High Frequency Electric Field Research Articles

On the Correct Averaging of the Equations of Ion Motion in High-Frequency Electric Fields

The pseudopotential approach is a useful tool for the qualitative description of ion motion in inhomogeneous high-frequency electric fields, often used in mass spectrometric devices. However, in the theoretical study of the motion of ions in high-frequency electric fields with close frequencies, mathematical ambiguity arises, caused by the nonequivalence of different mathematical approaches. The paper considers and compares the time-dependent pseudopotential model and the model of solenoidal (vortex) pseudoforces, that is, vortex drift. The vortex drift model in high-frequency electric fields with close frequencies can be replaced by the model of ion motion in a pseudopotential varying in time. The theory of almost periodic time signals with two characteristic time scales, fast and slow, eliminates the ambiguity in selecting the correct mathematical method for describing ion motion in high-frequency electric fields.

Generation of micron-sized droplet streams by high frequency electric fields

Generation and transfer of micron-sized droplets are of significant interest for several applications such as electronics cooling, lab-on-chip, microscale printing, etc. We report generation of microscale droplet streams when a larger droplet is exposed to high frequency (>10 kHz) electric fields using dielectric covered coplanar electrodes. Generation of these droplet streams is found to be a function of the actuation frequency and voltage. Our experiments rule out electrospray as the relevant mechanism. Experiments further reveal that the droplet streams are formed due to (1) Evaporation of the larger droplet due to Joule heating; and (2) Enhanced localized condensation on nucleation sites originating from the leakage currents at high electric fields. The condensed droplets are dragged along with the convection current of the larger droplet, leading to the observation of streams. A computational model is used to solve for the convection velocities which is compared with the experimental high-speed videos. The stream velocity is found to increase with the applied field, which is attributed to the smaller size of the condensed droplet at higher electric fields. Capability to generate microscale droplets and transfer them to other substrates is desired in current microfluidic platforms for various applications. This study reports a viable technique and presents critical information for its design.

Formation of Regular Domain Structures in Quenched Ferroelectrics Under the Influence of an External High-frequency Electric Field

Introduction: Within the framework of the phenomenological theory of phase transitions of the second kind of Ginzburg-Landau, the kinetics of ordering of a rapidly quenched highly nonequilibrium domain structure is considered using the lithium tantalate and lithium niobate crystals as an example. Experimental: Using the statistical approach, evolution equations describing the formation of the domain structure under the influence of a high-frequency alternating electric field in the form of a standing wave were obtained. Numerical analysis has shown the possibility of forming thermodynamically stable mono- and polydomain structures. It turned out that the process of relaxation of the system to the state of thermodynamic equilibrium can proceed directly or with the formation of intermediate quasi-stationary polydomain asymmetric phases. Results: It is shown that the formation of Regular Domain Structures (RDS) is of a threshold character and occurs under the influence of an alternating electric field with an amplitude less than the critical value, whose value depends on the field frequency. The conditions for the formation of RDSs with a micrometer spatial scale were determined. Conclusion: As shown by numerical studies, the RDSs obtained retain their stability, i.e. do not disappear even after turning off the external electric field. Qualitative analysis using lithium niobate crystals as an example has shown the possibility of RDSs formation in high-frequency fields with small amplitude under resonance conditions

Live electrooptic imaging with a low-coherence optical LO signal source for suppression of interference noises.

Reported in this paper is the first application, to our knowledge, of a low-coherence optical local oscillator signal source to the live electrooptic imaging (LEI) scheme, where high frequency electric field (EF) distributions are visualized in real time. A fiber-optic super luminescent diode (SLD) in conjunction with a LiNbO3 Mach-Zehnder modulator (MZM) was found to work well for the real-time imaging of gigahertz-range EF distributions with high suppression of interference pattern image noises (IPINs), which have long been a problem to be solved. While the SLD-based LEI system works up to the MZM bandwidth (10GHz), IPINs caused by microscopic defects in an electrooptic sensor appear, suggesting a limitation given by the SLD coherence length.

