessly to Runge-Kutta discontinuous Galerkin methods. The IMEX schemes enable us to use large CFL numbers even in the presence of stiff source terms. Several accuracy analyses are presented showing that our method meets its design accuracy in the MHD limit as well as in the limit of electromagnetic wave propagation. Several stringent test problems are also presented. We also present a relativistic version of the GEM problem, which shows that our algorithm can successfully adapt to challenging problems in high energy astrophysics.

Micro-resonator-based electric field sensors with long durations of sensitivity

NASA Astrophysics Data System (ADS)

Ali, Amir R.

2017-05-01

In this paper, we present a new fabrication method for the whispering gallery mode (WGM) micro-sphere based electric field sensor that which allows for longer time periods of sensitivity. Recently, a WGM-based photonic electric field sensor was proposed using a coupled dielectric microsphere-beam. The external electric field imposes an electrtrostriction force on the dielectric beam, deflecting it. The beam, in turn compresses the sphere causing a shift in its WGM. As part of the fabrication process, the PDMS micro-beams and the spheres are curied at high-temperature (100oC) and subsequently poled by exposing to strong external electric field ( 8 MV/m) for two hours. The poling process allows for the deposition of surface charges thereby increasing the electrostriction effect. This methodology is called curing-then-poling (CTP). Although the sensors do become sufficiently sensitive to electric field, they start de-poling after a short period (within 10 minutes) after poling, hence losing sensitivity. In an attempt to mitigate this problem and to lock the polarization for a longer period, we use an alternate methodology whereby the beam is poled and cured simultaneously (curing-while-poling or CWP). The new fabrication method allows for the retention of polarization (and hence, sensitivity to electric field) longer ( 1500 minutes). An analysis is carried out along with preliminary experiments. Results show that electric fields as small as 100 V/m can be detected with a 300 μm diameter sphere sensor a day after poling.

Effect of partially ionized impurities and radiation on the effective critical electric field for runaway generation

NASA Astrophysics Data System (ADS)

Hesslow, L.; Embréus, O.; Wilkie, G. J.; Papp, G.; Fülöp, T.

2018-07-01

We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the classical Connor–Hastie field, and even exceeds the value obtained by replacing the free electron density by the total electron density (including both free and bound electrons). Using a kinetic equation solver with an inductive electric field, we show that the runaway current decay after an impurity injection is expected to be linear in time and proportional to the effective critical electric field in highly inductive tokamak devices. This is relevant for the efficacy of mitigation strategies for runaway electrons since it reduces the required amount of injected impurities to achieve a certain current decay rate.

Sound diffraction at wall impedance discontinuities in a circular cylinder - Investigated using Wiener-Hopf technique

NASA Technical Reports Server (NTRS)

Cho, Y.-C.

1983-01-01

The results of ground observations as well as high resolution rocket electric field and particle observations during a breakup event of an intense magnetospheric substorm over northern Scandinavia are discussed. In particular, the characteristics of the substorm-associated electric field, ionospheric currents, and power dissipation during a time period about 15 minutes after substorm onset are addressed. A comparison of the observations with those of a pre-breakup event earlier in the day (Marklund et al., 1982) showed that the ionospheric substorm-related electric field could be split up into two parts: (1) an ambient LT-dependent field, probably of magnetospheric origin; and (2) a small-scale electric field associated with the bright auroral structures, which is superimposed on the LT-dependent field. The consequences for the location of the ionospheric currents and the Joule energy dissipation relative to the auroral forms are discussed. Previously announced in STAR as N83-23117

Images of Bottomside Irregularities Observed at Topside Altitudes (Postprint)

DTIC Science & Technology

2012-04-04

pairs of 20 m tip-to-tip double probes and a fluxgate magnetometer on a 0.6 m boom [Pfaff et al., 2010]. Vector electric fields are obtained with 16-bit... magnetometer out- puts. AC electric fields are measured by passing VEFI data streams though low (0–6 Hz) and high-pass (3–8,000 Hz) filters. AC magnetic field

Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water.

PubMed

Underwood, H R; Peterson, A F; Magin, R L

1992-02-01

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

Towards more Global Coordination of Atmospheric Electricity Measurements (GloCAEM)

NASA Astrophysics Data System (ADS)

Nicoll, Keri; Harrison, Giles

2017-04-01

Earth's atmospheric electrical environment has been studied since the 1750s but its more recent applications to science questions around clouds and climate highlight the incompleteness of our understanding, in part due to lack of suitable global measurements. The Global Electric Circuit (GEC) sustains the near-surface fair weather (FW) electric field, which is present globally in regions which are not strongly electrically disturbed by weather or pollution. It can be measured routinely at the surface using well established instrumentation such as electric field mills. Despite the central role of lightning as a weather hazard and the potentially widespread importance of charge for atmospheric processes, research is hampered by the fragmented nature of surface atmospheric electricity measurements. This makes anything other than local studies in fortuitous fair weather conditions difficult. In contrast to detection of global lightning using satellite measurements and ground-based radio networks, the FW electric field and GEC cannot be measured by remote sensing and no similar measurement networks exist for its study. This presents an opportunity as many researchers worldwide now make high temporal resolution measurements of the FW electric field routinely, which is neither coordinated nor exploited. The GLOCAEM (Global Coordination of Atmospheric Electricity Measurements) project is currently bringing some of these experts together to make the first steps towards an effective global network for FW atmospheric electricity monitoring. A specific objective of the project is to establish the first modern archive of international FW atmospheric electric field data in close to real time to allow global studies of atmospheric electricity to be straightforwardly and robustly performed. Data will be archived through the UK Centre for Environmental Data Analysis (CEDA) and will be available for download by users from early 2018. Both 1 second and 1 minute electric field data will be archived, along with meteorological measurements (if available) for ease of interpretation of electrical measurements. Although the primary aim of the project is to provide a close to real time electric field database, archiving of existing historical electric field datasets is also planned to extend the range of studies possible. This presentation will provide a summary of progress with the GLOCAEM project.

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.

Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects

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

VanGordon, James A.; Kovaleski, Scott D., E-mail: kovaleskis@missouri.edu; Norgard, Peter

The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-opticmore » effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model for a wider range of electrical load impedances under test.« less

Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects.

PubMed

VanGordon, James A; Kovaleski, Scott D; Norgard, Peter; Gall, Brady B; Dale, Gregory E

2014-02-01

The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model for a wider range of electrical load impedances under test.

Maxwell-Wagner relaxation in electrical imaging.

PubMed

Korjenevsky, A V

2005-04-01

The electric field tomography (EFT) method exploits interaction of high-frequency electric field with an inhomogeneous conductive medium without contact with the electrodes. The interaction is accompanied by a high-frequency redistribution of free charges inside the medium and leads to small and regular phase shifts of the field in the area surrounding an object. Such a kind of phenomenon is referred to as the Maxwell-Wagner relaxation. Measuring the perturbations of the field using the set of electrodes placed around the object enables us to reconstruct the internal structure of the medium, generally the spatial distribution of a nonlinear combination of permittivity and resistivity. In the case of biomedical applications the result of measurements is determined mainly by the resistivity of the tissues. Three-dimensional simulation based on the finite element method has demonstrated the feasibility of the technique.

Electric Field Measurements During the Genesis and Rapid Intensification Processes (GRIP) Field Program

NASA Technical Reports Server (NTRS)

Bateman, Monte G.; Blakeslee, Richard J.; Mach, Douglas M.

2010-01-01

During the Genesis and Rapid Intensification Processes (GRIP) field program, a system of 6 electric field mills was flown on one of NASA's Global Hawk aircraft. We placed several mills on the aircraft to enable us to measure the vector electric field. We created a distributed, ethernet-connected system so that each sensor has its own embedded Linux system, complete with web server. This makes our current generation system fully "sensor web enabled." The Global Hawk has several unique qualities, but relevant to quality storm electric field measurements are high altitude (20 km) and long duration (20-30 hours) flights. There are several aircraft participating in the GRIP program, and coordinated measurements are happening. Lightning and electric field measurements will be used to study the relationships between lightning and other storm characteristics. It has been long understood that lightning can be used as a marker for strong convective activity. Past research and field programs suggest that lightning flash rate may serve as an indicator and precursor for rapid intensification change in tropical cyclones and hurricanes. We have the opportunity to sample hurricanes for many hours at a time and observe intensification (or de-intensification) periods. The electrical properties of hurricanes during such periods are not well known. American

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.

Computational dosimetry of induced electric fields during realistic movements in the vicinity of a 3 T MRI scanner

NASA Astrophysics Data System (ADS)

Laakso, Ilkka; Kännälä, Sami; Jokela, Kari

2013-04-01

Medical staff working near magnetic resonance imaging (MRI) scanners are exposed both to the static magnetic field itself and also to electric currents that are induced in the body when the body moves in the magnetic field. However, there are currently limited data available on the induced electric field for realistic movements. This study computationally investigates the movement induced electric fields for realistic movements in the magnetic field of a 3 T MRI scanner. The path of movement near the MRI scanner is based on magnetic field measurements using a coil sensor attached to a human volunteer. Utilizing realistic models for both the motion of the head and the magnetic field of the MRI scanner, the induced fields are computationally determined using the finite-element method for five high-resolution numerical anatomical models. The results show that the time-derivative of the magnetic flux density (dB/dt) is approximately linearly proportional to the induced electric field in the head, independent of the position of the head with respect to the magnet. This supports the use of dB/dt measurements for occupational exposure assessment. For the path of movement considered herein, the spatial maximum of the induced electric field is close to the basic restriction for the peripheral nervous system and exceeds the basic restriction for the central nervous system in the international guidelines. The 99th percentile electric field is a considerably less restrictive metric for the exposure than the spatial maximum electric field; the former is typically 60-70% lower than the latter. However, the 99th percentile electric field may exceed the basic restriction for dB/dt values that can be encountered during tasks commonly performed by MRI workers. It is also shown that the movement-induced eddy currents may reach magnitudes that could electrically stimulate the vestibular system, which could play a significant role in the generation of vertigo-like sensations reported by people moving in a strong static magnetic field.

Depoling and fatigue behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal at megahertz frequencies under bipolar electric field

NASA Astrophysics Data System (ADS)

Chen, Zhaojiang; Li, Shiyang; Zhang, Yang; Cao, Wenwu

2017-05-01

Bipolar electric field induced degradation in [001]c poled Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-0.29PT) single crystals was investigated at megahertz frequencies. The electromechanical coupling factor kt, dielectric constant ɛr, dielectric loss D, and piezoelectric constant d33 were measured as a function of amplitude, frequency, and number of cycles of the applied electric field. Our results showed that samples degrade rapidly when the field amplitude is larger than a critical value due to the onset of domain switching. We define this critical value as the effective coercive field Ec at high frequencies, which increases drastically with frequency. We also demonstrate an effective counter-depoling method by using a dc bias, which could help the design of high field driven devices based on PMN-PT single crystals and operated at megahertz frequencies.

Electric field tomography for contactless imaging of resistivity in biomedical applications.

PubMed

Korjenevsky, A V

2004-02-01

The technique of contactless imaging of resistivity distribution inside conductive objects, which can be applied in medical diagnostics, has been suggested and analyzed. The method exploits the interaction of a high-frequency electric field with a conductive medium. Unlike electrical impedance tomography, no electric current is injected into the medium from outside. The interaction is accompanied with excitation of high-frequency currents and redistribution of free charges inside the medium leading to strong and irregular perturbation of the field's magnitude outside and inside the object. Along with this the considered interaction also leads to small and regular phase shifts of the field in the area surrounding the object. Measuring these phase shifts using a set of electrodes placed around the object enables us to reconstruct the internal structure of the medium. The basics of this technique, which we name electric field tomography (EFT), are described, simple analytical estimations are made and requirements for measuring equipment are formulated. The realizability of the technique is verified by numerical simulations based on the finite elements method. Results of simulation have confirmed initial estimations and show that in the case of EFT even a comparatively simple filtered backprojection algorithm can be used for reconstructing the static resistivity distribution in biological tissues.

Exploration to generate atmospheric pressure glow discharge plasma in air

NASA Astrophysics Data System (ADS)

Wenzheng, LIU; Chuanlong, MA; Shuai, ZHAO; Xiaozhong, CHEN; Tahan, WANG; Luxiang, ZHAO; Zhiyi, LI; Jiangqi, NIU; Liying, ZHU; Maolin, CHAI

2018-03-01

Atmospheric pressure glow discharge (APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge (DBD) in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in air-gap is suppressed effectively and a large space of APGD plasma in air is generated. Further, through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.

Electrical tweezer for highly parallelized electrorotation measurements over a wide frequency bandwidth.

PubMed

Rohani, Ali; Varhue, Walter; Su, Yi-Hsuan; Swami, Nathan S

2014-07-01

Electrorotation (ROT) is a powerful tool for characterizing the dielectric properties of cells and bioparticles. However, its application has been somewhat limited by the need to mitigate disruptions to particle rotation by translation under positive DEP and by frictional interactions with the substrate. While these disruptions may be overcome by implementing particle positioning schemes or field cages, these methods restrict the frequency bandwidth to the negative DEP range and permit only single particle measurements within a limited spatial extent of the device geometry away from field nonuniformities. Herein, we present an electrical tweezer methodology based on a sequence of electrical signals, composed of negative DEP using 180-degree phase-shifted fields for trapping and levitation of the particles, followed by 90-degree phase-shifted fields over a wide frequency bandwidth for highly parallelized electrorotation measurements. Through field simulations of the rotating electrical field under this wave-sequence, we illustrate the enhanced spatial extent for electrorotation measurements, with no limitations to frequency bandwidth. We apply this methodology to characterize subtle modifications in morphology and electrophysiology of Cryptosporidium parvum with varying degrees of heat treatment, in terms of shifts in the electrorotation spectra over the 0.05-40 MHz region. Given the single particle sensitivity and the ability for highly parallelized electrorotation measurements, we envision its application toward characterizing heterogeneous subpopulations of microbial and stem cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Alekseev, I. S.; Ivanov, I. E.; Strelkov, P. S., E-mail: strelkov@fpl.gpi.ru

A method based on the detection of emission of a dielectric screen with metal microinclusions in open air is applied to visualize the transverse structure of a high-power microwave beam. In contrast to other visualization techniques, the results obtained in this work provide qualitative information not only on the electric field strength, but also on the structure of electric field lines in the microwave beam cross section. The interpretation of the results obtained with this method is confirmed by numerical simulations of the structure of electric field lines in the microwave beam cross section by means of the CARAT code.

Visualization of Electrical Field of Electrode Using Voltage-Controlled Fluorescence Release

PubMed Central

Jia, Wenyan; Wu, Jiamin; Gao, Di; Wang, Hao; Sun, Mingui

2016-01-01

In this study we propose an approach to directly visualize electrical current distribution at the electrode-electrolyte interface of a biopotential electrode. High-speed fluorescent microscopic images are acquired when an electric potential is applied across the interface to trigger the release of fluorescent material from the surface of the electrode. These images are analyzed computationally to obtain the distribution of the electric field from the fluorescent intensity of each pixel. Our approach allows direct observation of microscopic electrical current distribution around the electrode. Experiments are conducted to validate the feasibility of the fluorescent imaging method. PMID:27253615

High-order harmonic generation driven by inhomogeneous plasmonics fields spatially bounded: influence on the cut-off law

NASA Astrophysics Data System (ADS)

Neyra, E.; Videla, F.; Ciappina, M. F.; Pérez-Hernández, J. A.; Roso, L.; Lewenstein, M.; Torchia, G. A.

2018-03-01

We study high-order harmonic generation (HHG) in model atoms driven by plasmonic-enhanced fields. These fields result from the illumination of plasmonic nanostructures by few-cycle laser pulses. We demonstrate that the spatial inhomogeneous character of the laser electric field, in a form of Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength. Precise description of the spatial form of the plasmonic-enhanced field allows us to predict this relationship. We combine the numerical solutions of the time-dependent Schrödinger equation (TDSE) with the plasmonic-enhanced electric fields obtained from 3D finite element simulations. We additionally employ classical simulations to supplement the TDSE outcomes and characterize the extended HHG spectra by means of their associated electron trajectories. A proper definition of the spatially inhomogeneous laser electric field is instrumental to accurately describe the underlying physics of HHG driven by plasmonic-enhanced fields. This characterization opens up new perspectives for HHG control with various experimental nano-setups.

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

Carbon nanotubes for voltage reduction and throughput enhancement of electrical cell lysis on a lab-on-a-chip.

PubMed

Shahini, Mehdi; Yeow, John T W

2011-08-12

We report on the enhancement of electrical cell lysis using carbon nanotubes (CNTs). Electrical cell lysis systems are widely utilized in microchips as they are well suited to integration into lab-on-a-chip devices. However, cell lysis based on electrical mechanisms has high voltage requirements. Here, we demonstrate that by incorporating CNTs into microfluidic electrolysis systems, the required voltage for lysis is reduced by half and the lysis throughput at low voltages is improved by ten times, compared to non-CNT microchips. In our experiment, E. coli cells are lysed while passing through an electric field in a microchannel. Based on the lightning rod effect, the electric field strengthened at the tip of the CNTs enhances cell lysis at lower voltage and higher throughput. This approach enables easy integration of cell lysis with other on-chip high-throughput sample-preparation processes.

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.

Ionization and current growth in N/sub 2/ at very high electric field to gas density ratios

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

Gylys, V.T.; Jelenkovic, B.M.; Phelps, A.V.

1989-05-01

Measurements and analyses have been made of electron impact ionization and of current growth in pulsed, low-current, prebreakdown discharges in parallel-plane geometry in N/sub 2/ at very high electric field to gas density ratios E/n and low products of the gas density n and electrode separation d. The E/n range and nd ranges were 1

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.

Effects of magnetic fields during high voltage live-line maintenance

NASA Astrophysics Data System (ADS)

Göcsei, Gábor; Kiss, István, Dr; Németh, Bálint

2015-10-01

In case of transmission and distribution networks, extra low frequency (typically 50 or 60 Hz) electric and magnetic fields have to be taken into consideration separately from each other. Health effects have been documented from exposures to both types of fields. Magnetic fields are qualified as possibly carcinogenic to humans (category “2B”) by WHO's cancer research institute, International Agency for Research on Cancer (IARC), so it is essential to protect the workers against their harmful effects. During live-line maintenance (LLM) electric fields can be shielded effectively by different kinds of conductive clothing, which are enclosed metal surfaces acting as a Faraday-cage. In practice laboratory measurements also prove their efficiency, the required shielding ratio is above 99% by the related standard.. A set of measurements have proved that regular conductive clothing used against the electric fields cannot shield the magnetic fields effectively at all. This paper introduces the possible risks of LLM from the aspect of the health effects of magnetic fields. Although in this case the principle of shielding the electric fields cannot be applied, new considerations in equipment design and technology can be used as a possible solution. Calculations and simulations based on the data of the Hungarian transmission network - which represents the European grid as a part of ENTSO-E - and high-current laboratory measurement results also prove the importance of the topic.

Apparatus for improving performance of electrical insulating structures

DOEpatents

Wilson, Michael J.; Goerz, David A.

2004-08-31

Removing the electrical field from the internal volume of high-voltage structures; e.g., bushings, connectors, capacitors, and cables. The electrical field is removed from inherently weak regions of the interconnect, such as between the center conductor and the solid dielectric, and places it in the primary insulation. This is accomplished by providing a conductive surface on the inside surface of the principal solid dielectric insulator surrounding the center conductor and connects the center conductor to this conductive surface. The advantage of removing the electric fields from the weaker dielectric region to a stronger area improves reliability, increases component life and operating levels, reduces noise and losses, and allows for a smaller compact design. This electric field control approach is currently possible on many existing products at a modest cost. Several techniques are available to provide the level of electric field control needed. Choosing the optimum technique depends on material, size, and surface accessibility. The simplest deposition method uses a standard electroless plating technique, but other metalization techniques include vapor and energetic deposition, plasma spraying, conductive painting, and other controlled coating methods.

Apparatus for improving performance of electrical insulating structures

DOEpatents

Wilson, Michael J.; Goerz, David A.

2002-01-01

Removing the electrical field from the internal volume of high-voltage structures; e.g., bushings, connectors, capacitors, and cables. The electrical field is removed from inherently weak regions of the interconnect, such as between the center conductor and the solid dielectric, and places it in the primary insulation. This is accomplished by providing a conductive surface on the inside surface of the principal solid dielectric insulator surrounding the center conductor and connects the center conductor to this conductive surface. The advantage of removing the electric fields from the weaker dielectric region to a stronger area improves reliability, increases component life and operating levels, reduces noise and losses, and allows for a smaller compact design. This electric field control approach is currently possible on many existing products at a modest cost. Several techniques are available to provide the level of electric field control needed. Choosing the optimum technique depends on material, size, and surface accessibility. The simplest deposition method uses a standard electroless plating technique, but other metalization techniques include vapor and energetic deposition, plasma spraying, conductive painting, and other controlled coating methods.

Frequency and Voltage Dependence of the Dielectrophoretic Trapping of Short Lengths of DNA and dCTP in a Nanopipette

PubMed Central

Ying, Liming; White, Samuel S.; Bruckbauer, Andreas; Meadows, Lisa; Korchev, Yuri E.; Klenerman, David

2004-01-01

The study of the properties of DNA under high electric fields is of both fundamental and practical interest. We have exploited the high electric fields produced locally in the tip of a nanopipette to probe the motion of double- and single-stranded 40-mer DNA, a 1-kb single-stranded DNA, and a single-nucleotide triphosphate (dCTP) just inside and outside the pipette tip at different frequencies and amplitudes of applied voltages. We used dual laser excitation and dual color detection to simultaneously follow two fluorophore-labeled DNA sequences with millisecond time resolution, significantly faster than studies to date. A strong trapping effect was observed during the negative half cycle for all DNA samples and also the dCTP. This effect was maximum below 1 Hz and decreased with higher frequency. We assign this trapping to strong dielectrophoresis due to the high electric field and electric field gradient in the pipette tip. Dielectrophoresis in electrodeless tapered nanostructures has potential applications for controlled mixing and manipulation of short lengths of DNA and other biomolecules, opening new possibilities in miniaturized biological analysis. PMID:14747337

Electric-Field-Induced Degradation of Methylammonium Lead Iodide Perovskite Solar Cells.

