Direct Electric Field Research Articles

Shorting Factor In-Flight Calibration for the Van Allen Probes DC Electric Field Measurements in the Earth's Plasmasphere.

Satellite-based direct electric field measurements deliver crucial information for space science studies. Yet, they require meticulous design and calibration. In-flight calibration of double-probe instruments is usually presented in the most common case of tenuous plasmas, where the presence of an electrostatic structure surrounding the charged spacecraft alters the geophysical electric field measurements. To account for this effect and the uncertainty in the boom length, the measured electric field is multiplied by a parameter called the shorting factor (sf ). In the plasmasphere, the Debye length is very small in comparison with spacecraft dimension and there is no shorting of the electric field measurements (sf = 1). However, the electric field induced by spacecraft motion greatly exceeds any geophysical electric field of interest in the plasmasphere. Thus, the highest level of accuracy in calibration is required. The objective of this work is to discuss the accuracy of the setting Sf =1 and therefore to examine the accuracy of Van Allen Probes electric field measurements below L = 2. We introduce a method to determine the shorting factor near perigee. It relies on the idea that the value of the geophysical electric field measured in the Earth's rotating frame of reference is independent of whether the spacecraft is approaching perigee or past perigee, i.e. it is independent of spacecraft velocity. We obtain that Sf =0.994 ± 0.001. The resulting margins of errors in individual electric drift measurements are of the order of ± 0.1% of spacecraft velocity (a few meters per second).

Abstract #22: First report of recording transcranial direct current stimulation-generated electric fields in subthalamic nuclei using directional leads

Abstract #22: First report of recording transcranial direct current stimulation-generated electric fields in subthalamic nuclei using directional leads

Direct electric field imaging of graphene defects

Material properties are sensitive to atomistic structure defects such as vacancies or impurities, and it is therefore important to determine not only the local atomic configuration but also their chemical bonding state. Annular dark-field scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy has been utilized to investigate the local electronic structures of such defects down to the level of single atoms. However, it is still challenging to two-dimensionally map the local bonding states, because the electronic fine-structure signal from a single atom is extremely weak. Here, we show that atomic-resolution differential phase-contrast STEM imaging can directly visualize the anisotropy of single Si atomic electric fields in monolayer graphene. We also visualize the atomic electric fields of Stone–Wales defects and nanopores in graphene. Our results open the way to directly examine the local chemistry of the defective structures in materials at atomistic dimensions.

Direct electric field control of the skyrmion phase in a magnetoelectric insulator

Magnetic skyrmions are topologically protected spin-whirls currently considered as promising for use in ultra-dense memory devices. Towards achieving this goal, exploration of the skyrmion phase response and under external stimuli is urgently required. Here we show experimentally, and explain theoretically, that in the magnetoelectric insulator Cu2OSeO3 the skyrmion phase can expand and shrink significantly depending on the polarity of a moderate applied electric field (few V/μm). The theory we develop incorporates fluctuations around the mean-field that clarifies precisely how the electric field provides direct control over the free energy difference between the skyrmion and the surrounding conical phase. The quantitative agreement between theory and experiment provides a solid foundation for the development of skyrmionic applications based on magnetoelectric coupling.

Effect of ferromagnetic exchange field on band gap and spin polarisation of graphene on a TMD substrate

We calculate the electronic band dispersion of graphene monolayer on a two-dimensional transition metal dichalcogenide substrate (GrTMD) around K and $$\mathbf{K}^{\prime }$$ points by taking into account the interplay of the ferromagnetic impurities and the substrate-induced interactions. The latter are (strongly enhanced) intrinsic spin–orbit interaction (SOI), the extrinsic Rashba spin–orbit interaction (RSOI) and the one related to the transfer of the electronic charge from graphene to substrate. We introduce exchange field (M) in the Hamiltonian to take into account the deposition of magnetic impurities on the graphene surface. The cavalcade of the perturbations yield particle–hole symmetric band dispersion with an effective Zeeman field due to the interplay of the substrate-induced interactions with RSOI as the prime player. Our graphical analysis with extremely low-lying states strongly suggests the following: The GrTMDs, such as graphene on $$\hbox {WY}_{2}$$ , exhibit (direct) band-gap narrowing / widening (Moss–Burstein (MB) gap shift) including the increase in spin polarisation (P) at low temperature due to the increase in the exchange field (M) at the Dirac points. The polarisation is found to be electric field tunable as well. Finally, there is anticrossing of non-parabolic bands with opposite spins, the gap closing with same spins, etc. around the Dirac points. A direct electric field control of magnetism at the nanoscale is needed here. The magnetic multiferroics, like $$\hbox {BiFeO}_{3}$$ (BFO), are useful for this purpose due to the coupling between the magnetic and electric order parameters.