Effect of kHz electrical stimulation on hippocampal brain slice excitability and network dynamics

Understanding the cellular mechanisms of kHz electrical stimulation is of broad interest in neuromodulation including forms of transcranial electrical stimulation (tES), interferential stimulation, and high-rate spinal cord stimulation (SCS). Yet, the well-established low-pass filtering by neuronal membrane suggests minimal neuronal polarization in response to charge-balanced kHz stimulation. The hippocampal brain slice model is among the most characterized systems in neuroscience and exhaustively studied in screening the effects of electrical stimulation. Testing for changes in neuronal excitability by kHZ electrical stimulation in brain slices is a litmus test for feasibility and mechanism. High-frequency electric field of varied amplitudes (1-120 V/m), waveforms (sinusoidal, symmetrical pule, asymmetrical pulse) and frequencies (1 or 10 kHz) were tested. Single and paired-pulse field excitatory post-synaptic potentials (fEPSP) in CA1 were measured before, during, and after stimulation in radial and tangential direction and for different application time (30 s acute,30 min). Small polarization of individual neurons leads to changes in network dynamic through nonlinear amplification mechanisms at the cellular and/or network level resulting a more sensitive system to an exogenous electric field. Effect of kHZ stimulation on ongoing endogenous network activity was evaluated in carbachol-induced gamma oscillation of CA3a region of rat hippocampal slices. Extracellular local field potential oscillations were recorded and analyzed before, during and after 2s of kHZ stimulation. In order to fully investigate the opportunities in kHZ stimulation, ongoing work on kHz stimulation should consider different mechanisms of action absent in this tested system and different cortical and spinal neurons.

Erratum to: The Model of Electric Connection of a Low-Conductivity Liquid in High-Frequency Electric Field

In the original publication, there are several misprints. 1. In page header, the author’s name was misspelled. It should read “Ponomareva” instead of “Ponomarev.” 2. In title, it should read “The Model of Electric Convection of a Low-Conductivity Liquid in High-Frequency Electric Field” instead of “The Model of Electric Connection of a Low-Conductivity Liquid in High-Frequency Electric Field.”

THE EFFECTIVENESS OF PHYSICAL REHABILITATION COMPLEX FOR FACIAL NERVE PALSY

The issue of treatment and rehabilitation of patients with facial nerve palsy is still unresolved. An essential role in functional recovery of the facial nerve during its lesion can play physical rehabilitation methods. The objective – to establish the effectiveness of the physical rehabilitation complex for facial nerve palsy. Methods. 40 patients with severe facial nerve dysfunction (grade V of House-Brackmann facial nerve grading system). Treatment was carried out in accordance with existing regulatory documents. The complex of physical rehabilitation included morning hygienic gymnastics, vocal gymnastics, mimic gymnastics, therapeutic massage of the neck and collar zone, paraffin wax applied to the affected face side, therapeutic facial massage, therapeutic massage of the hairy part of the head, ultra high frequency electric field (UHF) to the facial nerve branching zone and face self-massage. The course of the treatment and rehabilitation required 10-12 procedures of each physiotherapeutic procedure carried out daily. Results. After 14 days of physical rehabilitation, in 60% of cases (24/40) a moderate severe dysfunction is recorded, and in 40% of cases (16/40), a moderate facial nerve dysfunction is observed with all patients initially diagnosed with a severe nerve dysfunction. The symmetry of nasolabial folds, normal lachrymation and salivation also rehabilitate. Conclusions. The use of a complex of physical rehabilitation including vocal gymnastics, mimic gymnastics, massage and instrumental physiotherapy can significantly improve the clinical conditions of patients with facial nerve palsy.facial nerve palsy, physical rehabilitation, gymnastics, massage, paraffin, ultra high frequency electric field

Visualization of Exo- and Endocytosis of AMPA Receptors During Hippocampal Synaptic Plasticity Around Postsynaptic-Like Membrane Formed on Glass Surface.