PubMed

Bae, Soohyun; Kim, Seongtak; Lee, Sang-Won; Cho, Kyung Jin; Park, Sungeun; Lee, Seunghun; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2016-08-18

Perovskite solar cells have great potential for high efficiency generation but are subject to the impact of external environmental conditions such as humidity, UV and sun light, temperature, and electric fields. The long-term stability of perovskite solar cells is an important issue for their commercialization. Various studies on the stability of perovskite solar cells are currently being performed; however, the stability related to electric fields is rarely discussed. Here the electrical stability of perovskite solar cells is studied. Ion migration is confirmed using the temperature-dependent dark current decay. Changes in the power conversion efficiency according to the amount of the external bias are measured in the dark, and a significant drop is observed only at an applied voltage greater than 0.8 V. We demonstrate that perovskite solar cells are stable under an electric field up to the operating voltage.

Direct measurement of the electric-field distribution in a light-emitting electrochemical cell

NASA Astrophysics Data System (ADS)

Slinker, Jason D.; Defranco, John A.; Jaquith, Michael J.; Silveira, William R.; Zhong, Yu-Wu; Moran-Mirabal, Jose M.; Craighead, Harold G.; Abruña, Héctor D.; Marohn, John A.; Malliaras, George G.

2007-11-01

The interplay between ionic and electronic charge carriers in mixed conductors offers rich physics and unique device potential. In light-emitting electrochemical cells (LEECs), for example, the redistribution of ions assists the injection of electronic carriers and leads to efficient light emission. The mechanism of operation of LEECs has been controversial, as there is no consensus regarding the distribution of electric field in these devices. Here, we probe the operation of LEECs using electric force microscopy on planar devices. We show that obtaining the appropriate boundary conditions is essential for capturing the underlying device physics. A patterning scheme that avoids overlap between the mixed-conductor layer and the metal electrodes enabled the accurate in situ measurement of the electric-field distribution. The results show that accumulation and depletion of mobile ions near the electrodes create high interfacial electric fields that enhance the injection of electronic carriers.

Electric field induced spin-polarized current

DOEpatents

Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

2006-05-02

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

Magnetic and Electric Field Testing of the Amtrak Northeast Corridor and New Jersey/North Jersey coast line rail systems. v. 2. Appendices.

DOT National Transportation Integrated Search

1993-04-01

The safety of magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is the responsibility of the Federal Railroad Administration (FRA). The characterization of electric and magnetic fields (EMF...

Magnetic and electric field testing of the AMTRAK Northeast Corridor and New Jersey/North Jersey coast line rail systems. Volume 1 : analysis

DOT National Transportation Integrated Search

1993-04-01

The safety of magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is the responsibility of the Federal Railroad Administration (FRA). The characterization of electric and magnetic fields (EMF...

Electric fields induced in the human body by time-varying magnetic field gradients in MRI: numerical calculations and correlation analysis.

PubMed

Bencsik, Martin; Bowtell, Richard; Bowley, Roger

2007-05-07

The spatial distributions of the electric fields induced in the human body by switched magnetic field gradients in MRI have been calculated numerically using the commercial software package, MAFIA, and the three-dimensional, HUGO body model that comprises 31 different tissue types. The variation of |J|, |E| and |B| resulting from exposure of the body model to magnetic fields generated by typical whole-body x-, y- and z-gradient coils has been analysed for three different body positions (head-, heart- and hips-centred). The magnetic field varied at 1 kHz, so as to produce a rate of change of gradient of 100 T m(-1) s(-1) at the centre of each coil. A highly heterogeneous pattern of induced electric field and current density was found to result from the smoothly varying magnetic field in all cases, with the largest induced electric fields resulting from application of the y-gradient, in agreement with previous studies. By applying simple statistical analysis to electromagnetic quantities within axial planes of the body model, it is shown that the induced electric field is strongly correlated to the local value of resistivity, and the induced current density exhibits even stronger correlation with the local conductivity. The local values of the switched magnetic field are however shown to bear little relation to the local values of the induced electric field or current density.

Cellular effects of acute exposure to high peak power microwave systems: Morphology and toxicology.

PubMed

Ibey, Bennett L; Roth, Caleb C; Ledwig, Patrick B; Payne, Jason A; Amato, Alayna L; Dalzell, Danielle R; Bernhard, Joshua A; Doroski, Michael W; Mylacraine, Kevin S; Seaman, Ronald L; Nelson, Gregory S; Woods, Clifford W

2016-03-15

Electric fields produced by advanced pulsed microwave transmitter technology now readily exceed the Institute of Electrical and Electronic Engineers (IEEE) C.95.1 peak E-field limit of 100 kV/m, highlighting a need for scientific validation of such a specific limit. Toward this goal, we exposed Jurkat Clone E-6 human lymphocyte preparations to 20 high peak power microwave (HPPM) pulses (120 ns duration) with a mean peak amplitude of 2.3 MV/m and standard deviation of 0.1 with the electric field at cells predicted to range from 0.46 to 2.7 MV/m, well in excess of current standard limit. We observed that membrane integrity and cell morphology remained unchanged 4 h after exposure and cell survival 24 h after exposure was not statistically different from sham exposure or control samples. Using flow cytometry to analyze membrane disruption and morphological changes per exposed cell, no changes were observed in HPPM-exposed samples. Current IEEE C95.1-2005 standards for pulsed radiofrequency exposure limits peak electric field to 100 kV/m for pulses shorter than 100 ms [IEEE (1995) PC95.1-Standard for Safety Levels with Respect to Human Exposure to Electric, Magnetic and Electromagnetic Fields, 0 Hz to 300 GHz, Institute of Electrical and Electronic Engineers: Piscataway, NJ, USA]. This may impose large exclusion zones that limit HPPM technology use. In this study, we offer evidence that maximum permissible exposure of 100 kV/m for peak electric field may be unnecessarily restrictive for HPPM devices. Bioelectromagnetics. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

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.

Space-charge-limited currents for cathodes with electric field enhanced geometry

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

Lai, Dingguo, E-mail: laidingguo@nint.ac.cn; Qiu, Mengtong; Xu, Qifu

This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that themore » space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.« less

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).

Effects of shock waves, ultraviolet light, and electric fields from pulsed discharges in water on inactivation of Escherichia coli.

PubMed

Sun, Bing; Xin, Yanbin; Zhu, Xiaomei; Gao, Zhiying; Yan, Zhiyu; Ohshima, Takayuki

2018-04-01

In this work, the bacterial inactivation effects of shock waves, ultraviolet (UV) light, and electric field produced by high-voltage pulsed discharge in liquid with needle-plate configurations were studied. The contributions of each effect on the bacterial killing ratio in the discharge process were obtained individually by modifying reactor type and usage of glass, quartz, and black balloons. The results showed that the location from the discharge center axis significantly influenced the effects of shock waves and electric fields, although the effect of UV light was not affected by the location in the reactor. The effects of shock waves and electric fields were improved by decreasing the distance from the discharge center axis. Under this experimental condition, the effects of shock waves, UV light, and electric fields produced by discharges on bacterial inactivation were approximately 36.1%, 30.8%, 12.7%, respectively. Other contributions seemed to be due to activated species. Copyright © 2017 Elsevier B.V. All rights reserved.

Note: Versatile sample stick for neutron scattering experiments in high electric fields

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

Bartkowiak, M., E-mail: marek.bartkowiak@psi.ch; White, J. S.; Laboratory for Quantum Magnetism, Ecole Polytechnique Fédérale de Lausanne

2014-02-15

We present a versatile high voltage sample stick that fits into all cryomagnets and standard cryostats at the Swiss Spallation Neutron Source, Paul Scherrer Institut, and which provides a low effort route to neutron scattering experiments that combine electric field with low temperature and magnetic field. The stick allows for voltages up to 5 kV and can be easily adapted for different scattering geometries. We discuss the design consideration and thermal behavior of the stick, and give one example to showcase the abilities of the device.

Transparent electrodes for high E-field production using a buried indium tin oxide layer

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

Gunton, Will; Polovy, Gene; Semczuk, Mariusz

2016-03-15

We present a design and characterization of optically transparent electrodes suitable for atomic and molecular physics experiments where high optical access is required. The electrodes can be operated in air at standard atmospheric pressure and do not suffer electrical breakdown even for electric fields far exceeding the dielectric breakdown of air. This is achieved by putting an indium tin oxide coated dielectric substrate inside a stack of dielectric substrates, which prevents ion avalanche resulting from Townsend discharge. With this design, we observe no arcing for fields of up to 120 kV/cm. Using these plates, we directly verify the production ofmore » electric fields up to 18 kV/cm inside a quartz vacuum cell by a spectroscopic measurement of the dc Stark shift of the 5{sup 2}S{sub 1/2} → 5{sup 2}P{sub 3/2} transition for a cloud of laser cooled rubidium atoms. We also report on the shielding of the electric field and on the residual electric fields that persist within the vacuum cell once the electrodes are discharged. In addition, we discuss observed atom loss that results from the motion of free charges within the vacuum. The observed asymmetry of these phenomena on the bias of the electrodes suggests that field emission of electrons within the vacuum is primarily responsible for these effects and may indicate a way of mitigating them.« less

Dependence of B1+ and B1- Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency.

PubMed

Vaidya, Manushka V; Collins, Christopher M; Sodickson, Daniel K; Brown, Ryan; Wiggins, Graham C; Lattanzi, Riccardo

2016-02-01

In high field MRI, the spatial distribution of the radiofrequency magnetic ( B 1 ) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green's functions, or experimentally measured over a range of frequencies inside an object whose electrical properties were varied to illustrate a variety of transmit [Formula: see text] and receive [Formula: see text] field patterns. In this work, we examine how changes in polarization of the field and interference of propagating waves in an object can affect the B 1 spatial distribution. Results are explained conceptually using Maxwell's equations and intuitive illustrations. We demonstrate that the electrical conductivity alters the spatial distribution of distinct polarized components of the field, causing "twisted" transmit and receive field patterns, and asymmetries between [Formula: see text] and [Formula: see text]. Additionally, interference patterns due to wavelength effects are observed at high field in samples with high relative permittivity and near-zero conductivity, but are not present in lossy samples due to the attenuation of propagating EM fields. This work provides a conceptual framework for understanding B 1 spatial distributions for surface coils and can provide guidance for RF engineers.

Ab initio molecular dynamics in a finite homogeneous electric field.

PubMed

Umari, P; Pasquarello, Alfredo

2002-10-07

We treat homogeneous electric fields within density functional calculations with periodic boundary conditions. A nonlocal energy functional depending on the applied field is used within an ab initio molecular dynamics scheme. The reliability of the method is demonstrated in the case of bulk MgO for the Born effective charges, and the high- and low-frequency dielectric constants. We evaluate the static dielectric constant by performing a damped molecular dynamics in an electric field and avoiding the calculation of the dynamical matrix. Application of this method to vitreous silica shows good agreement with experiment and illustrates its potential for systems of large size.

High-injection effects in near-field thermophotovoltaic devices.

PubMed

Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe

2017-11-20

In near-field thermophotovoltaics, a substantial enhancement of the electrical power output is expected as a result of the larger photogeneration of electron-hole pairs due to the tunneling of evanescent modes from the thermal radiator to the photovoltaic cell. The common low-injection approximation, which considers that the local carrier density due to photogeneration is moderate in comparison to that due to doping, needs therefore to be assessed. By solving the full drift-diffusion equations, the existence of high-injection effects is studied in the case of a GaSb p-on-n junction cell and a radiator supporting surface polaritons. Depending on doping densities and surface recombination velocity, results reveal that high-injection phenomena can already take place in the far field and become very significant in the near field. Impacts of high injection on maximum electrical power, short-circuit current, open-circuit voltage, recombination rates, and variations of the difference between quasi-Fermi levels are analyzed in detail. By showing that an optimum acceptor doping density can be estimated, this work suggests that a detailed and accurate modeling of the electrical transport is also key for the design of near-field thermophotovoltaic devices.

Role of IMF B y in the prompt electric field disturbances over equatorial ionosphere during a space weather event

DOE PAGES

Chakrabarty, Dipu; Hui, Debrup; Rout, Diptiranjan; ...

2017-02-04

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) B z condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarcamore » intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF B z remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF B y component under southward IMF B z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Therefore, in conclusion, the present investigation shows that the variations in IMF B y are fundamentally important to understand the prompt penetration effects over low latitudes.« less

Role of IMF B y in the prompt electric field disturbances over equatorial ionosphere during a space weather event

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

Chakrabarty, Dipu; Hui, Debrup; Rout, Diptiranjan

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) B z condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarcamore » intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF B z remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF B y component under southward IMF B z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Therefore, in conclusion, the present investigation shows that the variations in IMF B y are fundamentally important to understand the prompt penetration effects over low latitudes.« less

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

Role of IMF By in the prompt electric field disturbances over equatorial ionosphere during a space weather event

NASA Astrophysics Data System (ADS)

Chakrabarty, D.; Hui, Debrup; Rout, Diptiranjan; Sekar, R.; Bhattacharyya, Archana; Reeves, G. D.; Ruohoniemi, J. M.

2017-02-01

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45-16:30 UT. However, the electric field was found to be eastward during 14:45-15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10-15:15 UT. First, during 14:10-14:45 UT, despite increasing southward interplanetary magnetic field (IMF) Bz condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarca intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45-15:00 UT similar to Jicamarca. Third, during 15:00-15:15 UT, despite IMF Bz remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF By component under southward IMF Bz condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Thus, the present investigation shows that the variations in IMF By are fundamentally important to understand the prompt penetration effects over low latitudes.

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.

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.

Safety of High Speed Guided Ground Transportation Systems : Review of Existing EMF Guidelines, Standards and Regulations

DOT National Transportation Integrated Search

1993-08-01

To assess the state of knowledge about anticipated electric and magnetic field (EMF) exposures from electrical transportation systems, including electrically powered rail and magnetically levitated (maglev), research concerning biological effects of ...

Unusual magnetoelectric memory and polarization reversal in the kagome staircase compound N i3V2O8

NASA Astrophysics Data System (ADS)

Liu, Y. J.; Wang, J. F.; He, Z. Z.; Lu, C. L.; Xia, Z. C.; Ouyang, Z. W.; Liu, C. B.; Chen, R.; Matsuo, A.; Kohama, Y.; Kindo, K.; Tokunaga, M.

2018-05-01

We study the electric polarization of the kagome staircase N i3V2O8 in magnetic fields up to 30 T and report a magnetoelectric memory effect controlled by bias electric fields. The explored ferroelectric phase in 19 -24 T is electrically controlled, whereas the ferroelectric phase in 2 -11 T exhibits unusual memory effects. We determine a characteristic critical magnetic field H3=11 T , below which strong memory exists and the polarization is frozen even in opposite bias fields. But when magnetic fields exceed H3, the frozen polarization is released and polarization reversal appears by tuning bias electric fields. We ascribe these phenomena to the pinning-depinning mechanism: nucleation and the accompanying pinning of chiral domain walls cooperatively induce the frozen behavior; the polarization reversal results from the depinning through the ferroelectrtic-to-paraelectric phase transition in high magnetic fields. Our experimental results reveal that the first-order phase transition plays an important role in these unusual memory effects.

LEVELS OF EXTREMELY LOW-FREQUENCY ELECTRIC AND MAGNETIC FIELDS FROM OVERHEAD POWER LINES IN THE OUTDOOR ENVIRONMENT OF RAMALLAH CITY-PALESTINE.

PubMed

Abuasbi, Falastine; Lahham, Adnan; Abdel-Raziq, Issam Rashid

2018-05-01

In this study, levels of extremely low-frequency electric and magnetic fields originated from overhead power lines were investigated in the outdoor environment in Ramallah city, Palestine. Spot measurements were applied to record fields intensities over 6-min period. The Spectrum Analyzer NF-5035 was used to perform measurements at 1 m above ground level and directly underneath 40 randomly selected power lines distributed fairly within the city. Levels of electric fields varied depending on the line's category (power line, transformer or distributor), a minimum mean electric field of 3.9 V/m was found under a distributor line, and a maximum of 769.4 V/m under a high-voltage power line (66 kV). However, results of electric fields showed a log-normal distribution with the geometric mean and the geometric standard deviation of 35.9 and 2.8 V/m, respectively. Magnetic fields measured at power lines, on contrast, were not log-normally distributed; the minimum and maximum mean magnetic fields under power lines were 0.89 and 3.5 μT, respectively. As a result, none of the measured fields exceeded the ICNIRP's guidelines recommended for general public exposures to extremely low-frequency fields.

The Galileo plasma wave investigation

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Kurth, W. S.; Shaw, R. R.; Roux, A.; Gendrin, R.; Kennel, C. F.; Scarf, F. L.; Shawhan, S. D.

1992-01-01

The purpose of the Galileo plasma wave investigation is to study plasma waves and radio emissions in the magnetosphere of Jupiter. The plasma wave instrument uses an electric dipole antenna to detect electric fields, and two search coil magnetic antennas to detect magnetic fields. The frequency range covered is 5 Hz to 5.6 MHz for electric fields and 5 Hz to 160 kHz for magnetic fields. Low time-resolution survey spectrums are provided by three on-board spectrum analyzers. In the normal mode of operation the frequency resolution is about 10 percent, and the time resolution for a complete set of electric and magnetic field measurements is 37.33 s. High time-resolution spectrums are provided by a wideband receiver. The wideband receiver provides waveform measurements over bandwidths of 1, 10, and 80 kHz. Compared to previous measurements at Jupiter this instrument has several new capabilities. These new capabilities include (1) both electric and magnetic field measurements to distinguish electrostatic and electromagnetic waves, (2) direction finding measurements to determine source locations, and (3) increased bandwidth for the wideband measurements.

The development of the time dependence of the nuclear EMP electric field

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

Eng, C

The nuclear electromagnetic pulse (EMP) electric field calculated with the legacy code CHAP is compared with the field given by an integral solution of Maxwell's equations, also known as the Jefimenko equation, to aid our current understanding on the factors that affect the time dependence of the EMP. For a fair comparison the CHAP current density is used as a source in the Jefimenko equation. At first, the comparison is simplified by neglecting the conduction current and replacing the standard atmosphere with a constant density air slab. The simplicity of the resultant current density aids in determining the factors thatmore » affect the rise, peak and tail of the EMP electric field versus time. The three dimensional nature of the radiating source, i.e. sources off the line-of-sight, and the time dependence of the derivative of the current density with respect to time are found to play significant roles in shaping the EMP electric field time dependence. These results are found to hold even when the conduction current and the standard atmosphere are properly accounted for. Comparison of the CHAP electric field with the Jefimenko electric field offers a direct validation of the high-frequency/outgoing wave approximation.« less

14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure...

14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure...

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

PubMed Central

Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

2016-01-01

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

DOE PAGES

Green, B.; Kovalev, S.; Asgekar, V.; ...

2016-02-29

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields andmore » the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.« less

Current-level triggered plasma-opening switch

DOEpatents

Mendel, C.W.

1987-06-29

An opening switch for very high power electrical pulses uses a slow magnetic field to confine a plasma across a gap between two electrodes. The plasma conducts the electric pulse across the gap while the switch is closed. A magnetic field generated by the pulse repels the slow magnetic field from the negative electrode to push the plasma from the electrode, opening the switch. A plurality of radial vanes may be used to enhance the slow magnetic field. 5 figs.

Thermal and high magnetic field treatment of materials and associated apparatus

DOEpatents

Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail

2010-06-29

An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.

Current-level triggered plasma-opening switch

DOEpatents

Mendel, Clifford W.

1989-01-01

An opening switch for very high power electrical pulses uses a slow magnetic field to confine a plasma across a gap between two electrodes. The plasma conducts the electric pulse across the gap while the switch is closed. A magnetic field generated by the pulse repels the slow magnetic field from the negative electrode to push the plasma from the electrode, opening the switch. A plurality of radial vanes may be used to enhance the slow magnetic field.

Thermal and high magnetic field treatment of materials and associated apparatus

DOEpatents

Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail

2007-01-09

An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.

Fourier analysis of polar cap electric field and current distributions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1984-01-01

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Monitoring Induced Fractures with Electrical Measurements using Depth to Surface Resistivity: A Field Case Study

NASA Astrophysics Data System (ADS)

Wilt, M.; Nieuwenhuis, G.; Sun, S.; MacLennan, K.

2016-12-01

Electrical methods offer an attractive option to map induced fractures because the recovered anomaly is related to the electrical conductivity of the injected fluid in the open (propped) section of the fracture operation. This is complementary to existing micro-seismic technology, which maps the mechanical effects of the fracturing. In this paper we describe a 2014 field case where a combination of a borehole casing electrode and a surface receiver array was used to monitor hydrofracture fracture creation and growth in an unconventional oil field project. The fracture treatment well was 1 km long and drilled to a depth of 2.2 km. Twelve fracture events were induced in 30 m intervals (stages) in the 1 km well. Within each stage 5 events (clusters) were initiated at 30 m intervals. Several of the fracture stages used a high salinity brine, instead of fresh water, to enhance the electrical signal. The electrical experiment deployed a downhole source in a well parallel to the treatment well and 100 m away. The source consisted of an electrode attached to a wireline cable into which a 0.25 Hz square wave was injected. A 60-station electrical field receiver array was placed above the fracture and extending for several km. Receivers were oriented to measure electrical field parallel with the presumed fracture direction and those perpendicular to it. Active source electrical data were collected continuously during 7 frac stages, 3 of which used brine as the frac fluid over a period of several days. Although the site was quite noisy and the electrical anomaly small we managed to extract a clear frac anomaly using field separation, extensive signal averaging and background noise rejection techniques. Preliminary 3D modeling, where we account for current distribution of the casing electrode and explicitly model multiple thin conductive sheets to represent fracture stages, produces a model consistent with the field measurements and also highlights the sensitivity of the measurements to the high salinity frac stages. Data inversion is presently ongoing.

The ac and dc electric field meters developed for the US Department of Energy

NASA Technical Reports Server (NTRS)

Kirkham, H.; Johnston, A.; Jackson, S.; Sheu, K.

1987-01-01

Two space-potential electric field meters developed at the Jet Propulsion Laboratory under the auspices of the U.S. Department of Energy are described. One of the meters was designed to measure dc fields, the other ac fields. Both meters use fiber optics to couple a small measuring probe to a remote readout device, so as to minimize field perturbation due to the presence of the probe. By using coherent detection, it has been possible to produce instruments whose operating range extends from about 10 V/m up to about 2.5 kV/cm, without the need for range switching on the probe. The electrical and mechanical design of both meters are described in detail. Data from laboratory tests are presented, as well as the results of the tests at the National Bureau of Standards and the Electric Power Research Institute's High Voltage Transmission Research Facility.

Relationship between large horizontal electric fields and auroral arc elements

NASA Astrophysics Data System (ADS)

Lanchester, B. S.; Kailá, K.; McCrea, I. W.

