Magnitude Of Electric Field Research Articles

Near‐wall velocities of particles suspended in shear flow and a streamwise electric field

Particles with a diameter of ∼0.5µm in a dilute (volume fractions φ∞ <4×10-3 ) suspension assemble into highly elongated structures called "bands" under certain conditions in combined Poiseuille and electroosmotic flows in opposite directions through microchannels at particle-based Reynolds numbers Rep <<1. The particles are first concentrated near, then form "bands" within ∼6µm of, the channel wall. The experiments described here examine the near-wall dynamics of individual "tracer" particles during the initial concentration, or accumulation, of particles, and the steady-state stage when the particles have formed relatively stable bands at different near-wall shear rates and electric field magnitudes. Surprisingly, the near-wall upstream particle velocities are found to be consistently greater in magnitude than the expected values based on the particles being convected by the superposition of both flows and subject to electrophoresis, which is in the same direction as the Poiseuille flow. However, the particle velocities scale linearly with the change in electric field magnitude, suggesting that the particle dynamics are dominated by linear electrokinetic phenomena. If this discrepancy with theory is only due to changes in particle electrophoresis, electrophoresis is significantly reduced to values as small as 20%-50% of the Smoluchowski relation, or well below previous model predictions, even for high particle potentials.

Automated Experiment in 4D-STEM: Exploring Emergent Physics and Structural Behaviors.

Automated experiments in 4D scanning transmission electron microscopy (STEM) are implemented for rapid discovery of local structures, symmetry-breaking distortions, and internal electric and magnetic fields in complex materials. Deep kernel learning enables active learning of the relationship between local structure and 4D-STEM-based descriptors. With this, efficient and "intelligent" probing of dissimilar structural elements to discover desired physical functionality is made possible. This approach allows effective navigation of the sample in an automated fashion guided by either a predetermined physical phenomenon, such as strongest electric field magnitude, or in an exploratory fashion. We verify the approach first on preacquired 4D-STEM data and further implement it experimentally on an operational STEM. The experimental discovery workflow is demonstrated using graphene and subsequently extended toward a lesser-known layered 2D van der Waals material, MnPS3. This approach establishes a pathway for physics-driven automated 4D-STEM experiments that enable probing the physics of strongly correlated systems and quantum materials and devices, as well as exploration of beam-sensitive materials.

Influence of Twist-Angle and Concentration Disorder on the Density of Electronic States of Twisted Graphene

In this paper, we present an approach that makes it possible to describe, from unified physical considerations, the influence of rotation-angle and concentration disorder on the density of electronic states of two-layer twisted graphene. The electron relaxation time and the density of electronic states near the Fermi level are calculated by considering the multiple elastic scattering of electrons by impurities and structural inhomogeneities of the short-range order type. An analysis is presented of the change in the contributions to the density of electronic states from electron scattering on foreign atoms with variations in the defectiveness of the structure, impurity concentration, temperature, and the external electric field magnitude. It is shown that the formation of short-range order areas by foreign atoms in the first coordination sphere relative to the surface of the material can lead to the opening of a gap in the density of electronic states of twisted graphene. Point defects and short-range order regions formed by foreign atoms in the second coordination sphere lead to metallization of twisted graphene.

Near-field mapping of high permittivity dielectric microwave resonator modes via optically induced conductance.

In this paper, we demonstrate a straightforward, low-cost, and high resolution optical-based method to measure the three-dimensional relative electric field magnitude in microwave circuits without the need to monitor reflected laser beams or the requirement of photoconductive substrates for the device under test. The technique utilizes optically induced conductance, where a focused laser beam excites electron-hole-pairs (EHPs) in a semiconductor thin film placed in the near-field of a microwave circuit. The generated EHPs create localized loss in the resonator and modulate the transmitted microwave signal, proportional to the local microwave electric field. As a proof of principle, several different modes of a high permittivity (ɛ ∼ 80) cylindrical dielectric resonator are mapped.