Regulation of exo- and endocytosis of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor (AMPAR) plays a critical role in the expression of synaptic plasticity such as long-term potentiation (LTP) and long-term depression (LTD) at excitatory central synapses. Enhanced AMPAR exocytosis or endocytosis has been suggested to contribute to LTP or LTD, respectively. However, several unsettled fundamental questions have remained about AMPAR exo- and endocytosis in the basal condition and during synaptic plasticity: (1) Does the size of each exo- or endocytosis event, and/or do the frequencies of these events change during LTP or LTD? If they change, what are the time courses of the respective changes? (2) Where does the exo- or endocytosis preferentially occur in each condition: inside or in the vicinity of postsynaptic membrane, or in the extrasynaptic membrane? (3) Do different types of AMPAR, such as GluA1 homo-tetramer, GluA1/2 hetero-tetramer and GluA2/3 hetero-tetramer, show distinct exo- and endocytosis changes? To address these questions, we developed new methods to observe individual events of AMPAR exo- or endocytosis with a high signal to noise (SN) ratio in a culture preparation using total internal reflection fluorescence microscopy (TIRFM). In these studies, hippocampal neurons were cultured on a neurexin (NRX)-coated glass coverslip, which induced formation of postsynaptic-like membrane (PSLM) directly on the glass surface. Then, a super-ecliptic pHluorin (SEP)-tagged AMPAR subunit such as GluA1 (GluA1-SEP) was expressed in neurons and its fluorescence changes during LTP induced by high frequency electrical field stimulation were observed with TIRFM, which showed different time courses of exocytosis changes of GluA1-, GluA2-, or GluA3-SEP in and around PSLM. In addition, a new method to detect individual endocytosis events of AMPAR was developed by combining TIFRM observation of GluA-SEP around PSLM with a rapid extracellular pH exchange method using a U-tube. Recent results on exo- and endocytosis changes of GluA-SEP during N-methyl-D-aspartate (NMDA)-induced LTD suggested that suppression of AMPAR exocytosis rather than enhancement of AMPAR endocytosis primarily contributes to LTD expression, although the NMDA application transiently enhances clathrin-dependent endocytosis of GluA1-containing AMPAR.

Verification of turbulent simulations using PoPe: quantifying model precision and numerical error with data mining of simulation output

Verification of a 1D-1V kinetic code with the PoPe method [1] is presented. Investigation of the impact of reducing the precision of the numerical scheme is analysed by following 3 indicators of the physics solved by the code, namely the plasma response to an external high frequency electric field wave. The response of the distribution function in the vicinity of the particle-wave resonance is found to be most sensitive to the resolution. Consistently, a rapid growth of the error indicator determined with PoPe is observed. However, no critical value of this indicator allowing us to retain the physics in a situation of degraded precision could be observed. The response of the amplitude of the electric potential fluctuations is characterised by a transient growth followed by a plateau. It is found that the loss of this plateau is governed by the resolution in v-space, but due to the generation of a symmetry in the problem rather than to errors in the numerical scheme. The analysis of the transient indicates that the growth rate of the amplitude of the electric potential is very robust down to very low resolution, step in velocity of 2 thermal velocities. However, a transition prior to this resolution, with step 0.5 thermal velocity, can be identified corresponding to a PoPe indicator of order zero, namely for errors of order 100 %.

Phase evolution of Mo-W-Cu alloy rapid prepared by spark plasma sintering

In this paper, a novel Mo-W-Cu alloy with the relative density of 94%, fine microstructure, good electrical conductivity and hardness is prepared at a low temperature (800 °C) in a short time (5 min) under the combined action of discharge plasma, high frequency impulse, electric field and hot pressed sintering. The phase evolution and the phase structure of new phases are discussed based on the comprehensive analysis of XRD and TEM. The results show that Mo-W-Cu alloy consists of W, Mo, Cu phase and the new phases including Mo-W ordered phase at the Mo/W interface, Cu0.4W0.6 intermetallic compound at the W/Cu interface and Mo-Cu solid solution at the Mo/Cu interface. All of the new phases are BCC structure. The type of new phases obtained in this experiment is consistent with the calculation results based on the theory of Hume-Rothery, the correction theory of solid solution formation, and the theory of electronegativity. This presented research is expected to provide reference for the further research of Mo-W-Cu alloy.

