Electric Field Changes Research Articles

Modeling Trans-Spinal Direct Current Stimulation in the Presence of Spinal Implants.

Trans-spinal direct current stimulation (tsDCS) is a technique considered for the treatment of corticospinal damage or dysfunction. TsDCS aims to induce functional modulation in the corticospinal circuitry via a direct current (DC) generated an electric field (EF). To ensure subject safety, subjects with metallic implants are generally excluded from receiving neural dc stimulation. However, spinal injuries often require spinal implants for stabilization. Our goal was to investigate implant imposed changes to EF and current density (CD) magnitude during tsDCS. We simulated the EF and CD, generated by tsDCS in the presence of spinal rods for two electrode configurations and four implant locations along the spinal cord. For each scenario, a no-implant condition was computed for comparison. We assessed changes in EF and CD at the implant location and the EF inside the spinal cord. Our results show that implant presence was able to influence peak CD, compared to the no-implant condition. Nonetheless, the highest calculated CD levels were a factor six lower than those thought to lead to hazardous tissue-damaging effects. Additionally, implant presence did not considerably affect the average EF inside the spinal cord. Our findings do therefore not indicate potentially unsafe CD levels, or significant alterations to stimulation intensity inside the spinal cord, caused by a spinal implant during tsDCS. Our results are relevant to the safety of transcutaneous spinal stimulation applied in the presence of metallic spinal implants.

Piezoelectric–Piezoresistive Coupling MEMS Sensors for Measurement of Electric Fields of Broad Bandwidth and Large Dynamic Range

Electric-field microelectro-mechanical systems sensors with broad bandwidth and large dynamic range are an enabling technology for real-time monitoring of fast transient overvoltage in the power grid. They significantly alter lightning damage and operation faults and therefore help establish a more secure grid. In this paper, we propose a new method and architecture for electric-field sensing, which overcomes the incompatibilities between electric-field measurements of broad spectrum and large dynamic range. Scientifically, this compound structure with coupled piezoelectric effect and piezoresistive effect transduces electric field changes into resistance alterations via internal pressure. This structure has an hour-glass-shaped cavity, which contains a piezoelectric crystal and leaves the piezoresistive membrane vibrating freely. The newly proposed sensors have a broadened frequency bandwidth of up to 100 kHz and a 15-fold improved sensing magnitude. In addition, this sensor decreases the cost by two orders and reduces energy consumption to 0.018%, which makes them readily implantable into electrical appliances in the power grid.

Effects of RMP-induced changes of radial electric fields on microturbulence in DIII-D pedestal top

Gyrokinetic simulations of DIII-D tokamak with axisymmetric equilibrium show that the reduction in the radial electric field shear at the top of the pedestal during edge localized mode (ELM) suppression with the n = 2 resonant magnetic perturbations (RMPs) leads to enhanced drift-wave turbulence and extended turbulence spreading to the top of the pedestal relative to ELMing plasmas with similar RMP and pedestal parameters. The simulated turbulent transport at the top of the pedestal in ELM suppressed conditions is consistent with experimental observations of enhanced turbulence at the top of the pedestal during ELM suppression by the RMPs. These results imply that enhanced drift-wave turbulence due to reduced shear at the pedestal top can contribute to the additional transport required to prevent the pedestal growing to a width that is unstable to ELMs.

Role of Electric Field Changes in Fluorescence Response of Red Fluorescent Genetically-Encoded Ca2+ Indicators

Role of Electric Field Changes in Fluorescence Response of Red Fluorescent Genetically-Encoded Ca2+ Indicators

A Simulation Study on the Latitudinal Variations of Ionospheric Zonal Electric Fields Under Geomagnetically Quiet Conditions

AbstractThe influence of zonal electric fields as well as E × B plasma drifts on the ionosphere has been widely investigated, but the latitudinal variations of zonal electric fields have not been well understood. In this study, we investigate the driving mechanisms responsible for the latitudinal variations of zonal electric fields under geomagnetically quiet conditions using the Thermosphere‐Ionosphere Electrodynamics General Circulation Model (TIEGCM). A series of case‐controlled TIEGCM simulations were conducted to explore the effects of neutral wind and ionospheric conductivity on the latitudinal variations of zonal electric fields. The major results are given as follows: (1) The eastward electric field at noon increases with latitude, which is mainly associated with latitudinal changes of poleward neutral winds. (2) The prominent latitudinal variations of zonal electric fields at sunrise and sunset are attributed to the strong longitudinal gradients of zonal winds, that is, the curl‐free mechanism. (3) The changes of the zonal electric fields at a given location are affected by the dynamo effect globally, which also produces the latitudinal structure of zonal electric fields.