A strategy toward therapeutic improvement of electric field-sensitive gemcitabine prodrugs in 2D metal–organic frameworks in view of their structure and interactions

• The interaction energy of the drug-polymer with MON stronger than the free drug. • Higher value of external electric field will help in better absorption. • A 10% defect leads to a 50% increase in the total interaction energies of the carrier with the PPY-GEM molecules. Gemcitabine, among other chemotherapeutic agents, helps to save many lives in fighting cancers of various types. Nevertheless, many side effects arise from the high dosage required for effective treatment. Nanotechnology-based drug delivery systems (DDSs) are among the newly proposed strategies proposed to send chemotherapeutic agents directly to tumor cells and reduce their hazardous concentrations in healthy tissues. In this paper, through density functional theory (DFT) calculations and molecular dynamics (MD) simulations, a new DDS is designed in which gemcitabine is conjugated to an electric field-responsive polymer called polypyrrole and loaded on a metal–organic nanosheet (MON). DFT calculations reveal that covalent bonding between the drug and polymer has a limited impact on the chemical properties of the drug. On the other hand, the MD simulation suggested that the adsorption of the drug on the CuBDC nanoparticle is highly improved by conjunction with polymer. The interaction energy of the drug-polymer complex with MON is approximately 138 kJ/mol stronger than the corresponding value for the free drug. Furthermore, implementation of a lower magnitude of the external electric field may reduce the adsorption interaction energies, while a higher value will help in better absorption.

Study of the charged particle flow near the plasma grid in negative ion source

Flows of the charged particles in hydrogen (H) and deuterium (D) plasmas were measured with the single-tip directional Langmuir probe. The flow patterns of positive and negative ions have been constructed from the data by moving the probe near the plasma grid. The positive ion flow from driver to extraction regions showed the different velocity equivalent to the mass difference between H and D. The negative ion flow indicated the surface production of negative ions on the plasma grid, and changed the direction corresponding to the magnitude of the extraction electric field.

Statistical Study of Seasonal and Solar Activity Dependence of Nighttime MSTIDs Occurrence Using the SuperDARN Hokkaido Pair of Radars

AbstractWe conduct a statistical analysis on nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) using the Super Dual Auroral Radar Network (SuperDARN) Hokkaido East (43.53°N, 143.61°E) high‐frequency (HF) radar data from 2009 to 2019 and the SuperDARN Hokkaido West (43.54°N, 143.61°E) HF radar data from 2016 to 2019. We analyze the line‐of‐sight Doppler velocity data, corresponding to the magnitude of the polarization electric field associated with nighttime MSTIDs. We find that the propagation direction of the nighttime MSTIDs is mainly southwestward and rotates clockwise with progressing local time. In addition, we identify a negative correlation between the nighttime MSTIDs amplitude and the solar F10.7 index. These tendencies can be explained by the Perkins instability, which is considered to be associated with the growth of nighttime MSTIDs. This study is the first to find the solar activity dependence of the polarization electric field fluctuations associated with the nighttime MSTIDs.

Mapping 1D Confined Electromagnetic Edge States in 2D Monolayer Semiconducting MoS2 Using 4D-STEM.

Four-dimensional (4D) scanning transmission electron microscopy is used to study the electric fields at the edges of 2D semiconducting monolayer MoS2. Sub-nanometer 1D features in the 2D electric field maps are observed at the outermost region along zigzag edges and also along nanowire MoS-terminated MoS2 edges. Atomic-scale oscillations are detected in the magnitude of the 1D electromagnetic edge state, with spatial variations that depend on the specific periodic edge reconstructions. Electric field reconstructions, along with integrated differential phase contrast reconstructions, reveal the presence of low Z number atoms terminating many of the uniform edges, which are difficult to detect by annular dark field scanning transmission electron microscopy due to its limited dynamic range. Density functional theory calculations support the formation of periodic 1D edge states and also show that enhancement of the electric field magnitude can occur for some edge terminations. The experimentally observed electric fields at the edges are attributed to the absence of an opposing electric field from a nearest neighbor atom when the electron beam propagates through the 2D monolayer and interacts. These results show the potential of 4D-STEM to map the atomic scale structure and fluctuations of electric fields around edge atoms with different bonding states than bulk atoms in 2D materials, beyond conventional imaging.