1996-03-01

High time resolution optical measurements in the magnetic zenith are compared with European Incoherent Scatter (EISCAT) field-aligned measurements of electron density at 0.2-s resolution and with horizontal electric field measurements made at 278 km with resolution of 9 s. In one event, 20 min after a spectacular auroral breakup, a system of narrow and active arc elements moved southward into the magnetic zenith, where it remained for several minutes. During a 30-s interval of activity in a narrow arc element very close to the radar beam, the electric field vectors at 3-s resolution were found to be extremely large (up to 400 mVm-1) and to point toward the bright optical features in the arc, which moved along its length. It is proposed that the large electric fields are short-lived and are directly associated with the particle precipitation that causes the bright features in auroral arc elements.

Electric Field Effects on the Hidden Order of Microstructured URu 2Si 2

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

Stritzinger, Laurel Elaine Winter; Mcdonald, Ross David; Harrison, Neil

2017-03-23

Despite being studied for over 30 years there is still continual interest in they heavy-fermion URu 2Si 2 due largely in part to the still disagreed upon origin of the so-called hidden-order (HO) state that arises below THO = 17.5 K. While both the application of pressure and high magnetic fields have been shown to suppress the HO state, one mechanism that has yet to be explored is the application of an electric field, most likely due to the difficulty of measuring such an effect in a metal. To overcome this challenge we have used focused ion beam (FIB) lithographymore » to obtain the necessary sample geometry to create an electric field across a small section of the sample by applying a voltage. Our results suggest that at low temperatures the application of an electric field is able to suppress the hidden order state.« less

The sub-auroral electric field as observed by DMSP and the new SuperDARN mid-latitude radars

NASA Astrophysics Data System (ADS)

Talaat, E. R.; Sotirelis, T.; Hairston, M. R.; Ruohoniemi, J. M.; Greenwald, R. A.; Lester, M.

2008-12-01

In this paper we present analyses of the sub-auroral electric field environment as observed from both space and ground. We discuss the dependency of the configuration and strength of the sub-auroral electric field on IMF and geomagnetic activity, longitudinal, seasonal, and solar cycle variability. Primarily, e use ~20 years of electric field measurement dataset derived from the suite of DMSP ion drift meters. A major component of our analysis is correctly specifying the aurora boundary, as the behavior and magnitude of these fields will be drastically different away from the high-conductance auroral oval. As such, we use the coincident particle flux measurements from the DMSP SSJ4 monitors. We also present the solar minimum observations of the sub-auroral flow newly available from the mid-latitude SuperDARN radars at Wallops and Blackstone in Virginia. Preliminary comparisons between these flows and the DMSP climatology are discussed.

Electric dipole spin resonance in a quantum spin dimer system driven by magnetoelectric coupling

NASA Astrophysics Data System (ADS)

Kimura, Shojiro; Matsumoto, Masashige; Akaki, Mitsuru; Hagiwara, Masayuki; Kindo, Koichi; Tanaka, Hidekazu

2018-04-01

In this Rapid Communication, we propose a mechanism for electric dipole active spin resonance caused by spin-dependent electric polarization in a quantum spin gapped system. This proposal was successfully confirmed by high-frequency electron spin resonance (ESR) measurements of the quantum spin dimer system KCuCl3. ESR measurements by an illuminating linearly polarized electromagnetic wave reveal that the optical transition between the singlet and triplet states in KCuCl3 is driven by an ac electric field. The selection rule of the observed transition agrees with the calculation by taking into account spin-dependent electric polarization. We suggest that spin-dependent electric polarization is effective in achieving fast control of quantum spins by an ac electric field.

Retrieving Storm Electric Fields from Aircraft Field Mill Data. Part 1; Theory

NASA Technical Reports Server (NTRS)

Koshak, W. J.

2006-01-01

It is shown that the problem of retrieving storm electric fields from an aircraft instrumented with several electric field mill sensors can be expressed in terms of a standard Lagrange multiplier optimization problem. The method naturally removes aircraft charge from the retrieval process without having to use a high voltage stinger and linearly combined mill data values. It allows a variety of user-supplied physical constraints (the so-called side constraints in the theory of Lagrange multipliers) and also helps improve absolute calibration. Additionally, this paper introduces an alternate way of performing the absolute calibration of an aircraft that has some benefits over conventional analyses. It is accomplished by using the time derivatives of mill and pitch data for a pitch down maneuver performed at high (greater than 1 km) altitude. In Part II of this study, the above methods are tested and then applied to complete a full calibration of a Citation aircraft.

Retrieving Storm Electric Fields From Aircraft Field Mill Data. Part I: Theory

NASA Technical Reports Server (NTRS)

Koshak, W. J.

2005-01-01

It is shown that the problem of retrieving storm electric fields from an aircraft instrumented with several electric field mill sensors can be expressed in terms of a standard Lagrange multiplier optimization problem. The method naturally removes aircraft charge from the retrieval process without having to use a high voltage stinger and linearly combined mill data values. It also allows a variety of user-supplied physical constraints (the so-called side constraints in the theory of Lagrange multipliers). Additionally, this paper introduces a novel way of performing the absolute calibration of an aircraft that has several benefits over conventional analyses. In the new approach, absolute calibration is completed by inspecting the time derivatives of mill and pitch data for a pitch down maneuver performed at high (greater than 1 km) altitude. In Part II of this study, the above methods are tested and then applied to complete a full calibration of a Citation aircraft.

Spectral response of atmospheric electric field measurements near AC high voltage power lines

NASA Astrophysics Data System (ADS)

Silva, H. G.; Matthews, J. C.; Wright, M. D.; Shallcross, D. E.

2015-10-01

To understand the influence of corona ion emission on the atmospheric electrical field, measurements were made near to two AC high voltage power lines. A JCI 131 field-mill recorded the atmospheric electric field over one year. Meteorological measurements were also taken. The data series is divided in four zones (dependent on wind direction): whole zones, Z0; zone 1, Z1; zone 2, Z2; zone 3, Z3. Z3 is the least affected by corona ion emission and for that reason it is used as a reference against Z1 and Z2, which are strongly influenced by this phenomena. Analysis was undertaken for all weather days and dry days only. The Lomb-Scargle strategy developed for unevenly spaced time-series is used to calculate the spectral response of the aforementioned zones. Only frequencies above 1 minute are considered.

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.

Laboratory investigation of dust impacts on antennas in space

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Malaspina, D.; Gruen, E.; Drake, K.

2013-10-01

Recent observations of sharp voltage spikes by the WAVES electric field experiments onboard the twin STEREO spacecraft have been attributed to plasma clouds generated by the impact ionization of high velocity dust particles. The reported dust fluxes are much higher than those measured by dedicated dust detectors at 1 AU, which leads to the interpretation that the STEREO observations are due to nanometer-sized dust particles originating from the inner solar system and accelerated to high velocities by the solar wind magnetic field. However, this interpretation is based on a simplified model of coupling between the expanding plasma cloud from the dust impact and the WAVES electric field instrument. A series of laboratory measurements are performed to validate this model and to calibrate/investigate the effect of various impact parameters on the signals measured by the electric field instrument. The dust accelerator facility operating at the University of Colorado is used for the measurement with micron and submicron sized particles accelerated to 50 km/s. The first set of measurements is performed to calibrate the impact charge generated from materials specific the STEREO spacecraft and will help to interpret electric field data.

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation

PubMed Central

Janssen, A M; Rampersad, S M; Lucka, F; Lanfer, B; Lew, S; Aydin, Ü; Wolters, C H; Stegeman, D F; Oostendorp, T F

2013-01-01

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation (TMS). One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between the CSF and GM (Thielscher et al. 2011; Bijsterbosch et al. 2012), or by resizing the whole brain (Wagner et al. 2008). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images (MRI), was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location. PMID:23787706

Positron Annihilation Ratio Spectroscopy (PsARS) Applied to Positronium Formation Studies

DTIC Science & Technology

2010-03-01

POSITRON ANNIHILATION RATIO SPECTROSCOPY (PsARS) APPLIED TO POSITRONIUM FORMATION STUDIES THESIS...AFIT/GNE/ENP/10-M07 POSITRON ANNIHILATION RATIO SPECTROSCOPY (PsARS) APPLIED TO POSITRONIUM FORMATION STUDIES ...lifetime studies in local electric field experiments. High local electric fields can polarize a positron -electron pair, which may result in an extended

Observation of a westward travelling surge from satellites at low, medium and high altitudes

NASA Technical Reports Server (NTRS)

Ungstrup, E.; Sharp, R. D.; Cattell, C. A.; Anderson, R. R.; Fitzenreiter, R. J.; Evans, D. S.; Baker, D. N.

1984-01-01

The motion of discontinuity; electric potential and current structure of the event; energy source and flow; wave-particle interactions; and particle acceleration are addressed using wave, electron, ion mass spectrometer, dc electric field, and magnetic field observation from the Isee-1, NOAA-6, and the 1976-059 geostationary satellite.

Remote electrical arc suppression by laser filamentation.

PubMed

Schubert, Elise; Mongin, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre

2015-11-02

We investigate the interaction of narrow plasma channels formed in the filamentation of ultrashort laser pulses, with a DC high voltage. The laser filaments prevent electrical arcs by triggering corona that neutralize the high-voltage electrodes. This phenomenon, that relies on the electric field modulation and free electron release around the filament, opens new prospects to lightning and over-voltage mitigation.

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.

Evolution of the radial electric field in high-Te ECH heated plasmas on LHD

NASA Astrophysics Data System (ADS)

Pablant, Novimir; Bitter, Manfred; Delgado Aparicio, Luis F.; Dinklage, Andreas; Gates, David; Goto, Motoshi; Ido, Takeshi; Hill, Kenneth H.; Kubo, Shin; Morita, Shigeru; Nagaoka, Kenichi; Oishi, Tetsutarou; Satake, Shinsuke; Takahashi, Hiromi; Yokoyama, Masayuki; LHD Experiment Group Team

2014-10-01

A detailed study is presented on the evolution of the radial electric field (Er) under a range of densities and injected ECH powers on the Large Helical Device (LHD). These plasmas focused on high-electron temperature ECH heated plasmas which exhibit a transition of Er from the ion-root to the electron-root when either the density is reduced or the ECH power is increased. Measurements of poloidal rotation were achieved using the X-Ray Imaging Crystal Spectrometer (XICS) and are compared with neo-classical predictions of the radial electric field using the GSRAKE and FORTEC-3D codes. This study is based on a series of experiments on LHD which used fast modulation of the gyrotrons on LHD to produce a detailed power scan with a constant power deposition profile. This is a novel application of this technique to LHD, and has provided the most detailed study to date on dependence of the radial electric field on the injected power. Detailed scans of the density at constant injected power were also made, allowing a separation of the power and density dependence.

Highly Polarized Fluorescent Illumination Using Liquid Crystal Phase.

PubMed

Gim, Min-Jun; Turlapati, Srikanth; Debnath, Somen; Rao, Nandiraju V S; Yoon, Dong Ki

2016-02-10

Liquid crystal (LC) materials are currently the dominant electronic materials in display technology because of the ease of control of molecular orientation using an electric field. However, this technology requires the fabrication of two polarizers to create operational displays, reducing light transmission efficiency below 10%. It is therefore desirable to develop new technologies to enhance the light efficiency while maintaining or improving other properties such as the modulation speed of the molecular orientation. Here we report a uniaxial-oriented B7 smectic liquid crystalline film, using fluorescent bent-core LC molecules, a chemically modified substrate, and an in-plane electric field. A LC droplet under homeotropic boundary conditions of air/LC as well as LC/substrate exhibits large focal conic like optical textures. The in-plane electric field induced uniaxial orientation of the LC molecules, in which molecular polar directors are aligned in the direction of the electric field. This highly oriented LC film exhibits linearly polarized luminescence and microsecond time-scale modulation characteristics. The resultant device is both cheap and easy to fabricate and thus has great potential for electro-optic applications, including LC displays, bioimaging systems, and optical communications.

Externally controlled on-demand release of anti-HIV drug using magneto-electric nanoparticles as carriers.

PubMed

Nair, Madhavan; Guduru, Rakesh; Liang, Ping; Hong, Jeongmin; Sagar, Vidya; Khizroev, Sakhrat

2013-01-01

Although highly active anti-retroviral therapy has resulted in remarkable decline in the morbidity and mortality in AIDS patients, inadequately low delivery of anti-retroviral drugs across the blood-brain barrier results in virus persistence. The capability of high-efficacy-targeted drug delivery and on-demand release remains a formidable task. Here we report an in vitro study to demonstrate the on-demand release of azidothymidine 5'-triphosphate, an anti-human immunodeficiency virus drug, from 30 nm CoFe2O4@BaTiO3 magneto-electric nanoparticles by applying a low alternating current magnetic field. Magneto-electric nanoparticles as field-controlled drug carriers offer a unique capability of field-triggered release after crossing the blood-brain barrier. Owing to the intrinsic magnetoelectricity, these nanoparticles can couple external magnetic fields with the electric forces in drug-carrier bonds to enable remotely controlled delivery without exploiting heat. Functional and structural integrity of the drug after the release was confirmed in in vitro experiments with human immunodeficiency virus-infected cells and through atomic force microscopy, spectrophotometry, Fourier transform infrared and mass spectrometry studies.

Occupational Exposure to Electric Shocks and Magnetic Fields and Amyotrophic Lateral Sclerosis in Sweden.

PubMed

Fischer, Heidi; Kheifets, Leeka; Huss, Anke; Peters, Tracy L; Vermeulen, Roel; Ye, Weimin; Fang, Fang; Wiebert, Pernilla; Vergara, Ximena P; Feychting, Maria

2015-11-01

Amyotrophic lateral sclerosis (ALS) has been consistently related to "electric occupations," but associations with magnetic field levels were generally weaker than those with electrical occupations. Exposure to electric shock has been suggested as a possible explanation. Furthermore, studies were generally based on mortality or prevalence of ALS, and studies often had limited statistical power. Using two electric shock and three magnetic field job-exposure matrices, we evaluated the relationship of occupational magnetic fields, electric shocks, electric occupations, and incident ALS in a large population-based nested case-control study in Sweden. Subanalyses, specified a priori, were performed for subjects by gender and by age (less than and more than 65 years). Overall, we did not observe any associations between occupational magnetic field or electric shock exposure and ALS. For individuals less than 65 years old, high electric shock exposure was associated with an odds ratio (OR) of 1.22 (95% confidence interval [CI] = 1.03, 1.43). The corresponding result for the age group 65 years or older was OR = 0.92 (95% CI = 0.81, 1.05). Results were similar regardless which job exposure matrices, exposure definitions, or cutpoints were used. For electric occupations, ORs were close to unity, regardless of age. For welders, no association was observed overall, although for welders <65 years the OR was 1.52 (95% CI = 1.05, 2.21). In this very large population-based study based on incident ALS case subjects, we did not confirm previous observations of higher risk of ALS in electrical occupations, and provided only weak support for associations between electric shocks and ALS.

Discussion of Electrode Conditioning Mechanism Based on Pre-breakdown Current under Non-uniform Electric Field in Vacuum

NASA Astrophysics Data System (ADS)

Yasuoka, Takanori; Kato, Tomohiro; Kato, Katsumi; Okubo, Hitoshi

Electrode conditioning is very important technique for improvement of the insulation performance of vacuum circuit breakers (VCBs). This paper discusses the spark conditioning mechanism under non-uniform electric field focused on the pre-breakdown current. We quantitatively evaluated the spark conditioning effect by analyzing the pre-breakdown current based on Fowler-Nordheim equation. As a result, field enhancement factor β decreased with the increasing in breakdown voltage in the beginning of conditioning process, and finally β was saturated with the saturation of breakdown voltage. In addition, in case of non-uniform field, we found that β on high voltage rod electrode after conditioning varied according to the electric field strength on the rod electrode.

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

From organized high throughput data to phenomenological theory: The example of dielectric breakdown

NASA Astrophysics Data System (ADS)

Kim, Chiho; Pilania, Ghanshyam; Ramprasad, Rampi

Understanding the behavior (and failure) of dielectric insulators experiencing extreme electric fields is critical to the operation of present and emerging electrical and electronic devices. Despite its importance, the development of a predictive theory of dielectric breakdown has remained a challenge, owing to the complex multiscale nature of this process. Here, we focus on the intrinsic dielectric breakdown field of insulators--the theoretical limit of breakdown determined purely by the chemistry of the material, i.e., the elements the material is composed of, the atomic-level structure, and the bonding. Starting from a benchmark dataset (generated from laborious first principles computations) of the intrinsic dielectric breakdown field of a variety of model insulators, simple predictive phenomenological models of dielectric breakdown are distilled using advanced statistical or machine learning schemes, revealing key correlations and analytical relationships between the breakdown field and easily accessible material properties. The models are shown to be general, and can hence guide the screening and systematic identification of high electric field tolerant materials.

Charge sniffer for electrostatics demonstrations

NASA Astrophysics Data System (ADS)

Dinca, Mihai P.

2011-02-01

An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.

Computational findings of metastable ferroelectric phases of squaric acid

NASA Astrophysics Data System (ADS)

Ishibashi, Shoji; Horiuchi, Sachio; Kumai, Reiji

2018-05-01

Antiferroelectric-to-ferroelectric transitions in squaric acid are simulated by computationally applying a static electric field. Depending on the direction of the electric field, two different metastable ferroelectric (and piezoelectric) phases have been found. One of them corresponds to the experimentally confirmed phase, whereas the other is an optimally polarized phase. The structural details of these phases have been determined as a function of the electric field. The spontaneous polarization values of the phases are 14.5 and 20.5 μ C /cm2, respectively, and are relatively high among those of the existing organic ferroelectrics.

Optoelectronic tweezers for medical diagnostics

NASA Astrophysics Data System (ADS)

Kremer, Clemens; Neale, Steven; Menachery, Anoop; Barrett, Mike; Cooper, Jonathan M.

2012-01-01

Optoelectronic tweezers (OET) allows the spatial patterning of electric fields through selected illumination of a photoconductive surface. This enables the manipulation of micro particles and cells by creating non-uniform electrical fields that then produce dielectrophoretic (DEP) forces. The DEP responses of cells differ and can produce negative or positive (repelled or attracted to areas of high electric field) forces. Therefore OET can be used to manipulate individual cells and separate different cell types from each other. Thus OET has many applications for medical diagnostics, demonstrated here with work towards diagnosing Human African Trypanosomiasis, also known as sleeping sickness.

A Compact Microwave Microfluidic Sensor Using a Re-Entrant Cavity.

PubMed

Hamzah, Hayder; Abduljabar, Ali; Lees, Jonathan; Porch, Adrian

2018-03-19

A miniaturized 2.4 GHz re-entrant cavity has been designed, manufactured and tested as a sensor for microfluidic compositional analysis. It has been fully evaluated experimentally with water and common solvents, namely methanol, ethanol, and chloroform, with excellent agreement with the expected behaviour predicted by the Debye model. The sensor's performance has also been assessed for analysis of segmented flow using water and oil. The samples' interaction with the electric field in the gap region has been maximized by aligning the sample tube parallel to the electric field in this region, and the small width of the gap (typically 1 mm) result in a highly localised complex permittivity measurement. The re-entrant cavity has simple mechanical geometry, small size, high quality factor, and due to the high concentration of electric field in the gap region, a very small mode volume. These factors combine to result in a highly sensitive, compact sensor for both pure liquids and liquid mixtures in capillary or microfluidic environments.

Influence of thermal agitation on the electric field induced precessional magnetization reversal with perpendicular easy axis

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

Cheng, Hongguang, E-mail: chenghg7932@gmail.com; Deng, Ning

2013-12-15

We investigated the influence of thermal agitation on the electric field induced precessional magnetization switching probability with perpendicular easy axis by solving the Fokker-Planck equation numerically with finite difference method. The calculated results show that the thermal agitation during the reversal process crucially influences the switching probability. The switching probability can be achieved is only determined by the thermal stability factor Δ of the free layer, it is independent on the device dimension, which is important for the high density device application. Ultra-low error rate down to the order of 10{sup −9} can be achieved for the device of thermalmore » stability factor Δ of 40. Low damping factor α material should be used for the free layer for high reliability device applications. These results exhibit potential of electric field induced precessional magnetization switching with perpendicular easy axis for ultra-low power, high speed and high density magnetic random access memory (MRAM) applications.« less

Deformation of an elastic capsule in a uniform electric field

NASA Astrophysics Data System (ADS)

Karyappa, Rahul B.; Deshmukh, Shivraj. D.; Thaokar, Rochish. M.

2014-12-01

The deformation of a thin elastic capsule subjected to a uniform electric field is investigated in the Stokes flow regime. The electrohydrodynamic flow is analyzed using a perfect conductor and a perfect dielectric model for the capsule and the fluid phase, respectively. A theoretical analysis is carried out using an asymptotic expansion in the electric capillary number (Ca) (a ratio of the electric stress to the elastic tension) in the small deformation limit using the finite deformation Hooke's law. The analysis is used to determine the elasticity of polysiloxane capsules suspended in oil, the deformation of which is obtained using videography. The boundary element method is implemented to seek numerical solutions to the hydrodynamic, elastic, and electrostatics equations. The finite deformation Hooke's law, the Mooney-Rivlin, and Skalak's model for elasticity are employed. The effect of electric capillary number, unstressed geometry, and the type of membrane material on the deformation of a capsule is presented in the high Ca number limit using numerical simulation. Capsules synthesized with higher monomer concentration displayed electric stress induced wrinkling process at high electric field strengths. Burst of a capsule is characterized by poration of the polymer membrane, which could be symmetric or asymmetric at the two poles, depending upon the value of the capillary number. The results should be useful in understanding the response of elastic capsules such as red blood cells and polymerized membranes, to an electric field, in applications such as electrodeformation and electroporation. It also provides a theoretical framework for a possible way of determining the elastic parameters of a capsule.

Input-output relationship in galvanotactic response of Dictyostelium cells.

PubMed

Sato, Masayuki J; Ueda, Michihito; Takagi, Hiroaki; Watanabe, Tomonobu M; Yanagida, Toshio; Ueda, Masahiro

2007-04-01

Under a direct current electric field, Dictyostelium cells exhibit migration towards the cathode. To determine the input-output relationship of the cell's galvanotactic response, we developed an experimental instrument in which electric signals applied to the cells are highly reproducible and the motile response are analyzed quantitatively. With no electric field, the cells moved randomly in all directions. Upon applying an electric field, cell migration speeds became about 1.3 times faster than those in the absence of an electric field. Such kinetic effects of electric fields on the migration were observed for cells stimulated between 0.25 and 10 V/cm of the field strength. The directions of cell migrations were biased toward the cathode in a positive manner with field strength, showing galvanotactic response in a dose-dependent manner. Quantitative analysis of the relationship between field strengths and directional movements revealed that the biased movements of the cells depend on the square of electric field strength, which can be described by one simple phenomenological equation. The threshold strength for the galvanotaxis was between 0.25 and 1 V/cm. Galvanotactic efficiency reached to half-maximum at 2.6 V/cm, which corresponds to an approximate 8 mV voltage difference between the cathode and anode direction of 10 microm wide, round cells. Based on these results, possible mechanisms of galvanotaxis in Dictyostelium cells were discussed. This development of experimental system, together with its good microscopic accessibility for intracellular signaling molecules, makes Dictyostelium cells attractive as a model organism for elucidating stochastic processes in the signaling systems responsible for cell motility and its regulations.

