Electric Field Configuration Research Articles

Electric-field-generated topological states in a silicene nanotube

Applying an electric field perpendicular to the axis of a silicene armchair nanotube allows us to numerically study the formation of eight topological edge states as silicene’s intrinsic spin–orbit gap is closed by the sublattice-staggered electrostatic potential created by the electric field. Following their evolution with electric field, it is revealed that, at very small fields, these eight states are very broad, spin-locked, and sublattice constrained, inheriting their properties from the K and K′ states in a silicene two-dimensional honeycomb lattice. Four of those states are centered at the very top of the nanotube and the other four states are centered at the very bottom. As the field increases, each state starts to become narrower and to spread its spectral weight to the other sublattice. With further increase of the field, each state starts to spatially split, while the sublattice spreading continues. Once the spectral weight of each state is distributed evenly among both sublattices, the state has also effectively split into two spatially disconnected parts, after which, further increasing of the field will spread apart the two halves, moving them to the lateral regions of the nanotube, at the same time that the state halves become narrower. This is consistent with the formation of topological edge states, which delimit four ribbon-like topologically different regions: top and bottom topologically trivial ‘ribbons’ (where the electric field has induced a topological phase transition) that are adjacent to two topologically nontrivial ‘ribbons’ located at opposing sides of the nanotube. We also briefly access the possibility of observing these edge states by calculating the electronic properties for an electric field configuration that can be more readily produced in the laboratory.

Time resolution and efficiency of SPADs and SiPMs for photons and charged particles

We give an analytic treatment of the time resolution and efficiency of Single Photon Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs). We provide closed-form expressions for structures with uniform electric fields and efficient numerical prescriptions for arbitrary electric field configurations. We discuss the sensor performance for single photon detection and also for charged particle detection.

Electrophoretic Effects for Environmental Safety Technologies: Evacuation of Micro-Particle Conglomerations from the Surfaces

The actuality of the problem of contamination of objects by macro-molecular compounds is a growing problem today (especially given the terrible consequences of the pandemic). In fact, macromolecular complexes are mostly located on the surface layers of the surface covered with fine dust. Therefore, the development of technology for the removal of macromolecular components is actually a problem of fine (so we will call it) dust removal. This problem cannot be effectively solved by traditional mechanical removal methods alone, as contaminated objects have a rather complex, not even Euclidian, surface morphology. Therefore, it is important to develop effective technologies based on the use of properties of special configurations of external inhomogeneous electric field and removable components by means of a specially configured inhomogeneous electric field. The paper analyzes modern technologies of fine dust cleaning both mechanically and with the help of external electrical fields under the particular conditions and creation of levitation and electrophoretic motion. It has been found exact solutions of the model, which indicate in favor of the theoretical validity of decontamination technology using electric field with manipulative properties; the conditions of the most effective use of levitation-electrophoretic technology in the tasks of dust cleaning and decontamination, including decontamination of the surface-distributed macromolecular contaminants such as coronaviruses. Index Terms dust pollution dust cleaning levitation electrophoresis macromolecular pollution coronavirus

An Alfvenic reconnecting plasmoid thruster

A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The generated low-temperature plasma is simulated in a global annular geometry using the extended magnetohydrodynamic model. Because the system-size plasmoid is an Alfvenic outflow from the reconnection site, its thrust is proportional to the square of the magnetic field strength and does not ideally depend on the mass of the ion species of the plasma. Exhaust velocities in the range of 20 to $500\ \textrm {km}\ \textrm {s}^{-1}$ , controllable by the coil currents, are observed in the simulations.

Impact of the pre-deposited surface charge on the breakdown in a dielectric barrier discharge in the air

The electrical charge deposited on a dielectric barrier of dielectric barrier discharge (DBD) changes markedly the configuration and strength of the local electric field both on the barrier and in the gas gap. In turn, a change in the local electric field affects the rate of ionization multiplication of electrons in this area and, accordingly, influences the breakdown conditions providing the appearance of microdischarges in a barrier discharge. The features of the DBD breakdown in the presence of the pre-deposited charge on a dielectric barrier were investigated by the example of the plane-to-plane DBD operating in the ambient air at atmospheric pressure. The electric charge deposition on the barrier was performed in advance with the use of the pulsed pin-to-plane barrier corona. Corona discharge allows one to control both the amount and location of the pre-deposited charge. The slow increasing voltage of the needed polarity was used to initiate the breakdown in the plane-to-plane DBD. The slow increasing applied voltage provides the multiple breakdowns forming the “one by one” sequence of MDs. The analysis of the obtained results was performed on the base of the conception of the necessary and sufficient conditions for the MDs formation.

