Mean Electric Field Research Articles

Study on the plume self-neutralization of ionic liquid electrospray thruster based on median potential

Abstract Ionic liquid electrospray thruster (ILET) has the advantages of high specific impulse, precise thrust control, and low structural mass, which make it ideal for small satellites. The charged particles of ILET’s plume may lead to device charging or even damage, restricting its engineering applications. Thus, this paper examines the self-neutralization effectiveness of the ILET's plume under various emission conditions using particle-in-cell simulations. In order to accurately evaluate the self-neutralization effectiveness of the ILET’s plume, the median potential is explained in this paper and its reasonableness as the evaluation criterion for self-neutralization of the plume is verified. The working envelope for achieving self-neutralization of the ILET’s plume is determined by simulating the bipolar plume under various emission conditions. The results indicate that when the highest and lowest potentials are the same, the mean electric field strength between two points in space with a better degree of neutrality is 200% higher compared to points with a lesser degree of neutrality. The study determines the working envelope to realize self-neutralization of the ILET’s plume with an effectiveness of 70%. When the emission voltage of the anode thruster is fixed, the range of the cathode thruster’s voltage ranges from 108.36 V to 228.74 V. The asymmetry between the anode and cathode emissions of the ILET prototype significantly influences the operational range of the cathode thruster. Greater asymmetry leads to a narrower operating range for the ILET to achieve self-neutralization of the plume. This study serves as a guide for the ILET to achieve self-neutralization of the plume.

Short-term effects of transcranial direct current stimulation on motor speech in Parkinson’s disease: a pilot study

Introduction: Hypokinetic dysarthria (HD) is a common motor speech symptom of Parkinson’s disease (PD) which does not respond well to PD treatments. We investigated short-term effects of transcranial direct current stimulation (tDCS) on HD in PD using acoustic analysis of speech. Based on our previous studies we focused on stimulation of the right superior temporal gyrus (STG) - an auditory feedback area. Methods: In 14 PD patients with HD, we applied anodal, cathodal and sham tDCS to the right STG using a cross-over design. A protocol consisting of speech tasks was performed prior to and immediately after each stimulation session. Linear mixed models were used for the evaluation of the effects of each stimulation condition on the relative change of acoustic parameters. We also performed a simulation of the mean electric field induced by tDCS. Results: Linear mixed model showed a statistically significant effect of the stimulation condition on the relative change of median duration of silences longer than 50 ms (p = 0.015). The relative change after the anodal stimulation (mean = -5.9) was significantly lower as compared to the relative change after the sham stimulation (mean = 12.8), p = 0.014. We also found a correlation between the mean electric field magnitude in the right STG and improvement of articulation precision after anodal tDCS (R = 0.637; p = 0.019). Conclusions: The exploratory study showed that anodal tDCS applied over the auditory feedback area may lead to shorter pauses in a speech of PD patients.

Mean Electric Field of Dielectric Nanoparticle

The nanoscale effect of the formation of an electric field near the surface of a dielectric nanoparticle is discussed within the framework of the proposed model based on the reconstruction of the crystal surface, including the splitting of the surface atomic layer into two parallel sublayers consisting of atoms with only positive or only negative effective static electric charges, respectively. The mean electric field potential and strength are obtained depending on the distance from the surface and the numerical values of their parameters for hexagonal boron nitride are estimated.

Non-equilibrium dynamics of dipole-charged fields in the Proca theory

We discuss the dynamics of field configurations encoded in the certain class of electric (magnetic) dipole-charged states in the Proca theory of the real massive vector field. We construct such states so as to ensure that the long-distance structure of the mean electromagnetic field in them is initially set by the formula describing the electromagnetic field of the electric (magnetic) dipole. We analyze then how such a mean electromagnetic field evolves in time. We find that far away from the center of the initial field configuration, the long-range component of the mean electromagnetic field harmonically oscillates, which leads to the phenomenon of the periodic oscillations of the electric (magnetic) dipole moment. We also find that near the center of the initial field configuration, the mean electromagnetic field escapes from its initial arrangement and a spherical shock wave propagating with the speed of light appears in the studied system. A curious configuration of the axisymmetric mean electric field is found to accompany the mean magnetic field in magnetic dipole-charged states.