Asymmetric photon transport in organic semiconductor nanowires through electrically controlled exciton diffusion

PubMed Central

Cui, Qiu Hong; Peng, Qian; Luo, Yi; Jiang, Yuqian; Yan, Yongli; Wei, Cong; Shuai, Zhigang; Sun, Cheng; Yao, Jiannian; Zhao, Yong Sheng

2018-01-01

The ability to steer the flow of light toward desired propagation directions is critically important for the realization of key functionalities in optical communication and information processing. Although various schemes have been proposed for this purpose, the lack of capability to incorporate an external electric field to effectively tune the light propagation has severely limited the on-chip integration of photonics and electronics. Because of the noninteractive nature of photons, it is only possible to electrically control the flow of light by modifying the refractive index of materials through the electro-optic effect. However, the weak optical effects need to be strongly amplified for practical applications in high-density photonic integrations. We show a new strategy that takes advantage of the strong exciton-photon coupling in active waveguides to effectively manipulate photon transport by controlling the interaction between excitons and the external electric field. Single-crystal organic semiconductor nanowires were used to generate highly stable Frenkel exciton polaritons with strong binding and diffusion abilities. By making use of directional exciton diffusion in an external electric field, we have realized an electrically driven asymmetric photon transport and thus directional light propagation in a single nanowire. With this new concept, we constructed a dual-output single wire–based device to build an electrically controlled single-pole double-throw optical switch with fast temporal response and high switching frequency. Our findings may lead to the innovation of concepts and device architectures for optical information processing. PMID:29556529

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.

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.

Rapid Transition of the Hole Rashba Effect from Strong Field Dependence to Saturation in Semiconductor Nanowires

NASA Astrophysics Data System (ADS)

Luo, Jun-Wei; Li, Shu-Shen; Zunger, Alex

2017-09-01

The electric field manipulation of the Rashba spin-orbit coupling effects provides a route to electrically control spins, constituting the foundation of the field of semiconductor spintronics. In general, the strength of the Rashba effects depends linearly on the applied electric field and is significant only for heavy-atom materials with large intrinsic spin-orbit interaction under high electric fields. Here, we illustrate in 1D semiconductor nanowires an anomalous field dependence of the hole (but not electron) Rashba effect (HRE). (i) At low fields, the strength of the HRE exhibits a steep increase with the field so that even low fields can be used for device switching. (ii) At higher fields, the HRE undergoes a rapid transition to saturation with a giant strength even for light-atom materials such as Si (exceeding 100 meV Å). (iii) The nanowire-size dependence of the saturation HRE is rather weak for light-atom Si, so size fluctuations would have a limited effect; this is a key requirement for scalability of Rashba-field-based spintronic devices. These three features offer Si nanowires as a promising platform for the realization of scalable complementary metal-oxide-semiconductor compatible spintronic devices.

Flexible electronic control system based on FPGA for liquid-crystal microlens

NASA Astrophysics Data System (ADS)

Zhang, Bo; Xin, Zhaowei; Li, Dapeng; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

Traditional imaging based on common optical lens can only be used to collect intensity information of incident beams, but actually lightwave also carries other mode information about targets and environment, including: spectrum, wavefront, and depth of target, and so on. It is very important to acquire those information mentioned for efficiently detecting and identifying targets in complex background. There is a urgent need to develop new high-performance optical imaging components. The liquid-crystal microlens (LCMs) only by applying spatial electrical field to change optical performance, have demonstrated remarkable advantages comparing conventional lenses, and therefore show a widely application prospect. Because the physical properties of the spatial electric fields between electrode plates in LCMs are directly related to the light-field performances of LCMs, the quality of voltage signal applied to LCMs needs high requirements. In this paper, we design and achieve a new type of digital voltage equipment with a wide adjustable voltage range and high precise voltage to effectively drive and adjust LCMs. More importantly, the device primarily based on field-programmable gate array(FPGA) can generate flexible and stable voltage signals to cooperate with the various functions of LCMs. Our experiments show that through the electronic control system, the LCMs already realize several significant functions including: electrically swing focus, wavefront imaging, electrically tunable spectral imaging and light-field imaging.

TEC Variations Over Korean Peninsula During Magnetic Storm

NASA Astrophysics Data System (ADS)

Ji, E.-Y.; Choi, B.-K.; Kim, K.-H.; Lee, D.-H.; Cho, J.-H.; Chung, J.-K.; Park, J.-U.

2008-03-01

By analyzing the observations from a number of ground- and space-based instruments, including ionosonde, magnetometers, and ACE interplanetary data, we examine the response of the ionospheric TEC over Korea during 2003 magnetic storms. We found that the variation of vertical TEC is correlated with the southward turning of the interplanetary magnetic field B_z. It is suggested that the electric fields produced by the dynamo process in the high-latitude region and the prompt penetration in the low-latitude region are responsible for TEC increases. During the June 16 event, dayside TEC values increase more than 15%. And the ionospheric F2-layer peak height (hmF2) was ˜300km higher and the vertical E×B drift (estimated from ground-based magnetometer equatorial electrojet delta H) showed downward drift, which may be due to the ionospheric disturbance dynamo electric field produced by the large amount of energy dissipation into high-latitude regions. In contr! ast, during November 20 event, the nightside TEC increases may be due to the prompt penetration westward electric field. The ionospheric F2-layer peak height was below 200km and the vertical E×B drift showed downward drift. Also, a strong correlation is observed between enhanced vertical TEC and enhanced interplanetary electric field. It is shown that, even though TEC increases are caused by the different processes, the electric field disturbances in the ionosphere play an important role in the variation of TEC over Korea.

Atmospheric pressure ion focusing in a high-field asymmetric waveform ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Guevremont, Roger; Purves, Randy W.

1999-02-01

The focusing of ions at atmospheric pressure and room temperature in a high-field asymmetric waveform ion mobility spectrometer (FAIMS) has been investigated. FAIMS operates with the application of a high-voltage, high-frequency asymmetric waveform across parallel plates. This establishes conditions wherein an ion migrates towards one of the plates because of a difference in the ion mobility at the low and high electric field conditions during application of the waveform. The migration can be stopped by applying a dc compensation voltage (CV) which serves to create a "balanced" condition wherein the ion experiences no net transverse motion. This method has also been called "transverse field compensation ion mobility spectrometry" and "field ion spectrometry®." If this experiment is conducted using a device with cylindrical geometry, rather than with flat plates, an ion focusing region can exist in the annular space between the two concentric cylinders. Ion trajectory modeling showed that the behavior of the ions in the cylindrical geometry FAIMS analyzer was unlike any previously described atmospheric pressure ion optics system. The ions appeared to be trapped, or focused by being caught between two opposing forces. Requirements for establishing this focus for a given ion were identified: the applied waveform must be asymmetric, the electric field must be sufficiently high that the mobility of the ion deviates from its low-field value during the high-voltage portion of the asymmetric waveform, and finally, the electric field must be nonuniform in space (e.g., cylindrical or spherical geometry). Experimental observations with a prototype FAIMS device, which was designed to measure the radial distribution of ions in the FAIMS analyzer region, have confirmed the results of ion trajectory modeling.

Complex interaction of subsequent surface streamers via deposited charge: a high-resolution experimental study

NASA Astrophysics Data System (ADS)

Hoder, T.; Synek, P.; Chorvát, D.; Ráhel', J.; Brandenburg, R.; Černák, M.

2017-07-01

The coplanar barrier discharge in synthetic air at 30 kPa pressure was studied by time-correlated single photon counting enhanced optical emission spectroscopy, far-field microscopy enhanced intensified CCD camera and sensitive current measurements. The discharge operated in a regime where two subsequent microdischarges appeared within the same voltage half-period. The electrical analysis of the barrier discharge setup enabled us to quantify charge transfer and the effective electric field development. During the second microdischarge the positive surface streamers follow the interface (triple-line) between the area of deposited charge from the previous one and the area of uncharged dielectric surface. It is shown that additional branching and flashes of surface streamers are responsible for the increased spatial complexity of the deposited surface charges at high overvoltage. A suppressed streamer propagating over the area of deposited surface charge was tracked and the evidence of surface streamer reconnection is presented. A spatiotemporal distribution (resolution of 120 ps and 100 μm) of the reduced electric field strength was obtained for both microdischarges from the recorded luminosities of the molecular nitrogen. The reduced electric field of positive streamers in the first microdischarge reached 1200 Td. For the second one, the electric field values for the streamer at the triple-line are slightly lower than that, while for the suppressed streamers are even higher.

Mathematical modelling of the destruction degree of cancer under the influence of a RF hyperthermia

NASA Astrophysics Data System (ADS)

Paruch, Marek; Turchan, Łukasz

2018-01-01

The article presents the mathematical modeling of the phenomenon of artificial hyperthermia which is caused by the interaction of an electric field. The electric field is induced by the applicator positioned within the biological tissue with cancer. In addition, in order to estimate the degree of tumor destruction under the influence of high temperature an Arrhenius integral has been used. The distribution of electric potential in the domain considered is described by the Laplace system of equations, while the temperature field is described by the Pennes system of equations. These problems are coupled by source function being the additional component in the Pennes equation and resulting from the electric field action. The boundary element method is applied to solve the coupled problem connected with the heating of biological tissues.

Initial Characterization of Colombian High School Physics Teachers' Pedagogical Content Knowledge on Electric Fields

NASA Astrophysics Data System (ADS)

Melo-Niño, Lina Viviana; Cañada, Florentina; Mellado, Vicente

2017-02-01

We explore the initial characterization of the pedagogical content knowledge of four, in-service, Colombian pre-university secondary education physics teachers on the concept of electric field. Two of them teach the content in English as a second language. The aim of the study was to obtain an image of the participants' teaching of electric field and the inherent complexities that go with that. The results revealed that factors which involved their personal educational models, such as, how they interpret their school's curriculum, the relationship they see between physics and mathematics, the most effective strategies for teaching physics, and the time they have available to develop the topic played a significant role. The teachers considered it essential to establish new strategies that would motivate the pupils by helping them visualize the electric field.

Electric-field control of spin waves in multiferroic BiFeO3: Theory

NASA Astrophysics Data System (ADS)

de Sousa, Rogério; Rovillain, P.; Gallais, Y.; Sacuto, A.; Méasson, M. A.; Colson, D.; Forget, A.; Bibes, M.; Barthélémy, A.; Cazayous, M.

2011-03-01

Our recent experiment demonstrated gigantic (30%) electric-field tuning of magnon frequencies in multiferroic BiFeO3. We demonstrate that the origin of this effect is related to two linear magnetoelectric interactions that couple the component of electric field perpendicular to the ferroelectric vector to a quadratic form of the Néel vector. We calculate the magnon spectra due to each of these interactions and show that only one of them is consistent with experimental data. At high electric fields, this interaction induces a phase transition to a homogeneous state, and the multi-magnon spectra will fuse into two magnon frequencies. We discuss the possible microscopic mechanisms responsible for this novel interaction and the prospect for applications in magnonics. We acknowledge support from NSERC-Discovery (Canada) and the Agence Nationale pour la Recherche (France).

Estimation of electric fields and current from ground-based magnetometer data

NASA Technical Reports Server (NTRS)

Kamide, Y.; Richmond, A. D.

1984-01-01

Recent advances in numerical algorithms for estimating ionospheric electric fields and currents from groundbased magnetometer data are reviewed and evaluated. Tests of the adequacy of one such algorithm in reproducing large-scale patterns of electrodynamic parameters in the high-latitude ionosphere have yielded generally positive results, at least for some simple cases. Some encouraging advances in producing realistic conductivity models, which are a critical input, are pointed out. When the algorithms are applied to extensive data sets, such as the ones from meridian chain magnetometer networks during the IMS, together with refined conductivity models, unique information on instantaneous electric field and current patterns can be obtained. Examples of electric potentials, ionospheric currents, field-aligned currents, and Joule heating distributions derived from ground magnetic data are presented. Possible directions for future improvements are also pointed out.

Synthesis of zirconium oxynitride in air under DC electric fields

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

Morisaki, Nobuhiro; Tokunaga, Tomoharu; Sasaki, Katsuhiro

We synthesized zirconium oxynitride from yttria-stabilized zirconia (YSZ) in air by applying DC electric fields that produced a controlled electric current in the specimen. When YSZ was heated under an applied DC electric field, the electric current of the specimen steeply increased at a critical temperature, called a flash event, during flash sintering. By keeping the electric current of the specimen constant during the flash event and then holding the specimen at the critical temperature, YSZ was transformed into zirconium oxynitride under the optimal conditions of 50 V/cm, 500 mA, and 1000 °C. We confirmed that zirconium oxynitride formed using high-resolution transmission electronmore » microscopy, electron energy-loss spectroscopy, and energy-dispersive spectrometry. To convert oxides to nitrides, reducing conditions are necessary to form excess oxygen vacancies. Our technique produced the strong reducing conditions necessary to form nitrides from the oxides by delivering a controlled electric current to the specimen.« less

Controlling stray electric fields on an atom chip for experiments on Rydberg atoms

NASA Astrophysics Data System (ADS)

Davtyan, D.; Machluf, S.; Soudijn, M. L.; Naber, J. B.; van Druten, N. J.; van Linden van den Heuvell, H. B.; Spreeuw, R. J. C.

2018-02-01

Experiments handling Rydberg atoms near surfaces must necessarily deal with the high sensitivity of Rydberg atoms to (stray) electric fields that typically emanate from adsorbates on the surface. We demonstrate a method to modify and reduce the stray electric field by changing the adsorbate distribution. We use one of the Rydberg excitation lasers to locally affect the adsorbed dipole distribution. By adjusting the averaged exposure time we change the strength (with the minimal value less than 0.2 V /cm at 78 μ m from the chip) and even the sign of the perpendicular field component. This technique is a useful tool for experiments handling Rydberg atoms near surfaces, including atom chips.

FAST TRACK COMMUNICATION: The origin of Bohm diffusion, investigated by a comparison of different modelling methods

NASA Astrophysics Data System (ADS)

Bultinck, E.; Mahieu, S.; Depla, D.; Bogaerts, A.

2010-07-01

'Bohm diffusion' causes the electrons to diffuse perpendicularly to the magnetic field lines. However, its origin is not yet completely understood: low and high frequency electric field fluctuations are both named to cause Bohm diffusion. The importance of including this process in a Monte Carlo (MC) model is demonstrated by comparing calculated ionization rates with particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations. A good agreement is found with a Bohm diffusion parameter of 0.05, which corresponds well to experiments. Since the PIC/MCC method accounts for fast electric field fluctuations, we conclude that Bohm diffusion is caused by fast electric field phenomena.

Properties of radiation stable insulation composites for fusion magnet

NASA Astrophysics Data System (ADS)

Wu, Zhixiong; Huang, Rongjin; Huang, Chuanjun; Li, Laifeng

2017-09-01

High field superconducting magnets made of Nb3Al will be a suitable candidate for future fusion device which can provide magnetic field over 15T without critical current degradation caused by strain. The higher magnetic field and the larger current will produce a huge electromagnetic force. Therefore, it is necessary to develop high strength cryogenic structural materials and electrical insulation materials with excellent performance. On the other hand, superconducting magnets in fusion devices will experience significant nuclear radiation exposure during service. While typical structural materials like stainless steel and titanium have proven their ability to withstand these conditions, electrical insulation materials used in these coils have not fared as well. In fact, recent investigations have shown that electrical insulation breakdown is a limiting factor in the performance of high field magnets. The insulation materials used in the high field fusion magnets should be characterized by excellent mechanical properties, high radiation resistivity and good thermal conductivity. To meet these objectives, we designed various insulation materials based on epoxy resins and cyanate ester resins and investigated their processing characteristic and mechanical properties before and after irradiation at low temperature. In this paper, the recent progress of the radiation stable insulation composites for high field fusion magnet is presented. The materials have been irradiated by 60Co γ-ray irradiation in air at ambient temperature with a dose rate of 300 Gy/min. The total doses of 1 MGy, 5 MGy and 10 MGy were selected to the test specimens.

Electric field variations measured continuously in free air over a conductive thin zone in the tilted Lias-epsilon black shales near Osnabrück, Northwest Germany

NASA Astrophysics Data System (ADS)

Gurk, M.; Bosch, F. P.; Tougiannidis, N.

2013-04-01

Common studies on the static electric field distribution over a conductivity anomaly use the self-potential method. However, this method is time consuming and requires nonpolarizable electrodes to be placed in the ground. Moreover, the information gained by this method is restricted to the horizontal variations of the electric field. To overcome the limitation in the self-potential technique, we conducted a field experiment using a non conventional technique to assess the static electric field over a conductivity anomaly. We use two metallic potential probes arranged on an insulated boom with a separation of 126 cm. When placed into the electric field of the free air, a surface charge will be induced on each probe trying to equalize with the potential of the surrounding atmosphere. The use of a plasma source at both probes facilitated continuous and quicker measurement of the electric field in the air. The present study shows first experimental measurements with a modified potential probe technique (MPP) along a 600-meter-long transect to demonstrate the general feasibility of this method for studying the static electric field distribution over shallow conductivity anomalies. Field measurements were carried out on a test site on top of the Bramsche Massif near Osnabrück (Northwest Germany) to benefit from a variety of available near surface data over an almost vertical conductivity anomaly. High resolution self-potential data served in a numerical analysis to estimate the expected individual components of the electric field vector. During the experiment we found more anomalies in the vertical and horizontal components of the electric field than self-potential anomalies. These contrasting findings are successfully cross-validated with conventional near surface geophysical methods. Among these methods, we used self-potential, radiomagnetotelluric, electric resistivity tomography and induced polarization data to derive 2D conductivity models of the subsurface in order to infer the geometrical properties and the origin of the conductivity anomaly in the survey area. The presented study demonstrates the feasibility of electric field measurements in free air to detect and study near surface conductivity anomalies. Variations in Ez correlate well with the conductivity distribution obtained from resistivity methods. Compared to the self-potential technique, continuously free air measurements of the electric field are more rapid and of better lateral resolution combined with the unique ability to analyze vertical components of the electric field which are of particular importance to detect lateral conductivity contrasts. Mapping Ez in free air is a good tool to precisely map lateral changes of the electric field distribution in areas where SP generation fails. MPP offers interesting application in other geophysical techniques e.g. in time domain electromagnetics, DC and IP. With this method we were able to reveal a ca. 150 m broad zone of enhanced electric field strength.

Energy regeneration model of self-consistent field of electron beams into electric power*

NASA Astrophysics Data System (ADS)

Kazmin, B. N.; Ryzhov, D. R.; Trifanov, I. V.; Snezhko, A. A.; Savelyeva, M. V.

2016-04-01

We consider physic-mathematical models of electric processes in electron beams, conversion of beam parameters into electric power values and their transformation into users’ electric power grid (onboard spacecraft network). We perform computer simulation validating high energy efficiency of the studied processes to be applied in the electric power technology to produce the power as well as electric power plants and propulsion installation in the spacecraft.

Field strengths and dissipated powers in microwave-excited high-pressure sulphur discharges

NASA Astrophysics Data System (ADS)

van Dongen, Menno; Körber, Achim; van der Heijden, Harm; Jonkers, Jeroen; Scholl, Robert; van der Mullen, Joost

1998-11-01

A method which makes it is possible to measure the electric field strength in microwave discharges is presented. A condition for this method is that the plasma has such a low conductivity that the associated skin depth is larger than the discharge radius. It is found that the field strength in high-pressure sulphur lamps is around 400 V 0022-3727/31/21/015/img10. Furthermore, this method allows the determination of the power absorbed in the resonator's wall and in the plasma and the estimation of the effective electric conductivity in the discharge.

Comparison of effectiveness between cork-screw and peg-screw electrodes for transcranial motor evoked potential monitoring using the finite element method.

PubMed

Tomio, Ryosuke; Akiyama, Takenori; Ohira, Takayuki; Yoshida, Kazunari

2016-01-01

Intraoperative monitoring of motor evoked potentials by transcranial electric stimulation is popular in neurosurgery for monitoring motor function preservation. Some authors have reported that the peg-screw electrodes screwed into the skull can more effectively conduct current to the brain compared to subdermal cork-screw electrodes screwed into the skin. The aim of this study was to investigate the influence of electrode design on transcranial motor evoked potential monitoring. We estimated differences in effectiveness between the cork-screw electrode, peg-screw electrode, and cortical electrode to produce electric fields in the brain. We used the finite element method to visualize electric fields in the brain generated by transcranial electric stimulation using realistic three-dimensional head models developed from T1-weighted images. Surfaces from five layers of the head were separated as accurately as possible. We created the "cork-screws model," "1 peg-screw model," "peg-screws model," and "cortical electrode model". Electric fields in the brain radially diffused from the brain surface at a maximum just below the electrodes in coronal sections. The coronal sections and surface views of the brain showed higher electric field distributions under the peg-screw compared to the cork-screw. An extremely high electric field was observed under cortical electrodes. Our main finding was that the intensity of electric fields in the brain are higher in the peg-screw model than the cork-screw model.

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

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

Lee, Hyeon Jun; Guo, Er-Jia; Min, Taewon

Atomic movement under application of external stimuli (i.e., electric field or mechanical stress) in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO 3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscopy, time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO 3 film, the hysteresis loop of the reflected X-ray intensity was found to resultmore » from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO 3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-fieldinduced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. In conclusion, the effect of external stress on the BiFeO 3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.« less

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

DOE PAGES

Lee, Hyeon Jun; Guo, Er-Jia; Min, Taewon; ...