Non-invasive nanosecond electroporation for biocontrol of surface infections: an in vivo study

Invasive infections caused by drug-resistant bacteria are frequently responsible for fatal sepsis, morbidity and mortality rates. In this work, we propose a new methodology based on nanosecond high frequency electric field bursts, which enables successful eradication of bacteria in vivo. High frequency (15 kHz) 15–25 kV/cm 300–900 ns pulsing bursts were used separately and in combination with acetic acid (0.1–1%) to treat Pseudomonas aeruginosa in a murine model. Acetic acid 1% alone was effective resulting in almost 10-fold reduction of bacteria viability, however combination of nanosecond electric field and acetic acid 1% treatment was the most successful showing almost full eradication (0.01% survival compared to control) of the bacteria in the contaminated area. The short duration of the pulses (sub-microsecond) and high frequency (kHz range) of the burst enabled reduction of the muscle contractions to barely detectable level while the proposed applicators ensured predominantly topical treatment, without electroporation of deeper tissues. The results of our study have direct application for treatment of wounds and ulcers when chemical treatment is no longer effective.

Experimental assessment of spark and corona igniters energy release

The Radio-Frequency (RF) Corona Ignition System is an innovative and promising technology able to produce multiple streamers to ignite the fuel throughout the combustion chamber. This system, compared to a conventional spark ignition system, involves wider initial combustion volumes and allows the engine to operate in stable conditions at leaner mixtures, higher EGR dilutions, with faster burning rates and enabling advanced combustion strategies. Due to the intrinsic operating features of the RF corona ignition system, the production of a plasma generated by a high frequency electrical field, the energy released to the surrounding medium is a fundamental parameter to understand its behaviour and impact on a given air-fuel mixture.The aim of this paper is the energetic characterization of a prototype of corona igniter, called Advanced Corona Ignition System (ACIS), by measuring the pressure increase caused by the streamers in a controlled environment, a pressure based calorimeter. The ACIS results are also compared with a multiple spark discharges (MSD) ignition system based on standard Federal Mogul spark plug technology characterized by an integrated electronics capable of managing up to 17 consecutive discharges. The energy evaluation was carried out at room temperature with air at different pressure levels, up to 10 bar.

Separation of biological ion in asymmetric nanochannels through alternating electric field

Using non-equilibrium molecular dynamics, we have studied the separation of biological ions in asymmetric nanochannels through an alternating (AC) electric field. Asymmetry of the channel and the frequency of electric field, which change the velocity distribution of ions, are the key conditions to form directed transport. The relationship between the transport velocity and the field’s frequency depends on the amplitude of electric field, the number of ions, the temperature and the type of ions. The directed transport velocity of ions tends to a stable value at a low frequency electric field. However, it cannot appear at a high frequency electric field. At a low frequency electric field, the transport velocity of sodion is larger than potassium ion, and if we add a direct current electric field into the AC electric field, the velocity of K+ ions is negative but that of Na+ ions is positive. We can separate Na+ from K+. Our results suggest a path to separate Na+ ions and K+ ions in a biological ion channel by controlling the AC electric field.

Theoretical study of extended interaction frequency‐locking oscillator based on carbon nanotube cold cathodes

An extended interaction frequency-locking oscillator based on carbon nanotube (CNT) cold cathode is proposed to overcome locked-frequency limits of the conventional oscillator. Compared with the conventional oscillators, the oscillation frequency is locked by a modulation electron beam, which can be obtained in a field emission CNT cold cathode electron gun. The frequency-locking signal does not enter the high-frequency (HF) system but imposes an additional HF electric field on the cathode surface by a microstrip structure, which consumes considerably less power to lock the oscillation frequency. A ladder structure extended interaction oscillator operating in 2π mode is numerically investigated by three-dimensional Particle-In-Cell simulation code. By analysing the impacts of different frequency-locking power on the locked ranges, the results show that the average output power of 30.6 W is achieved at 35.11 GHz when the frequency-locking power consumption is 460 mW. The 3-dB bandwidth of a frequency-locking region reaches 100 MHz.

Computational modeling of finite deformation piezoelectric material behavior coupling transient electrical and mechanical fields

This paper develops a finite element formulation and computational model for coupling electric and finite strain dynamic fields with widely discrepant frequencies, governing the behavior of piezoelectric materials. The piezoelectric materials are defined by time-dependent nonlinear constitutive laws. A fully coupled, total Lagrangian finite element formulation is developed for modeling the electric and mechanical fields. A challenge in computational modeling of piezoelectric devices arise due to large discrepancy in the frequencies of the electrical signal and mechanical vibrations, especially when a large number of mechanical cycles need to be simulated. A wavelet transformation induced multi-time scaling (WATMUS) algorithm is developed for dynamic piezoelectric simulations. The WATMUS algorithm projects the high frequency electric fields on to the lower frequency of displacement and velocity fields, on which time integration is performed. The method significantly enhances the computational efficiency in comparison with single time scale integration methods. The accuracy and efficiency of the WATMUS algorithm are validated through piezo-electric applications.