Quantum sensing of electric field distributions of liquid electrolytes with NV-centers in nanodiamonds

To use batteries as large-scale energy storage systems it is necessary to measure and understand their degradation in-situ and in-operando. As a battery’s degradation is often the result of molecular processes inside the electrolyte, a sensing platform which allows to measure the ions with a high spatial resolution is needed. Primary candidates for such a platform are NV-centers in diamonds. We propose to use a single NV-center to deduce the electric field distribution generated by the ions inside the electrolyte through microwave pulse sequences. We show that the electric field can be reconstructed with great accuracy by using a protocol which includes different variations of the free induction decay to obtain the mean electric field components and a pulse sequence consisting of three polarized π-pulses to measure the electric field’s standard deviation . From a semi-analytical ansatz we find that for a lithium ion battery there is a direct relationship between and the ionic concentration. Our results show that it is therefore possible to use NV-centers as sensors to measure both the electric field distribution and the local ionic concentration inside electrolytes.

Electrical and Optical Investigation of an Electric Arc in Hydrogen for short gaps

Hydrogen or mixtures containing hydrogen represent attractive gases for low-voltage switching devices because of increased arc quenching behaviour. However, fundamental electrical properties of arcs in hydrogen are still not well known. In this paper, first results of a study of a DC switching arc in pure hydrogen at 1 bar between graphite electrodes are presented for low currents of 8 and 16 A. The arc voltage and current are measured during contact separation. High-speed images of the arc are processed to determine the arc length considering the high arc dynamics with erratic elongations and jumps of the electrode attachment. The arc voltage dependence on the length results in a typical sheath voltage of approximately 23 V and mean electric fields in the arc column of 18.7 V/mm at 8 A and 10.8 V/mm at 16A.

Periodic charge oscillations in the Proca theory

We consider the Proca theory of the real massive vector field. There is a locally conserved 4-current operator in such a theory, which one may use to define the charge operator. Accordingly, there are charged states in which the expectation value of the charge operator is non-zero. We take a close look at the charge operator and study the dynamics of the certain class of charged states. For this purpose, we discuss the mean electric field and 4-current in such states. The mean electric field has the periodically oscillating Coulomb component, whose presence explains the periodic charge oscillations. A complementary insight at such a phenomenon is provided by the mean 4-current, whose discussion leads to the identification of a certain paradox. Last but not least, we show that there is a shock wave propagating in the studied system, which affects analyticity of the mean electric field and 4-current.

Rayleigh‐Taylor Instability Observed at the Dayside Magnetopause Under Northward Interplanetary Magnetic Field

AbstractUnder northward interplanetary magnetic field, periodical fluctuations with the period of 85 s have been observed by one of the Time History of Events and Macroscale Interactions during Substorms spacecraft at the dayside magnetopause when the solar wind dynamic pressure suddenly dropped. The observed magnetic field distortions, characterized by the compression of the main component as well as the flapping of the perpendicular components, are in line with the theoretical predictions of the Rayleigh‐Taylor (R‐T) instability excited at the magnetopause. With the convective electric field and the mean electric field removed, the perturbations in the electric field are identified as typical two sinusoidal signals with a 90° phase difference, consistent with previous prediction of the attendant electrostatic field arising from the R‐T instability. The transverse motions of the plasmas resulting from the electric drifting driven by the electrostatic field are observed both in pitch‐angle distributions and in distribution functions. The growth rate of the R‐T instability is about 43 s, implying that the instability has time to grow during the disturbances. Using the Gauss theorem, the calculated net charge density based on the electric field observation is one part of 27 compared to the totally observed plasma density, indicating that only a tiny fraction of the charge separates to set up the electrostatic field, which is due to a collective effect in the plasma.

