External Direct Current Electric Field Research Articles

A reconfigurable band-stop filter using piezoelectric-piezomagnetic superlattices with an external DC electric field

A novel reconfigurable band-stop filter using piezomagnetic-piezoelectric superlattices with the external direct-current (DC) electric field (PPSED) is presented. The center frequency of the forbidden band is reduced from to Hz in the band-stop filter as the thickness ratio of the piezoelectric domain to the piezomagnetic domain increases from to 9. The change of the forbidden bandwidth and the center frequency shows that the band-stop filter constructed by the PPSED is reconfigurable. The coupled polaritonic band structure is asymmetric with respect to the forward and backward directions and the forbidden bandwidth can be tuned by the DC electric field via the electro-optic effect. Unlike pure piezoelectric superlattices with the DC electric field, the forbidden bandwidth decreases with the increase of the electric field in the PPSED. The bandwidth tunability by the DC electric field can provide a guidance for the reconfigurable band-stop filter design to work in broadband frequencies.

Effect of external direct current electric field on the inhibition behavior of Zn-MOFs for Cu in 0.5 mol/L NaCl solution

The effect of an external DC electric field on the inhibition behavior of Zn-MOFs in 0.5 mol/L NaCl solution for copper was investigated via electrochemical measurements and various characterization techniques. Results indicated that the corrosion inhibition efficiency of the Zn-MOFs decreased under strong electric field intensities, which went from 94.2% to 61.7%. The corrosion inhibition efficiency of the materials decreased with increasing electric field duration when maintained at a certain electric field intensity. When the electric field duration time was 6 h, 12 h, 18 h and 24 h, the corresponding efficiency was 90.4%, 86.8%, 78.2% and 61.7% respectively. The effect of an electric field on the corrosion inhibition performance of the Zn-MOFs could essentially be attributed to changes in the structure of the material framework.

Fractionation of stable oxygen and clumped isotopes during acid digestion of calcite in the presence of an external direct current electric field.

Phosphoric acid digestion of carbonate generates CO2 for stable oxygen and clumped isotope analysis using a gas source isotope ratio mass spectrometer. The initial step of the digestion reaction is protonation of calcite while the product CO2 equilibrates with the system allowing further exchange of isotopes to various extents depending on the nature of the acid digestion methods. An external electric field is introduced in the break seal method to demonstrate the role of the protonation reaction and the post-digestion isotopic exchanges in the final isotopic composition of product CO2 . An acid digestion experiment following the break seal method was conducted at a constant temperature of 25 ± 0.5°C in the presence of a uniform external electric field of 0.5 kV/cm within a specially fabricated corona chamber. Replicate samples of a calcite powder of a reference standard (MAR J1) were reacted for 24 h in the presence and absence of an external electric field for varying exposure times (6 to 24 h) and the evolved CO2 was analyzed using a dual-inlet MAT 253 isotope ratio mass spectrometer. The CO2 yield from the phosphoric acid digestion of MAR J1 calcite was 20% lower during the reaction in presence of an electric field for an exposure time of 24 h, while the corresponding δ18 O value and Δ47 composition were 0.3‰ and 0.1‰ less, respectively, than without any electric field. We documented the systematic control of oxygen and clumped isotope ratios in CO2 evolved from the carbonate acid digestion reaction with varying exposure time to the external electric field. We provide a new method involving use of an external electric field to manipulate the isotopic fractionation during the acid digestion reaction of calcite. The experimental observation enabled theoretical understanding of the reaction mechanism of carbonate with phosphoric acid which will be useful for stable and clumped isotope studies.

Effect of external direct current electric field on the inhibition behavior of cyclohexylamine and sodium nitrite under thin electrolyte layers

The effect of external direct current electric field on the inhibition behavior of cyclohexylamine and sodium nitrite under simulated atmospheric environments with thin electrolyte layers was investigated by surface characterizations and electrochemical measurements. Results confirmed that the vertical electric field from top to bottom increased the inhibition efficiency of cyclohexylamine but decreased that of sodium nitrite. The opposite electric field weakened the inhibition efficiency of cyclohexylamine but enhanced that of sodium nitrite. Surface analysis indicated that the external vertical electric field can affect the migration of inhibitors under thin electrolyte layers.

