Intense Electric Field Research Articles

The Dynamic Behaviour of Multi-Phase Flow on a Polymeric Surface with Various Hydrophobicity and Electric Field Strength.

The dynamic behaviour of rain droplets on the insulator surface is a key measure to its reliability and performance. This is due to the fact that the presence and motion of rain droplets cause intensive discharge activities, such as corona and low current arcing, which accelerate the ageing process and flashovers. This article aims to investigate and characterize the movement of a rain droplet placed on an inclined insulator surface subject to an intensive electric field. The rain droplets’ movement on hydrophobic surfaces in the absence of an electric field is investigated. A high speed camera is used to capture the footage and finite element method (FEM) is used to simulate the multi-physics phenomenon on two polymeric surfaces, namely, silicon rubber (SiR) and PTFE (polytetrafluoroethylene). A ‘creepage’ motion was observed. The inception of motion and the movement speed are analysed in correlation with various surface conditions. Models are established to estimate the moisture and potential discharge characteristics on the inclined polymeric surfaces. They are further utilized to analyse the actual insulators subject to wet conditions.

A novel microscale platform for leukemia tumor treating field therapy and electrochemical screening

Currently, chemotherapy methods are among the most commonly used strategies for all cancer treatments, including leukemia. Despite the marked successes of such therapies, their inevitable side-effects and dose-limiting complications hinder reaching the maximum efficacy. Recently, Tumor Treating Fields (TTFields) that exploits low intensity and intermediate frequency electric fields has shown great promise as a noninvasive cancer therapy. Combining TTFields and conventional chemotherapies allows treatment with lower drug doses, resulting in significant clinical outcomes and fewer side effects. Although such combinational therapies have been used to treat a wide range of cancer types, their potential applications on leukemia have yet to be explored. This study investigates the effects of TTFields on the leukemia cells in combination with imatinib using a novel microelectrode array platform enabling the on-chip application of TTFields. Microfabrication allows applying TTFields by conventional signal generators with a maximum 20 V peak-to-peak external voltage eliminating commonly used high voltage amplifiers. We evaluated the effectiveness of our method with several biological assays, including flow cytometry, Annexin-V staining, and MTT. Our results indicate that combining TTFields and imatinib can halve the required drug dose (1 μM to 0.5 μM) to reach the apoptotic rate (68.55%±2.4%) obtained by imatinib alone. By comparing the cells numbers, after 72 h, the K562 cells number in our combinational treatment were 7% lower than the initial values seeded, suggesting a considerable net reduction in the tumor cell. Furthermore, to explore the underlying mechanism, an electrochemical approach is employed to measure the secreting contents of the leukemia cells after treatment. We concluded that the enhancement in treatment efficacy could be attributed to the induction of intracellular reactive oxygen species by TTFields, resulting in increased cell apoptosis. Our method provides an in vitro basis to assess the application of TTFields in combination with chemotherapy for leukemia cells.

Conformer Selection by Electrostatic Hexapoles: A Theoretical Study on 1-Chloroethanol and 2-Chloroethanol

The electrostatic hexapole is a versatile device that has been used for many years in gas-phase experiments. Its inhomogeneous electric field has been employed for many purposes such as the selection of rotational states, the selection of clusters, the focusing of molecular beams, and molecular alignment as a precursor for molecular orientation. In the last few years, the hexapolar electric field has been demonstrated to be able to control the conformer composition of molecular beams. The key point is that conformers, where the component of the permanent electric dipole moment with respect to the largest of the principal axes of inertia is close to zero, require more intense hexapolar electric fields to be focused with respect to the other conformers. Here, we simulated the focusing curves of the conformers of 1-chloroethanol and 2-chloroethanol under hypothetical beam conditions, identical for all conformers, in a hypothetical and realistic experimental setup with three different hexapole lengths: 0.5, 1, and 2 m. The objective was to characterize this selection process to set up collision experiments on conformer-selected beams that provide information on the van der Waals clusters formed in collision processes.

Intense electric field effects on microtubules

Microtubules (MTs) are indispensable for numerous vital cellular activities such as cell division, cell function, intracellular transport, etc. Therefore, anomalies in these can give molecular diseases for example, Alzheimer and Parkinson¯s diseases. These components of the cytoskeleton are composed of tubulin protein, which has an exceptionally high structural electric charge and dipole moment. Consequently, it is probable that microtubules could be a susceptible target to electric field through which one could modulate the function of biological systems.