Tolerability of transcranial magnetic stimulation language mapping in children

ObjectiveTranscranial Magnetic Stimulation (TMS) has emerged as a viable non-invasive method for mapping language networks. Little is known about the tolerability of transcranial magnetic stimulation language mapping in children. MethodsChildren aged 5–18 years underwent bilateral language mapping using repetitive transcranial magnetic stimulation (rTMS) to target 33 sites/hemisphere. Stimulation was delivered at 5 Hz, in 1–2 second bursts, during visual naming and auditory verb generation. Pain unpleasantness and pain intensity were assessed using an unpleasantness visual analog scale (VAS). Results49 participants tolerated motor mapping and had repetitive transcranial magnetic stimulation. 35/49 (71%) completed visual naming and 26/49 (53%) completed both visual naming and verb generation. Mean electrical field per participant was 115 V/m. Young age and lower language ability were associated with lower completion. Visual analogue scale scores were significantly higher (6.1 vs. 2.8) in participants who withdrew early compared to those who completed at least visual naming. ConclusionsPain measured by VAS was a major contributor to early withdrawal. However, a complete bilateral map was obtained with one paradigm in 71% of participants. Future studies designed to reduce pain during repetitive transcranial magnetic stimulation over language cortex will boost viability. SignificanceThis study represents the first attempt to characterize tolerability of bilateral repetitive transcranial magnetic stimulation language mapping in healthy children.

Large-area mobile measurement of outdoor exposure to radio frequencies

A rapid outdoor sampling technique was tested to measure human exposure to radio frequencies in a city of 96,000 inhabitants. The technique consisted of taking measurements with a personal exposure meter inside a moving vehicle. Tests were carried out to quantify the alteration produced by the vehicle's structure and obtain correction factors in order to minimize this alteration. Data were collected at 3065 points where signals in the FM radio and mobile phone wavebands were detected. The coefficients of exposure to sources with multiple frequencies due to thermal effects were calculated from the measured values of the electric field. Kriging was used to generate maps of these coefficients, and these maps were then merged with aerial photographs of the city to readily identify the areas with greater or lesser exposure. The results indicated that the vehicle increased the FM broadcasting radiation readings by a factor of 1.66, but attenuated those of mobile telephony by factors of 0.54–0.66. The mean electric field levels detected throughout the city were 0.231, 0.057, 0.140, 0.124, and 0.110 V/m for the frequency bands FM, LTE 800 (DL), GSM + UMTS 900(DL), GSM 1800(DL), and UMTS 2100(DL), respectively. The mean coefficient of exposure to sources with multiple frequencies was 2.05 × 10−4, and the maximum was 9.81 × 10−3. It can be concluded from the study that it is possible to assess radio frequency exposure using this method, and that the technique is scalable to different sized cities. It also allows measurement at different times so as to analyse the temporal variation of radio frequency levels.

Electric field simulations of transcranial direct current stimulation in children with perinatal stroke.

Perinatal stroke (PS) is a focal vascular brain injury and the leading cause of hemiparetic cerebral palsy. Motor impairments last a lifetime but treatments are limited. Transcranial direct-current stimulation (tDCS) may enhance motor learning in adults but tDCS effects on motor learning are less studied in children. Imaging-based simulations of tDCS-induced electric fields (EF) suggest differences in the developing brain compared to adults but have not been applied to common pediatric disease states. We created estimates of tDCS-induced EF strength using five tDCS montages targeting the motor system in children with PS [arterial ischemic stroke (AIS) or periventricular infarction (PVI)] and typically developing controls (TDC) aged 6-19 years to explore associates between simulation values and underlying anatomy. Simulations were performed using SimNIBS https://simnibs.github.io/simnibs/build/html/index.html using T1, T2, and diffusion-weighted images. After tissue segmentation and tetrahedral mesh generation, tDCS-induced EF was estimated based on the finite element model (FEM). Five 1mA tDCS montages targeting motor function in the paretic (non-dominant) hand were simulated. Estimates of peak EF strength, EF angle, field focality, and mean EF in motor cortex (M1) were extracted for each montage and compared between groups. Simulations for eighty-three children were successfully completed (21 AIS, 30 PVI, 32 TDC). Conventional tDCS montages utilizing anodes over lesioned cortex had higher peak EF strength values for the AIS group compared to TDC. These montages showed lower mean EF strength within target M1 regions suggesting that peaks were not necessarily localized to motor network-related targets. EF angle was lower for TDC compared to PS groups for a subset of montages. Montages using anodes over lesioned cortex were more sensitive to variations in underlying anatomy (lesion and tissue volumes) than those using cathodes over non-lesioned cortex. Individualized patient-centered tDCS EF simulations are prudent for clinical trial planning and may provide insight into the efficacy of tDCS interventions in children with PS.