2017-12-28

Atomic movement under application of external stimuli (i.e., electric field or mechanical stress) in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO 3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscopy, time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO 3 film, the hysteresis loop of the reflected X-ray intensity was found to resultmore » from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO 3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-fieldinduced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. In conclusion, the effect of external stress on the BiFeO 3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.« less

Nano-funnels as electro-osmotic ``tweezers and pistons''

NASA Astrophysics Data System (ADS)

Wang, Yanqian; Panyukov, Sergey; Zhou, Jinsheng; Menard, Laurent D.; Ramsey, J. Michael; Rubinstien, Michael

2014-03-01

An electric field is used to force a DNA molecule into a nano-channel by compensating the free energy penalty that results from the reduced conformational entropy of the confined macromolecule. Narrow nano-channels require high critical electric fields to achieve DNA translocation, leading to short dwell times of DNA in these channels. We demonstrate that nano-funnels integrated with nano-channels reduce the free energy barrier and lower the critical electric field required for DNA translocation. A focused electric field within the funnel increases the electric force on the DNA, compresses the molecule, and increases the osmotic pressure at the nano-channel entrance. This ``electro-osmotic piston'' forces the molecule into the nano-channel at lower electric fields than those observed without the funnel. Appropirately designed nano-funnels can also function as tweezers that allow manipulation of the position of the DNA molecule. The predictions of our theory describing double-stranded DNA behavior in nano-funnel - nano-channel devices are consistent with experimental results. Thanks for the financial support from NSF (DMR-1309892, DMR-1121107, DMR-1122483), NIH (1-P50-HL107168, 1-P01-HL108808-01A1, R01HG02647), NHGRI and CF Foundation.

Investigation of electrorheological properties of biodegradable modified cellulose/corn oil suspensions.

PubMed

Tilki, Tahir; Yavuz, Mustafa; Karabacak, Ciğdem; Cabuk, Mehmet; Ulutürk, Mehmet

2010-03-30

Considerable scientific and industrial interest is currently being focused on a class of materials known as electrorheological (ER) fluids, which display remarkable rheological behaviour, being able to convert rapidly and repeatedly from a liquid to solid when an electric field (E) is applied or removed. In this study, biodegradable cellulose was modified and converted to their carboxyl salts. Modified cellulose is characterised by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and conductivity measurements. Suspensions of cellulose (C) and modified cellulose (MC) were prepared in insulated corn oil (CO). The effects of electric field strength, shear rate, shear stress, temperature, etc. of these suspensions onto ER activity were determined. Rheological measurements were carried out via a rotational rheometer with a high-voltage generator to investigate the effects of electric field strength and particle concentration on ER performance. The results show that the ER properties are enhanced by increasing the particle concentration and electric field strength. Also the cellulose-based ER fluids exhibit viscoelastic behaviour under an applied electric field due to the chain formation induced by electric polarization between particles. Copyright 2009 Elsevier Ltd. All rights reserved.

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.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Technical Reports Server (NTRS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell-lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a-Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two "control plates" are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (gladwater) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

Tuning the Electronic, Optical, and Magnetic Properties of Monolayer GaSe with a Vertical Electric Field

NASA Astrophysics Data System (ADS)

Ke, Congming; Wu, Yaping; Guo, Guang-Yu; Lin, Wei; Wu, Zhiming; Zhou, Changjie; Kang, Junyong

2018-04-01

Inspired by two-dimensional material with their unique physical properties and innovative device applications, here we report a design framework on monolayer GaSe, an important member of the two-dimensional material family, in an effort to tune the electronic, optical, and magnetic properties through a vertical electric field. A transition from indirect to direct band gap in monolayer GaSe is found with an electric field of 0.09 V /Å . The giant Stark effect results in a reduction of the band gap with a Stark coefficient of 3.54 Å. Optical and dielectric properties of monolayer GaSe are dependent on the vertical electric field. A large regulation range for polarization E ∥c ^ is found for the static dielectric constant. The optical anisotropy with the dipole transition from E ∥c ^ to E ⊥c ^ is achieved. Induced by the spin-orbit coupling, spin-splitting energy at the valence band maximum increases linearly with the electric field. The effective mass of holes is highly susceptible to the vertical electric field. Switchable spin-polarization features in spin texture of monolayer GaSe are predicted. The tunable electronic, optical, and magnetic properties of monolayer GaSe hold great promise for applications in both the optoelectronic and spintronic devices.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Astrophysics Data System (ADS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-04-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a- Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two ''control plates'' are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (glass/water) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

Coupling behaviors of graphene/SiO2/Si structure with external electric field

NASA Astrophysics Data System (ADS)

Onishi, Koichi; Kirimoto, Kenta; Sun, Yong

2017-02-01

A traveling electric field in surface acoustic wave was introduced into the graphene/SiO2/Si sample in the temperature range of 15 K to 300 K. The coupling behaviors between the sample and the electric field were analyzed using two parameters, the intensity attenuation and time delay of the traveling-wave. The attenuation originates from Joule heat of the moving carriers, and the delay of the traveling-wave was due to electrical resistances of the fixed charge and the moving carriers with low mobility in the sample. The attenuation of the external electric field was observed in both Si crystal and graphene films in the temperature range. A large attenuation around 190 K, which depends on the strength of external electric field, was confirmed for the Si crystal. But, no significant temperature and field dependences of the attenuation in the graphene films were detected. On the other hand, the delay of the traveling-wave due to ionic scattering at low temperature side was observed in the Si crystal, but cannot be detected in the films of the mono-, bi- and penta-layer graphene with high conductivities. Also, it was indicated in this study that skin depth of the graphene film was less than thickness of two graphene atomic layers in the temperature range.

Static Measurements on HTS Coils of Fully Superconducting AC Electric Machines for Aircraft Electric Propulsion System

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.; Hunker, Keith R.; Hartwig, Jason; Brown, Gerald V.

2017-01-01

The NASA Glenn Research Center (GRC) has been developing the high efficiency and high-power density superconducting (SC) electric machines in full support of electrified aircraft propulsion (EAP) systems for a future electric aircraft. A SC coil test rig has been designed and built to perform static and AC measurements on BSCCO, (RE)BCO, and YBCO high temperature superconducting (HTS) wire and coils at liquid nitrogen (LN2) temperature. In this paper, DC measurements on five SC coil configurations of various geometry in zero external magnetic field are measured to develop good measurement technique and to determine the critical current (Ic) and the sharpness (n value) of the super-to-normal transition. Also, standard procedures for coil design, fabrication, coil mounting, micro-volt measurement, cryogenic testing, current control, and data acquisition technique were established. Experimentally measured critical currents are compared with theoretical predicted values based on an electric-field criterion (Ec). Data here are essential to quantify the SC electric machine operation limits where the SC begins to exhibit non-zero resistance. All test data will be utilized to assess the feasibility of using HTS coils for the fully superconducting AC electric machine development for an aircraft electric propulsion system.

Roll-to-Roll Continuous Manufacturing Multifunctional Nanocomposites by Electric-Field-Assisted "Z" Direction Alignment of Graphite Flakes in Poly(dimethylsiloxane).

PubMed

Guo, Yuanhao; Chen, Yuwei; Wang, Enmin; Cakmak, Miko

2017-01-11

A roll-to-roll continuous process was developed to manufacture large-scale multifunctional poly(dimethylsiloxane) (PDMS) films embedded with thickness direction ("Z" direction) aligned graphite nanoparticles by application of electric field. The kinetics of particle "Z" alignment and chain formation was studied by tracking the real-time change of optical light transmission through film thickness direction. Benefiting from the anisotropic structure of aligned particle chains, the electrical and thermal properties of the nanocomposites were dramatically enhanced through the thickness direction as compared to those of the nanocomposites containing the same particle loading without electrical field alignment. With 5 vol % graphite loading, 250 times higher electrical conductivity, 43 times higher dielectric permittivity, and 1.5 times higher thermal conductivity was achieved in the film thickness direction after the particles were aligned under electrical field. Moreover, the aligned nanocomposites with merely 2 vol % graphite particles exhibit even higher electric conductivity and dielectric permittivity than those of the nonaligned nanocomposites at random percolation threshold (10 vol % particles), as the "electric-field-directed" percolation threshold concentration is substantially decreased using this process. As the graphite loading increases to 20 vol %, the aligned nanocomposites exhibit thermal conductivity as high as 6.05 W/m·K, which is 35 times the thermal conductivity of pure matrix. This roll-to-roll electric field continuous process provides a simple, low-cost, and commercially viable method to manufacture multifunctional nanocomposites for applications as embedded capacitor, electromagnetic (EM) shielding, and thermal interface materials.

Electrically reversible cracks in an intermetallic film controlled by an electric field

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

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

Electrically reversible cracks in an intermetallic film controlled by an electric field

DOE PAGES

Liu, Z. Q.; Liu, J. H.; Biegalski, M. D.; ...

2018-01-03

Cracks in solid-state materials are typically irreversible. We report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on-off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks canmore » reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.« less

Spontaneous electric polarization in the B-site magnetic spinel GeCu2O4

NASA Astrophysics Data System (ADS)

Yanda, Premakumar; Ghara, Somnath; Sundaresan, A.

2018-04-01

We report the observation of a spontaneous electric polarization at the antiferromagnetic ordering temperature (TN ∼ 33 K) of Cu2+ ions in the B-site magnetic spinel GeCu2O4, synthesized at high pressure and high temperature. This compound is known to crystallize in a tetragonal structure (space group I41/amd) due to Jahn-Teller distortion of Cu2+ ions and exhibit a collinear up-up-down-down (↑↑↓↓) antiferromagnetic spin configuration below TN. We found a clear dielectric anomaly at TN, where an electric polarization appears in the absence of applied magnetic field. The electric polarization is suppressed by applied magnetic fields, which demonstrates that the compound GeCu2O4 is a type-II multiferroic.

Assessment of foetal exposure to the homogeneous magnetic field harmonic spectrum generated by electricity transmission and distribution networks.

PubMed

Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

2015-04-01

During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

Assessment of Foetal Exposure to the Homogeneous Magnetic Field Harmonic Spectrum Generated by Electricity Transmission and Distribution Networks

PubMed Central

Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

2015-01-01

During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level. PMID:25837346

Microbial electricity generation in rice paddy fields: recent advances and perspectives in rhizosphere microbial fuel cells.

PubMed

Kouzuma, Atsushi; Kaku, Nobuo; Watanabe, Kazuya

2014-12-01

Microbial fuel cells (MFCs) are devices that use living microbes for the conversion of organic matter into electricity. MFC systems can be applied to the generation of electricity at water/sediment interfaces in the environment, such as bay areas, wetlands, and rice paddy fields. Using these systems, electricity generation in paddy fields as high as ∼80 mW m(-2) (based on the projected anode area) has been demonstrated, and evidence suggests that rhizosphere microbes preferentially utilize organic exudates from rice roots for generating electricity. Phylogenetic and metagenomic analyses have been conducted to identify the microbial species and catabolic pathways that are involved in the conversion of root exudates into electricity, suggesting the importance of syntrophic interactions. In parallel, pot cultures of rice and other aquatic plants have been used for rhizosphere MFC experiments under controlled laboratory conditions. The findings from these studies have demonstrated the potential of electricity generation for mitigating methane emission from the rhizosphere. Notably, however, the presence of large amounts of organics in the rhizosphere drastically reduces the effect of electricity generation on methane production. Further studies are necessary to evaluate the potential of these systems for mitigating methane emission from rice paddy fields. We suggest that paddy-field MFCs represent a promising approach for harvesting latent energy of the natural world.

Micro-cones on a liquid interface in high electric field: Ionization effects

NASA Astrophysics Data System (ADS)

Subbotin, Andrey V.; Semenov, Alexander N.

2018-02-01

We formulate and explore electrohydrodynamic equations for conductive liquids taking dissociation/recombination processes into account and discover a novel type of liquid cones which carry both surface and net bulk charge and can be formed on a liquid interface in an electric field. The bulk charge is generated by the corona discharge due to a high electric field at the cone apex. We establish correlation between the cone angle and physical parameters of the liquid on the one hand and the electric current passing through the cone on the other hand. It is shown that the current strongly increases when the cone angle tends to a critical value which is a function of the dielectric permittivity of the liquid. The cone stability with respect to axially symmetric perturbations is analyzed. It is shown that the cones with apex angles close to the critical angle are likely to be stable. The effect of the imposed flow on the cone apex stability is also discussed.

Carrier trajectory tracking equations for Simple-band Monte Carlo simulation of avalanche multiplication processes

NASA Astrophysics Data System (ADS)

Ong, J. S. L.; Charin, C.; Leong, J. H.

2017-12-01

Avalanche photodiodes (APDs) with steep electric field gradients generally have low excess noise that arises from carrier multiplication within the internal gain of the devices, and the Monte Carlo (MC) method is among popular device simulation tools for such devices. However, there are few articles relating to carrier trajectory modeling in MC models for such devices. In this work, a set of electric-field-gradient-dependent carrier trajectory tracking equations are developed and used to update the positions of carriers along the path during Simple-band Monte Carlo (SMC) simulations of APDs with non-uniform electric fields. The mean gain and excess noise results obtained from the SMC model employing these equations show good agreement with the results reported for a series of silicon diodes, including a p+n diode with steep electric field gradients. These results confirm the validity and demonstrate the feasibility of the trajectory tracking equations applied in SMC models for simulating mean gain and excess noise in APDs with non-uniform electric fields. Also, the simulation results of mean gain, excess noise, and carrier ionization positions obtained from the SMC model of this work agree well with those of the conventional SMC model employing the concept of a uniform electric field within a carrier free-flight. These results demonstrate that the electric field variation within a carrier free-flight has an insignificant effect on the predicted mean gain and excess noise results. Therefore, both the SMC model of this work and the conventional SMC model can be used to predict the mean gain and excess noise in APDs with highly non-uniform electric fields.

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.

Numerical modelling of geodesic acoustic mode relaxation in a tokamak edge

DOE PAGES

Dorf, M. A.; Cohen, R. H.; Dorr, M.; ...

2013-05-08

Here, the edge of a tokamak in a high confinement (H mode) regime is characterized by steep density gradients and a large radial electric field. Recent analytical studies demonstrated that the presence of a strong radial electric field consistent with a subsonic pedestal equilibrium modifies the conventional results of the neoclassical formalism developed for the core region. In the present work we make use of the recently developed gyrokinetic code COGENT to numerically investigate neoclassical transport in a tokamak edge including the effects of a strong radial electric field. The results of numerical simulations are found to be in goodmore » qualitative agreement with the theoretical predictions and the quantitative discrepancy is discussed. In addition, the present work investigates the effects of a strong radial electric field on the relaxation of geodesic acoustic modes (GAMs) in a tokamak edge. Numerical simulations demonstrate that the presence of a strong radial electric field characteristic of a tokamak pedestal can enhance the GAM decay rate, and heuristic arguments elucidating this finding are provided.« less

Influence of tissue resistivities on neuromagnetic fields and electric potentials studied with a finite element model of the head.

PubMed

Haueisen, J; Ramon, C; Eiselt, M; Brauer, H; Nowak, H

1997-08-01

Modeling in magnetoencephalography (MEG) and electroencephalography (EEG) requires knowledge of the in vivo tissue resistivities of the head. The aim of this paper is to examine the influence of tissue resistivity changes on the neuromagnetic field and the electric scalp potential. A high-resolution finite element method (FEM) model (452,162 elements, 2-mm resolution) of the human head with 13 different tissue types is employed for this purpose. Our main finding was that the magnetic fields are sensitive to changes in the tissue resistivity in the vicinity of the source. In comparison, the electric surface potentials are sensitive to changes in the tissue resistivity in the vicinity of the source and in the vicinity of the position of the electrodes. The magnitude (strength) of magnetic fields and electric surface potentials is strongly influenced by tissue resistivity changes, while the topography is not as strongly influenced. Therefore, an accurate modeling of magnetic field and electric potential strength requires accurate knowledge of tissue resistivities, while for source localization procedures this knowledge might not be a necessity.

A Power-Frequency Electric Field Sensor for Portable Measurement

PubMed Central

Xiao, Dongping; Ma, Qichao; Xie, Yutong; Zheng, Qi

2018-01-01

In this paper, a new type of electric field sensor is proposed for the health and safety protection of inspection staff in high-voltage environments. Compared with the traditional power frequency electric field measurement instruments, the portable instrument has some special performance requirements and, thus, a new kind of double spherical shell sensor is presented. First, the mathematical relationships between the induced voltage of the sensor, the output voltage of the measurement circuit, and the original electric field in free space are deduced theoretically. These equations show the principle of the proposed sensor to measure the electric field and the effect factors of the measurement. Next, the characteristics of the sensor are analyzed through simulation. The simulation results are in good agreement with the theoretical analysis. The influencing rules of the size and material of the sensor on the measurement results are summarized. Then, the proposed sensor and the matching measurement system are used in a physical experiment. After calibration, the error of the measurement system is discussed. Lastly, the directional characteristic of the proposed sensor is experimentally tested. PMID:29614753

Dielectric Breakdown Characteristics of Oil-pressboard Insulation System against AC/DC Superposed Voltage

NASA Astrophysics Data System (ADS)

Ebisawa, Yoshihito; Yamada, Shin; Mori, Shigekazu; Ikeda, Masami

This paper describes breakdown characteristics of an oil-pressboard insulation system to a superposition voltage of AC and DC voltages. Although AC electric field is decided by the ratio of the relative permittivity of a pressboard and insulating oil, DC electric field is decided by ratio α of volume resistivities. From the measurement in this study, 13—78 and 1.8—5.7 are obtained as the volume resistivity ratios α at temperature of 30°C and 80°C, respectively. The breakdown voltages against AC, DC, and those superposition voltages are surveyed to insulation models. In normal temperature, the breakdown voltage to the superposition voltage of AC and DC is determined by AC electric field applied to the oil duct. Since the α becomes as low as 2-3 at temperature of 80°C, AC and DC voltages almost equally contribute to the electric field of the oil duct as a result. That is, it became clear that superposed DC voltage boosts the electric field across oil ducts at operating high temperature.

A Power-Frequency Electric Field Sensor for Portable Measurement.

PubMed

Xiao, Dongping; Ma, Qichao; Xie, Yutong; Zheng, Qi; Zhang, Zhanlong

2018-03-31

In this paper, a new type of electric field sensor is proposed for the health and safety protection of inspection staff in high-voltage environments. Compared with the traditional power frequency electric field measurement instruments, the portable instrument has some special performance requirements and, thus, a new kind of double spherical shell sensor is presented. First, the mathematical relationships between the induced voltage of the sensor, the output voltage of the measurement circuit, and the original electric field in free space are deduced theoretically. These equations show the principle of the proposed sensor to measure the electric field and the effect factors of the measurement. Next, the characteristics of the sensor are analyzed through simulation. The simulation results are in good agreement with the theoretical analysis. The influencing rules of the size and material of the sensor on the measurement results are summarized. Then, the proposed sensor and the matching measurement system are used in a physical experiment. After calibration, the error of the measurement system is discussed. Lastly, the directional characteristic of the proposed sensor is experimentally tested.

Magnetic and electric control of multiferroic properties in monodomain crystals of BiFeO3

NASA Astrophysics Data System (ADS)

Tokunaga, Masashi

One of the important goals for multiferroics is to develop the non-volatile magnetic memories that can be controlled by electric fields with low power consumption. Among numbers of multiferroic materials, BiFeO3 has been the most extensively studied because of its substantial ferroelectric polarization and magnetic order up to above room temperature. Recent high field experiments on monodomain crystals of BiFeO3 revealed the existence of additional electric polarization normal to the three-fold rotational axis. This transverse component is coupled with the cycloidal magnetic domain, and hence, can be controlled by external magnetic fields. Application of electric fields normal to the trigonal axis modifies volume fraction of these multiferroic domains, which involves change in resistance of the sample, namely exhibits the bipolar resistive memory effect. In this talk, I will introduce the effects of magnetic and electric fields on magnetoelectric and structural properties observed in monodomain crystals of BiFeO3. This work was supported by JSPS Grant Number 16K05413 and by a research Grant from The Murata Science Foundation.

Electric Field Control of Interfacial Ferromagnetism in CaMnO3/CaRuO3 Heterostructures

NASA Astrophysics Data System (ADS)

Grutter, A. J.; Kirby, B. J.; Gray, M. T.; Flint, C. L.; Alaan, U. S.; Suzuki, Y.; Borchers, J. A.

2015-07-01

New mechanisms for achieving direct electric field control of ferromagnetism are highly desirable in the development of functional magnetic interfaces. To that end, we have probed the electric field dependence of the emergent ferromagnetic layer at CaRuO3/CaMnO3 interfaces in bilayers fabricated on SrTiO3. Using polarized neutron reflectometry, we are able to detect the ferromagnetic signal arising from a single atomic monolayer of CaMnO3, manifested as a spin asymmetry in the reflectivity. We find that the application of an electric field of 600 kV /m across the bilayer induces a significant increase in this spin asymmetry. Modeling of the reflectivity suggests that this increase corresponds to a transition from canted antiferromagnetism to full ferromagnetic alignment of the Mn4 + ions at the interface. This increase from 1 μB to 2.5 - 3.0 μB per Mn is indicative of a strong magnetoelectric coupling effect, and such direct electric field control of the magnetization at an interface has significant potential for spintronic applications.

Electric field characteristics of electroconvulsive therapy with individualized current amplitude: a preclinical study.

PubMed

Lee, Won Hee; Lisanby, Sarah H; Laine, Andrew F; Peterchev, Angel V

2013-01-01

This study examines the characteristics of the electric field induced in the brain by electroconvulsive therapy (ECT) with individualized current amplitude. The electric field induced by bilateral (BL), bifrontal (BF), right unilateral (RUL), and frontomedial (FM) ECT electrode configurations was computed in anatomically realistic finite element models of four nonhuman primates (NHPs). We generated maps of the electric field strength relative to an empirical neural activation threshold, and determined the stimulation strength and focality at fixed current amplitude and at individualized current amplitudes corresponding to seizure threshold (ST) measured in the anesthetized NHPs. The results show less variation in brain volume stimulated above threshold with individualized current amplitudes (16-36%) compared to fixed current amplitude (30-62%). Further, the stimulated brain volume at amplitude-titrated ST is substantially lower than that for ECT with conventional fixed current amplitudes. Thus individualizing the ECT stimulus current could compensate for individual anatomical variability and result in more focal and uniform electric field exposure across different subjects compared to the standard clinical practice of using high, fixed current for all patients.

