Weak Electric Field Research Articles

Coalescence-Induced Jumping of Nanodroplets in a Perpendicular Electric Field: A Molecular Dynamics Study.

Coalescence-induced jumping has promised a substantial reduction in the droplet detachment size and consequently shows great potential for heat-transfer enhancement in dropwise condensation. In this work, using molecular dynamics simulations, the evolution dynamics of the liquid bridge and the jumping velocity during coalescence-induced nanodroplet jumping under a perpendicular electric field are studied for the first time to further promote jumping. It is found that using a constant electric field, the jumping performance at the small intensity is weakened owing to the continuously decreased interfacial tension. There is a critical intensity above which the electric field can considerably enhance the stretching effect with a stronger liquid-bridge impact and, hence, improve the jumping performance. For canceling the inhibition effect of the interfacial tension under the condition of the weak electric field, a square-pulsed electric field with a paused electrical effect at the expansion stage of the liquid bridge is proposed and presents an efficient nanodroplet jumping even using the weak electric field.

A two-dimensional numerical study of ion-acoustic turbulence

We investigate the linear and nonlinear evolution of the current-driven ion-acoustic instability in a collisionless plasma via two-dimensional (2-D) Vlasov–Poisson numerical simulations. We initialise the system in a stable state and gradually drive it towards instability with an imposed, weak external electric field, thus avoiding physically unrealisable super-critical initial conditions. A comprehensive analysis of the nonlinear evolution of ion-acoustic turbulence (IAT) is presented, including the detailed characteristics of the evolution of the particles’ distribution functions, (2-D) wave spectrum and the resulting anomalous resistivity. Our findings reveal the dominance of 2-D quasi-linear effects around saturation, with nonlinear effects, such as particle trapping and nonlinear frequency shifts, becoming pronounced during the later stages of the system's nonlinear evolution. Remarkably, the Kadomtsev–Petviashvili (KP) spectrum is observed immediately after the saturation of the instability. Another crucial and noteworthy result is that no steady saturated nonlinear state is ever reached: strong ion heating suppresses the instability, which implies that the anomalous resistivity associated with IAT is transient and short-lived, challenging earlier theoretical results. Towards the conclusion of the simulation, electron-acoustic waves are triggered by the formation of a double layer and strong modifications to the particle distribution induced by IAT.

Dreicer Electric Field Definition and Runaway Electrons in Solar Flares

We analyze electron acceleration by a large-scale electric field E in a collisional hydrogen plasma under the solar flare coronal conditions based on approaches proposed by Dreicer and Spitzer for the dynamic friction force of electrons. The Dreicer electric field E Dr is determined as a critical electric field at which the entire electron population runs away. Two regimes of strong (E ≲ E Dr) and weak (E ≪ E Dr) electric field are discussed. It is shown that the commonly used formal definition of the Dreicer field leads to an overestimation of its value by about five times. The critical velocity at which the electrons of the “tail” of the Maxwell distribution become runaway under the action of the sub-Dreiser electric fields turns out to be underestimated by 3 times in some works because the Coulomb collisions between runaway and thermal electrons are not taken into account. The electron acceleration by sub-Dreicer electric fields generated in the solar corona faces difficulties.

Dual-coupling effect enables a high-performance self-powered UV photodetector.

Self-powered ultraviolet photodetectors generally operate by utilizing the built-in electric field within heterojunctions or Schottky junctions. However, the effectiveness of self-powered detection is severely limited by the weak built-in electric field. Hence, advances in modulating the built-in electric field within heterojunctions are crucial for performance breakthroughs. Here, we suggest a method to enhance the built-in electric field by taking advantage of the dual-coupling effect between heterojunction and the self-polarization field of ferroelectrics. Under zero bias, the fabricated AgNWs/TiO2/PZT/GaN device achieves a responsivity of 184.31 mA/W and a specific detectivity of 1.7 × 1013 Jones, with an on/off ratio of 8.2 × 106 and rise/decay times reaching 0.16 ms/0.98 ms, respectively. The outstanding properties are primarily attributed to the substantial self-polarization of PZT induced by the p-GaN and the subsequent enhancement of the built-in electric field of the TiO2/PZT heterojunction. Under UV illumination, the dual coupling of the enhanced heterojunction and the self-polarizing field synergistically boost the photo-generated carrier separation and transport, leading to breakthroughs in ferroelectric-based self-powered photodetectors.