Inter-postural changes in TDCS and TMS electric fields

Inter-postural changes in TDCS and TMS electric fields

An improved model analysis approach for hybrid thermo-piezoelectric micro actuator with thermo-piezoelectric coupling

This paper presents a new modeling and analysis approach for the bending characteristics of hybrid thermo-piezoelectric micro actuators by considering the effect of thermo-piezoelectric coupling, which helps to better capture the bending behavior of piezoelectric beams in various smart sensor or actuator applications. In particular, we investigate the temperature induced change on the piezoelectric coefficient, as well as the electric field and piezoelectric coefficient changes on the thermal expansion coefficient where the bending characteristics of thermo-piezoelectric micro actuators are further obtained subjected to the electric and temperature fields, under the thermo-piezoelectric coupling condition. The analysis of thickness ratio and curvature provides a guidance for geometry optimized of the thermo-piezoelectric micro actuator based on the design requirements. To verify the effectiveness of the proposed approach, simulations and experiments are also conducted for a thermo-piezoelectric micro actuator (PZT-5A) under various thermal and electric loads, where theoretical values agree well with experiments, outperforming existing results.

Spectrum and dissociation properties of fluoro trichloro methane molecule in radiational field

The ozone layer in the stratosphere of the earth’s atmosphere, which can be destroyed by CFC-11 molecule, plays a crucial role in human survival because it can absorb most of the harmful radiation from the sun and effectively protect the earth’s biology. Therefore, it is of evident significance to investigate the properties of CFC-11 molecule. By Motivated by this and the adoption of B3LYP complex function at a level of 6-311++g(3df, 3pd) basis set, we carry out a series of theoretical studies of the Freon material CFC-11 (CFCl3) molecules, including the studies of the equilibrium structure, electric dipole moment, total energy, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) level, energy gap, infrared and Raman spectrum, C—F dissociation characteristics of CFC-11 molecule, and the effect of the applied electric field on CFC-11 molecule as well. The results show that the maximum error between the theoretical calculation value and the experimental value is less than 2% for an optimized ground state structure; the C—F bond length and C—Cl bond length extend with the increase of electric field intensity, but the degree of change of C—F bond length is much stronger than that of C—Cl; the HOMO energy level and total energy go up and then come down as the external field rises, while the LUMO energy level goes up as the field increases. The energy gap <i>E</i><sub>g</sub> first increases and then decreases with the variation of <i>E</i><sub>H</sub> and <i>E</i><sub>L</sub>. The dipole moment without electric field is a minimum value, and the external electric field leads the molecular polarity to increase and the molecular activity to strengthen. The electric field influences the absorption intensity of infrared and Raman spectrum. The infrared and Raman spectrum move toward the long wave under the action of positive electric field, while they move toward the short wave under the action of negative electric field. The red- or blue-shift of infrared and Raman spectrum occur with the change of electric field. The electric field can be adopted as an auxiliary means to separate the overlapping or quasi-overlapping spectral lines. The potential well depth decreases with the increase of the reverse electric field until it vanishes, which causes the bound state ability of C—F bond of CFC-11 molecule to gradually degrade. This paper is expected to provide a feasible and effective tunable means for the final dissociation and degradation of CFC-11 molecules.

Dipole orientation polarization property of single-molecule manipulated by external electric field

The dipole orientation of single-molecule plays an important role in improving the fluorescence collection efficiency and promises to have applications in super-resolution imaging, protein folding, and Förster resonance energy transfer between fluorophores. However, these applications are realized usually by precisely manipulating the orientation of the dipole moment of single molecules. Here, the dipole orientation of 1,1′-dioctadecyl-3,3,3′,3′,-tetramethylindodicarbocyanine (DiD) single molecules with the permanent dipole moment of 14.9 D is manipulated by using an external electric field of 3500 V/mm. Single DiD molecules are prepared by using mixed solvent of chloroform and dimethyl sulfoxide. The dipole orientation of single molecules is manipulated by an external electric field during the evaporation of solvent. The fluorescence of single molecules is measured by splitting the fluorescence collected by an objective into the S-polarized and P-polarized beams, and the fluorescence polarization of single molecules can be calculated by measuring the intensities of two orthogonal channels (<i>I</i><sub>S</sub> and <i>I</i><sub>P</sub>). The distribution of dipole orientation angle (<i>α</i>) for single DiD molecules in poly-(methyl methacrylate) (PMMA) film is analyzed statistically, and its changes are compared under different electric fields. It is found that the dipole orientation angle <i>α</i> of single DiD molecules in the PMMA film without applying electric field obeys a single-peak Gaussian distribution with the most probable value of 41°, which results from the fluorescence dichroism signal of the high numerical aperture objective. Applying a perpendicular electric field to the surface of single-molecule sample, the distribution of dipole orientation angle <i>α</i> of single DiD molecules can be still fitted by a single-peak Gaussian function with the most probable value of 44.2°. The dipole orientation of single DiD molecules under the perpendicular electric field changes little. However, by applying a parallel electric field to the surface of single-molecule sample, the dipole orientation angle <i>α</i> of single DiD molecules changes prominently. It obeys a two-peak Gaussian distribution with the most probable values of ～ 32° and 55.5°, indicating that the orientation polarization of the dipole moment occurs to the single DiD molecules in PMMA film. The dipole orientation of single polar molecules tends to the parallel electric field in this case.