FUV observations of variations in thermospheric composition and topside ionospheric density during the November 2004 magnetic superstorm

We revisited the November 2004 superstorm by analyzing TIMED/GUVI data. The 135.6 nm limb radiances at 520-km are mainly due to the O+ and electron radiative recombination and represent the daytime ionosphere density at the altitude. The 135.6 nm radiances clearly showed a signature of ionospheric equatorial arcs and their variations during the November 2004 magnetic superstorm. When an intense eastward Interplanetary Electric Field (IEF) occurred, the dayside equatorial arcs were enhanced and their latitude separation increased. The enhanced equatorial arcs were hemispherically symmetric or asymmetric in the region with non-depleted O/N2 or hemispherically asymmetric O/N2 depletion, respectively. When O/N2 depletion reached the magnetic equator, there was no observable enhancement in the equatorial arcs regardless the IEF conditions, indicating O/N2 condition significantly modulated the variations in storm-time equatorial arcs. GUVI observations also showed that a westward IEF and/or disturbance dynamo electric field could also suppress the dayside equatorial arcs.

Axisymmetric thin film flow on a flat disk foil subject to intense radial electric fields

The presence of intense radial electric fields on a wetted disk foil of fingernail size results in the formation of a large number (up to ∼1000) of cone-jets and electrosprays (Wang et al., “Massively multiplexed electrohydrodynamic tip streaming from a thin disc,” Phys. Rev. Lett., 126, 064502, 2021). This massively multiplexed electrohydrodynamic tip streaming phenomenon offers a simple and convenient way of creating quasi-monodisperse droplets at high throughput. The structure of the axisymmetric liquid film flow on the disk determines the number and distribution of the cone-jets. In this work, we quantitively study the flow of the axisymmetric thin liquid film subjected to a radial electric field. The liquid film profile is found to be concave with a circular ridge, at which multiple Taylor cones are anchored. The liquid film thickness is experimentally quantified with a fluorescence imaging method, and the results are in decent agreement with the film profile model based on the lubrication theory. The velocity field in the liquid film was experimentally obtained by particle tracking velocimetry (PTV). The results shed light on the understanding of the multiplexed electrohydrodynamic tip streaming from a thin disk.

Atom probe analysis of electrode materials for Li-ion batteries: challenges and ways forward.

The worldwide development of electric vehicles as well as large-scale or grid-scale energy storage to compensate for the intermittent nature of renewable energy generation has led to a surge of interest in battery technology. Understanding the factors controlling battery capacity and, critically, their degradation mechanisms to ensure long-term, sustainable and safe operation requires detailed knowledge of their microstructure and chemistry, and their evolution under operating conditions, on the nanoscale. Atom probe tomography (APT) provides compositional mapping of materials in three dimensions with sub-nanometre resolution, and is poised to play a key role in battery research. However, APT is underpinned by an intense electric field that can drive lithium migration, and many battery materials are reactive oxides, requiring careful handling and sample transfer. Here, we report on the analysis of both anode and cathode materials and show that electric-field driven migration can be suppressed by using shielding by embedding powder particles in a metallic matrix or by using a thin conducting surface layer. We demonstrate that for a typical cathode material, cryogenic specimen preparation and transport under ultra-high vacuum leads to major delithiation of the specimen during the analysis. In contrast, the transport of specimens through air enables the analysis of the material. Finally, we discuss the possible physical underpinnings and discuss ways forward to enable shielding from the electric field, which helps address the challenges inherent to the APT analysis of battery materials.

Observations of Pitch Angle Changes of Electrons and High‐Frequency Wave Activities in the Magnetotail Plasma Bubble

AbstractPlasma bubble, a low‐entropy flux tube, is usually regarded as the bearer of plasma flux transport in the magnetotail. In this study, we perform a complete analysis of electron dynamics in a plasma bubble in the Earth's magnetotail based on the high time‐resolution data from the Magnetospheric Multiscale (MMS) mission. An electron jet is observed at the center of this plasma bubble. Simultaneously, intense electric field and significant current density, as well as the strong energy dissipation are detected associated with this electron jet. The pitch angle distributions (PADs) of high‐energy electrons exhibit different features at different substructures in this plasma bubble. In Region‐1 and Region‐3, pancake‐type PAD is formed; the PAD becomes isotropic type in Region‐2. The electrons pitch angle changes to field‐aligned distribution in Region‐4. All these changes of electron PADs in substructures can be interpreted mainly by the capture of magnetic mirror and betatron cooling. High‐frequency waves, including whistler waves and electrostatic waves, are detected in several parts of the plasma bubble. The observations of abundant electron‐scale phenomena or processes reveal that the electrons are very dynamic in the large‐scale plasma bubble.