EEG Microstate Differences in Medicated vs. Medication-Naïve First-Episode Psychosis Patients

There has been considerable interest in the role of synchronous brain activity abnormalities in the pathophysiology of psychotic disorders and their relevance for treatment; one index of such activity are EEG resting-state microstates. These reflect electric field configurations of the brain that persist over 60–120 ms time periods. A set of quasi-stable microstates classes A, B, C, and D have been repeatedly identified across healthy participants. Changes in microstate parameters coverage, duration and occurrence have been found in medication-naïve as well as medicated patients with psychotic disorders compared to healthy controls. However, to date, only two studies have directly compared antipsychotic medication effects on EEG microstates either pre- vs. post-treatment or between medicated and unmedicated chronic schizophrenia patients. The aim of this study was therefore to directly compare EEG resting-state microstates between medicated and medication-naïve (untreated) first-episode (FEP) psychosis patients (mFEP vs. uFEP). We used 19-channel clinical EEG recordings to compare temporal parameters of four prototypical microstate classes (A–D) within an overall sample of 47 patients (mFEP n = 17; uFEP n = 30). The results demonstrated significant decreases of microstate class A and significant increases of microstate class B in mFEP compared to uFEP. No significant differences between groups were found for microstate classes C and D. Further studies are needed to replicate these results in longitudinal designs that assess antipsychotic medication effects on neural networks at the onset of the disorder and over time during illness progression. As treatment response and compliance in FEP patients are relatively low, such studies could contribute to better understand treatment outcomes and ultimately improve treatment strategies.

Dielectric properties of silica based synthetic ester nanofluid

This work studies the impact of silica nanoparticles on the dielectric properties of synthetic ester oil. A stable nanofluid is prepared by addition of surfactant. With addition of nanoparticles there is an increment in dielectric constant and decrement in dielectric loss constant. An attempt is made to understand the conduction mechanisms in uniform field and non-uniform electric field configuration by means of analysing the mobility of ions. Under uniform electric field stress (<0.1 kV/mm), by means of conduction current measurement with polarity reversal, the ionic mobility, conductivity, ionic concentration and ionic radius are deduced. There is a reduction in ionic mobility by addition of nanoparticle and surfactant. To understand the conduction mechanisms in high electric field condition, the current-voltage characteristics of the nanofluid are measured. Using this data, apparent mobility due to electrohydrodynamic motion is estimated, giving a lower mobility in the case of nanofluid, which could be the cause of the increased corona inception voltage.

Evidence for modulation of EEG microstate sequence by vigilance level

The momentary global functional state of the brain is reflected in its electric field configuration and cluster analytical approaches have consistently shown four configurations, referred to as EEG microstate classes A to D. Changes in microstate parameters are associated with a number of neuropsychiatric disorders, task performance, and mental state establishing their relevance for cognition. However, the common practice to use eye-closed resting state data to assess the temporal dynamics of microstate parameters might induce systematic confounds related to vigilance levels. Here, we studied the dynamics of microstate parameters in two independent data sets and showed that the parameters of microstates are strongly associated with vigilance level assessed both by EEG power analysis and fMRI global signal. We found that the duration and contribution of microstate class C, as well as transition probabilities towards microstate class C were positively associated with vigilance, whereas the sign was reversed for microstate classes A and B. Furthermore, in looking for the origins of the correspondence between microstates and vigilance level, we found Granger-causal effects of vigilance levels on microstate sequence parameters. Collectively, our findings suggest that duration and occurrence of microstates have a different origin and possibly reflect different physiological processes. Finally, our findings indicate the need for taking vigilance levels into consideration in resting-sate EEG investigations.