Signatures of Sudden Storm Commencement on the equatorial thermospheric dayglow

It has been observed that the OI 630.0 nm dayglow emission over a dip equatorial station, Trivandrum (8.5° N, 77° E, dip 0.5° N), India registered an abrupt increase of ~ 2000 R during the compression phase of the magnetosphere as dictated by a sudden increase in solar wind ram pressure. Furthermore, an unusual depletion of these emissions has been observed during the eastward interplanetary electric field (IEF), concomitant with southward excursion of IMF Bz. The ionosonde and magnetometer observations confirmed the effects of prompt penetration electric field (PPEF). Associated with the eastward PPEF, formation of F3 layers were also noticed. These unique results, which emphasize the effect of Sudden Storm Commencement/IEF on these equatorial daytime airglow emissions are discussed in context of changes in the equatorial zonal electric field and F region height variations associated with polar/auroral activities due to the magnetosphere-ionosphere coupling.

Identification of the mechanisms responsible for anomalies in the tropical lower thermosphere/ionosphere caused by the January 2009 sudden stratospheric warming

We apply the Entire Atmosphere GLobal (EAGLE) model to investigate the upper atmosphere response to the January 2009 sudden stratospheric warming (SSW) event. The model successfully reproduces neutral temperature and total electron content (TEC) observations. Using both model and observational data, we identify a cooling in the tropical lower thermosphere caused by the SSW. This cooling affects the zonal electric field close to the equator, leading to an enhanced vertical plasma drift. We demonstrate that along with a SSW-related wind disturbance, which is the main source to form a dynamo electric field in the ionosphere, perturbations of the ionospheric conductivity also make a significant contribution to the formation of the electric field response to SSW. The post-sunset TEC enhancement and pre-sunrise electron content reduction are revealed as a response to the 2009 SSW. We show that at post-sunset hours the SSW affects low-latitude TEC via a disturbance of the meridional electric field. We also show that the phase change of the semidiurnal migrating solar tide (SW2) in the neutral wind caused by the 2009 SSW at the altitude of the dynamo electric field generation has a crucial importance for the SW2 phase change in the zonal electric field. Such changes lead to the appearance of anomalous diurnal variability of the equatorial electromagnetic plasma drift and subsequent low-latitudinal TEC disturbances in agreement with available observations.Plain Language Summary– Entire Atmosphere GLobal model (EAGLE) interactively calculates the troposphere, stratosphere, mesosphere, thermosphere, and plasmasphere–ionosphere system states and their response to various natural and anthropogenic forcing. In this paper, we study the upper atmosphere response to the major sudden stratospheric warming that occurred in January 2009. Our results agree well with the observed evolution of the neutral temperature in the upper atmosphere and with low-latitude ionospheric disturbances over America. For the first time, we identify an SSW-related cooling in the tropical lower thermosphere that, in turn, could provide additional information for understanding the mechanisms for the generation of electric field disturbances observed at low latitudes. We show that the SSW-related vertical electromagnetic drift due to electric field disturbances is a key mechanism for interpretation of an observed anomalous diurnal development of the equatorial ionization anomaly during the 2009 SSW event. We demonstrate that the link between thermospheric winds and the ionospheric dynamo electric field during the SSW is attained through the modulation of the semidiurnal migrating solar tide.