Low Loss Microwave Ceramic and other Microwave Dielectric Materials for Beam Physics Applications

Introduction. Relativistic, high intensity and small emittance electron bunches are the basis of a future linear collider and free electron laser projects. Drive beam generation in a wakefield structure employing for power extraction and acceleration low loss dielectrics like microwave ceramics, fused silica and Chemical Vapor Deposition (CVD) diamond were considered.Objective. We report here our experimental testing of a ceramic material with extremely low loss tangent at GHz frequency ranges allowing the realization of high efficiency wakefield acceleration. We also present Barium Strontium Titanium oxides (BST) ferroelectric material, which is a critical tuning element of the 400 MHz superconducting radiofrequency (RF) tuner developed and tested by the CERN/Euclid Techlabs collaboration. The materials discussed here also include quartz and CVD diamonds that are capable of supporting the high RF electric fields generated by electron beams or pulsed high power microwaves. These materials have been optimized or specially designed for accelerator applications.Materials and methods. The ceramic materials for accelerators, commonly used for the dielectric based accelerating structures, have to withstand high gradient accelerating fields, and prevent potential charging by electron beams. Correspondingly, the ceramic materials, fused silica and CVD diamond were tested with high power wakefield accelerating structures at Argonne Wakefield Accelerator of Argonne National Laboratory. Some of the presented here ceramic materials were tested at X-band 11.4 GHz magnicon high power source.Results. Low loss microwave ceramics, fused silica, and CVD diamonds have been considered as materials for dielectric based accelerating structures to study of the physical limitations encountered driving > 100 MV/m at microwave and ~ GV/m at THz frequencies in a dielectric based wakefield accelerator. Various ceramic compositions were high power and electron beam tested at X-band 11.4 GHz magnicon power source and Argonne Wakefield Accelerator correspondingly. Special attention was paid to the CVD diamond cylindrical Ka-band 35 GHz wakefield structure development. Finally, the dielectric based structure tuning was demonstrated by varying the permittivity of the BST ferroelectric layer by temperature changes and by applying an external direct current electric field across the ferroelectric. This allows us to control the effective dielectric constant of the composite system and therefore, to control the structure frequency during operation. The same type of ferroelectric material was used for the Ferroelectric Fast Reactive tuner (FE-FRT) development. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated.Conclusion. Recent results on the development and experimental testing of advanced dielectric materials for accelerator applications are presented. Low loss microwave ceramics, quartz and CVD diamond are considered. We presented our experimental results on wakefield generation in microwave frequency ranges with the dielectric based accelerating structures. Special attention was paid to the experimental results on high power testing at X-band of the externally powered dielectric based components. Finally, we present here first experimental demonstration of ferroelectric tunable microwave ceramic for accelerator application, which includes both tunable dielectric wakefield accelerating structure and ferroelectric based fast high power tuner for superconducting cavities. The experimental results presented here are critical for the advanced dielectric wakefield accelerating structures and other components development intended for the future linear collider projects.

The influence of different locations on copper corrosion with different external electric fields under a chloride-containing thin electrolyte layer

ABSTRACTThe influence of different locations on copper corrosion with different external electric fields under a chloride-containing thin electrolyte layer was studied using polarisation curve measurement and surface analysis techniques. The results indicated that, under an external direct current electric field, the anodic current densities near the positive plate were smaller than that near the negative plate, while the cathodic current densities near the positive plate were larger than that near the negative plate. However, at different locations in an external alternating current electric field, the anodic current densities were little change, while the cathodic current densities were obviously different.

Effects of electrolyte thickness, chloride ion concentration, and an external direct current electric field on corrosion behaviour of silver under a thin electrolyte layer

ABSTRACTEffects of electrolyte thickness, chloride ion concentration, and an external direct current electric field (DCEF) on the corrosion behaviour of silver under a thin electrolyte layer (TEL) were investigated using electrochemical and surface techniques. The results indicate the corrosion rate of silver increases with the decrease of TEL thickness and the increase of chloride ion concentration. Moreover, an interesting conclusion was drawn that the corrosion rate of silver near the positive plate of DCEF first increases and then decreases with the increase of electric field intensity. In a DCEF, different polarisation behaviours of silver at different positions were attributed to the differences of the local corrosion environment.