Three-Dimensional Particle-in-Cell Simulations of Bipolar Ionic Electrospray Thruster Plume

This paper presents a fully kinetic three-dimensional particle-in-cell (PIC) simulation study of the plume from a bipolar ionic electrospray thruster pair using 1-ethyl-3-methylimidazolium tetrafluoroborate () ionic liquid propellant. The results show a unique beam neutralization process, where there is little physical coupling between the positive cation and negative anion beam. These dynamics are likely attributed to the similar mass ratio between the two beams and the low current density of the beams at this scale. The small potential difference within the beam suggests that low-energy fragmented species will not be significantly scattered, ejected, or likely to return as backflow. The weak electric field magnitude within the beam suggests that the fragmentation of ion clusters within the plume may occur at a reduced rate compared to that measured in laboratory experiments. This implies that ionic electrospray thrusters may offer a relatively smaller contamination risk compared to other micro-electric propulsion devices.

Observation of variations in cosmic ray single count rates during thunderstorms and implications for large-scale electric field changes

We present the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of cosmic ray single count rate intensity over a 700 km2 area. Observations of variations in the secondary low-energy cosmic ray counting rate, using the TASD, allow us to study the electric field inside thunderstorms, on a large scale, as it progresses on top of the 700 km2 detector, without dealing with the limitation of narrow exposure in time and space using balloons and aircraft detectors. In this work, variations in the cosmic ray intensity (single count rate) using the TASD, were studied and found to be on average at the ∼(0.5–1)% and up to 2% level. These observations were found to be both in excess and in deficit. They were also found to be correlated with lightning in addition to thunderstorms. These variations lasted for tens of minutes; their footprint on the ground ranged from 6 km to 24 km in diameter and moved in the same direction as the thunderstorm. With the use of simple electric field models inside the cloud and between cloud to ground, the observed variations in the cosmic ray single count rate were recreated using CORSIKA simulations. Depending on the electric field model used and the direction of the electric field in that model, the electric field magnitude that reproduces the observed low-energy cosmic ray single count rate variations was found to be approximately between 0.2 GV–0.4 GV. This in turn allows us to get a reasonable insight on the electric field and its effect on cosmic ray air showers inside thunderstorms.2 MoreReceived 19 November 2021Accepted 3 January 2022DOI:https://doi.org/10.1103/PhysRevD.105.062002© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAtmospheric scienceCosmic rays & astroparticlesInterdisciplinary PhysicsParticles & Fields

Investigation of High Voltage Polymeric Insulators Performance under Wet Pollution.

In this paper, a unique approach based on electrical characteristics observed from measurements of contaminated polymeric insulators was established to calculate the electric field distribution over their surfaces. A case study using two different 33 kV polymeric insulator geometric profiles was performed to highlight the benefits of the proposed modeling approach. The conductance of the pollution layer was tested to establish a nonlinear field-dependent conductivity for pollution modeling. The leakage current (LC) of the polluted insulator was measured in a laboratory under clean and wet conditions. Then, using the finite element method (FEM), the electric field and current density distributions along the insulator were computed. The results showed that the insulators experienced an increase in the electric field (EF) magnitude ranging from 0.3 kV/cm to 3.6 kV/cm for the insulator with similar sheds (type I) and 2.2–4.5 kV/cm for the insulator with alternating sheds (big and small, type II) under the high rain condition with a flow rate of 9 L/h. Meanwhile, the highest electric field under fog was 1.74 kV/cm for the insulator with similar sheds and 2.32 kV/cm for an insulator with alternating sheds. Due to the larger diameter on the big shed and the longer leakage distance on the insulator with alternating sheds, the EF on the insulator with alternating sheds is higher than the EF on the insulator with similar sheds. The proposed modeling and simulation provided a detailed field condition estimation around the insulators. This is critical for forecasting the emergence of dry bands and the commencement of flashover on the surfaces of the insulators.