Ground-Based Observations of Terrestrial Gamma Ray Flashes Associated with Downward-Directed Lightning Leaders

Terrestrial gamma-ray flashes (TGFs) are bursts of gamma-rays initiated in the Earth’s atmosphere. TGFs were serendipitously first observed over twenty years ago by the BATSE gamma ray satellite experiment. Since then, several satellite experiments have shown that TGFs are produced in the upward negative breakdown stage at the start of intracloud lightning discharges. In this proceeding, we present ground-based observation of TGFs produced by downward negative breakdown occurring at the beginning of negative cloud-to-ground flashes.The Terrestrial gamma-ray flashes discussed in this work were detected between 2014-2017 at ground level by the Telescope Array surface detector (TASD) together with Lightning Mapping Array (LMA) and the slow electric field antenna (SA). The TASD detector is a 700 km2ultra high energy cosmic ray detector in the southwestern desert of Utah. It is comprised of 507 (3 m2) plastic scintillator detectors on a 1.2 km square grid. The LMA detector, a three-dimensional total lightning location system, is comprised of nine stations located within and around the array. The slow electric field antenna records the electric field change in lightning discharges.The observed Gamma ray showers were detected in the first 1-2 ms of downward negative breakdown prior to cloud-to-ground lightning strikes. The shower sources were observed by the LMA detector at altitudes of a few kilometers above ground level. The detected energetic burst showers have a footprint on the ground typically ~ 3-5 km in diameter. The bursts comprise of several (2-5) individual pulses, each of which have a span of a few to tens of microseconds and an overall duration of several hundred microseconds. Using a forward-beamed cone of half-angle of 16 degrees, GEANT simulation studies indicate that the showers are consistent with gamma rays of 1012- 1014primary photons. We hypothesize that the observed terrestrial gamma-ray flashes are similar to those detected by satellites, but that the ground-based observations are closer to the source and therefore are able to observe weaker sources and report on the structure of the temporal distribution at the source. This result and future studies will enable us to better identify and constrain the mechanisms of downward TGF production.

Numerical simulation of EWOD on a printed circuit board for cleanroom-less digital fluidic manufacturing applications

PurposeDigital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room facilities, while printed circuit board (PCB) technology provides high configurability and at low cost. This study aims to investigate the mechanism of electrowetting-on-a-dielectric (EWOD) on PCB by solving the multiphysics interaction between fluid droplet and electric field. The performance of system will be improved by inducing an efficient electric field inside the droplet.Design/methodology/approachTo induce an electric field inside the droplet on a PCB and change the initial contact angle, the mechanism of EWOD is studied based on energy minimization method and a set of simulations are carried out by considering multiphysics interaction between the fluid droplet and external electric field. The performance of EWOD on a PCB system is investigated using different electrode structures.FindingsSurface tension plays an efficient role in smaller sizes and can be used to move and control a fluid droplet on a surface by changing the interfacial surface tension. EWOD on a PCB system is studied. and it revealed that any change in electric field affects the droplet contact angle and as a result droplet deformation and movement. The electrode pattern is an important parameter which could change the electric potential distribution inside the droplet. Array of electrodes with square, zigzag interdigitated and crescent shapes are studied to enhance the EWOD force on a PCB substrate. Based on the results, the radial shape of the crescent electrodes keeps almost the same actuated contact line, applies uniform force on the droplet periphery and prevents the droplet from large deformation. A droplet velocity of 0.6 mm/s is achieved by exciting the crescent electrodes at 315 V. Furthermore, the behavior of system is characterized for process parameters such as actuation voltage, dielectric constant of insulator layer, fluidic material properties and the resultant velocity and contact angle. The study of contact angle distribution and droplet motion revealed that it is helpful to generate EWOD mechanism on a PCB which does not need more complicated fabrication processes.Originality/valueThe ability to handle and manipulate the droplets is very important for chemistry on-chip analysis such as immunoassay chips. Furthermore, a PCB-based electrowetting-on-dielectric device is of high interest because it does not need cleanroom facilities and avoids additional high-cost fabrication processes. In the present research, the EWOD mechanism is studied on a PCB by using different electrode patterns.

Numerical investigation of the current transition regimes in nanochannels.

The concentration polarization phenomena and its effects represent one of the main challenges for the optimal operation of many nanofluidic systems. A numerical investigation of the different electric current transition regimes observed during the concentration polarization phenomena in nanochannels is performed. This included a 2D-axisymmetric simulation of the nanofluidic system (reservoir-nanochannel-reservoir). From these simulations, a novel mechanism is discovered that explains that different current transition regimes. This driving mechanism involves the applied electric field penetration while the convective flow mechanism is found to be negligible. This differs with the classical statement that the mixing process with less depleted areas initiated by an electrokinetic vortex instability starts the overlimiting regime. Additionally, the numerical approach allows us to identify new characteristics of the linear-limiting transition such as source-like and saddle-like points of the electric field streamlines. The three voltage-current regimes (linear, limiting and overlimiting) are explained by observing and quantifying changes in electric field, potential, ion concentration and ion concentration gradients within the system.