Radiofrequency Exposure Levels in Greece.

Medical Physics Department (Medical School, University of Thessaly) participated in a Greek National EMF research program (EDBM34) with the scope to measure and evaluate radiofrequency (RF) exposure (27-3000 MHz) in areas of sensitive land use. A thousand (1000) measurements were carried out at two "metropolitan locations" (Athens and Thessaloniki: 624 points) and several rest urban/rural locations (376 points). SRM 3006 spectrum analyzer manufactured by Narda Safety Test Solutions was used. The broadband mean electric field in metropolitan areas was 0.41 V/m, while in the rest of Greece was 0.36 V/m. In metropolitan areas, the predominant RF source was the TV and Radio FM signals (36.2% mean contribution to the total RF exposure level). In the rest areas, the predominant source was the systems of the meteorological and military/defensive service (31.1%). The mobile sector contributed 14.9% in metropolitan areas versus 12.2% in the rest of Greece. The predominant mobile source was 900 MHz in both cases (4.5% in metropolitan areas vs. 3.3% in the rest of Greece). The total exposure from all RF sources complied with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2020 safety guidelines [ICNIRP, 2020]. The maximum exposure level was 0.129% of the limit for the metropolitan areas vs. 0.110% for the rest of Greece. Nonremarkable differences between metropolitan areas' exposure and the rest of Greece. In most cases, new 5 G antennas will be added to the existing base stations. Thus, the total exposure may be increased, leading to higher safety distances. © 2023 Bioelectromagnetics Society.

ITB formation in gyrokinetic flux-driven ITG/TEM turbulence

The formation mechanism of internal transport barriers (ITBs) in flux-driven turbulence is studied by means of the full-f gyrokinetic code GKNET. In the adiabatic electron case with a weak magnetic shear configuration, toroidal momentum injection can change the radial mean electric field through radial force balance, leading to a kind of driven ITB formation in which the ion thermal diffusivity by ion temperature gradient (ITG) turbulence decreases to the neoclassical transport level. Only cocurrent toroidal rotation in the outer core region can benefit the ITB formation, and this mechanism is identified to originate from a positive feedback loop between the radial shear and resultant momentum flux. On the other hand, in the kinetic electron case with a reversed magnetic shear configuration, robust co-intrinsic rotation is driven near the surface in ITG turbulence and sustains the shear through the radial force balance, leading to the spontaneous reduction of ion turbulent thermal diffusivity, while this is not observed in the adiabatic electron case. In the presence of electron heating, counter-intrinsic rotation by trapped electron mode turbulence is selectively driven in the negative magnetic shear region, which provides steeper shear formation and a resultant larger reduction of ion turbulent thermal diffusivity. This indicates that the co-existence of different modes can trigger the ‘discontinuity’ of mode structure, intrinsic rotation, and resultant mean near , leading to spontaneous ITB formation.

Simulation and experimental study of parameters in multiple-nozzle electrospinning: Effects of voltage and nozzle configuration on the electric field and electrospun jet attributes

Multiple-jet electrospinning techniques are devised to increase productivity and deposition area for large scale production of nanofibers. The electrospun jets in multiple-nozzle electrospinning behave differently than jets in the conventional single-nozzle setup, and the electric field and fiber non-uniformity becomes a main concern to address. The effects of different nozzle arrangements and voltages on the process and jet characteristics from each nozzle were examined for multiple-nozzle setups with up to five nozzles. Results show that the cone angle of the whipping jets and the length and deflection angle of the straight jets were influenced by the voltage and nozzle setup. From the electric field simulation, it shows that the electric field strength was reduced with the addition of nozzles, which also tend to lead to higher voltage requirement in order to initiate and sustain jets from all nozzles. The strength and distribution of electric field also varied with difference nozzle arrangements. Increasing the internozzle distance tends to increase the mean electric field strength. With four and five nozzles, unequal spacings with larger inner to outer distance ratio resulted in more uniform electric field distributions.