The optical tweezer of skyrmions

In a spin-driven multiferroic system, the magnetoelectric coupling has the form of effective dynamical Dzyaloshinskii–Moriya (DM) interaction. Experimentally, it is confirmed, for instance, for Cu2OSeO3, that the DM interaction has an essential role in the formation of skyrmions, which are topologically protected magnetic structures. Those skyrmions are very robust and can be manipulated through an electric field. The external electric field couples to the spin-driven ferroelectric polarization and the skyrmionic magnetic texture emerged due to the DM interaction. In this work, we demonstrate the effect of optical tweezing. For a particular configuration of the external electric fields it is possible to trap or release the skyrmions in a highly controlled manner. The functionality of the proposed tweezer is visualized by micromagnetic simulations and model analysis.

Numerical modeling of the gas gain of low-pressure Tissue-Equivalent Proportional Counters

Proportional counters are radiation detectors widely used in many applications. The design of the counter, to best fit each application, needs an accurate knowledge and physical modeling of the electron avalanche process. A particular proportional counter is the tissue-equivalent proportional counter (TEPC), the reference detector for experimental microdosimetry, which consists of a spherical or cylindrical chamber filled with low-density tissue-equivalent gas to simulate the energy deposition in tissue sites of micrometric size. The lower operation limit of standard TEPCs operated in the pulse-height analysis mode is about 0.3μm. In order to overcome this technological limit, different avalanche-confinement nano-microdosimetric TEPCs capable of measuring microdosimetric spectra in the nanometric domain were designed and constructed.In this work, a novel numerical tool developed for the Monte Carlo simulation of the electron avalanche process inside a low-pressure TEPC is described. The Monte Carlo code allows to simulate complex 3D electric field configurations exploiting COMSOL finite elements analysis. Several models for the electron interactions (i.e. scattering and ionization) are included in the code. The code has been benchmarked with the experimental results of a wall-less avalanche-confinement TEPC in terms of absolute gas gain for different operating conditions (i.e. gas pressures and electrode voltages).The results show that the code is capable of reproducing the absolute value of the gas gain for the avalanche-confinement TEPC simulating some tenths of nanometers in site size. Moreover, the code can reproduce both the extension and the shape of the proportional counter working windows.The code was also applied for simulating the probability of absorption of electrons by the central third electrode: the helix. The results show a non-negligible probability of absorption in the common range of operation. This code will be further applied for optimizing the TEPC design, capable of simulating site sizes closer to the nanometer region.

Drift velocity measurement in gas electron multiplier detectors for application in a time projection chamber polarimeter.

Drift velocity of electrons is an important parameter when signal formation is considered in detectors. In micro-pattern gas detectors such as the gas electron multiplier (GEM), the drift velocity is affected by non-uniform electric field configurations. In the context of x-ray polarimetric application of GEM, where the time projection chamber (TPC) configuration is used, the drift velocity plays an important role in forming time binned images. The accuracy of these images governs the information on polarization of incident photons. The work presented here proposes an experimental method to determine the drift velocity of electrons in such a gas detector. The gas under study is Ne/DME (50/50). The experimental setup comprising a single GEM is similar to the TPC polarimeter configuration. The effect of gas pressure and electric field on drift velocity is presented in the work. It is encouraging to find that the experimental values match well with the simulated values. We briefly discuss the effect of variation in the drift velocity on the performance parameters of the polarimeter. The implementation of this method in any future TPC polarimeter is also explored.

P300-mediated modulations in self-other processing under psychedelic psilocybin are related to connectedness and changed meaning: A window into the self-other overlap.

The concept of self and self‐referential processing has a growing explanatory value in psychiatry and neuroscience, referring to the cognitive organization and perceptual differentiation of self‐stimuli in health and disease. Conditions in which selfhood loses its natural coherence offer a unique opportunity for elucidating the mechanisms underlying self‐disturbances. We assessed the psychoactive effects of psilocybin (230 μg/kg p.o.), a preferential 5‐HT1A/2A agonist known to induce shifts in self‐perception. Our placebo‐controlled, double‐blind, within‐subject crossover experiment (n = 17) implemented a verbal self‐monitoring task involving vocalizations and participant identification of real‐time auditory source‐ (self/other) and pitch‐modulating feedback. Subjective experience and task performance were analyzed, with time‐point‐by‐time‐point assumption‐free multivariate randomization statistics applied to the spatiotemporal dynamics of event‐related potentials. Psilocybin‐modulated self‐experience, interacted with source to affect task accuracy, and altered the late phase of self‐stimuli encoding by abolishing the distinctiveness of self‐ and other‐related electric field configurations during the P300 timeframe. This last effect was driven by current source density changes within the supragenual anterior cingulate and right insular cortex. The extent of the P300 effect was associated with the intensity of psilocybin‐induced feelings of unity and changed meaning of percepts. Modulations of late encoding and their underlying neural generators in self‐referential processing networks via 5‐HT signaling may be key for understanding self‐disorders. This mechanism may reflect a neural instantiation of altered self–other and relational meaning processing in a stimulus‐locked time domain. The study elucidates the neuropharmacological foundation of subjectivity, with implications for therapy, underscoring the concept of connectedness.