Development of special fabrics protecting from electromagnetic radiation

The influence of electromagnetic radiation (EMR) on a person is connected with the existence of electromagnetic field - a special form of matter which conducts the effect of electrically charged particles. The causes of electromagnetic field formation are defined by the fact that the occurrence of electric field changing in time is the reason of magnetic field formation and magnetic field occurrence is the cause of vortex electric fields; both fields change in time and excite each other. Electromagnetic waves formed during these processes exist irrespective of a source of their initiation. Continuous impact of electromagnetic radiation on a person negatively affects various organs of human body. EMR leads to headaches, fatigue of the organism, disorders of the body. The maximum influence of EMR occurs on “blood and eyes, the incidence of cancer and cataract increases, the number of people suffering from skin diseases increases”. An important area today is the creation of fabrics protecting from electromagnetic radiation.

Nonlinear electrokinetic motion of electrically induced Janus droplets in microchannels

The nonlinear electrokinetic motion of electrically induced Janus droplets (EIJDs) in a microchannel is studied in this paper. The EIJDs were fabricated by operating the positively charged aluminum oxide nanoparticles to partially cover the oil droplets with electric field. The nanoparticle coverage of the EIJDs changes with the electric field strength, which leads to the variation of the electrophoretic mobility of the EIJDs. Therefore, the electrokinetic velocity of the EIJDs in a microchannel changes nonlinearly with the electric field strength. In this research, the variations of the nanoparticle coverage under both constant and time-varying electric fields were studied first. The results indicate that the nanoparticle coverage of the EIJDs decreases with the increase of the electric field strength, and an empirical equation for calculating nanoparticle coverage as a function of the electric field was derived. Under time-varying electric field, the variation of nanoparticle coverage lags behind the change of electric field, and the nanoparticle coverage changes differently under different time-varying electric fields. The experimental results of the electrokinetic motion of the EIJDs in a microchannel confirm that the electrokinetic velocity increases nonlinearly with the electric field. Due to the lag of the nanoparticle coverage change, the variation of the electrokinetic velocity in a microchannel is different between the increasing and decreasing periods of the time-varying electric field.

Vibroprotection System with the Elastic Element and the Electrically Controlled Damping

The study is performed to investigate the damping characteristics of the developed vibroprotection system with the double flat spring elastic element. Damping of vertical and horizontal natural oscillations of mass is studied under the change in the external electric field applied to the electrically controllable damping material. It is determined that the logarithmic decrement of vertical natural oscillations increased almost twofold, and the logarithmic decrement of horizontal natural oscillations increased by a factor of 6 with the change of electric field from 0 to 1.2 kV/mm. DOI: http://dx.doi.org/10.5755/j01.mech.24.5.21070

Model electrical activity of neuron under electric field

Continuous pump and transmission of charges such as calcium, potassium, sodium in the cell can induce time-varying electromagnetic field, and the induced electric field can further modulate the propagation of ions in the cell. Based on the physical laws of static electric field, the effect of electric field in isolate neuron is investigated by introducing additive variable E on the model. Each neuron is considered as a charged body with complex distribution of charges, and electric field is triggered to receive and give response to external electric field and electric stimulus. That is, the electric field is considered as a new variable to describe the polarization modulation of media resulting from external electric field and intrinsic change of density distribution in charges or ions. The dynamical behaviors in electrical activities are analyzed and discussed in the new neuron model, and it confirms that electric field can cause distinct mode transition in electrical activities of neuron exposed to different kinds of electric field. It could provide new insights to understand signal encoding and propagation in nervous system. Finally, it also suggests that new model can be used for signal propagation between neurons when synapse coupling is suppressed.

Analysis on lightning electromagnetic fields received by antenna and electric field change instrument

Analysis on lightning electromagnetic fields received by antenna and electric field change instrument

Effects of island chains on transport through changes in the radial electric field (TJ-II stellarator)

The opening of island chains in magnetically confined fusion plasma is a natural and common process. The effects on transport, however, are difficult to assess because of the complexity of the phenomenon, which often happens dynamically. In this work we investigate one basic way in which transport may be altered due to the presence of magnetic islands: the modification of the ambipolar radial electric field Er due to the distortion of the flux surfaces and the presence of a separatrix. For the latter, we first adapt the metric coefficients to a new configuration that excludes the island region; then we also perturb the original Er with a neoclassical scaling taken from Shaing’s formulation [Phys. Plasmas 9 3470 (2002)]. Some examples are shown for TJ-II plasmas with dynamic configuration scans, i.e., with some low-order rational of the rotational transform moving through the plasma minor radius during one discharge. It is suggested that a modification of transport properties other than neoclassical is necessary in order to explain the experimental results.