The Effects of Warmness Plasma, and High Frequency Electrical Field on Beam-1 Plasma Interaction in Plasma Waveguide

The Effects of Warmness Plasma, and High Frequency Electrical Field on Beam-1 Plasma Interaction in Plasma Waveguide

C-MEMS Device for Plasma Separation from Whole Blood

In this work, we report the fabrication of carbon-microelectromechanical system (C-MEMS) based contactless dielectrophoresis chip for the separation of Red Blood Cell (RBC) and plasma from whole blood. Blood is the most important functional body fluid and it is necessary to separate plasma and RBC for common disease diagnosis. Use of centrifugal force and microfilters are the conventional methods for this separation. To make a portable and cost effective device, researchers found a method of geometry driven separation by means of changing the blood flow channel shapes. This method was not popular because of the pressure driven flow of blood in the channel and the need of the apparatus including syringe pump, tubing, etc. Dielectrophoresis is one of the best methods for this application. But the contact dielectrophoresis (sample is in contact with the electrodes) damages the RBC because of the use of high voltage (more than 100V). It may also cause electrochemical effect, bubble formation and joule heating in the sample. In our development, one Indium Tin Oxide (ITO) coated glass was used as the bottom substrate. ITO coated side was used as the bottom electrode and microchannel was made in SU-8 by UV photolithography on the other side of the substrate. In a separate process, SU-8 derived carbon electrode was fabricated on Si/SiO2 substrate using the conventional C-MEMS process and transferred to 200µm thick PDMS layer. This polydimethylsiloxane (PDMS) layer was used to cover the microchannel in such a way that the carbon electrode was on the upper side of the device, aligned with the microchannel. These two electrodes (ITO and carbon) were capacitively coupled with the microchannel. The eletrostatic force is induced in the blood cells flow in the channel upon applying high frequency (1MHz) electric field to the electrodes. When blood flows in the channel, the electrostatic force combines with the capillary force and produces velocity difference between RBC and plasma resulting in their separation. In the preliminary experiment, we observed the separation of RBC and plasma at less than 1Vp-p with 1MHz frequency. Figure 1

Effect of ZnAl2O4 content on the microstructure and electrical properties of ZnO-based compound conductive ceramics

ZnO-ZnAl2O4-SiO2-Y2O3-MgO conductive ceramics were fabricated with different amount of ZnAl2O4 content. The effects of ZnAl2O4 on the microstructures and electrical properties of ZnO-based compound conductive ceramics were investigated. Results showed that the continuously adjustable resistivity could be obtained under the percolation threshold through increasing ZnAl2O4 content and improving the preparing technology. It was found that ZnAl2O4 grain would be encased in the major ZnO grains, with less than 5.0 mol%. When more ZnAl2O4 doping in the samples, it acted as a barrier blocking ZnO grain growth. Interestingly, the dielectric properties indicate that the Maxwell-Wagner interfacial polarization and the threshold effect exists in the matrixes. At the same time, the resistance-temperature (R-T) characteristics verify that the conduction mechanism of ZnO-based conductive compound ceramics is a thermally activated progress and the grain-boundary effect is negligible. The improvement of the microstructures and electrical properties has a potential application in the high frequency electrical fields.

The Model of Electric Connection of a Low-Conductivity Liquid in High-Frequency Electric Field

This paper describes the study of electroconvection of low-conductivity fluid in a capacitor with boundary conditions of adhesion on a solid surface in the case of rapid charge relaxation. The linear stability of fluid equilibrium in a constant electric field is investigated. The model describing the averaged fluid flow in a high-frequency electric field is obtained. The nonlinear regimes of electroconvection are described. A regime map is constructed. It is obtained that, depending on the frequency of the external field, the transition to chaotic state occurs through quasiperiodic or intermittent structures.

The Model of Electric Connection of a Low-Conducting Liquid in High-Frequency Electric Field

The Model of Electric Connection of a Low-Conducting Liquid in High-Frequency Electric Field