Building and characterizing a stylus ion-trap system

Cold trapped ions can be excellent sensors for ultra-precision detection of physical quantities, which strongly depends on the measurement situation at hand. The stylus ion trap, formed by two concentric cylinders over a ground plane, holds the promise of relatively simple structure and larger solid angle for optical access and fluorescence collection in comparison with the conventional ion traps. Here we report our fabrication and characterization of the first stylus ion trap constructed in China, aiming for studying quantum optics and sensing weak electric fields in the future. We have observed the stable confinement of the ion in the trapping potential for more than two hours and measured the heating rate of the trap to be dε/dt = 7.10 ± 0.13 meV/s by the Doppler recooling method. Our work starts a way to building practical quantum sensors with high efficiency of optical collection and with ultimate goal for contributing to future quantum information technology.

Changes in the stability of coal microstructure under the influence of weak electromagnetic fields

The article presents experimental results of research concerning the action of weak electric and magnetic fields on physicochemical transformations in samples of hard coal with a previously destabilized microstructure. The actions of electric and magnetic fields are fundamentally different by many parameters. It has been shown that after treatment with a weak electric field, coal posted an electret potential with an anomalously continuous charge relaxation. Compared to untreated coal samples, the rate of methane emission from methane-saturated samples is maximum for long-flame coal and decreases as it approaches anthracite. The electric field stimulates the grinding of microparticles, a decrease in the maximum gas outlet temperature, a decrease in the enthalpy value in the formation of a new phase, and an increase in the chemical activity of treated coal samples. Fundamentally different results were obtained with magnetic stimulation of coals. In X-ray diffractograms of coal powders after magnetic treatment, the values of the maxima of the main peaks are the largest in comparison with the original samples and those treated with an electric field, which is consistent with an increase in the size of microparticles in a magnetic field. There is an increase in the heat of combustion and a decrease (by 5 times) in the loss of coal mass during heating.

Defect recognition of oil‐pressboard insulation based on frequent arc reignition phenomenon under switching impulse voltage

AbstractIn the past three years, a number of oil‐immersed ultra‐high‐voltage shunt reactors have experienced discharge defects when being put into operation, resulting in an overload of acetylene. However, detecting and identifying these discharge defects caused by switching impulse voltage is challenging under steady‐state conditions. This poses unpredictable and difficult‐to‐assess safety risks for the longterm operation of the equipment and subsequent transient processes. Hence, comprehending the discharge behavior of oil‐pressboard (PB) insulation under switching impulse voltage and devising a method to identify defects becomes crucial. This study focuses on investigating the frequent arc reignition (FAR) pattern exhibited by typical defects under both standard and oscillation switching impulse voltages. The objective is to uncover the mechanism behind FAR and propose a defect recognition strategy suitable for transient processes. The study reveals the FAR process will occur at least once during the breakdown process; the FAR phenomenon is the weakest in the surface defect with a weak vertical electric field. The average recovery voltage percentage and the average discharge interval of the FAR process decrease with increasing impulse amplitude or oscillation frequency. Additionally, the average number of discharges decreases with higher oscillation frequency, while it initially increases and then decreases with increaseing amplitude. Based on the analysis of the number of FAR processes and their variation in terms of amplitude or discharge interval, a method for recognizing oil‐PB defects during switching transient processes is developed and successfully applied to a case study involving acetylene overload in a 1000 kV shunt reactor.