Factors that influence the trajectories of charged insulating particles in roll-type electrostatic separators

The electrostatic separation is known as an efficient and robust recycling technology, characterized by low cost, reduced energy consumption and ease of use. However, the separation process is multifactorial and requires a judicious choice of electrical and geometrical parameters in order to enable the processing of different material mixtures and obtain an optimal result. The aim of this paper was to study the different factors that influence the trajectories of charged insulating particles exposed to an intense DC electric field of a roll-type electrostatic separator. For this purpose, a numerical model, based on the fundamental principles of dynamics, was elaborated in order to simulate the behavior of the particles in such electrostatic devices. The numerical model considered the main electrical, mechanical, and aero-dynamical forces that govern the movement of the particles. To check the accuracy of the numerical model, several experiments were carried out on charged insulating particles in the roll-type electrostatic separator. The particle trajectories were recorded with a high-speed camera and compared with those obtained by numerical simulation. The results obtained validate the numerical model, as the simulated trajectories were similar to those captured by the camera.

Упрощенные представления вероятностей излучения фотона в постоянном внешнем электрическом поле

In the case of an intense external electric field, there exist many transition channels corresponding to the violation of the vacuum stability. It was shown that depending on the setting of a problem there is a number of integral representations for the probabilities of one photon emission due to a constant electric field. These representations are the Fourier transformations of the product of two Weber parabolic cylinder functions that are solutions of the same differential equation. To simplify the study of the probabilities, we expressed such a Fourier transformation via the confluent hypergeometric function.

Microbial inactivation of milk by low intensity direct current electric field: Inactivation kinetics model and milk characterization

Microbial inactivation by pulsed electric field (PEF) has been studied widely although with high operational risk, while few studies on the potential of low intensity electric fields for microbial inactivation have been reported. In this study, the feasibility of inactivating microorganisms in milk by low intensity direct current (DC) electric field was investigated. Then a kinetics model was proposed based on the inactivation curves. Finally, the effect of electric field on the microflora and physicochemical properties of milk was analyzed. Results showed that the bacterial reduction >5 log CFU/mL could be achieved at 50–55°C, 0.3 A–0.6 A, and with 5 min starting intensity of 5 V/cm-9 V/cm. The inactivation kinetics consisted of three stages, therein, the middle stage, main part of the inactivation curve, followed 1st-order reaction kinetics, and the effect of temperature on it was consistent with the Arrhenius Law, which implied that the electric field itself can inactivate bacteria without thermal inactivating effect. The microflora analysis showed that naturally occurring bacteria in the milk contained typical potential pathogenic bacteria (e.g., 56.9% of Acinetobacter spp.) and spoilage bacteria (e.g., 27.5% of Pseudomonas spp.), and the electric field can inactivate them. Moreover, the inactivation chemically preserved the milk's fresh-like characteristics (according to indexes of whey protein denaturation rate, furosine content), and physical stability (turbidity, zeta potential, particle size, color and so on). Therefore, a promising approach is provided for microbial inactivation in dairy industry.

A rationale for non-linear responses to strong electric fields in molecular dynamics simulations.

Many approaches for calculation of the field-dependent electric properties of water solutions rely on the Onsager and Kirkwood theories of polar dielectrics. Such basic theories implicitly consider the electric field intensity to fulfill the so-called 'weak field conditions', i.e. to produce a linear response in the system. In this work we made use of molecular dynamics simulations to investigate possible non-linear effects induced by high intensity electric fields, specifically continuous wave bursts with nanosecond duration, comparing them with the ones predicted by the theory. We found that field intensities above 0.15 V nm-1 produce remarkable nonlinear responses in the whole 100 MHz-100 GHz frequency window considered, with the onset of higher order polarization signals, which are the clear fingerprint of harmonic distorsions. That non-linear response turned out to depend on the considered frequency. We finally show that MD outcomes are consistent with a modelization based on an extended formulation of the Langevin function including a frequency-dependent parameter.