Magnetoacoustic Tomography with Magnetic Induction for Electrical Conductivity based Tissue imaging

NASA Astrophysics Data System (ADS)

Mariappan, Leo

Electrical conductivity imaging of biological tissue has attracted considerable interest in recent years owing to research indicating that electrical properties, especially electrical conductivity and permittivity, are indicators of underlying physiological and pathological conditions in biological tissue. Also, the knowledge of electrical conductivity of biological tissue is of interest to researchers conducting electromagnetic source imaging and in design of devices that apply electromagnetic energy to the body such as MRI. So, the need for a non-invasive, high resolution impedance imaging method is highly desired. To address this need we have studied the magnetoacoustic tomography with magnetic induction (MAT-MI) method. In MAT-MI, the object is placed in a static and a dynamic magnetic field giving rise to ultrasound waves. The dynamic field induces eddy currents in the object, and the static field leads to generation of acoustic vibrations from Lorentz force on the induced currents. The acoustic vibrations are at the same frequency as the dynamic magnetic field, which is chosen to match the ultrasound frequency range. These ultrasound signals can be measured by ultrasound probes and are used to reconstruct MAT-MI acoustic source images using possible ultrasound imaging approaches .The reconstructed high spatial resolution image is indicative of the object's electrical conductivity contrast. We have investigated ultrasound imaging methods to reliably reconstruct the MAT-MI image under the practical conditions of limited bandwidth and transducer geometry. The corresponding imaging algorithm, computer simulation and experiments are developed to test the feasibility of these different methods. Also, in experiments, we have developed a system with the strong static field of an MRI magnet and a strong pulsed magnetic field to evaluate MAT-MI in biological tissue imaging. It can be seen from these simulations and experiments that conductivity boundary images with millimeter resolution can be reliably reconstructed with MAT-MI. Further, to estimate the conductivity distribution throughout the object, we reconstruct a vector source image corresponding to the induced eddy currents. As the current source is uniformly present throughout the object, we are able to reliably estimate the internal conductivity distribution for a more complete imaging. From the computer simulations and experiments it can be seen that MAT-MI method has the potential to be a clinically applicable, high resolution, non-invasive method for electrical conductivity imaging.

A Sinusoidal Applied Electric Potential can Induce a Long-Range, Steady Electrophoretic Force

NASA Astrophysics Data System (ADS)

Amrei, Seyyed Hashemi; Ristenpart, William D.; Miller, Greg R.

2017-11-01

We use the standard electrokinetic model to numerically investigate the electric field in aqueous solutions between parallel electrodes under AC polarization. In contrast to prior work, we invoke no simplifying assumptions regarding the applied voltage, frequency, or mismatch in ionic mobilities. We find that the nonlinear electromigration terms significantly contribute to the overall shape of the electric potential vs. time, which at sufficiently high applied potentials develops multi-modal peaks. More surprisingly, we find that electrolytes with non-equal mobilities yield an electric field with non-zero time average at large distances from the electrodes. Our calculations indicate this long-range electric field suffices to levitate colloidal particles many microns away from the electrode against the gravitational field, in accord with experimental observations of such behavior (Woehl et al., PRX, 2015). Moreover, the results indicate that particles will aggregate laterally near electrodes in some electrolytes but separate in others, helping explain a longstanding but not well understood phenomenon.

Linear electric field mass spectrometry

DOEpatents

McComas, David J.; Nordholt, Jane E.

1992-01-01

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

Exploring the Emotions in Pedagogical Content Knowledge about the Electric Field

ERIC Educational Resources Information Center

Melo, Lina; Cañada, Florentina; Mellado, Vicente

2017-01-01

The objective of this study was to characterise the changes in the Pedagogical Content Knowledge (PCK) about electric fields of two Colombian physics teachers (Isabel and Alejandro) at the high school level (pupils of ages 17-19), the emotions and their relationship with PCK. The research was conducted during two consecutive years, before and…

A Method of Computing Electric Field Parameters on Boundaries between Two Media

ERIC Educational Resources Information Center

Rizhov, Alexander

2010-01-01

Many problems of electric field strength on a boundary between two media require college-level mathematical analysis. However, when the boundary between media is represented by a sphere or a flat plane, these types of problems can be solved algebraically, placing them within reach of high school students. This article presents a solution analysis…

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.

ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. II. RESISTIVE ELECTRIC FIELD EFFECTS

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

Zhou, X.; Gan, W.; Liu, S.

We investigate electron acceleration by electric fields induced by cascading reconnections in current sheets trailing coronal mass ejections via a test particle approach in the framework of the guiding-center approximation. Although the resistive electric field is much weaker than the inductive electric field, the electron acceleration is still dominated by the former. Anomalous resistivity η is switched on only in regions where the current carrier’s drift velocity is large enough. As a consequence, electron acceleration is very sensitive to the spatial distribution of the resistive electric fields, and electrons accelerated in different segments of the current sheet have different characteristics.more » Due to the geometry of the 2.5-dimensional electromagnetic fields and strong resistive electric field accelerations, accelerated high-energy electrons can be trapped in the corona, precipitating into the chromosphere or escaping into interplanetary space. The trapped and precipitating electrons can reach a few MeV within 1 s and have a very hard energy distribution. Spatial structure of the acceleration sites may also introduce breaks in the electron energy distribution. Most of the interplanetary electrons reach hundreds of keV with a softer distribution. To compare with observations of solar flares and electrons in solar energetic particle events, we derive hard X-ray spectra produced by the trapped and precipitating electrons, fluxes of the precipitating and interplanetary electrons, and electron spatial distributions.« less

Electric field enhanced hydrogen storage on polarizable materials substrates

PubMed Central

Zhou, J.; Wang, Q.; Sun, Q.; Jena, P.; Chen, X. S.

2010-01-01

Using density functional theory, we show that an applied electric field can substantially improve the hydrogen storage properties of polarizable substrates. This new concept is demonstrated by adsorbing a layer of hydrogen molecules on a number of nanomaterials. When one layer of H2 molecules is adsorbed on a BN sheet, the binding energy per H2 molecule increases from 0.03 eV/H2 in the field-free case to 0.14 eV/H2 in the presence of an electric field of 0.045 a.u. The corresponding gravimetric density of 7.5 wt% is consistent with the 6 wt% system target set by Department of Energy for 2010. The strength of the electric field can be reduced if the substrate is more polarizable. For example, a hydrogen adsorption energy of 0.14 eV/H2 can be achieved by applying an electric field of 0.03 a.u. on an AlN substrate, 0.006 a.u. on a silsesquioxane molecule, and 0.007 a.u. on a silsesquioxane sheet. Thus, application of an electric field to a polarizable substrate provides a novel way to store hydrogen; once the applied electric field is removed, the stored H2 molecules can be easily released, thus making storage reversible with fast kinetics. In addition, we show that materials with rich low-coordinated nonmetal anions are highly polarizable and can serve as a guide in the design of new hydrogen storage materials. PMID:20133647

Swelling characteristics of acrylic acid polyelectrolyte hydrogel in a dc electric field

NASA Astrophysics Data System (ADS)

Jabbari, Esmaiel; Tavakoli, Javad; Sarvestani, Alireza S.

2007-10-01

A novel application of environmentally sensitive polyelectrolytes is in the fabrication of BioMEMS devices as sensors and actuators. Poly(acrylic acid) (PAA) gels are anionic polyelectrolyte networks that exhibit volume expansion in aqueous physiological environments. When an electric field is applied to PAA polyelectrolyte gels, the fixed anionic polyelectrolyte charges and the requirement of electro-neutrality in the network generate an osmotic pressure, above that in the absence of the electric field, to expand the network. The objective of this research was to investigate the effect of an externally applied dc electric field on the volume expansion of the PAA polyelectrolyte gel in a simulated physiological solution of phosphate buffer saline (PBS). For swelling studies in the electric field, two platinum-coated plates, as electrodes, were wrapped in a polyethylene sheet to protect the plates from corrosion and placed vertically in a vessel filled with PBS. The plates were placed on a rail such that the distance between the two plates could be adjusted. The PAA gel was synthesized by free radical crosslinking of acrylic acid monomer with ethylene glycol dimethacrylate (EGDMA) crosslinker. Our results demonstrate that volume expansion depends on the intensity of the electric field, the PAA network density, network homogeneity, and the position of the gel in the field relative to positive/negative electrodes. Our model predictions for PAA volume expansion, based on the dilute electrolyte concentration in the gel network, is in excellent agreement with the experimental findings in the high-electric-field regime (250-300 Newton/Coulomb).

Initial Results from the Vector Electric Field Investigation on the C/NOFS Satellite

NASA Technical Reports Server (NTRS)

Pfaff, R.; Rowland, D.; Acuna, M.; Le, G.; Farrell, W.; Holzworth, R.; Wilson, G.; Burke, W.; Freudenreich, H.; Bromund, K.;

Plasma propulsion for space applications

NASA Astrophysics Data System (ADS)

Fruchtman, Amnon

2000-04-01

The various mechanisms for plasma acceleration employed in electric propulsion of space vehicles will be described. Special attention will be given to the Hall thruster. Electric propulsion utilizes electric and magnetic fields to accelerate a propellant to a much higher velocity than chemical propulsion does, and, as a result, the required propellant mass is reduced. Because of limitations on electric power density, electric thrusters will be low thrust engines compared with chemical rockets. The large jet velocity and small thrust of electric thrusters make them most suitable for space applications such as station keeping of GEO communication satellites, low orbit drag compensation, orbit raising and interplanetary missions. The acceleration in the thruster is either thermal, electrostatic or electromagnetic. The arcjet is an electrothermal device in which the propellant is heated by an electric arc and accelerated while passing through a supersonic nozzle to a relatively low velocity. In the Pulsed Plasma Thruster a solid propellant is accelerated by a magnetic field pressure in a way that is similar in principle to pulsed acceleration of plasmas in other, very different devices, such as the railgun or the plasma opening switch. Magnetoplasmadynamic thrusters also employ magnetic field pressure for the acceleration but with a reasonable efficiency at high power only. In an ion thruster ions are extracted from a plasma through a double grid structure. Ion thrusters provide a high jet velocity but the thrust density is low due to space-charge limitations. The Hall thruster, which in recent years has enjoyed impressive progress, employs a quasi-neutral plasma, and therefore is not subject to a space-charge limit on the current. An applied radial magnetic field impedes the mobility of the electrons so that the applied potential drops across a large region inside the plasma. Methods for separately controlling the profiles of the electric and the magnetic fields will be described. The role of the sonic transition in plasma accelerators will be discussed. It will be shown that large potential drops can be localized to regions of an abrupt sonic transition in a Hall plasma. A configuration with segmented side electrodes can be used to further control the electric field profile and to increase the efficiency.

Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

NASA Astrophysics Data System (ADS)

Shimoi, Norihiro

2015-12-01

Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, the blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.

Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

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

Shimoi, Norihiro, E-mail: shimoi@mail.kankyo.tohoku.ac.jp

2015-12-07

Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, themore » blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.« less

Multi-point observations of large-amplitude electric fields during substorms obtained by THEMIS

NASA Astrophysics Data System (ADS)

Ogasawara, K.; Kasaba, Y.; Nishimura, Y.; Hori, T.; Takada, T.; Miyashita, Y.; Angelopoulos, V.; Bonnell, J. W.; McFadden, J. P.

2009-12-01

Large-amplitude electric fields over 100 mV/m have been observed around the equatorial magnetosphere. These electric fields may contribute to energy transport and particle acceleration in the magnetosphere [e.g., Wygant et al., 2000, 2002], and seem to be related to fast plasma flows with a size of a few Re [Nakamura et al., 2001]. In order to understand their macroscopic characteristics and the effects to magnetic activities, it is important to observe both fields and particles simultaneously at multiple locations within several Re. Five THEMIS probes can frequently provide such chances. In this paper, we show the several events with large-amplitude electric fields during substorms obtained by THEMIS. One of the events is found in 05:50-06:00 UT on 11 March 2008, when TH-D (Xsm=-10.7 Re, Ysm=4.8 Re) and TH-E (Xsm=-10.3 Re, Ysm=5.6 Re) observed intense electric fields. At 05:54 UT, THEMIS GBO-s clearly showed the auroral onset signature. The great intensification was near the SNKQ station, and this structure moved westward with the speed of ~6 km/s. It corresponds to ~200 km/s, as mapped to the TH-D/E location. The footprints of TH-A (Xsm=-6.8 Re, Ysm=-0.4 Re), D, and E were close to the site of the aurora. The location of TH-D was beside that of TH-E, and TH-A was located earthward and eastward from the former two. The enhanced electric fields observed by TH-D and E were associated with magnetic dipolarization and earthward high-speed plasma flow. They were also associated with the depletion of electron density estimated by the spacecraft potential. These features are consistent with the model of plasma bubbles [e.g., Pontius and Wolf, 1990]. The Y components of plasma flows were 200-300 km/s, roughly consistent with the westward auroral motion as mapped to the equatorial magnetosphere. Also, we found that Poynting flux of low frequency was efficient to illuminate the auroral emissions. This fact suggests that electromagnetic energy is transported to the ionosphere. On the other hand, TH-A also observed the large-amplitude electric field greater than TH-D/E. However, TH-A did not detect the high-speed plasma flow nor the depletion of the electron density. In the drift electric field, VxB, estimated from particle and magnetic field observations, TH-D and E detected intense fields, but TH-A found almost zero. This result shows a difference in the role of the electric fields in location of TH-D/E and TH-A. We will show the possible contribution from other factors, such as pressure gradient, current system, and the ionospheric conductivity.

Electric-field-induced motion of colloid particles in smectic liquid crystals

NASA Astrophysics Data System (ADS)

Jakli, Antal

2005-03-01

We present the first observations of DC electric-field-induced rotational and translational motion of finite particles in liquid crystals. The electro-rotation is basically identical to the well known Quincke rotation, which triggers the translational motion at higher fields. From the electric field dependence of the angular velocity of the rotation we obtain the viscosity of the liquid crystals. The analysis of the translational motion in smectic liquid crystals indicates elastic responses near the threshold for translation. At increasing fields the speed of the particles is increasing and at sufficiently high speeds the flow of the smectic A and smectic C liquid crystal around the beads become purely viscous. Colloid particles in smectic materials maybe considered as model systems for understanding motion of proteins in cell membranes.

Slightly uneven electric field trigatron employed in tens of microseconds charging time.

PubMed

Lin, Jiajin; Yang, Jianhua; Zhang, Jiande; Zhang, Huibo; Yang, Xiao

2014-09-01

To solve the issue of operation instability for the trigatron switch in the application of tens of microseconds or even less charging time, a novel trigatron spark gap with slightly uneven electric field was presented. Compared with the conventional trigatron, the novel trigatron was constructed with an obvious field enhancement on the edge of the opposite electrode. The selection of the field enhancement was analyzed based on the theory introduced by Martin. A low voltage trigatron model was constructed and tested on the tens of microseconds charging time platform. The results show that the character of relative range was improved while the trigger character still held a high level. This slightly uneven electric field typed trigatron is willing to be employed in the Tesla transformer - pulse forming line system.

THREE-DIMENSIONAL NON-VACUUM PULSAR OUTER-GAP MODEL: LOCALIZED ACCELERATION ELECTRIC FIELD IN THE HIGHER ALTITUDES

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

Hirotani, Kouichi

2015-01-10

We investigate the particle accelerator that arises in a rotating neutron-star magnetosphere. Simultaneously solving the Poisson equation for the electro-static potential, the Boltzmann equations for relativistic electrons and positrons, and the radiative transfer equation, we demonstrate that the electric field is substantially screened along the magnetic field lines by pairs that are created and separated within the accelerator. As a result, the magnetic-field-aligned electric field is localized in higher altitudes near the light cylinder and efficiently accelerates the positrons created in the lower altitudes outward but does not accelerate the electrons inward. The resulting photon flux becomes predominantly outward, leadingmore » to typical double-peak light curves, which are commonly observed from many high-energy pulsars.« less

Enhancing dielectric permittivity for energy-storage devices through tricritical phenomenon

PubMed Central

Gao, Jinghui; Wang, Yan; Liu, Yongbin; Hu, Xinghao; Ke, Xiaoqin; Zhong, Lisheng; He, Yuting; Ren, Xiaobing

2017-01-01

Although dielectric energy-storing devices are frequently used in high voltage level, the fast growing on the portable and wearable electronics have been increasing the demand on the energy-storing devices at finite electric field strength. This paper proposes an approach on enhancing energy density under low electric field through compositionally inducing tricriticality in Ba(Ti,Sn)O3 ferroelectric material system with enlarged dielectric response. The optimal dielectric permittivity at tricritical point can reach to εr = 5.4 × 104, and the associated energy density goes to around 30 mJ/cm3 at the electric field of 10 kV/cm, which exceeds most of the selected ferroelectric materials at the same field strength. The microstructure nature for such a tricritical behavior shows polarization inhomogeneity in nanometeric scale, which indicates a large polarizability under external electric field. Further phenomenological Landau modeling suggests that large dielectric permittivity and energy density can be ascribed to the vanishing of energy barrier for polarization altering caused by tricriticality. Our results may shed light on developing energy-storing dielectrics with large permittivity and energy density at low electric field. PMID:28098249

Blocking and guiding adult sea lamprey with pulsed direct current from vertical electrodes

USGS Publications Warehouse

Johnson, Nicholas S.; Thompson, Henry T.; Holbrook, Christopher M.; Tix, John A.

2014-01-01

Controlling the invasion front of aquatic nuisance species is of high importance to resource managers. We tested the hypothesis that adult sea lamprey (Petromyzon marinus), a destructive invasive species in the Laurentian Great Lakes, would exhibit behavioral avoidance to dual-frequency pulsed direct current generated by vertical electrodes and that the electric field would not injure or kill sea lamprey or non-target fish. Laboratory and in-stream experiments demonstrated that the electric field blocked sea lamprey migration and directed sea lamprey into traps. Rainbow trout (Oncorhynchus mykiss) and white sucker (Catostomus commersoni), species that migrate sympatrically with sea lamprey, avoided the electric field and had minimal injuries when subjected to it. Vertical electrodes are advantageous for fish guidance because (1) the electric field produced varies minimally with depth, (2) the electric field is not grounded, reducing power consumption to where portable and remote deployments powered by solar, wind, hydro, or a small generator are feasible, and (3) vertical electrodes can be quickly deployed without significant stream modification allowing rapid responses to new invasions. Similar dual-frequency pulsed direct current fields produced from vertical electrodes may be advantageous for blocking or trapping other invasive fish or for guiding valued fish around dams.

Synthesis of In2O3 nanowire-decorated Ga2O3 nanobelt heterostructures and their electrical and field-emission properties.

PubMed

Lin, Jing; Huang, Yang; Bando, Yoshio; Tang, Chengchun; Li, Chun; Golberg, Dmitri

2010-04-27

We report on the synthesis of In2O3 nanowire-decorated Ga2O3 nanobelt heterostructures via a simple catalyst-free method. A typical heterostructure, where an In2O3 nanowire forms a sort of a "dorsal fin" on the Ga2O3 nanobelt, exhibits the T-shaped cross-section. The structure, electrical porperties, and field-emission properties of this material are systematically investigated. The heterostructures possess a typical n-type semiconducting behavior with enhanced conductivity. Field-emission measurements show that they have a low turn-on field (approximately 1.31 V/microm) and a high field-enhancement factor (over 4000). The excellent field-emission characteristics are attributed to their special geometry and good electrical properties. The present In2O3-decorated Ga2O3 heterostructures are envisaged to be decent field-emitters useful in advanced electronic and optoelectronic nanodevices.

Do dielectric nanostructures turn metallic in high-electric dc fields?

PubMed

Silaeva, E P; Arnoldi, L; Karahka, M L; Deconihout, B; Menand, A; Kreuzer, H J; Vella, A

2014-11-12

Three-dimensional dielectric nanostructures have been analyzed using field ion microscopy (FIM) to study the electric dc field penetration inside these structures. The field is proved to be screened within a few nanometers as theoretically calculated taking into account the high-field impact ionization process. Moreover, the strong dc field of the order of 0.1 V/Å at the surface inside a dielectric nanostructure modifies its band structure leading to a strong band gap shrinkage and thus to a strong metal-like optical absorption near the surface. This metal-like behavior was theoretically predicted using first-principle calculations and experimentally proved using laser-assisted atom probe tomography (APT). This work opens up interesting perspectives for the study of the performance of all field-effect nanodevices, such as nanotransistor or super capacitor, and for the understanding of the physical mechanisms of field evaporation of dielectric nanotips in APT.

Reverse Current in Solar Flares

NASA Technical Reports Server (NTRS)

Knight, J. W.; Sturrock, P. A.

1976-01-01

The theory that impulsive X ray bursts are produced by high energy electrons streaming from the corona to the chromosphere is investigated. Currents associated with these streams are so high that either the streams do not exist or their current is neutralized by a reverse current. Analysis of a simple model indicates that the primary electron stream leads to the development of an electric field in the ambient corona which decelerates the primary beam and produces a neutralizing reverse current. It appears that, in some circumstances, this electric field could prevent the primary beam from reaching the chromosphere. In any case, the electric field acts as an energy exchange mechanism, extracting kinetic energy from the primary beam and using it to heat the ambient plasma. This heating is typically so rapid that it must be expected to have important dynamical consequences.

Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance

NASA Astrophysics Data System (ADS)

Longtin, Rémi; Sanchez-Valencia, Juan Ramon; Shorubalko, Ivan; Furrer, Roman; Hack, Erwin; Elsener, Hansrudolf; Gröning, Oliver; Greenwood, Paul; Rupesinghe, Nalin; Teo, Kenneth; Leinenbach, Christian; Gröning, Pierangelo

2015-02-01

The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag-Cu-Ti alloy and at 880 °C with a Cu-Sn-Ti-Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm-1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected.

Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance

PubMed Central

Longtin, Rémi; Ramon Sanchez-Valencia, Juan; Shorubalko, Ivan; Furrer, Roman; Hack, Erwin; Elsener, Hansrudolf; Gröning, Oliver; Greenwood, Paul; Rupesinghe, Nalin; Teo, Kenneth; Leinenbach, Christian; Gröning, Pierangelo

2015-01-01

The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag–Cu–Ti alloy and at 880 °C with a Cu–Sn–Ti–Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm−1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected. PMID:27877755

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.

High sensitivity electric field monitoring system for control of field-induced CD degradation in reticles (EFM)

NASA Astrophysics Data System (ADS)

Sebald, Thomas; Rider, Gavin

2009-04-01

It has recently been reported [1] that production reticles are subject to progressive CD degradation during use and intense study is under way to try and identify the causes of it. One damage mechanism which has already been identified and quantified [2] is electric field induced migration of chrome (EFM). This can be caused by electric fields that are more than 100x weaker than those that cause ESD. Such low level electric fields can be experienced by a reticle during normal handling and processing steps, as well as coming from external sources during transportation and storage. The field strength of concern is lower than most electrostatic field meters are designed to measure and it can be difficult or impossible to measure such fields inside the cramped environment of equipment. To measure this risk a new sensor device ("E-Reticle") has been developed having the same materials of construction and form factor as a standard chrome-on-quartz reticle. It allows the electric field that a reticle would experience during normal use and handling to be measured and recorded. Results from testing of this device in a semiconductor production facility are reported, showing that certain processes like reticle washing are inherently hazardous. It also enables identification of problems with electrostatic protection measures inside equipment, such as unbalanced ionizers or poor load port grounding. The device is shown to be capable of recording electric fields in the reticle handling environment that are below the recommended maximum that is being proposed for the 2009 ITRS guidelines.