Electron and ion emission characteristics of metal irradiated by nanosecond laser

Clarifying the electron and ion emission characteristics of metals irradiated by nanosecond focused laser in low pressure environment is crucial for improving applications based on laser-produced plasmas. This paper investigates the emission characteristics through electrical and optical diagnosis. The emission process is investigated through joint analysis of electrons and ions behavior, and relevant influencing factors are studied. The emission process of electrons and ions is divided into four stages, characterized by the arrival of prompt electrons e1, ultrafast electrons e2/ions i1, fast ions i2 and thermal electrons e3/ions i3, respectively. e1 is mainly related to thermal emission and photoemission, which can be improved by high electric field, gas pressure (within a certain range), laser energy and melting boiling points of target. e2/e3 and i1/i2/i3 mainly originate from laser ablation, and their expansion process follows obvious bipolar diffusion characteristics, while the latter is related to the different mass and charge states of the ions. The amplitude of i2 and e3 can be improved by using low density and melting point metals, and they are easily blocked by background gas, almost independent of the weak electric field.

Antifungal Activity of a Wireless Electroceutical Dressing

Background:Fusarium and Mucor are two filamentous fungus strains that can cause infections in humans. Fusarium is known for causing corneal infections. Patients who have diabetes mellitus or are immunocompromised are at a higher risk of mucormycosis. Wireless electroceutical dressing (WED) contains embedded silver and zinc nanoparticles in a geometric pattern. Both zinc and silver have been known to be antimicrobial; yet the combination results in a weak electric field when exposed to an electrolyte-containing solution. WED has been found to have antifungal effects against Candida albicans and Aspergillus fumigatus.
 Methods:We investigated the antifungal effect of WED against Fusarium and Mucor growth and survival through daily radial growth and optic density readings.
 Results:Our results show that the WED weakly inhibits radial growth of Fusarium strains and strongly inhibits radial growth of Mucor strains, with greater inhibition near physiologic temperatures. Although zinc and silver-only fabric inhibited the radial growth of Mucor, no growth occurred on WED (Ag-Zn) plates for Mucor strains. Optic density readings had mixed results; Ag-Zn liquid cultures had reduced absorbance than control cultures for both strains. Zone of inhibition studies of Fusarium showed no growth on Ag-Zn fabrics with full coverage on all other control and metal containing plates. WED had a greater effect on reducing Mucor growth than Fusarium.
 Conclusions:WED utilizes a weak electrical field created by silver and zinc nanoparticles to create an antifungal effect. This leads to strong inhibition of Mucor, Candida, and Aspergillus growth and weak inhibition of Fusarium growth. Further studies are needed to determine the specific effect of WED on fungal viability, the mechanism, and in vivo efficacy. This work could increase patient treatment options for fungal wound infections.

Mitigation of fouling problem and optimization of treatment effect in the polyvinylidene fluoride (PVDF) based electrochemical membrane bioreactor (EMBR)

The hydrophobic polyvinylidene fluoride (PVDF) membrane is one of the most widely used membrane material in the treatment of domestic sewage, while it still endures the fouling problem. Many studies have focused on the fouling control, among which the electrochemical membrane bioreactor (EMBR) is promising because of its chemical-free nature, but the specific influence of applied electric field on the mitigation of membrane fouling and the treatment effect are unclear and need further exploration. In this work, the influence and interaction of operation parameters (operation voltage, electrode spacing, power-on mode, and hydraulic retention time) on fouling development and pollutants removals in a PVDF based EMBR were carefully explored for the optimal operating conditions. Results showed that the run time of EMBR system under optimal conditions was 23.4 % longer than that of the MBR system without a weak electric field, indicating that the membrane fouling problem was well alleviated. In addition, the effluent quality of EMBR was also improved than that treated by the MBR system. The removal rates of chemical oxygen demand, ammonia nitrogen, total phosphorus, and total nitrogen were increased by 2.25 %, 2.64 %, 9.02 %, and 12.1 %, respectively, revealing the improvement of this EMBR system in sewage treatment. This work shows that introduction of a weak electric field in MBR system not only effectively controls membrane fouling, but also increases the effluent quality, and thus endows EMBR as a candidate for sustainable and green technique in sewage treatment.