A New DC Electric Field Sensor and Direct Measurements of Ionosphere Sq Electric Fields

A new type of DC electric field sensor has been developed. It is not mill type electric field sensor whose principle is to measure electric potentials in the atmosphere. The new type DC sensor can directly detect electric fields in all spaces. For minimizing disturbances of electric field configuration in the space, the new type sensor uses a simple linear dipole antenna. The key point in the detection method is to measure a potential difference between only two equipotential lines connecting to each dipole element. The validity of the configuration of equipotential lines around the dipole elements was confirmed by numerical analysis. It has been confirmed that angular dependence of the DC electric field intensities measured by a prototype of the new sensor was consistent with theoretical one. Then we began to observe natural DC electric fields in electrically quiet environment, installing its practical three antennas (5 m tip‐to‐tip) orthogonal with each other. We have found, from the measured electric fields, that behaviors of the measured electric fields suggest those of ionosphere Sq (solar quiet) electric fields. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

The Effect of Electric Field Configuration on the Thermo-Chemical Conversion of Straw Pellets

Abstract With the aim to control and improve the thermo-chemical conversion of straw pellets, the experimental investigations of the DC electric field effect on the combustion dynamics and heat energy production were made. The electric field effect on the gasification/combustion characteristics was studied using three different positions of the positively charged electrode in flame. First, the electrode was positioned coaxially downstream the flame flow. Next, the electrode was positioned coaxially upstream the flame flow and, finally, the electrode was positioned across the downstream flow. The bias voltage of the electrode varied in the range from 0.6 up to 1.8 kV, while the ion current in flame was limited to 5 mA. The results of experimental investigations show that the DC electric field intensifies the thermal decomposition of straw pellets and enhances mixing of volatiles with air causing changes in combustion dynamics and heat energy production, which depend on position and the bias voltage of the electrode. The increase in the average volume fraction of CO2 (by 6 %) and the decrease in the mass fraction of unburned volatiles in the products (CO by 60 % and H2 by 73 %) for the upstream field configuration of the electrode and the ion current 0.5–1.8 mA indicate more complete combustion of volatiles.

Control of electrical resistance and magnetoresistance by electric-field-driven oxygen ion migration in a single GdOx wire

Electric-field-driven ion migration can significantly modulate the electric and magnetic properties of solids, creating novel functionalities useful for advanced electromagnetic devices. Earlier works have used vertically stacked structures for this purpose, in which the redox process results from ion migration driven by a vertical electric field through the interfaces. However, the existence of the interfaces between the dissimilar layers causes the oxidation and reduction processes to have high and asymmetric energy barriers, which means that a large electric field is required to control the devices. Here, we show that in a partially oxidized single GdOx wire using a lateral electric field configuration, low and symmetric energy barriers for the oxidation and reduction processes can be achieved. We provide evidence that the redox process is the result of the lateral motion of oxygen ions by directly visualizing the electric-field-driven real-time ionic motion using an optical microscope. An electric field as low as 105 V/m was able to drive oxygen ions at room temperature, allowing controllable modulation of the electrical resistance using a lateral electric field. A large negative magnetoresistance was also observed in the GdOx wire, and its magnitude was significantly enhanced up to 20% at 9 T through oxygen ion control. Our results suggest that the electrical and magnetic properties of single GdOx can be efficiently controlled through oxygen ion motion driven by a lateral electric field, which paves the way for fully functional electromagnetic devices such as artificial synapses.