In-silico optimisation of ICD defibrillation efficacy by modifying lead/can configurations using a cohort of high-resolution whole-torso heart models

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Medical Research Council, UK Background ICD is an effective direct therapy against VT/VF by applying a strong electrical shock across the heart between the shocking coil and can. Conventionally, patients will have a shocking coil inside the right ventricle (RV) and a can at the upper left chest. However, due to infections or other conditions, the can may need to place towards the right chest. The placement of the RV coil may also vary in different cases, for example avoiding scar. However, it is unclear how defibrillation efficacy may be altered by these unavoidable modifications to conventional lead/can configurations and whether optimisation may be possible. Purpose To compare defibrillation efficacy of modifications of ICD configurations in a cohort of whole-torso models. Methods A cohort of 15 whole torso models was generated from high resolution CT data and contrast CT cardiac scans, including 5 dilated cardiomyopathy (DCM), 5 hypertrophic cardiomyopathy (HCM) and 5 structurally normal patients (Fig A). Transvenous ICDs were represented by a shocking coil inside the RV (near apex) and a (ground) can at the upper left chest as default settings. Configurations were then varied by moving the can to the right chest, moving the RV coil up the mid-septum or adding extra grounds (Superior Vena Cava (SVC) coil, coronary sinus (CS) coil (Fig A)). Defibrillation-strength shocks were applied to all models (Fig B). DFTs and mean electrical field were evaluated across the whole heart as well as specific LV, RV, RV insertion regions, along with overall impedance. Results Shifting the can from left to right significantly increased DFT for the whole heart (23 J vs 15 J, P=0.03) and LV (25 J vs 17 J, P=0.03) (Fig C) and reduced the mean electrical field. Moving the RV coil further up the septum did not significantly alter DFT (Fig D), but did reduce mean electrical field for all regions and reduce impedance significantly. Additional separate coils significantly reduced DFT for all regions (Fig D) by increasing mean electrical field, whilst adding both coils significantly reduced DFT the most (whole heart: 15 J vs 6 J, P=0.03) (Fig E). Impedance was increased significantly by adding SVC coil, but reduced significantly by adding CS coil. Adding both coils increased impedance slightly. Conclusions Although a right-sided can increases DFT by over 50%, additional leads (grounds) may mitigate this increase by increasing mean electrical field. Moving the RV coil closer to the mid-septum reduces DFT slightly, but also reduces mean electrical field and impedance significantly.

Numerical mesoscale tissue model of electrochemotherapy in liver based on histological findings

Electrochemotherapy (ECT) and irreversible electroporation (IRE) are being investigated for treatment of hepatic tumours. The liver is a highly heterogeneous organ, permeated with a network of macro- and microvasculature, biliary tracts and connective tissue. The success of ECT and IRE depends on sufficient electric field established in whole target tissue; therefore, tissue heterogeneity may affect the treatment outcome. In this study, we investigate electroporation in the liver using a numerical mesoscale tissue model. We numerically reconstructed four ECT experiments in healthy porcine liver and computed the electric field distribution using our treatment planning framework. We compared the computed results with histopathological changes identified on microscopic images after treatment. The mean electric field threshold that best fitted the zone of coagulation necrosis was 1225 V/cm, while the mean threshold that best fitted the zone of partially damaged liver parenchyma attributed to IRE was 805 V/cm. We evaluated how the liver macro- and microstructures affect the electric field distribution. Our results show that the liver microstructure does not significantly affect the electric field distribution on the level needed for treatment planning. However, major hepatic vessels and portal spaces significantly affect the electric field distribution, and should be considered when planning treatments.

Understanding the characteristics of non-equilibrium alternating current gliding arc discharge in a variety of gas mixtures (air, N2, Ar, Ar/O2, and Ar/CH4) at elevated pressures (1–5 atm)

This work aims at clarifying the fundamental mechanisms of non-equilibrium alternating current gliding arc discharge (GAD) by investigating effects of gas compositions and pressures on the GAD characteristics with electrical and optical methods. Interestingly, the glow-to-spark transition was found by adding O2 or CH4 into the argon or modulating the power supply. This transition occurs attributed to the fact that the discharge mode is largely affected by the effective electron decay time (τ) as well as the feedback response of the power supply to the free electron density in the GAD. Short τ or low free electron density tends to result in the spark-type discharge. It further implies that the power supply characteristics is crucial for discharge mode control. The pressure effects on the GAD characteristics were found to vary with gas composition when the same alternating current power supply was used. In N2 or air, the emission intensity from the plasma column increases with pressure while the mean electric field strength (E) along the plasma column decreases with pressure. Differently, in Ar, the emission intensity and E do not change much with pressure. It can be explained by the different energy partition and transfer pathways between monatomic and molecular species. The molecular gases have vibrational excitation pathways to facilitate the electronic excitation and ionization that is different from the monatomic gas.