Full control of the orientation of non-symmetric molecules using weak and moderate electric fields.

We investigate the full control over the orientation of a planar non-symmetric molecule by using moderate and weak electric fields. Quantum optimal control techniques allow us to orient any axis of 6-chloropyridazine-3-carbonitrile, which is taken as prototype example here, along the electric field direction. We perform a detailed analysis by exploring the impact on the molecular orientation of the time scale and strength of the control field. The underlying physical phenomena allowing for the control of the orientation are interpreted in terms of the frequencies contributing to the field-dressed dynamics and to the driving field by a spectral analysis.

Electric field-modulated evaporative thin film deposition of bio-particles for piezoelectric applications.

Bio-based functional materials can be used to replace or limit the use of synthetic materials sourced from unsustainable sources. However, the potential of such materials remains largely unexplored. In this study, we demonstrate the use of weak AC electric fields to deposit ultra-thin piezoelectric films from cellulose nanocrystals (CNC). This is the first time electric fields are used to realize <50 nm thick uniform bio-based piezoelectric films wherein the bioparticles exhibit unidirectional arrangement. Interestingly, we found that the use of weak AC electric fields of suitable frequencies completely mitigates the coffee ring effect (CRE), which results in defect-free uniform ultra-thin films. Additionally, the electric fields appear to help in realizing unidirectional alignment of particles in the films, which enhances their piezoelectric properties. The method was also tested for chitin nanocrystals (ChNC), which have a similar aspect ratio but bear opposite polarity surface charges, and the influence of the field on coffee ring formation and particle orientation in CNC thin film deposition was validated. The phenomena can be attributed to the constant spatio-temporal curvature of the evaporating liquid film, the transient state between the three-phase contact (TPC) line, the electric field-dependent contact angle, and the permanent and field-induced dipole moments. These factors lead to particle polarization and alignment. The films have an optimum electrical frequency of deposition at which they are continuous and uniformly thin, have unidirectional alignment of particles, and function as a single dipole.

Electromagnetically induced transparency spectra of cesium Rydberg atoms decorated by radio-frequency fields

&lt;sec&gt;The large electric dipole moment of the Rydberg atom allows for strong coupling with weak electric fields, and is widely used in electric field measurements because of its reproducibility, precision and stability. The combination of Rydberg atoms and electromagnetically induced transparency (EIT) technology has been used for detecting and characterizing radio-frequency (RF) electric fields. &lt;/sec&gt;&lt;sec&gt;In this work, by selecting probe light (852 nm), dressed light (1470 nm), and coupled light (780 nm), the Rydberg state (49&lt;i&gt;P&lt;/i&gt;&lt;sub&gt;3/2&lt;/sub&gt;) of Cs atom is prepared by using a three-photon excitation scheme through using all-infrared light excitation of Rydberg atoms. We experimentally observe the EIT spectra of the Rydberg states decorated by radio-frequency electric fields, which optically detects Rydberg atoms. The effect of the amplitude and frequency of the RF electric field on the spectrum is explored in light of changes in the EIT spectrum. The results show that in the region of weak electric field, only the ac Stark energy shift and spectral broadening occur. As the electric field is further enhanced, the sideband phenomenon occurs in both the primary peak and secondary peak of the EIT. In the region of strong field, the Rydberg energy level produces a series of Floquet states with higher-order terms, as well as state shifting and mixing, resulting in asymmetry in the spectra of the EIT sideband peaks. The effect of frequency on the shielding effect of the Cs vapor cell is further discussed based on the shift of the main peak of the EIT.&lt;/sec&gt;&lt;sec&gt;The demodulation of the electric field in a range of 50 Hz–1 kHz with a fidelity of 95% is achieved by modulating the low-frequency electric field to the RF electric field. The results can provide valuable references for spectral detection and traceable measurements of low-frequency electric fields.&lt;/sec&gt;

Magnetic polarons reach a hundred thousand Bohr magnetons.