Electric Field Strength Of Coherent Radio Emission In Rock Salt Concerning Ultra High-Energy Neutrino Detection

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

Watanabe, Y.; Chiba, M.; Yasuda, O.

2006-07-12

Detection possibility of ultra high-energy (UHE) neutrino (E >1015 eV) in natural huge rock salt formation has been studied. Collision between the UHE neutrino and the rock salt produces electromagnetic (EM) shower. Charge difference (excess electrons) between electrons and positrons in EM shower radiates radio wave coherently (Askar'yan effect). Angular distribution and frequency spectrum of electric field strength of radio wave radiated from 3-dimensional EM shower in rock salt are presented.

A Spherical Electro Optic High Voltage Sensor

DTIC Science & Technology

1989-06-01

electro - optic (EO) crystal is introduced for photonic measurement of pulsed high-voltage fields. A spherical shape is used in order to reduce electric field gradients in the vicinity of the sensor. The sensor is pure dielectric and is interrogated remotely using a laser. The sensor does not require the connection of any conducting components, which results in the highest electrical isolation. The spherical nature of the crystal coupled with the incident laser beam, and crossed polarizers (intensity modulation scheme). automatically produces interference figures. The

Non-Equilibrium Effects on the Hidden Order of Microstructured URu2Si2

NASA Astrophysics Data System (ADS)

Winter, Laurel E.; Moll, Philip J. W.; Ramshaw, B. J.; Shekhter, Arkady; Harrison, N.; Bauer, Eric D.; McDonald, Ross D.

Despite extensive studies on the heavy-fermion URu2Si2, the order parameter associated with the hidden order state has yet to be established. It is known, however that the hidden order can be suppressed with pressure and high magnetic fields, which results in the development of antiferromagnetism, and the realization of a polarized state respectively. Focused Ion Beam lithography (FIB) of URu2Si2 has enabled high magnetic field observation of quantum oscillations in the resistance, indicating the preservation of sample quality to micron scale structures. These recent advances in FIB lithography have enabled the application of unprecedented electric fields while minimizing the effects of Joule heating in highly conductive metals at cryogenic temperatures. To this end, we have been able to create the necessary sample geometry to study the effect of an electric field upon hidden order in magnetic fields up to 15 T. Preliminary results suggest that above a characteristic threshold electric field, hidden order is suppressed revealing a state with similar magnetoresistive properties to the Kondo lattice in the absence of hidden order. Work supported by US Dept. of Energy through LANL/LDRD Program and G.T. Seaborg Institute, as well as NSF DMR-1157490 and the State of Florida.

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).

Effects of ionic concentration gradient on electroosmotic flow mixing in a microchannel.

PubMed

Peng, Ran; Li, Dongqing

2015-02-15

Effects of ionic concentration gradient on electroosmotic flow (EOF) mixing of one stream of a high concentration electrolyte solution with a stream of a low concentration electrolyte solution in a microchannel are investigated numerically. The concentration field, flow field and electric field are strongly coupled via concentration dependent zeta potential, dielectric constant and electric conductivity. The results show that the electric field and the flow velocity are non-uniform when the concentration dependence of these parameters is taken into consideration. It is also found that when the ionic concentration of the electrolyte solution is higher than 1M, the electrolyte solution essentially cannot enter the channel due to the extremely low electroosmotic flow mobility. The effects of the concentration dependence of zeta potential, dielectric constant and electric conductivity on electroosmotic flow mixing are studied. Copyright © 2014 Elsevier Inc. All rights reserved.

Effect of interphase permittivity on the electric field distribution of epoxy nanocomposites

NASA Astrophysics Data System (ADS)

Pradeep, Lavanya; Nelson, Avinash; Preetha, P.

2018-05-01

Epoxy plays a vital role in high voltage insulation system due to its superior electrical and thermal properties. Literature reports the enhancement in these properties by the addition of nanofillers to epoxy and this enhancement is attributed to the effect of interphase. Characterization of polymer nanocomposites proves the importance of interphase formed between the polymer and nanoparticle in the composite. It was observed that the permittivity of the interphase is having a significant effect on the properties of these materials. In this work, a three dimensional Epoxy nanocomposite with 0.5 vol%, 1 vol% of alumina particles are modeled using unit cell approach in COMSOL Multiphysics. Simulation is done using several existing interphase permittivity models and field distribution is observed. Results shows the noticeable influence of interphase permittivity on the electric field distribution. A good correlation of electric field distribution with the AC breakdown strength is observed.

Schwinger mechanism with energy dissipation in ``glasma''

NASA Astrophysics Data System (ADS)

Iwazaki, Aiichi

2011-12-01

Initial states of “glasma” in high-energy heavy-ion collisions are longitudinal classical color electric and magnetic fields. Assuming finite color electric conductivity, we show that the color electric field decays by quark pair production with the lifetime of the order of Qs-1, i.e., the inverse of the saturation momentum. Quarks and antiquarks created in the pair production are immediately thermalized as long as their temperature β-1 is lower than Qs. Namely, the relaxation time of the quarks to be thermalized is much shorter than Qs-1 when β-1≪Qs. We also show that the quarks acquire longitudinal momentum of the order of Qs by the acceleration of the electric field. To discuss the quark pair production, we use chiral anomaly, which has been shown to be a very powerful tool in the presence of strong magnetic field.

IMP 8. Volume 1: EM field experiment

NASA Technical Reports Server (NTRS)

1980-01-01

The electromagnetic fields experiment on IMP-J used two electric dipole antennas and a triaxial search coil magnetic antenna to sense the electric and magnetic field of plasma waves in space. The electric dipole antennas consisted of a fine wire, 0.021 inches in diameter, with a nominal extended tip-to-tip length of 400 ft. The outermost 50 ft. of each element was conducting and the rest of the antenna was covered with an insulating coating. The search coil antennas each consisted of a high mu core with two separate windings of 40,000 turns each to sense ac magnetic fields. The search coils had a length of 18 inches tip-to-tip and are mounted on the end of a boom. The axes of the x prime and y prime search coil antennas were parallel to the x prime and y prime electric antenna axes.

Effects of high-intensity power-frequency electric fields on implanted modern multiprogrammable cardiac pacemakers.

PubMed

Butrous, G S; Meldrum, S J; Barton, D G; Male, J C; Bonnell, J A; Camm, A J

1982-05-01

The effect on an implanted, multiprogrammable pacemaker of power-frequency (50 Hz) electric fields up to an intensity (unperturbed value measured at 1.7 m) of 20 kV/m were assessed in ten paced patients. Radiotelemetric monitoring of the electrocardiogram allowed supervision of the electrocardiogram throughout exposure to the alternating electric field. Displacement body currents of up to 300μA were achieved depending on the position and height of the patient. None of the pacemakers was inhibited, triggered or reverted to fixed rate operation during the exposure. The programmable functions, programmability or output characteristics were not affected. Small changes in cardiac rate and rhythm elicited the correct pacemaker responses. Unlike earlier models of pacemaker, this modern implanted pacemaker, which represents `the state of the art', is not affected by 50 Hz electric fields likely to be encountered when standing underneath power lines.

Electric field in a plasma channel in a high-pressure nanosecond discharge in hydrogen: a coherent anti-stokes Raman scattering study.

PubMed

Yatom, S; Tskhai, S; Krasik, Ya E

2013-12-20

Experimental results of a study of the electric field in a plasma channel produced during nanosecond discharge at a H2 gas pressure of (2-3)×10(5)  Pa by the coherent anti-Stokes scattering method are reported. The discharge was ignited by applying a voltage pulse with an amplitude of ∼100  kV and a duration of ∼5  ns to a blade cathode placed at a distance of 10 and 20 mm from the anode. It was shown that this type of gas discharge is characterized by the presence of an electric field in the plasma channel with root-mean-square intensities of up to 30  kV/cm. Using polarization measurements, it was found that the direction of the electric field is along the cathode-anode axis.

Reexamination of Induction Heating of Primitive Bodies in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Menzel, Raymond L.; Roberge, Wayne G.

2013-10-01

We reexamine the unipolar induction mechanism for heating asteroids originally proposed in a classic series of papers by Sonett and collaborators. As originally conceived, induction heating is caused by the "motional electric field" that appears in the frame of an asteroid immersed in a fully ionized, magnetized solar wind and drives currents through its interior. However, we point out that classical induction heating contains a subtle conceptual error, in consequence of which the electric field inside the asteroid was calculated incorrectly. The problem is that the motional electric field used by Sonett et al. is the electric field in the freely streaming plasma far from the asteroid; in fact, the motional field vanishes at the asteroid surface for realistic assumptions about the plasma density. In this paper we revisit and improve the induction heating scenario by (1) correcting the conceptual error by self-consistently calculating the electric field in and around the boundary layer at the asteroid-plasma interface; (2) considering weakly ionized plasmas consistent with current ideas about protoplanetary disks; and (3) considering more realistic scenarios that do not require a fully ionized, powerful T Tauri wind in the disk midplane. We present exemplary solutions for two highly idealized flows that show that the interior electric field can either vanish or be comparable to the fields predicted by classical induction depending on the flow geometry. We term the heating driven by these flows "electrodynamic heating," calculate its upper limits, and compare them to heating produced by short-lived radionuclides.

Nerve-muscle activation by rotating permanent magnet configurations.

PubMed

Watterson, Peter A; Nicholson, Graham M

2016-04-01

The standard method of magnetic nerve activation using pulses of high current in coils has drawbacks of high cost, high electrical power (of order 1 kW), and limited repetition rate without liquid cooling. Here we report a new technique for nerve activation using high speed rotation of permanent magnet configurations, generating a sustained sinusoidal electric field using very low power (of order 10 W). A high ratio of the electric field gradient divided by frequency is shown to be the key indicator for nerve activation at high frequencies. Activation of the cane toad sciatic nerve and attached gastrocnemius muscle was observed at frequencies as low as 180 Hz for activation of the muscle directly and 230 Hz for curved nerves, but probably not in straight sections of nerve. These results, employing the first prototype device, suggest the opportunity for a new class of small low-cost magnetic nerve and/or muscle stimulators. Conventional pulsed current systems for magnetic neurostimulation are large and expensive and have limited repetition rate because of overheating. Here we report a new technique for nerve activation, namely high-speed rotation of a configuration of permanent magnets. Analytical solutions of the cable equation are derived for the oscillating electric field generated, which has amplitude proportional to the rotation speed. The prototype device built comprised a configuration of two cylindrical magnets with antiparallel magnetisations, made to rotate by interaction between the magnets' own magnetic field and three-phase currents in coils mounted on one side of the device. The electric field in a rectangular bath placed on top of the device was both numerically evaluated and measured. The ratio of the electric field gradient on frequency was approximately 1 V m(-2) Hz(-1) near the device. An exploratory series of physiological tests was conducted on the sciatic nerve and attached gastrocnemius muscle of the cane toad (Bufo marinus). Activation was readily observed of the muscle directly, at frequencies as low as 180 Hz, and of nerves bent around insulators, at frequencies as low as 230 Hz. Nerve-muscles, with the muscle elevated to avoid its direct activation, were occasionally activated, possibly in the straight section of the nerve, but more likely in the nerve where it curved up to the muscle, at radius of curvature 10 mm or more, or at the nerve end. These positive first results suggest the opportunity for a new class of small, low-cost devices for magnetic stimulation of nerves and/or muscles. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section, each electrical and electronic system that performs a function whose failure would prevent the continued safe...

Aerodynamic generation of electric fields in turbulence laden with charged inertial particles.

PubMed

Di Renzo, M; Urzay, J

2018-04-26

Self-induced electricity, including lightning, is often observed in dusty atmospheres. However, the physical mechanisms leading to this phenomenon remain elusive as they are remarkably challenging to determine due to the high complexity of the multi-phase turbulent flows involved. Using a fast multi-pole method in direct numerical simulations of homogeneous turbulence laden with hundreds of millions of inertial particles, here we show that mesoscopic electric fields can be aerodynamically created in bi-disperse suspensions of oppositely charged particles. The generation mechanism is self-regulating and relies on turbulence preferentially concentrating particles of one sign in clouds while dispersing the others more uniformly. The resulting electric field varies over much larger length scales than both the mean inter-particle spacing and the size of the smallest eddies. Scaling analyses suggest that low ambient pressures, such as those prevailing in the atmosphere of Mars, increase the dynamical relevance of this aerodynamic mechanism for electrical breakdown.

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

NASA Technical Reports Server (NTRS)

Ramakumar, R.; Bahrami, K.

1981-01-01

This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Janssen, A. M.; Rampersad, S. M.; Lucka, F.; Lanfer, B.; Lew, S.; Aydin, Ü.; Wolters, C. H.; Stegeman, D. F.; Oostendorp, T. F.

2013-07-01

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation. One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between cerebrospinal fluid (CSF) and grey matter (Thielscher et al 2011 NeuroImage 54 234-43, Bijsterbosch et al 2012 Med. Biol. Eng. Comput. 50 671-81), or by resizing the whole brain (Wagner et al 2008 Exp. Brain Res. 186 539-50). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images, was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location.

Observations of ionospheric electric fields above atmospheric weather systems

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Aggson, T. L.; Rodgers, E. B.; Hanson, W. B.

1994-01-01

We report on the observations of a number of quasi-dc electric field events associated with large-scale atmospheric weather formations. The observations were made by the electric field experiment onboard the San Marco D satellite, operational in an equatorial orbit from May to December 1988. Several theoretical studies suggest that electric fields generated by thunderstorms are present at high altitudes in the ionosphere. In spite of such favorable predictions, weather-related events are not often observed since they are relatively weak. We shall report here on a set of likely E field candidates for atmospheric-ionospheric causality, these being observed over the Indonesian Basin, northern South America, and the west coast of Africa; all known sites of atmospheric activity. As we shall demonstrate, individual events often be traced to specific active weather features. For example, a number of events were associated with spacecraft passages near Hurricane Joan in mid-October 1988. As a statistical set, the events appear to coincide with the most active regions of atmospheric weather.

Health hazard evaluation report HETA 94-0300-2528, Cape May County Board of Taxation, Cape May Court House, New Jersey

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

Moss, C.E.; Ragab, M.

1995-09-01

In response to a request from the County Tax Administrator, an investigation was begun into exposure to electric and magnetic fields at the Cape May County Board of Taxation (SIC-7389), Cape May Court House, New Jersey. Employees there suspected they were receiving high exposure to extremely low frequency (ELF) electric and magnetic fields. Measurements were taken with particular attention given to the areas around four large switchboards which were located directly behind the wall of the the tax office. At the outside corners of the building and in the parking lot outside, the magnetic field levels ranged from 0.1 tomore » 10.7 milligauss (mG). At similar locations, electric field levels ranged from 1.9 to 6.9 volts/meter (V/m). Inside the building, magnetic and electric field levels ranged from 0.1 to 900mG and 1.4 to 5.7V/m, respectively.« less

High Performance Polymer Memory and Its Formation

DTIC Science & Technology

2007-04-26

the retention time of the device was performed to estimate the barrier height of the charge trap . The activation energy was approximated to be about...characteristics and presented a model to explain the mechanism of electrical switching in the device. By exploiting an electric-field induced charge transfer...electrical current in the high conductivity state would be due to some temperature-independent charge tunneling processes. The IV curves could be

Initiation of non-tropical thunderstorms by solar activity

NASA Technical Reports Server (NTRS)

Herman, J. R.; Goldberg, R. A.

1976-01-01

Correlative evidence accumulating since 1926 suggests that there must be some physical coupling mechanism between solar activity and thunderstorm occurrence in middle to high latitudes. Such a link may be provided by alteration of atmospheric electric parameters through the combined influence of high-energy solar protons and decreased cosmic ray intensities, both of which are associated with active solar events. The protons produce excess ionization near and above 20km, while the Forbush decreases a lowered conductivity and enhanced fair-weather atmospheric electric field below that altitude. Consequent effects ultimately lead to a charge distribution similar to that found in thunderclouds, and then other cloud physics processes take over to generate the intense electric fields required for lightning discharge.

Electrically detected magnetic resonance in a W-band microwave cavity

NASA Astrophysics Data System (ADS)

Lang, V.; Lo, C. C.; George, R. E.; Lyon, S. A.; Bokor, J.; Schenkel, T.; Ardavan, A.; Morton, J. J. L.

2011-03-01

We describe a low-temperature sample probe for the electrical detection of magnetic resonance in a resonant W-band (94 GHz) microwave cavity. The advantages of this approach are demonstrated by experiments on silicon field-effect transistors. A comparison with conventional low-frequency measurements at X-band (9.7 GHz) on the same devices reveals an up to 100-fold enhancement of the signal intensity. In addition, resonance lines that are unresolved at X-band are clearly separated in the W-band measurements. Electrically detected magnetic resonance at high magnetic fields and high microwave frequencies is therefore a very sensitive technique for studying electron spins with an enhanced spectral resolution and sensitivity.

Wide-view transflective liquid crystal display for mobile applications

NASA Astrophysics Data System (ADS)

Kim, Hyang Yul; Ge, Zhibing; Wu, Shin-Tson; Lee, Seung Hee

2007-12-01

A high optical efficiency and wide-view transflective liquid crystal display based on fringe-field switching structure is proposed. The transmissive part has a homogenous liquid crystal (LC) alignment and is driven by a fringe electric field, which exhibits excellent electro-optic characteristics. The reflective part has a hybrid LC alignment with quarter-wave phase retardation and is also driven by a fringe electric field. Consequently, the transmissive and reflective parts have similar gamma curves.

Effect of planar dielectric interfaces on fluorescence emission and detection. Evanescent excitation with high-aperture collection.

PubMed Central

Burghardt, T P; Thompson, N L

1984-01-01

We consider the effect of planar dielectric interfaces (e.g., solid/liquid) on the fluorescence emission of nearby probes. First, we derive an integral expression for the electric field radiated by an oscillating electric dipole when it is close to a dielectric interface. The electric field depends on the refractive indices of the interface, the orientation of the dipole, the distance from the dipole to the interface, and the position of observation. We numerically calculate the electric field intensity for a dipole on an interface, as a function of observation position. These results are applicable to fluorescent molecules excited by the evanescent field of a totally internally reflected laser beam and thus very close to a solid/liquid interface. Next, we derive an integral expression for the electric field radiated when a second dielectric interface is also close to the fluorescent molecule. We numerically calculate this intensity as observed through the second interface. These results are useful when the fluorescence is collected by a high-aperture microscope objective. Finally, we define and calculate a "dichroic factor," which describes the efficiency of collection, in the two-interface system, of polarized fluorescence. The limit when the first interface is removed is applicable for any high-aperture collection of polarized or unpolarized fluorescence. The limit when the second interface is removed has application in the collection of fluorescence with any aperture from molecules close to a dielectric interface. The results of this paper are required for the interpretation of order parameter measurements on fluorescent probes in supported phospholipid monolayers (Thompson, N.L., H. M. McConnell, and T. P. Burghardt, 1984, Biophys. J., 46:739-747). PMID:6518253

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.

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.

Micro-ARES, an electric-field sensor for ExoMars 2016: Electric fields modelling, sensitivity evaluations and end-to-end tests.

NASA Astrophysics Data System (ADS)

Déprez, Grégoire; Montmessin, Franck; Witasse, Olivier; Lapauw, Laurent; Vivat, Francis; Abbaki, Sadok; Granier, Philippe; Moirin, David; Trautner, Roland; Hassen-Khodja, Rafik; d'Almeida, Éric; Chardenal, Laurent; Berthelier, Jean-Jacques; Esposito, Francesca; Debei, Stefano; Rafkin, Scott; Barth, Erika

2014-05-01

For the past few years, LATMOS has been involved in the development of micro-ARES, an electric field sensor part of the science payload (DREAMS) of the ExoMars 2016 Schiaparelli entry, descent and landing demonstrator. It is dedicated to the very first measurement and characterization of the Martian atmospheric electricity which is suspected to be at the very basis of various phenomenon such as dust lifting, formation of oxidizing agents or Schumann resonances. Although the data collection will be restricted to a few days of operations, these first results will be of importance to understand the Martian dust cycle, the electrical environment and possibly relevant to atmospheric chemistry. The instrument, a compact version of the ARES instrument for the ExoMars Humboldt payload, is composed of an electronic board, with an amplification line and a real-time data processing DSP, which handles the electric signal measured between the spherical electrode (located at the top of a 27-cm high antenna) that adjusts itself to the local atmospheric potential, and the lander chassis, connected to the mechanical ground. Since the electric fields on Mars have never been measured before, we can rely on two sources in order to know their expected order of magnitude. The first one is the measurement of the atmospheric electric fields on Earth, at the surface (in dust storms or the so-called dust-devils) or in the high atmosphere (closer to the Martian temperature and pressure conditions). The second one is the computer simulation of the phenomenon, that we obtained by combining two models. On the one hand, the mesoscale PRAMS model, developed at SwRI, which has the ability to simulate the dust transportation, and on the other hand the implementation made at LATMOS of Farell's 2005 dust-triboelectricity equations. Those models allowed us to simulate electric fields up to tens or even hundreds of kilo-volts per meter inside dust devils, which corresponds to the observations made on Earth and transposed to the Martian atmospheric parameters. Knowing the expected electric fields and simulating them, the next step in order to evaluate the performance of the instrument is to determine its sensitivity by modelling the response of the instrument. The last step is to confront the model of the instrument, and the expected results for a given signal with the effective outputs of the electric board with the same signal as an input. To achieve this end-to-end test, we use a signal generator followed by an electrical circuit reproducing the electrode behaviour in the Martian environment, in order to inject a realistic electric signal in the processing board and finally compare the produced formatted data with the expected ones.

Simulated electron beam trajectories toward a field ion microscopy specimen

NASA Astrophysics Data System (ADS)

Larson, D. J.; Camus, P. P.; Kelly, T. F.

1993-04-01

This article explores the conditions under which a directed electron beam originating nearly normal to the specimen axis can be made to impact the near-apex region of a field ion microscopy specimen in a high electric field. Electron trajectories were calculated using a modified Runge-Kutta numerical method. The results indicate that an electron beam can be directed to a specimen under typical field ion microscopy conditions using two methods: by varying initial beam tilt (less than 60 mrad) or by translating the initial beam position relative to the specimen apex (less than 5 mm). The net focusing effect of the high electric field on the electron beam can be treated, to first order, as an astigmatism and may be correctable by a post-lens deflection system.

Effects of microstructural defects on the performance of base-metal multilayer ceramic capacitors

NASA Astrophysics Data System (ADS)

Samantaray, Malay M.