Transcranial Electrical Stimulation generates electric fields in deep human brain structures

BackgroundTranscranial electrical stimulation (TES) efficiency is related to the electric field (EF) magnitude delivered on the target. Very few studies (n = 4) have estimated the in-vivo intracerebral electric fields in humans. They have relied mainly on electrocorticographic recordings, which require a craniotomy impacting EF distribution, and did not investigate deep brain structures. ObjectiveTo measure the electric field in deep brain structures during TES in humans in-vivo. Additionally, to investigate the effects of TES frequencies, intensities, and montages on the intracerebral EF. MethodsSimultaneous bipolar transcranial alternating current stimulation and intracerebral recordings (SEEG) were performed in 8 drug-resistant epileptic patients. TES was applied using small high-definition (HD) electrodes. Seven frequencies, two intensities and 15 montages were applied on one, six and one patients, respectively. ResultsAt 1 mA intensity, we found mean EF magnitudes of 0.21, 0.17 and 0.07 V·m−1 in the amygdala, hippocampus, and cingulate gyrus, respectively. An average of 0.14 ± 0.07 V·m−1 was measured in these deep brain structures. Mean EF magnitudes in these structures at 1Hz were 11% higher than at 300Hz (+0.03 V·m−1). The EF was correlated with the TES intensities. The TES montages that yielded the maximum EF in the amygdalae were T7-T8 and in the cingulate gyri were C3-FT10 and T7-C4. ConclusionTES at low intensities and with small HD electrodes can generate an EF in deep brain structures, irrespective of stimulation frequency. EF magnitude is correlated to the stimulation intensity and depends upon the stimulation montage.

ASHLEY: A New Empirical Model for the High‐Latitude Electron Precipitation and Electric Field

AbstractIn this study, a new high‐latitude empirical model is introduced, named for Auroral energy Spectrum and High‐Latitude Electric field variabilitY (ASHLEY). This model improves specifications of soft electron precipitations and electric field variability that are not well represented in existing high‐latitude empirical models. ASHLEY consists of three components, ASHLEY‐A, ASHLEY‐E, and ASHLEY‐Evar, which are developed based on the electron precipitation and bulk ion drift measurements from the Defense Meteorological Satellite Program (DMSP) satellites during the most recent solar cycle. On the one hand, unlike most existing high‐latitude electron precipitation models, which have assumptions about the energy spectrum of incident electrons, the electron precipitation component of ASHLEY, ASHLEY‐A, provides the differential energy fluxes in the 19 DMSP energy channels under different geophysical conditions without making any assumptions about the energy spectrum. It has been found that the relaxation of spectral assumptions significantly improves soft electron precipitation specifications with respect to a Maxwellian spectrum (up to several orders of magnitude). On the other hand, ASHLEY provides consistent mean electric field and electric field variability under different geophysical conditions by ASHLEY‐E and ASHLEY‐Evar components, respectively. This is different from most existing electric field models which only focus on the large‐scale mean electric field and ignore the electric field variability. Furthermore, the consistency between the electric field and electron precipitation is better taken into account in ASHLEY.

Testing Quantum Electrodynamics with Exotic Atoms.

Precision study of few-electron, high-Z ions is a privileged field for probing high-field, bound-state quantum electrodynamics (BSQED). However, the accuracy of such tests is plagued by nuclear uncertainties, which are often larger than the BSQED effects under investigation. We propose an alternative method with exotic atoms and show that transitions may be found between circular Rydberg states where nuclear contributions are vanishing while BSQED effects remain large. When probed with newly available quantum sensing detectors, these systems offer gains in sensitivity of 1 to 2 orders of magnitude, while the mean electric field largely exceeds the Schwinger limit.