Simulation and experimental study of DC electric field distribution characteristics of rat hippocampal slices in vitro.

Direct current (DC) electric field is a noninvasive neuromodulation tool that can inhibit or facilitate excitability of neurons. Despite its efficacy, the dielectric constant of artificial cerebrospinal fluid and the position and direction of brain slices and other factors can affect the field intensity and distribution acting on the surface of rat hippocampus slices, thus causing errors. In this study, we describe a new analytical method optimized for DC electric fields acting on brain slices, and the design of an external DC electric field stimulator to allow scientific evaluation of brain slices. We investigated parameters regarding the uniformity of electric field distribution and identified the maximal parameters using the finite element method. Then, we selected and simplified slice images using magnetic resonance imaging data and calculated the electric field intensity of the original and simplified models. The electric field simulator induced action potential and excitatory postsynaptic current with intensities of 1, 5, and 10 V/m. This study describes the development of a new electric field stimulator and successfully demonstrates its practicability for scientific evaluation of tissue slices.

Effects of direct-current electric fields on flame shape and combustion characteristics of ethanol in small scale

The aim of this work is to investigate the effects of direct-current electric fields on the behavior of the small-scale diffusion ethanol flame. The flow rate of liquid ethanol, the flame temperatures, and the flame shapes were measured. The results showed that the stable working ranges of a small-scale combustor became narrower under the direct-current electric field. The main reason was that the evaporation velocity of liquid ethanol limited by great heat loss effect cannot keep up with the increasing of combustion velocity by the ionic wind effect. The movements of those charged particles in flame enhanced the combustion process, resulting in higher flame temperatures under positive or negative direct-current electric field. The flame heights decreased with increasing applied voltages, due to the ionic wind effect increasing the flame temperature and the diffusivity. The flame voltage–current characteristic was also examined. Three regions can be divided: the subsaturation region, the saturation region, and the supersaturation region. Finally, the ratios of electric active power to actual burning thermal power of ethanol flame were calculated. It can be inferred that using the external direct-current electric field with little power consumption to control combustion and flame is a feasible method.

Mobile ions generated by external direct current electric field influence direct current measurement of giant magnetoresistance current sensors

The application of giant magnetoresistance (GMR) current sensors in power grid and other industrial fields has a great prospect benefitting from their wide bands, high sensitivity, and good linearity. This paper studies the influence of mobile ions on current measurement of GMR sensor under high external electric field. The R-H curves of GMR multilayer sensor were depicted when the external electric and magnetic fields were both changed under three orthogonal electric field orientations. The experiment results indicate slightly varying resistances of GMR sensor when the external electric field was changed, and simulation analysis reveals that the resistance variation is attributed to the movement of surface ions under high external electric field. Therefore, a Faraday box is essential for GMR sensors to avoid interferences under high-strength field conditions, which is especially significant for their application as current sensors of the power grid.

Exploring action potential initiation in neurons exposed to DC electric fields through dynamical analysis of conductance-based model

Noninvasive direct current (DC) electric stimulation of central nervous system is today a promising therapeutic option to alleviate the symptoms of a number of neurological disorders. Despite widespread use of this noninvasive brain modulation technique, a generalizable explanation of its biophysical basis has not been described which seriously restricts its application and development. This paper investigated the dynamical behaviors of Hodgkin’s three classes of neurons exposed to DC electric field based on a conductance-based neuron model. With phase plane and bifurcation analysis, the different responses of each class of neuron to the same stimulation are shown to derive from distinct spike initiating dynamics. Under the effects of negative DC electric field, class 1 neuron generates repetitive spike through a saddle-node on invariant circle (SNIC) bifurcation, while it ceases this repetitive behavior through a Hopf bifurcation; Class 2 neuron generates repetitive spike through a Hopf bifurcation, meanwhile it ceases this repetitive behavior also by a Hopf bifurcation; Class 3 neuron can generate single spike through a quasi-separatrix-crossing (QSC) at first, then it generates repetitive spike through a Hopf bifurcation, while it ceases this repetitive behavior through a SNIC bifurcation. Furthermore, three classes of neurons’ spiking frequency f–electric field E (f–E) curves all have parabolic shape. Our results highlight the effects of external DC electric field on neuronal activity from the biophysical modeling point of view. It can contribute to the application and development of noninvasive DC brain modulation technique.