Эффект влияния локализованных d-электронов на спиновую поляризацию вертикальных гетероструктур на основе нанопористого биграфена

The novel heterostructure based on nanoporous bigraphene (NPBG) stacked into AB configuration was designed. An effect of the valence shell of adsorbed transitional metal on its position in heterostructure was investigated. It was found that d-electrons can initiate spin-polarization of non-polarized NPBG (AB) in absence of the effect of intensive electric fields, which is common for NPBG(AA).

Electromagnetic field fluctuation and its correlation with the participant plane in Au+Au and isobaric collisions at sNN=200 GeV

Intense transient electric ({\bf E}) and magnetic ({\bf B}) fields are produced in the high energy heavy-ion collisions. The electromagnetic fields produced in such high-energy heavy-ion collisions are proposed to give rise to a multitude of exciting phenomenon including the Chiral Magnetic Effect. We use a Monte Carlo (MC) Glauber model to calculate the electric and magnetic fields, more specifically their scalar product $\bf{E}\cdot\bf{B}$, as a function of space-time on an event-by-event basis for the Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV for different centrality classes. We also calculate the same for the isobars Ruthenium and Zirconium at $\sqrt{s_{NN}}=200$ GeV. In the QED sector $\bf{E}\cdot\bf{B}$ acts as a source of Chiral Separation Effect, Chiral Magnetic Wave, etc., which are associated phenomena to the Chiral Magnetic Effect. We also study the relationships between the electromagnetic symmetry plane angle defined by $\bf{E}\cdot\bf{B}$ ($\psi_{E.B}$) and the participant plane angle $\psi_{P}$ defined from the participating nucleons for the second-fifth order harmonics.

Effect of adding an upper-substrate holder in the quartz-tube MPCVD on plasma parameters

An upper-substrate holder is introduced into the quartz-tube microwave plasma chemical vapor deposition (MPCVD) resonant cavity. For two configurations of substrate holder, standard without upper-substrate and modified with upper-substrate, the distribution of detected H, temperature (Te) and density (Ne) of electrons in the plasma above the substrate surface was monitored by optical emission spectroscopy. Finite element simulation of electric field distribution and intensity shows that in modified resonant cavity (with upper-substrate holder), the electric field intensity is more concentrated and higher than in traditional resonant cavity under the same discharge deposition parameters. As a consequence of a more intense electric field in the plasma above the substrate, an increase in Te and Ne was observed in modified resonant cavity. At the same time, the diamond coatings deposited in the modified resonant cavity has a significantly higher growth rate as well as higher phase purity, well (111) crystal plane considering the results of Raman spectroscopy (more intense peak 1332 cm−1, as well as less presence of sp2 phase) and XRD than deposits in traditional resonant cavity.

Efficient ionization of two-dimensional excitons by intense single-cycle terahertz pulses

External electric fields are highly attractive for dynamical manipulation of excitons in two-dimensional materials. Here, we theoretically study the ionization of excitons in monolayer transition metal dichalcogenides (TMDs) by intense pulsed electric fields in the terahertz (THz) regime. We find that THz pulses with realistic field strengths are capable of ionizing a significant fraction of photogenerated excitons in TMDs into free charge carriers. Short THz pulses are therefore an efficient, non-invasive method of dynamically controlling the free carrier concentration in monolayer TMDs, which is useful for applications such as THz modulators. We further demonstrate that exciton ionization probabilities should be experimentally measurable by comparing free carrier absorption before and after the THz pulse. Detailed results are provided for different TMDs in various dielectric environments.

Interfacial engineering improved internal electric field contributing to direct Z-scheme-dominated mechanism over CdSe/SL-ZnIn2S4/MoSe2 heterojunction for efficient photocatalytic hydrogen evolution