Separation of large DNA molecules by applying pulsed electric field to size exclusion chromatography-based microchip

Through electrophoresis driven by a pulsed electric field, we succeeded in separating large DNA molecules with an electrophoretic microchip based on size exclusion chromatography (SEC), which was proposed in our previous study. The conditions of the pulsed electric field required to achieve the separation were determined by numerical analyses using our originally proposed separation model. From the numerical results, we succeeded in separating large DNA molecules (λ DNA and T4 DNA) within 1600 s, which was approximately half of that achieved under a direct electric field in our previous study. Our SEC-based electrophoresis microchip will be one of the effective tools to meet the growing demand of faster and more convenient separation of large DNA molecules, especially in the field of epidemiological research of infectious diseases.

Direct electric field imaging inside atoms

Direct electric field imaging inside atoms

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

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

Quantification of glutathione in single cells from rat liver by microchip electrophoresis with chemiluminescence detection

Glutathione (GSH) is a major endogenous antioxidant that has a central role in cellular defense against toxins and free radicals. Rapid and accurate detection of GSH content in single cells is important to the early diagnosis of disease and biomedical research. In this work, a novel method based on microchip electrophoresis chemiluminescence (MCE-CL) detection was developed for the quantification of glutathione (GSH) in single cells from rat liver. The detection of GSH is based on the strong sensitization of mercapto compound to luminol-H2O2CL system. The injection, localization, and membrane dissolution of single cell were simply and rapidly carried out on the microchip by direct electric field force, which did not require any additional membrane dissolution reagent. Under optimized experimental conditions, single cell assay was achieved within 2min. The peak area of the GSH was taken as quantification of GSH, and a good linear relationship of GSH concentration to peak area in the range of 3.0 × 10−6M to 6.0 × 10−4M was obtained. The detection limit for GSH is 9.6 × 10−7M, calculated by S/N = 3. The measured GSH content in single cells from rat liver (n = 10) ranged from 7.8fmol to 13.fmol with a mean value of 10.8fmol.

Assessing potential impacts of energized submarine power cables on crab harvests

Offshore renewable energy facilities transmit electricity to shore through submarine power cables. Electromagnetic field emissions (EMFs) are generated from the transmission of electricity through these cables, such as the AC inter-array (between unit) and AC export (to shore) cables often used in offshore energy production. The EMF has both an electric component and a magnetic component. While sheathing can block the direct electric field, the magnetic field is not blocked. A concern raised by fishermen on the Pacific Coast of North America is that commercially important Dungeness crab (Metacarcinus magister Dana, 1852)) might not cross over an energized submarine power cable to enter a baited crab trap, thus potentially reducing their catch. The presence of operating energized cables off southern California and in Puget Sound (cables that are comparable to those within the arrays of existing offshore wind energy devices) allowed us to conduct experiments on how energized power cables might affect the harvesting of both M. magister and another commercially important crab species, Cancer productus Randall, 1839. In this study we tested the questions: 1) Is the catchability of crabs reduced if these animals must traverse an energized power cable to enter a trap and 2) if crabs preferentially do not cross an energized cable, is it the cable structure or the EMF emitted from that cable that deters crabs from crossing? In field experiments off southern California and in Puget Sound, crabs were given a choice of walking over an energized power cable to a baited trap or walking directly away from that cable to a second baited trap. Based on our research we found no evidence that the EMF emitted by energized submarine power cables influenced the catchability of these two species of commercially important crabs. In addition, there was no difference in the crabs’ responses to lightly buried versus unburied cables. We did observe that, regardless of the position of the cable, Cancer productus in southern California tended to move to the west and Metacarcinus magister tended to move to the east.