The ability of light to manipulate fundamental interactions in a medium is central to research in optomagnetism and applications in electronics. A prospective approach is to create composite quasiparticles, magnetic polarons, highly susceptible to external stimuli. To control magnetic and transport properties by weak magnetic and electric fields, it is important to find materials that support photoinduced magnetic polarons with colossal net magnetic moments. Here, we demonstrate that magnetic polarons with a record-high magnetic moment, reaching and exceeding a hundred thousand Bohr magnetons, can be optically generated in EuO, an archetypal ferromagnetic semiconductor. The phenomenon is established employing the photoinduced Faraday effect studied in EuO films by a two-color pump-probe technique. The giant magnetic polarons are generated just above the Curie temperature once EuO is exposed to photons of an energy exceeding the bandgap. Picosecond temporal dynamics of magnetic polarons follows relaxation processes in the spin-split 5d conduction band occupied by the photoexcited electron. The study is expected to provide a platform for implementation of an efficient optical control over the magnetic state in solids.

Combustion Of Methane With Microdroplets Of Water In A Weak Electric Field

The effect of a weak electric field on the flame of a Bunsen burner, including the case of an aerosol consisting of water microdroplets in an air-methane mixture has been studied in detail. The propagation velocities of the laminar flame have been determined. If the stabilization area (burner edge) and the flame tip are excluded from consideration, the average propagation velocity of a laminar flame in the absence of an electric field is constant. For a stoichiometric mixture of methane with air and aerosol combustion, it is equal to Su≈0.35 and 0.3 m/s, respectively. When an electric field is applied, there is a common trend for cases of combustion of methane and a gas-droplet mixture, i.e., maintaining the flame front propagation velocity from the anode side and increasing by about 8-10% from the cathode side.

XPS INVESTIGATION OF THE WORK FUNCTION OF GLASS CARBON COATINGS AFTER EXTENDED STAY ON THE INTERNATIONAL SPACE STATION (ISS)

Using XPS, the electron work function values on the surface of glassy carbon coatings of graphite samples, after an extended stay on a board of the ISS in open space conditions, were investigated. The results were compared with the characteristics of glassy carbon coatings of samples left on the ground for the same period. It was found that the electron work function does not change significantly, and this proves the possibilities of successfully application of these coatings, obtained by original Bulgarian technology, for space experiments on the board of satellites for measuring electric fields in the ionospheric-magnetospheric plasma. The minimal observed variations in the values of the electron work function are explained by small differences in the content of traces of different chemical elements on the surface of the coatings. It has been established that the glassy carbon coatings have stable characteristics after a long stay in space, despite the small fluctuations in the values of the electron work function. The results show that glassy carbon coatings are chemically and mechanically stable. The obtained results of this original technological experiment are unique for development of sensitive elements - sensors for measuring weak electric fields in the cosmic plasma.

Fabrication of breathable superhydrophobic composite fabric with moisture permeability and weak-electric-field bactericidal ability designed for protective clothing applications

Most protective clothing on the market today cannot provide both comfort properties and protectability, which would not match the requirement for preventing or killing the rapidly growing and changing virus. Hence, a novel breathable and waterproof composite fabric used in protective clothing was designed through the hot-press process with three functional layers. The waterproof ability, moisture permeability, mechanical property, electricity and bactericidal ability of three layers and composite fabric were studied. Results showed that the moisture permeability of coated thermoplastic polyurethane (TPU) membrane reached 19854 g m2 d−1. The composite fabric had still excellent moisture permeability of up to 13956 g m2 d−1 and water contact angle of 151.7°. The coated TPU membrane had good tensile strength and acid resistance. The voltage and current of composite fabric after 7 days were approximately 0.336 V and 1.4 μA. The composite fabric had a 97.5 % filtering effect for NaCl aerosols, a 99 % bacteriostatic rate, and the ability to withstand the Phy-X174 phage with a diameter of 0.027 μm. This composite fabric based on the principle of moisture permeability and weak electric field could be used in protective clothing, which would be of theoretical significance and guiding practical production.