Key factors in the cortical response to transcranial electrical Stimulations—A multi-scale modeling study

Transcranial electrode stimulation (tES), one of the techniques used to apply non-invasive brain stimulation (NIBS), modulates cortical activities by delivering weak electric currents through scalp-attached electrodes. This emerging technique has gained increasing attention recently; however, the results of tES vary greatly depending upon subjects and the stimulation paradigm, and its cellular mechanism remains unclear. In particular, there is a controversy over the factors that determine the cortical response to tES. Some studies have reported that the electric field's (EF) orientation is the determining factor, while others have demonstrated that the EF magnitude itself is the crucial factor. In this work, we conducted an in-depth investigation of cortical activity in two types of electrode montages used widely—the conventional (C)-tES and high-definition (HD)-tES—as well as two stimulation waveforms—direct current (DC) and alternating current (AC). To do so, we constructed a multi-scale model by coupling an anatomically realistic human head model and morphologically realistic multi-compartmental models of three types of cortical neurons (layer 2/3 pyramidal neuron, layer 4 basket cell, layer 5 pyramidal neuron). Then, we quantified the neuronal response to the C-/HD-tDCS/tACS and explored the relation between the electric field (EF) and the radial field's (RF: radial component of EF) magnitude and the cortical neurons' threshold. The EF tES induced depended upon the electrode montage, and the neuronal responses were correlated with the EF rather than the RF's magnitude. The electrode montages and stimulation waveforms caused a small difference in threshold, but the higher correlation between the EF's magnitude and the threshold was consistent. Further, we observed that the neurons' morphological features affected the degree of the correlation highly. Thus, the EF magnitude was a key factor in the responses of neurons with arborized axons. Our results demonstrate that the crucial factor in neuronal excitability depends upon the neuron models' morphological and biophysical properties. Hence, to predict the cellular targets of NIBS precisely, it is necessary to adopt more advanced neuron models that mimic realistic morphological and biophysical features of actual human cells.

OC20: Deep Intracerebral Electric Field Measurement with Stereoelectroencephalography during Transcranial Electrical Stimulations in Human in-vivo

Measuring the electric field generated in several deep brain structures during Transcranial electrical stimulation in humans in-vivo. In addition, we investigated the effects of TES intensities and montages on the intracerebral EF. Transcranial electrical stimulation (TES) has shown for the last decades promises as a treatment for several neurological and psychiatric disorders. Its efficiency is related to the amount of electric field (EF) magnitude delivered on the target. Very few studies (n=3) estimated the in-vivo intracerebral electric fields in human. They relied mainly on electrocorticographic recordings that require a craniotomy and did not precisely focus on targeting the deep cortical structures which can still lead to some discussion about the TES possibility to reach deep structures. We applied Transcranial alternating current stimulations simultaneously with intracerebral recordings (SEEG) in 7 drug-resistant epileptic patients. Two low intensities were used in 6 patients (0.5 and 1mA) and 15 different montages were used in 1 patient. We calculated the electric field by subtracting voltage measured on contiguous intracerebral contacts. We found EF magnitude up to 0.29, 0.38 and 0.54 V/m respectively in the amygdala, the hippocampus, and the cingulate gyrus. Among 91 montage combinations, the global EF difference in the brain was significant in 65% of cases. We also confirmed experimentally that EF magnitude is proportional to TES intensity. In conclusion, EF at a magnitude which can induces stochastic effects, is achievable in the deep brain structures using low intensities. EF is highly correlated to the stimulation intensity and depends on montages.

Near-Zero-Index Slabs on Bloch Surface Wave Platform for Long-Range Directional Couplers and Optical Logic Gates.