Purposefully design and steering charge flow in heterostructure remains a crucial challenge for realizing efficient solar-to-fuel conversion. Herein, a newfangled ternary dual direct Z-scheme-dominated heterostructure of CdSe/lower-coordinated S atoms (SL)-rich ZnIn2S4/MoSe2 (CdSe/SL-ZIS/MoSe2) is fabricated, where the lower-coordinated S atoms in ZIS can serve as the highly active sites for anchoring CdSe and MoSe2 on the surface of ZIS through Cd-S and Mo-S bonds. The optimized CdSe/SL-ZIS/MoSe2 displays the ultrahigh visible-light (λ > 420 nm) driven H2 production rate of 70789.2 umol·g−1·h−1 with an apparent quantum efficiency (AQE) of 44.1% at 420 nm. Mechanism analysis and DFT calculations reveal that the interfacial chemical bond contributes to the intense internal electric field (IEF) in CdSe/SL-ZIS/MoSe2, and finally lead to the direct Z-scheme-dominated and II-scheme-assisted charge transfer mechanism. This work establishes an atomic-scale interfacial engineering design model on directionally modulating charge transfer for efficient solar energy conversion applications.

Effects of Electron Precipitation on E‐Region Instabilities: Theoretical Analysis

AbstractDuring periods of strong geomagnetic activity, intense currents and electric fields originating in the magnetosphere inundate the high‐latitude E‐region ionosphere. These strong electric fields drive plasma instabilities, including the Farley‐Buneman instability (FBI). These instabilities give rise to small‐scale plasma turbulence that modifies the large‐scale ionospheric conductance that, in turn, affects the evolution of the magnetosphere‐ionosphere‐thermosphere system. Also, during geomagnetic storms, high‐energy precipitating electrons, ≳5 keV, frequently penetrate down to the same regions where the intense currents and electric fields exist. This research examines the effects of precipitating electrons on the generation of the FBI and shows that, under many common conditions, it can easily suppress the FBI in a predictable manner. We demonstrate that the plasma pressure of superthermal electrons may significantly exceed the regular plasma pressure of the cold ionospheric plasma. This effect will increase the FBI threshold and suppress the instability in auroral regions. However, our detailed theoretical analysis shows that the effect of the superthermal precipitating electrons on the FBI threshold is much stronger than the pressure effect. The energy dependence of the electron‐N2 collision frequency can greatly enhance the effect of this additional pressure, further suppressing the FBI, even at a moderate precipitation level. Therefore, we expect that precipitation will exert an additional significant feedback on the magnetosphere by preventing the elevated conductivity caused by FBI driven turbulence. Both the turbulence‐enhanced conductivities and this suppression should be taken into account in global modeling of the magnetosphere‐ionosphere coupling.

Smooth pyroelectric luminescence in β-BaB2O4 single crystals via Fowler-Nordheim tunneling

The smooth pyroelectric luminescence in β-BaB2O4 single crystals is investigated for low ambient pressures (down to 10-6 mbar) and temperature changes, in particular between 235–250 K for heating and 240–255 K for cooling cycles respectively. This faint, continuous emission of light due to temperature-induced changes of permanent polarization is brought about by charge carrier recombination inside the crystal, contrasting the well-known spike-like emission due to discharges in the ambient atmosphere. A microscopic model of the luminescence allows the description of the time-dependent pyroelectric luminescence, in particular the determination of deep trap potentials that are otherwise inaccessible to thermal activation. Using this model, we show that the behavior of this emission in the polar β-BaB2O4 crystals is consistent with the release of trapped electrons by Fowler-Nordheim tunneling under the influence of intense electric fields generated due to the pyroelectric effect. We also discuss the barrier lowering of both Coulomb and Dirac potentials through the Poole-Frenkel emission but only achieve good fitting of the experimental data for unrealistic combinations of values of the electron emission rates, capture cross-section, activation energies and high-frequency permittivity.

Gate induced modulation of electronic states in monolayer organic field-effect transistor

Organic field-effect transistors with ionic liquids have attracted much attention, since the ionic liquids induce an intense electric field at a semiconductor interface, resulting in a high concentration of charge carriers. It is expected that such strong electric fields and highly doped charges induce nontrivial effects on the electronic band structures. Recently, the blue shift of the peak wavelength in photo-absorption spectra for a DNBDT-monolayer transistor was experimentally observed by increasing an ionic-liquid gate voltage, although the origin of the shift is still under debate. Therefore, we investigate the hole-doping and external electric-field effects on the electronic states of the organic semiconducting monolayer within the framework of the density functional theory. The calculated results show that the photo-absorption energy is increased by hole doping while an external field decreases the photo-absorption energy. We demonstrated that the calculations give useful information to understand the origin of the experimentally observed wavelength shift of photo-absorption spectra.