Multilayer ceramic capacitors (MLCCs), owing to their processing conditions, can exhibit microstructure defects such as electrode porosity and roughness. The effect of such extrinsic defects on the electrical performance of these devices needs to be understood in order to achieve successful miniaturization into the submicron dielectric layer thickness regime. Specifically, the presence of non-planar and discontinuous electrodes can lead to local field enhancements while the relative morphologies of two adjacent electrodes determine variations in the local dielectric thickness. To study the effects of electrode morphologies, an analytical approach is taken to calculate the electric field enhancement and leakage current with respect to an ideal parallel-plate capacitor. Idealized electrode defects are used to simulate the electric field distribution. It is shown that the electrode roughness causes both the electric field and the leakage current to increase with respect to that of the ideal flat parallel-plate capacitor. Moreover, finite element methods are used to predict electric field enhancements by as high as 100% within capacitor structures containing rough interfaces and porosity. To understand the influence of microstructural defects on field distributions and leakage current, the real three-dimensional microstructure of local regions in MLCCs are reconstructed using a serial-sectioning technique in the focused ion beam. These microstructures are then converted into a finite element model in order to simulate the perturbations in electric field due to the presence of electrode defects. The electric field is three times the average value, and this leads to increase in current density of these devices. It is also shown that increasing sintering rates of MLCCs leads to improved electrode morphology with smoother more continuous electrodes, which in turn leads to a decrease in electric field enhancement and calculated leakage current density. To simulate scaling effects, the dielectric layer thickness is reduced from 2.0mum to 0.5mum in the three-dimensional microstructure keeping the same electrode morphology. It is seen that the effect of microstructure defects is more pronounced as one approaches thinner layers, leading to higher local electric field concentrations and a concomitant drop in insulation resistance. It is also seen that the electric field values are as high as 3.8 times the average field in termination regions due the disintegrated structure of the electrodes. In order to assess the effect of microstructure on MLCC performance, two sets of multilayer capacitors subjected to two vastly different sintering rates of 150ºC/hr and 3000ºC/hr are compared for their electrical properties. Capacitors with higher electrode continuity exhibit proportionally higher capacitance, provided the grain size distributions are similar. From the leakage current measurements, it is found that the Schottky barrier at the electrode-dielectric interface controls the conduction mechanism. This barrier height is calculated to be 1.06 eV for slow-fired MLCCs and was 1.15 for fast-fired MLCCs. This shows that high concentration of electrode defects cause field perturbations and subsequent drop in the net Schottky barrier height. These results are further supported by frequency-dependent impedance measurements. With temperature dependence behavior of current-voltage trends we note that below temperatures of 135°C, the conduction is controlled by interfacial effects, whereas at higher temperatures it is consistent with bulk-controlled space charge limited current for the samples that are highly reoxidized. The final part of this work studies the various aspects of the initial stages of degradation of MLCCs. MLCCs subjected to unipolar and bipolar degradation are studied for changes in microstructure and electrical properties. With bipolar degradation studies new insights into degradation are gained. First, the ionic accumulation with oxygen vacancies at cathodes is only partially reversible. This has implications on the controlling interface with electronic conduction. Also, it is shown that oxygen vacancy accumulation near the cathodes leads to a drop in insulation resistance. The capacitance also increases with progressive steps of degradation due to the effective thinning of dielectric layer. The reduction in interfacial resistance is also confirmed by impedance analysis. Finally, it is observed that on degradation, the dominant leakage current mechanism changes from being controlled by cathodic injection of electrons to being controlled by their anodic extraction. (Abstract shortened by UMI.)

Electrical conductivity and magnetic field dependent current-voltage characteristics of nanocrystalline nickel ferrite

NASA Astrophysics Data System (ADS)

Ghosh, P.; Bhowmik, R. N.; Das, M. R.; Mitra, P.

2017-04-01

We have studied the grain size dependent electrical conductivity, dielectric relaxation and magnetic field dependent current voltage (I - V) characteristics of nickel ferrite (NiFe2O4) . The material has been synthesized by sol-gel self-combustion technique, followed by ball milling at room temperature in air environment to control the grain size. The material has been characterized using X-ray diffraction (refined with MAUD software analysis) and Transmission electron microscopy. Impedance spectroscopy and I - V characteristics in the presence of variable magnetic fields have confirmed the increase of resistivity for the fine powdered samples (grain size 5.17±0.6 nm), resulted from ball milling of the chemical routed sample. Activation energy of the material for electrical charge hopping process has increased with the decrease of grain size by mechanical milling of chemical routed sample. The I - V curves showed many highly non-linear and irreversible electrical features, e.g., I - V loop and bi-stable electronic states (low resistance state-LRS and high resistance state-HRS) on cycling the electrical bias voltage direction during I-V curve measurement. The electrical dc resistance for the chemically routed (without milled) sample in HRS (∼3.4876×104 Ω) at 20 V in presence of magnetic field 10 kOe has enhanced to ∼3.4152×105 Ω for the 10 h milled sample. The samples exhibited an unusual negative differential resistance (NDR) effect that gradually decreased on decreasing the grain size of the material. The magneto-resistance of the samples at room temperature has been found substantially large (∼25-65%). The control of electrical charge transport properties under magnetic field, as observed in the present ferrimagnetic material, indicate the magneto-electric coupling in the materials and the results could be useful in spintronics applications.

Rapid Transition of the Hole Rashba Effect from Strong Field Dependence to Saturation in Semiconductor Nanowires.

PubMed

Luo, Jun-Wei; Li, Shu-Shen; Zunger, Alex

2017-09-22

The electric field manipulation of the Rashba spin-orbit coupling effects provides a route to electrically control spins, constituting the foundation of the field of semiconductor spintronics. In general, the strength of the Rashba effects depends linearly on the applied electric field and is significant only for heavy-atom materials with large intrinsic spin-orbit interaction under high electric fields. Here, we illustrate in 1D semiconductor nanowires an anomalous field dependence of the hole (but not electron) Rashba effect (HRE). (i) At low fields, the strength of the HRE exhibits a steep increase with the field so that even low fields can be used for device switching. (ii) At higher fields, the HRE undergoes a rapid transition to saturation with a giant strength even for light-atom materials such as Si (exceeding 100 meV Å). (iii) The nanowire-size dependence of the saturation HRE is rather weak for light-atom Si, so size fluctuations would have a limited effect; this is a key requirement for scalability of Rashba-field-based spintronic devices. These three features offer Si nanowires as a promising platform for the realization of scalable complementary metal-oxide-semiconductor compatible spintronic devices.

Integrated Sensing and Information Processing Theme-Based Redesign of the Undergraduate Electrical and Computer Engineering Curriculum at Duke University

ERIC Educational Resources Information Center

Ybarra, Gary A.; Collins, Leslie M.; Huettel, Lisa G.; Brown, April S.; Coonley, Kip D.; Massoud, Hisham Z.; Board, John A.; Cummer, Steven A.; Choudhury, Romit Roy; Gustafson, Michael R.; Jokerst, Nan M.; Brooke, Martin A.; Willett, Rebecca M.; Kim, Jungsang; Absher, Martha S.

2011-01-01

The field of electrical and computer engineering has evolved significantly in the past two decades. This evolution has broadened the field of ECE, and subfields have seen deep penetration into very specialized areas. Remarkable devices and systems arising from innovative processes, exotic materials, high speed computer simulations, and complex…

Linear electric field mass spectrometry

DOEpatents

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

1992-12-01

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

Significantly improved dielectric performances of nanocomposites via loading two-dimensional core-shell structure Bi2Te3@SiO2 nanosheets

NASA Astrophysics Data System (ADS)

Chen, Jianwen; Wang, Xiucai; Yu, Xinmei; Fan, Yun; Duan, Zhikui; Jiang, Yewen; Yang, Faquan; Zhou, Yuexia

2018-07-01

Polymer/semiconductor-insulator nanocomposites can display high dielectric constants with a relatively low dissipation factor under low electric fields, and thus seem to promising for high energy density capacitors. Here, a novel nanocomposite films is developed by loading two-dimensional (2D) core-shell structure Bi2Te3@SiO2 nanosheets in the poly (vinylidene fluoride-hexafluoro propylene) (P(VDF-HFP)) polymer matrix. The 2D Bi2Te3 nanosheets were prepared through simple microwave-assisted method. The experimental results suggesting that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the dielectric constant, dielectric loss, AC conductivity, and breakdown strength of composites films. The composite films load with 10 vol.% 2D Bi2Te3@SiO2 nanosheets exhibits a high dielectric constant of 70.3 at 1 kHz and relatively low dielectric loss of 0.058 at 1 kHz. The finite element simulation of electric field and electric current density distribution revealed that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the energy loss, local electric field strength, and breakdown strength of composite films. Therefore, this work will provide a promising route to achieve high-performance capacitors.

A new RF window designed for high-power operation in an S-band LINAC RF system

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Kim, Seung-Hwan; Hwang, Woonha; Ryu, Jiwan; Roh, Sungjoo

2016-09-01

A new RF window is designed for high-power operation at the Pohang Light Source-II (PLSII) S-band linear accelerator (LINAC) RF system. In order to reduce the strength of the electric field component perpendicular to the ceramic disk, which is commonly known as the main cause of most discharge breakdowns in ceramic disk, we replace the pill-box type cavity in the conventional RF window with an overmoded cavity. The overmoded cavity is coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the iris and the number of possible mode competitions. The finite-difference time-domain (FDTD) simulation, CST MWS, was used in the design process. The simulated maximum electric field component perpendicular to the ceramic for the new RF window is reduced by an order of magnitude compared with taht for the conventional RF window, which holds promise for stable high-power operation.

Enhancing electric-field control of ferromagnetism through nanoscale engineering of high-Tc MnxGe1-x nanomesh.

PubMed

Nie, Tianxiao; Tang, Jianshi; Kou, Xufeng; Gen, Yin; Lee, Shengwei; Zhu, Xiaodan; He, Qinglin; Chang, Li-Te; Murata, Koichi; Fan, Yabin; Wang, Kang L

2016-10-20

Voltage control of magnetism in ferromagnetic semiconductor has emerged as an appealing solution to significantly reduce the power dissipation and variability beyond current CMOS technology. However, it has been proven to be very challenging to achieve a candidate with high Curie temperature (T c ), controllable ferromagnetism and easy integration with current Si technology. Here we report the effective electric-field control of both ferromagnetism and magnetoresistance in unique Mn x Ge 1-x nanomeshes fabricated by nanosphere lithography, in which a T c above 400 K is demonstrated as a result of size/quantum confinement. Furthermore, by adjusting Mn doping concentration, extremely giant magnetoresistance is realized from ∼8,000% at 30 K to 75% at 300 K at 4 T, which arises from a geometrically enhanced magnetoresistance effect of the unique mesh structure. Our results may provide a paradigm for fundamentally understanding the high T c in ferromagnetic semiconductor nanostructure and realizing electric-field control of magnetoresistance for future spintronic applications.

Enhancing electric-field control of ferromagnetism through nanoscale engineering of high-Tc MnxGe1−x nanomesh

PubMed Central

Nie, Tianxiao; Tang, Jianshi; Kou, Xufeng; Gen, Yin; Lee, Shengwei; Zhu, Xiaodan; He, Qinglin; Chang, Li-Te; Murata, Koichi; Fan, Yabin; Wang, Kang L.

2016-01-01

Voltage control of magnetism in ferromagnetic semiconductor has emerged as an appealing solution to significantly reduce the power dissipation and variability beyond current CMOS technology. However, it has been proven to be very challenging to achieve a candidate with high Curie temperature (Tc), controllable ferromagnetism and easy integration with current Si technology. Here we report the effective electric-field control of both ferromagnetism and magnetoresistance in unique MnxGe1−x nanomeshes fabricated by nanosphere lithography, in which a Tc above 400 K is demonstrated as a result of size/quantum confinement. Furthermore, by adjusting Mn doping concentration, extremely giant magnetoresistance is realized from ∼8,000% at 30 K to 75% at 300 K at 4 T, which arises from a geometrically enhanced magnetoresistance effect of the unique mesh structure. Our results may provide a paradigm for fundamentally understanding the high Tc in ferromagnetic semiconductor nanostructure and realizing electric-field control of magnetoresistance for future spintronic applications. PMID:27762320

2d axisymmetric "beam-bulk" modelling of the generation of runaway electrons by streamers.

NASA Astrophysics Data System (ADS)

Chanrion, Olivier; Bonaventura, Zdenek; Bourdon, Anne; Neubert, Torsten

2017-04-01

We present results from a 2d axisymmetric numerical model of streamers based on a "beam-bulk" approach which describes cold electrons with a fluid model and high energy electrons with a particle model. The interest is motivated by the generation of runaway electrons by streamers which may participate in the recently observed TGFs and which challenge the modelling. Runaway electrons are known to be generated from streamers when the electric field in its negative tip is of sufficient magnitude. After overtaking the streamer tip, runaways can affect the streamer propagation ahead and may produce high energy photons through the bremsstrahlung process. In conventional model of streamers, the evolution of the streamer discharge is mostly governed by cold electrons. By including runaway electrons, we model their production, their impact on the discharge propagation and can address their role in TGFs. Results of streamer propagation in leader electric field show that the runaway electrons accelerate the streamers, reduce the electric field in its tip and enlarge its radius by pre-ionizing the gas ahead. We observed that if we increase the electric field, the discharge is getting more diffuse, with a pattern driven by the increase in runaway induced ionisation.

Electrostatic coupling between DNA and its counterions modulates the observed translational diffusion coefficients.

PubMed

Stellwagen, Earle; Stellwagen, Nancy C

2015-09-01

Free solution capillary electrophoresis (CE) is a useful technique for measuring the translational diffusion coefficients of charged analytes. The measurements are relatively fast if the polarity of the electric field is reversed to drive the analyte back and forth past the detection window during each run. We have tested the validity of the resulting diffusion coefficients using double-stranded DNA molecules ranging in size from 20 to 960 base pairs as the model system. The diffusion coefficients of small DNAs are equal to values in the literature measured by other techniques. However, the diffusion coefficients of DNA molecules larger than ∼30 base pairs are anomalously high and deviate increasingly from the literature values with increasing DNA molar mass. The anomalously high diffusion coefficients are due to electrostatic coupling between the DNA and its counterions. As a result, the measured diffusion coefficients vary with the diffusion coefficient of the counterion, as well as with cation concentration and electric field strength. These effects can be reduced or eliminated by measuring apparent diffusion coefficients of the DNA at several different electric field strengths and extrapolating the results to zero electric field.

Electric Field Tuning Molecular Packing and Electrical Properties of Solution-Shearing Coated Organic Semiconducting Thin Films

DOE PAGES

Molina-Lopez, Francisco; Yan, Hongping; Gu, Xiaodan; ...

2017-01-17

Recent improvements in solution-coated organic semiconductors (OSCs) evidence their high potential for cost-efficient organic electronics and sensors. Molecular packing structure determines the charge transport property of molecular solids. However, it remains challenging to control the molecular packing structure for a given OSC. Here, the application of alternating electric fields is reported to fine-tune the crystal packing of OSC solution-shearing coated at ambient conditions. First, a theoretical model based on dielectrophoresis is developed to guide the selection of the optimal conditions (frequency and amplitude) of the electric field applied through the solution-shearing blade during coating of OSC thin films. Next, electricmore » field-induced polymorphism is demonstrated for OSCs with both herringbone and 2D brick-wall packing motifs in 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene and 6,13-bis(triisopropylsilylethynyl) pentacene, respectively. Favorable molecular packing can be accessible in some cases, resulting in higher charge carrier mobilities. In conclusion, this work provides a new approach to tune the properties of solution-coated OSCs in functional devices for high-performance printed electronics.« less

Characterization of Microwave-Induced Electric Discharge Phenomena in Metal–Solvent Mixtures

PubMed Central

Chen, Wen; Gutmann, Bernhard; Kappe, C Oliver

2012-01-01

Electric discharge phenomena in metal–solvent mixtures are investigated utilizing a high field density, sealed-vessel, single-mode 2.45 GHz microwave reactor with a built-in camera. Particular emphasis is placed on studying the discharges exhibited by different metals (Mg, Zn, Cu, Fe, Ni) of varying particle sizes and morphologies in organic solvents (e.g., benzene) at different electric field strengths. Discharge phenomena for diamagnetic and paramagnetic metals (Mg, Zn, Cu) depend strongly on the size of the used particles. With small particles, short-lived corona discharges are observed that do not lead to a complete breakdown. Under high microwave power conditions or with large particles, however, bright sparks and arcs are experienced, often accompanied by solvent decomposition and formation of considerable amounts of graphitized material. Small ferromagnetic Fe and Ni powders (<40 μm) are heated very rapidly in benzene suspensions and start to glow in the microwave field, whereas larger particles exhibit extremely strong discharges. Electric discharges were also observed when Cu metal or other conductive materials such as silicon carbide were exposed to the microwave field in the absence of a solvent in an argon or nitrogen atmosphere. PMID:24551491

Characterization of microwave-induced electric discharge phenomena in metal-solvent mixtures.

PubMed

Chen, Wen; Gutmann, Bernhard; Kappe, C Oliver

2012-02-01

Electric discharge phenomena in metal-solvent mixtures are investigated utilizing a high field density, sealed-vessel, single-mode 2.45 GHz microwave reactor with a built-in camera. Particular emphasis is placed on studying the discharges exhibited by different metals (Mg, Zn, Cu, Fe, Ni) of varying particle sizes and morphologies in organic solvents (e.g., benzene) at different electric field strengths. Discharge phenomena for diamagnetic and paramagnetic metals (Mg, Zn, Cu) depend strongly on the size of the used particles. With small particles, short-lived corona discharges are observed that do not lead to a complete breakdown. Under high microwave power conditions or with large particles, however, bright sparks and arcs are experienced, often accompanied by solvent decomposition and formation of considerable amounts of graphitized material. Small ferromagnetic Fe and Ni powders (<40 μm) are heated very rapidly in benzene suspensions and start to glow in the microwave field, whereas larger particles exhibit extremely strong discharges. Electric discharges were also observed when Cu metal or other conductive materials such as silicon carbide were exposed to the microwave field in the absence of a solvent in an argon or nitrogen atmosphere.

Effects of high voltage nanosecond electric pulses on eukaryotic cells (in vitro): A systematic review.

PubMed

Batista Napotnik, Tina; Reberšek, Matej; Vernier, P Thomas; Mali, Barbara; Miklavčič, Damijan

2016-08-01

For this systematic review, 203 published reports on effects of electroporation using nanosecond high-voltage electric pulses (nsEP) on eukaryotic cells (human, animal, plant) in vitro were analyzed. A field synopsis summarizes current published data in the field with respect to publication year, cell types, exposure configuration, and pulse duration. Published data were analyzed for effects observed in eight main target areas (plasma membrane, intracellular, apoptosis, calcium level and distribution, survival, nucleus, mitochondria, stress) and an additional 107 detailed outcomes. We statistically analyzed effects of nsEP with respect to three pulse duration groups: A: 1-10ns, B: 11-100ns and C: 101-999ns. The analysis confirmed that the plasma membrane is more affected with longer pulses than with short pulses, seen best in uptake of dye molecules after applying single pulses. Additionally, we have reviewed measurements of nsEP and evaluations of the electric fields to which cells were exposed in these reports, and we provide recommendations for assessing nanosecond pulsed electric field effects in electroporation studies. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Charge transport model in solid-state avalanche amorphous selenium and defect suppression design

NASA Astrophysics Data System (ADS)

Scheuermann, James R.; Miranda, Yesenia; Liu, Hongyu; Zhao, Wei

2016-01-01

Avalanche amorphous selenium (a-Se) in a layer of High Gain Avalanche Rushing Photoconductor (HARP) is being investigated for its use in large area medical imagers. Avalanche multiplication of photogenerated charge requires electric fields greater than 70 V μm-1. For a-Se to withstand this high electric field, blocking layers are used to prevent the injection of charge carriers from the electrodes. Blocking layers must have a high injection barrier and deep trapping states to reduce the electric field at the interface. In the presence of a defect in the blocking layer, a distributed resistive layer (DRL) must be included into the structure to build up space charge and reduce the electric field in a-Se and the defect. A numerical charge transport model has been developed to optimize the properties of blocking layers used in various HARP structures. The model shows the incorporation of a DRL functionality into the p-layer can reduce dark current at a point defect by two orders of magnitude by reducing the field in a-Se to the avalanche threshold. Hole mobility in a DRL of ˜10-8 cm2 V-1 s-1 at 100 V μm-1 as demonstrated by the model can be achieved experimentally by varying the hole mobility of p-type organic or inorganic semiconductors through doping, e.g., using Poly(9-vinylcarbozole) doped with 1%-3% (by weight) of poly(3-hexylthiopene).

RSRM top hat cover simulator lightning test, volume 1

NASA Technical Reports Server (NTRS)

1990-01-01

The test sequence was to measure electric and magnetic fields induced inside a redesigned solid rocket motor case when a simulated lightning discharge strikes an exposed top hat cover simulator. The test sequence was conducted between 21 June and 17 July 1990. Thirty-six high rate-of-rise Marx generator discharges and eight high current bank discharges were injected onto three different test article configurations. Attach points included three locations on the top hat cover simulator and two locations on the mounting bolts. Top hat cover simulator and mounting bolt damage and grain cover damage was observed. Overall electric field levels were well below 30 kilowatts/meter. Electric field levels ranged from 184.7 to 345.9 volts/meter and magnetic field levels were calculated from 6.921 to 39.73 amperes/meter. It is recommended that the redesigned solid rocket motor top hat cover be used in Configuration 1 or Configuration 2 as an interim lightning protection device until a lightweight cover can be designed.

Effect of pulsed electric field treatment during cold maceration and alcoholic fermentation on major red wine qualitative and quantitative parameters.

PubMed

El Darra, Nada; Rajha, Hiba N; Ducasse, Marie-Agnès; Turk, Mohammad F; Grimi, Nabil; Maroun, Richard G; Louka, Nicolas; Vorobiev, Eugène

2016-12-15

This work studies the effect of pulsed electric field (PEF) treatment at moderate and high field strengths (E=0.8kV/cm & 5kV/cm) prior and during alcoholic fermentation (AF) of red grapes on improving different parameters of pre-treated extracts: pH, °Brix, colour intensity (CI), total polyphenols content (TPI) of Cabernet Sauvignon red wine. Similar trends were observed for treating grapes using moderate and high electric field strength on the enhancement of CI and TPI of the wine after AF. The application of PEF using moderate strengths at different times during cold maceration (CM) (0, 2 and 4days) was more efficient for treatment during CM. The treatment during AF showed lower extraction rate compared to treating during CM and prior to AF. Our results clearly show that the best time for applying the PEF-treatment through the red fermentation is during the CM step. Copyright © 2016. Published by Elsevier Ltd.