Near-zero-index materials and structures, with their extraordinary optical behaviors of phase-free propagation resulting in directional radiation, provide a possible approach for directional coupling and optical logic gates in photonic integrated circuits. However, the radiation from the near-zero-index structures is limited to a short range of a few hundreds of nanometers. A Bloch surface wave (BSW), an electromagnetic surface wave that can be excited at the interface between an all-dielectric multilayer and a dielectric medium with a low-loss optical mode, provides a solution to increase the propagation length. In this work, we present a nanostructured near-zero-index slab integrated on the all-dielectric metal-free BSW platform for long-range surface wave radiation. By employing the long-range directional surface-wave radiation, a directional coupler and optical logic gates based on the BSW near-zero-index slabs are realized. The proposed directional couplers achieve long coupling distances (the electric-field magnitude ratio between the input slab and output slab is 0.22 with a 50 μm coupling distance), which is 2 orders of magnitude longer than that of conventional directional couplers based on evanescent wave coupling. By controlling the interference pattern of the BSW between the slabs, the XOR logic gate is experimentally demonstrated with a significant extinction ratio of 27.9 dB at telecommunications wavelengths. The BSW near-zero-index logic gates and the directional coupler with long-range light propagation provide an approach to the development of photonic integrated circuits and metal-free surface wave-based applications.

Voltage sensitive ion channels: hardware or soft matter? Can we participate in a dialogue?

Standard models of voltage sensing in voltage-sensitive ion channels assume rigidity in gates and other everyday devices, but if rigidity requires the cooperation of numerous strong interatomic bonds, can it exist in a macromolecule at physiological temperature? Can an ion channel be pierced by a water-filled pore without suffering electrical breakdown? The Channel Activation by Electrostatic Repulsion (CAbER) hypothesis proposes that threshold reduction of the electric field magnitude across the excitable channel allows thermal disorder to overcome a partial order of electric dipoles induced by the high resting field.

Theoretical model of the influence of irreversibly electroporated cells on post pulse drug delivery to reversibly electroporated cells.

This study numerically investigates the drug uptake by a population that includes both reversibly and irreversibly electroporated cells. A theoretical continuum model is developed and simulations are conducted in conditions representing low porosity (cells in tissues) and high porosity (cells in suspension). This model considers only passive diffusion following the electroporation pulse and estimates the permeability increases of reversibly electroporated cells using empirically based predictions that relate the long-lived electropore density to the electric field magnitude. A parametric study investigates whether the permeability and resealing rate of irreversibly electroporated cells influence the delivery to the surviving reversibly electroporated cells. The results show that this influence is negligible when the cell number density is low (cells in dilute suspensions). For conditions of cells in tissue when both the fraction of the total cells that are irreversibly electroporated and the permeability of the irreversibly electroporated cells are high enough, the irreversibly electroporated cells rapidly take up the drug and deplete the extracellular space of the available drug. This lowered extracellular concentration can result in less drug delivery to reversibly electroporated cells.

Effect of Negative Ion Concentration and Magnetic Field on Electronegative Plasma Sheath

Plasma is the ionized state of matter and is of interest as it has found applications in diverse fields. In all practical applications of plasma, it interacts with the material surface via non-neutral region that is formed between bulk plasma and surface known as the sheath, which plays a vital role in overall plasma properties. In this work, the characteristics of electronegative magnetized plasma sheath have been presented employing the kinetic trajectory simulation method based on kinetic theory. It is found that magnetic field and volumetric composition of negatively charged particles have significantly affected the characteristics of electronegative plasma sheath. Although the particle densities deplete towards the wall, the decreasing rate of negative charged particles is steeper than that of positive ions. The magnitude of electric field slowly increases close to the sheath entrance, whereas it sharply increases close to the wall. The positive ion density decreases in both cases when the concentration of negative ion is increased or when the magnetic field is increased. On increasing the magnetic field from 0 to 250 mT, the ion density reaching the wall decreases from 0.331 to 0.305 n ps. The results are similar and agree with similar works following different models and our model provides a satisfactory basis for the study of electronegative plasma sheath.

The controllable tuning of nanofriction on atomically thin hexagonal boron nitride with external electric field

Hexagonal boron nitride (h-BN) with good lubricity as well as excellent insulation and hydrophobicity has many potential applications in micro/nano-electromechanical devices. The nanofriction of h-BN on SiO2/Si substrate was studied under an external electric field using atomic force microscopy. The nanofriction increased after applying a bias voltage to the substrate. The increase of nanofriction under the positive bias was relatively greater than under the negative bias. The nanofriction on h-BN can be tuned controllably, dynamically, and reversibly by regulating the direction and magnitude of the external electric field. Electrostatic interaction plays the dominant role in the increase of nanofriction based on the calculation of the electrostatic force and adhesion measurements. Both the inherent potential difference and the ice-like water layer confined between the SiO2/Si substrate and h-BN layers contribute to the asymmetric influence of the electric field. The potential barrier between the tip and h-BN increased with the increase of the external electric field, resulting in a transition of stick–slip behavior from single-slip to multi-slip. The stronger the interaction potential, the greater the energy dissipation required in the friction process. These findings indicate that h-BN may be more suitable as a tunable insulating lubricant in micro/nano-electromechanical devices in charged environments.