Long-term root electrotropism reveals habituation and hysteresis.

Plant roots sense many physical and chemical cues in soil, such as gravity, humidity, light, and chemical gradients, and respond by redirecting their growth toward or away from the source of the stimulus. This process is called tropism. While gravitropism is the tendency to follow the gravitational field downwards, electrotropism is the alignment of growth with external electric fields and the induced ionic currents. Although root tropisms are at the core of their ability to explore large volumes of soil in search of water and nutrients, the molecular and physical mechanisms underlying most of them remain poorly understood. We have previously provided a quantitative characterization of root electrotropism in Arabidopsis (Arabidopsis thaliana) primary roots exposed for 5 h to weak electric fields, showing that auxin asymmetric distribution is not necessary for root electrotropism but that cytokinin biosynthesis is. Here, we extend that study showing that long-term electrotropism is characterized by a complex behavior. We describe overshoot and habituation as key traits of long-term root electrotropism in Arabidopsis and provide quantitative data about the role of past exposures in the response to electric fields (hysteresis). On the molecular side, we show that cytokinin, although necessary for root electrotropism, is not asymmetrically distributed during the bending. Overall, the data presented here represent a step forward toward a better understanding of the complexity of root behavior and provide a quantitative platform for future studies on the molecular mechanisms of electrotropism.

Anomalous Water Wetting on a Hydrophilic Substrate under a High Electric Field.

Macroscopically, the traditional Young-Lippmann equation is used to describe the water contact angle under a weak electric field. Here we report a new wetting mechanism of deionized water under a strong electric field that defies the conventional Young-Lippmann equation. The contact angle of the deionized water droplet on a model hexagonal lattice with a different initial wettability is extensively modulated by the vertical electric field. The cosine of water contact angle on a hydrophilic substrate displays an anomalous linear relationship with the field, in contrast to the hydrophobic case, which shows an inverse parabolic relationship. Such anomalous wetting is verified by experimental measurements of water droplets on a pyroelectric substrate. Moreover, we identify that this anomaly arises from the linear modulation of the solid-liquid interfacial tension of hydrophilic substrates by the electric field. Our findings provide atomistic insight into the fundamental laws and new phenomena of water-surface interactions under extreme electric fields.

Rejoint of Carbon Nitride Fragments into Multi-Interfacial Order-Disorder Homojunction for Robust Photo-Driven Generation of H2 O2.

Photocatalytic technology based on carbon nitride (C3 N4 ) offers a sustainable and clean approach for hydrogen peroxide (H2 O2 ) production, but the yield is severely limited by the sluggish hot carriers due to the weak internal electric field. In this study, a novel approach is devised by fragmenting bulk C3 N4 into smaller pieces (CN-NH4 ) and then subjecting it to a directed healing process to create multiple order-disorder interfaces (CN-NH4 -NaK).The resulting junctions in CN-NH4 -NaK significantly boost charge dynamics and facilitate more spatially and orderly separated redox centers. As a result, CN-NH4 -NaK demonstrates outstanding photosynthesis of H2 O2 via both two-step single-electron and one-step double-electron oxygen reduction pathways, achieving a remarkable yield of 16675µmol h-1 g-1 , excellent selectivity (>91%), and a prominent solar-to-chemical conversion efficiency exceeding 2.3%. These remarkable results surpass pristine C3 N4 by 158 times and outperform previously reported C3 N4 -based photocatalysts. This work represents a significant advancement in catalyst design and modification technology, inspiring the development of more efficient metal-free photocatalysts for the synthesis of highly valued fuels.