Electrophoresis of Cellular Membrane Components Creates the Directional Cue Guiding Keratocyte Galvanotaxis

Motile cells exposed to an external direct current electric field will reorient and migrate along the direction of the electric potential in a process known as galvanotaxis. The underlying physical mechanism that allows a cell to sense an electric field is unknown, although several plausible hypotheses have been proposed. In this work we evaluate the validity of each of these mechanisms. We find that the directional motile response of fish epidermal cells to the cathode in an electric field does not require extracellular sodium or potassium, is insensitive to membrane potential, and is also insensitive to perturbation of calcium, sodium, hydrogen, or chloride ion transport across the plasma membrane. Cells migrate in the direction of applied forces from laminar fluid flow, but reversal of electro-osmotic flow did not affect the galvanotactic response. Galvanotaxis fails when extracellular pH is below 6, suggesting that the effective charge of membrane components might be a crucial factor. Slowing the migration of membrane components with an increase in aqueous viscosity slows the kinetics of the galvanotactic response. In addition, inhibition of PI3K reverses the cell's response to the anode, suggesting the existence of multiple signaling pathways downstream of the galvanotactic signal. Our results are most consistent with the hypothesis that electrophoretic redistribution of membrane components of the motile cell is the primary physical mechanism for motile cells to sense an electric field. This chemical polarization of the cellular membrane is then transduced by intracellular signaling pathways canonical to chemotaxis to dictate the cell's direction of travel.

Electrostatic potential distribution of high-order weakly nonlinear composites under external direct current electric field

By using the homotopy analysis method (HAM), the electrostatic potential distribution problems of a type of high-order weakly nonlinear composite with a cylindrical inclusion randomly embedded in a host medium, which obeyes a current-field constitutive relation of J = σ E + χ |E|2E + η|E|4E, are investigated under the action of an external direct current electric field. With the mode expansion method, the current-field constitutive relation and their boundary conditions are transformed into a series of boundary value problems of nonlinear ordinary differential equations. Then the HAM is used to solve the boundary value problems of nonlinear ordinary differential equations and the asymptotic analytical solutions of electrostatic potential distribution in the inclusion and the host regions are given.

Effective response to external DC and AC electric field in nonlinear cylindrical coated composite

By using the perturbation method, an effective nonlinear direct current (DC) and alternating current (AC) response of nonlinear composites with cylindrical coated inclusions randomly embedded in a host medium is studied under the action of an external electric field Ea=E0 + E1 sinωt+E3 sin3ωt with different amplitudes and frequencies. The local potentials of composite at all harmonics are given in the inclusion core, the coated layer and the host regions. All effective nonlinear responses of composites and the relationship between the effective nonlinear responses at all harmonics are also deduced for the cylindrical coated inclusions in a dilute limit.

Amplification of hippersound in graphene under external direct current electric field

We present a theoretical investigation on the hippersound generation and amplification in n-type graphene in the presence of a dc driving electric field. By investigating the consequences of electron-acoustic phonon interaction in a gated graphene, we have found the conditions for phonon amplification to be obtained, namely vD>ṽs,vD being the drift velocity of electrons in the dc field and and ṽs being the effective sound velocity in the graphene sheet and Rq→>Γq→, where Rq→ is the phonon generation rate and Γq→ is the phonon linear losses. By considering two extreme values of the electron mobility in graphene, namely μ = 20 000 cm2/Vs and 1.2 V/cm for μ = 190 000 cm2/Vs, the critical external electric fields for hippersound amplification were obtained as much as 10 V/cm 1.2 V/cm, respectively. These threshold dc fields are smaller when compared with the corresponding applied fields for phonon amplification in semiconducting bulk and nanostructures. The study is relevant to the application of graphene as acoustoelectric devices as well as in the construction of a high-frequency phonon spectrometer.