Alternating current breakdown voltage of ice electret

Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

Printed Planar Supercapacitors (SCs) Having High Energy Density

Although SCs (Fig. 1a) are known for their very high power density, very long cycle life, and being relatively innocuous, their energy densities are about 10 - 25X lower as compared to lithium ion batteries (LIBs). Despite this shortcoming, replacement of traction LIBs with SCs in hybrid electric vehicles is now commonplace but the opposite is not. However, SCs have rather long road ahead. For example, the specific energy of the recently launched Maxwell 2.85V DuraBlue SC cell is only 7.7 Wh/kg which is one fourth of that for the lead acid batteries (35 Wh/kg), the capacity target for the next generation of SCs. Recently, graphene or activated carbon based microsupercapacitors having planar interdigitated electrodes and current collectors (Fig. 1b) showed high energy densities rivaling or surpassing those of thin film LIBs and lead acid batteries were reported by several groups [1]. These results gave us a glimpse of the possibility of competing with LIBs in both consumer electronics and EVs in the future and inspired us to invent new planar SC designs in order to achieve even higher energy density. The first question we asked was "Is the MSC design shown in Fig. 1b scalable?" And our initial response was “unlikely” because the driving force for ion movement between the positive and negative carbon electrodes is limited to the relatively weak fringe electric field (shown as the yellow dash lines in Fig. 1b) which cannot effectively drive the ion movement through the entire thickness of the carbon electrode (t2) as it increases into the micron range. In order to overcome the lack of driving force for facile ion movement, we came up with several new designs in a recent patent application [2]. One of them is shown in Fig. 2 as an example, wherein the current collectors are coated on the sidewalls of the carbon electrodes and gives raise to the direct electric field, as indicated by the purple arrow. In this presentation we will discuss other planar designs, their corresponding pack designs, as well as low cost fabrication methods involving printing processes. 1. (a) D. Pech et al., Nature Nanotech. 2010, 5, 651; (b) W. Gao et al. ibid., 2011, 6, 496; (c) M. F. El-Kady et al., Science, 2012, 335, 1326; (d) M. F. El-Kady; R. B. Kaner, Nature Comm. 2013, 4, 1475; (e) Z.-S. Wu et al., ibid., 2013, 4, 2487; (f) T. Lin et al., Science, 2015, 350, 1508. 2. B. R. Hsieh, US patent application US20160133396A1 (2016). Figure 1

Electric-field control of magnetism in the flexible CoFeB/P(VDF–TrFE) multiferroic heterostructures

Flexible multiferroic heterostructures of ferromagnetic Co40Fe40B20/ferroelectric copolymer poly-vinylidene fluoride-trifluoroethylene [CoFeB/P(VDF-TrFE)] were fabricated by DC sputtering. The structure, ferroelectric behaviours along with remnant polarization (2Pr) of 2.4μC/cm2 at room temperature, saturated magnetizations around 900emu/cm3 were measured in the novel composites. Moreover, the direct electric field control of magnetic properties and the mechanisms of magnetoelectric (ME) coupling in the flexible CoFeB/P(VDF-TrFE) heterostructures were investigated, and the strong strain-mediated ME effect originating from voltage-induced piezo-strain was demonstrated. These results show the good prospects in application of flexible spintronic devices.

Transformer Impulse Surges Calculation by FEM Coupled to Circuit

This paper presents a new technique for the transient analysis of power transformers under standard impulse excitations. Based on a 2-D finite element method magnetic and electric field simulation coupled to an electric circuit, the technique allows for an analysis of a wide range of winding and insulation designs of a transformer. Also, a 2-D approximation and a direct electric and magnetic field computation (without an equivalent circuit modeling) make this technique effective for engineering applications. Results of calculations of a three-phase power transformer 125MVA-220/10 kV are presented to validate the accuracy of the approach.

Interferometric time-domain ptychography for ultrafast pulse characterization.