Partial Discharge Imaging Correlated with Phase-Resolved Patterns in Non-Uniform Electric Fields with Various Dielectric Barrier Materials

This paper describes a correlation of partial discharge phase-resolved patterns with an optical imaging performed in a non-uniform electric field configuration. The influence of different dielectric barrier materials, placed on the plane electrode, on the discharge propagation and surface landing was investigated. The investigations were focused on the corona at positive polarity of AC high voltage. It was found that the initial positive corona stage is similar for all cases whereas the discharge propagation and surface landing strongly depends on the barrier material properties. The observed streamer discharge modes have been described by the geometrical measures such as stem length, stretch of a discharge profile on the dielectric barrier surface and an hemispherical envelope of discharge filaments. Since various dielectrics reveal different properties of charge accumulation and surface neutralization, the charge memory effect may be visible and can be related to the ability to create and sustain of additional electric field component. It may refer to subsequent discharges as well as to conditions faced at the voltage polarity reversal. The correspondence between different forms of phase-resolved patterns have been associated with the modes of streamer discharges observed by optical imaging. Presented methodology poses huge potential for both scientific investigations on underlying discharge phenomena as well as on the application in future diagnostic systems of HV insulation.

Direct measurements of the properties of Thick-GEM reflective photocathodes

In the context of the development of novel Thick GEM based detectors of single photons, the high spatial resolution optical system, nicknamed Leopard, providing a detailed surface scanning of these electron multipliers, has been used for a set of systematic measurements of their key properties. In particular, gain uniformity and photoelectron extraction dependence on geometry and electric field configuration have been studied. These results are reported and discussed. They improve the understanding of the Thick GEM properties by novel measurements and confirmation of previous indirect measurements and they answer to relevant questions related to their use as photocathode substrates in novel gaseous photon detectors.

Controlling of Vibrations in Micro-Cantilever Beam Using a Layer of Active Electrorheological Fluid Support

The development of vibration control with smart fluids within flexible structures has been of significant interest in recent times. Although much research has been done on structures with embedded electrorheological fluids (ERF) and magnetorheological fluids (MRF), there has been a little investigation into localizing smart fluids under micro-structures. Research into the damping of micro-structures using ERF is very limited. The research in this article presented a comprehensive study into the controllability of the vibration characteristics of a micro-piezoelectric transducer with ERF support. This structure is made from piezoelectric material with a layer of ERF localized at the tip micro-cantilever beam (MCB). The structural behaviour of the MCB-ERF is alternated by applying an external electric field to activate the ERF. The MCB-ERF was tested under different electric field configurations ranging from 0kV/mm-2kV/mm. The effects of the activation of the ERF were outlined based on the results obtained. The increase in the frequency of MCB as the applied electric field to the ERF increased at 12.4 % experimentally with an electric field of 2kV/mm. The simulation and the analytical results, on the other hand, showed an increase in the frequency of the MCB from 16.2% and 13.46% respectively. The results demonstrated that the stiffness and damping structural characteristics of the MCB are controlled. This confirms the vibration controlling capabilities of MCB-ERF as structural elements.

Performance of Prototype of Optically Readout TPC with a 55Fe source

The performances of an optical readout of Time Projection Chambers (TPCs) with multiple Gas Electron Multipliers (GEMs) amplification stages are presented. The detector is characterized by using 55Fe photons converting inside a 7 litre sensitive volume detector in different electric field configurations. This prototype is developed as part of the R&D for the CYGNO project for an application to direct Dark Matter search by detection of tracks of nuclear recoils in the gas within the keV energy range.

Vacuum instability in a constant inhomogeneous electric field: a new example of exact nonperturbative calculations

Basic quantum processes (such as particle creation, reflection, and transmission on the corresponding Klein steps) caused by inverse-square electric fields are calculated. These results represent a new example of exact nonperturbative calculations in the framework of QED. The inverse-square electric field is time-independent, inhomogeneous in the x -direction, and is inversely proportional to x squared. We find exact solutions of the Dirac and Klein–Gordon equations with such a field and construct corresponding in- and out-states. With the help of these states and using the techniques developed in the framework of QED with x-electric potential steps, we calculate characteristics of the vacuum instability, such as differential and total mean numbers of particles created from the vacuum and vacuum-to-vacuum transition probabilities. We study the vacuum instability for two particular backgrounds: for fields widely stretches over the x-axis (small-gradient configuration) and for the fields sharply concentrates near the origin x=0 (sharp-gradient configuration). We compare exact results with ones calculated numerically. Finally, we consider the electric field configuration, composed by inverse-square fields and by an x-independent electric field between them to study the role of growing and decaying processes in the vacuum instability.