Electric field distribution and effective nonlinear AC and DC responses of graded cylindrical composites

The perturbation method is used to study the localization of electric field distribution and the effective nonlinear response of graded composites under an external alternating-current (AC) and direct-current (DC) electric field Eapp = E0(1 + sin ωt). The dielectric profile of the cylindrical inclusions is modeled by function ∊i(r) = Ckrk (r ≤ a), where r is the radius of the cylindrical inclusion, and Ck, k, a are parameters. In the dilute limit, the local potentials and the effective nonlinear responses at all harmonics are derived. Meanwhile, the general effective nonlinear responses are also derived and compared with the effective nonlinear responses at harmonics under the AC and DC external field. It is found that the effective nonlinear AC and DC responses at harmonics can be calculated by those of the general effective nonlinear of the graded composites under the external DC electric field. Moreover, the obtained local electrical fields show that the electrical field distribution in the cylindrical inclusions is controllable, and the maximum of the electric field inside the cylinder is at its center.

Asymmetric cancer-cell filopodium growth induced by electric-fields in a microfluidic culture chip

We combine a micro-fluidic electric-field cell-culture (MEC) chip with structured-illumination nano-profilometry (SINAP) to quantitatively study the variations of cancer cell filopodia under external direct-current electric field (dcEF) stimulations. Because the lateral resolution of SINAP is better than 150 nm in bright-field image modality, filopodia with diameters smaller than 200 nm can be observed clearly without fluorescent labeling. In the MEC chip, a homogeneous EF is generated inside the culture area that simulates the endogenous EF environment. With this MEC chip-SINAP system, we directly observe and quantify the biased growth of filopodia of lung cancer cells toward the cathode. The epidermal growth factor receptors around the cell edges are also redistributed to the cathodal side. These results suggest that cancer-cell filopodia respond to the changes in EFs in the microenvironment.

Bioinspired Assembly of Colloidal Nanoplatelets by Electric Field

This paper reports a simple electrodeposition technology that enables rapid production of large-area polymer nanocomposites with layered structures that mimic the nacreous layer of mollusk shells. Uniform, electrostatically stabilized gibbsite nanoplatelets with high aspect ratio are preferentially oriented parallel to the electrode surface when an external direct current electric field is applied. The electroplated ceramic films have uniform thickness, and the thickness can be controlled by adjusting the nanoplatelet concentration of the electroplating baths. Homogeneous, optically transparent nanocomposites are obtained when the interstitials between the aligned nanosheets are infiltrated with polymer. The resulting ceramic−polymer nanocomposites exhibit four-times higher tensile strength and nearly 1 order of magnitude higher modulus than pure polymer films. The covalent linkage between the nanoplatelets and the polymer matrix plays an important role in determining the mechanical properties of these bi...

EPR Study of Cr3+ Center in Fast-Proton Conductor K3H(SO4)2

We have studied a K3H(SO4)2 (KHS) crystal doped with Cr3+ ions by X-band continuous-wave electron paramagnetic resonance spectroscopy. The spin Hamiltonian parameters, direction cosines and coordination of the Cr3+ impurity in the crystal matrices were determined at room temperature. The line width ΔH pp versus temperature and an external direct current electric field was measured. The line width anomaly of Cr3+ is compared with our earlier results for KHS:Mn2+ indicating the molecular mechanisms responsible for both anomalies in the 25–460 K temperature range.

Effects of electric field on recrystallization texture evolution in cold-rolled high-purity aluminum sheet during annealing

The effects of an external DC (direct current) electric field on recrystallization texture evolution in the cold-rolled aluminum sheets with 99.99% purity were investigated by means of X-ray diffraction techniques. The cold-rolled high-purity aluminum sheets were annealed for 60 min at 200, 300 and 400 °C, respectively with and without an external DC electric field of 800 V/mm. The results show that with DC electric field, the recrystallization cube texture is strengthened at the stage of grain growth. Possible reason for the strengthening of the recrystallization cube texture with the applied electric field may be attributed to both selected nucleation and selected growth of cube oriented crystal nuclei.