Insights into CrS2 monolayer and [formula omitted]-CrS2/[formula omitted]-HfN2 interface for low-power digital and analog nanoelectronics

CrS2 monolayers exhibit excellent mechanical, electronic, piezoelectric and thermal properties as compared to other well-known transition metal dichalcogenides. CrS2/HfN2 van der Waals heterobilayer (vdWH) forms a pn-heterojunction where CrS2 and HfN2 act as an n-type and p-type semiconductor respectively, thereby suggesting its utility in nano-electronics and photodetectors. The perpendicular electric field is effective in manipulating band alignments and band gap in CrS2/HfN2 vdWH. Weaker electric field is able to close the band gap in the vdWH relative to CrS2 ML. Therefore, the vdWH may be a promising candidate in low-power analog and digital nano-electronics. Vertical electric field is found to drive the nearly free electron gas (NFEG) states to near the Fermi level in CrS2 ML. These surface states, reported in a few low-dimensional materials, will enhance charge transport and conductivity in electronics. Furthermore, the combined effect of spin–orbit coupling and a small magnitude of vertical electric field helps to reach a type-II band alignment in the CrS2/HfN2 vdWH. It unusually shows a large spin splitting at both conduction and valence band edges, which is very crucial for ambipolar spin transport. This work demonstrates possibilities for futuristic nano-electronic devices based on CrS2 ML & CrS2 based vdWH.

Determination of Current Flow Induced by Transcutaneous Electrical Nerve Stimulation for the Treatment of Migraine: Potential for Optimization.

Introduction: Transcutaneous electrical nerve stimulation (TENS) for migraine involves the application of pulsatile stimulation through electrodes placed on the forehead to target the underlying trigeminal nerves. It is a simple, safe modality and has secured clinical approval in several markets including the European Union and the United States. Despite nearing almost 7 years of use (postclinical approval), the exact mechanism of action is not fully known. Guided by the need to stimulate the trigeminal nerves bilaterally, electrode dimensions are simply required to extend enough to cover the underlying nerves. The goal of this study is to examine induced current flow [magnitude and spatial distribution of electric field (EF)] and another driver of stimulation [activating function (AF)] due to TENS therapy for migraine for the first time. We further consider the effect of changing the electrode dimension and shape and propose a design modification to deliver optimal flow.Methods: We developed the first ultra-high-resolution finite element (FE) model of TENS for migraine incorporating the target supratrochlear (ST) and the supraorbital (SO) nerves. We first simulated the clinically approved V-shaped geometry. We then considered three additional designs: extended V-shaped, idealized pill-shaped, and finally an extended V-shaped but with greater contact spacing (extended V-shaped +CS).Results: Our findings revealed that the clinically approved electrode design delivered substantially higher mean current flow to the ST nerve in comparison with the SO nerves (Medial: 53% and Lateral: 194%). Consideration of an extended design (~10 mm longer and ~ 4 mm shorter) and a pill-like design had negligible impact on the induced current flow pattern. The extended V-shaped +CS montage delivered relatively comparable current flow to each of the three target nerves. The EF induced in the ST nerve was 49 and 141% higher in the Medial and Lateral SO nerve, respectively. When considering maximum induced values, the delivery of comparable stimulation was further apparent. Given the existing electrode design's established efficacy, our results imply that preferential targeting of the ST nerve is related to the mechanism of action. Additionally, if comparable targeting of all three nerves continues to hold promise, the extended V-shaped +CS montage presents an optimized configuration to explore in clinical studies.