A novel pulse characterization method is presented, favorably combining interferometric frequency-resolved optical gating (FROG) and time-domain ptychography. This new variant is named ptychographic-interferometric frequency-resolved optical gating (πFROG). The measurement device is simple, bearing similarity to standard second-harmonic FROG, yet with a collinear beam geometry and an added bandpass filter in one of the correlator arms. The collinear beam geometry allows tight focusing and circumvents possible geometrical distortion effects of noncollinear methods, making πFROG especially suitable for the characterization of unamplified few-cycle pulses. Moreover, the direction-of-time ambiguity afflicting most second-order FROG variants is eliminated. Possible group delay dispersion of pulses leads to a characteristic tilt in the πFROG traces, allowing the detection of uncompensated dispersion without a retrieval. Using nanojoule, three-cycle pulses at 800nm, the πFROG method is tested, and the results are compared with spectral phase interferometry for direct electric field reconstruction measurements. Measured pulse durations agree within a fraction of a femtosecond. As a further test, the πFROG measurements are repeated with added group delay dispersion, and found to accurately reproduce the dispersion computed with Sellmeier equations.

Impact of high strength electromagnetic fields generated by Tesla transformer on plant cell ultrastructure

Non-thermal effects of direct electric fields and alternating electromagnetic fields (EMF) have been successfully used in a number of studies and applications in agriculture and biotechnology. Among different kinds of high strength EMF generators, the Tesla transformer (TT) is known as a widely applied, low cost, and troubleproof device, which generates EMF in the range of 2–8MHz. Despite of a number of developed and perspective applications of high strength EMFs in agriculture and biotechnology, the EMFs generated by TT, as well as the 1–50MHz range of high strength EMF still remain unexplored in the fields of plant physiology, ultrastructure studies and biochemistry. In this work, we have shown that TT-EMFs (4MHz) induced fast stem and petiole bending, disappearance of cell organelles, vacuolar membranes, and increase of a non-photochemical chlorophyll fluorescence quenching in petioles. It is intriguing that such fatal effects can be evoked in plants by EMFs which are well known as harmless for man at the applied strength and frequency.

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

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.

HfO2/porous anodic alumina composite films for multifunctional data storage media materials under electric field control

New materials for achieving direct electric field control of ferromagnetism and resistance behavior are highly desirable in the development of multifunctional data storage devices. In this paper, HfO2 nanoporous films have been fabricated on porous anodic alumina (PAA) substrates by DC-reactive magnetron sputtering. Electrically induced resistive switching (RS) and modulated room temperature ferromagnetism are simultaneously found in a Ag/HfO2/PAA/Al (Ag/HP/Al) heterostructure. The switching mechanism between low resistance state and high resistance state is generally attributed to the formation/rupture of conductive filaments which may consist of oxygen vacancies. The combination of the electric field control of magnetization change and RS makes HP films possible for the multifunctional data storage media materials.

Unstable and Multiple Pulsing Can Be Invisible to Ultrashort Pulse Measurement Techniques

Multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to measure such unstable multi-pulsing has not been studied. Here we report calculations and simulations finding that allowing variations in just the relative phase of a satellite pulse causes the second pulse to completely disappear from a spectral interferometry for direct electric field reconstruction (SPIDER) measurement. We find that, although neither frequency-resolved optical gating (FROG) nor autocorrelation can determine the precise properties of satellite pulses due to the presence of instability, they always succeed in, at least, seeing the satellite pulses. Also, additional post-processing of the measured FROG trace can determine the correct approximate relative height of the satellite pulse and definitively indicate the presence of unstable multiple-pulsing.

Purely bianisotropic scatterers

The polarization response of molecules or meta-atoms to external electric and magnetic fields, which defines the electromagnetic properties of materials, can either be direct (electric field induces electric moment and magnetic field induces magnetic moment) or indirect (magnetoelectric coupling in bianisotropic scatterers). Earlier studies suggest that there is a fundamental bound on the indirect response of all passive scatterers: It is believed to be always weaker than the direct one. In this paper, we prove that there exist scatterers which overcome this bound substantially. Moreover, we show that the amplitudes of electric and magnetic polarizabilities can be negligibly small as compared to the magnetoelectric coupling coefficients. However, we prove that if at least one of the direct-excitation coefficients vanishes, magnetoelectric coupling effects in passive scatterers cannot exist. Our findings open a way to a new class of electromagnetic scatterers and composite materials.