Effect Of Direct Current Electric Field Research Articles

Electrophoretic coalescence behavior of oil droplets in oil-in-water emulsions containing SDS under DC electric field: A molecular dynamics study

The presence of oil droplets in oil-in-water (O/W) emulsions seriously affects the efficiency of wastewater purification, and the appropriate addition of surfactants can effectively improve the demulsification process. In this paper, the electrophoretic coalescence behavior of oil droplets containing anionic surfactant sodium dodecyl sulfate (SDS) under a direct current (DC) electric field was studied based on molecular dynamics (MD) simulations, and four typical stages of oil droplet migration coalescence were defined. The weak interactions between SDS and water and between SDS and n-hexane are mainly van der Waals interactions, while a small number of hydrogen bonds are formed between SDS and water and between water molecules internally. With the increase of electric field strength (E), the deformation of oil droplets after aggregation increases, and the contact angle with the electrode plate becomes smaller. The interfacial tension between oil and water decreases and then increases with increasing surfactant concentration, reaching a minimum value of 32.52 mN/m when the number of SDS molecules (n) around each oil droplet is 55. When E = 1.2 V/nm and n = 55, the coalescence time of oil droplets reaches the minimum value of 2.425 ns. The migration rate of oil droplet far from the anode is greater than that of oil droplet near the anode, which is due to the larger combined forces on the former. The results reveal the microscopic mechanism of oil droplet migration and coalescence under the coupling effect of DC electric field and anionic surfactant, which could provide theoretical guidance for the improvement of oily wastewater purification process.

Direct current electric field regulates endothelial permeability under physiologically relevant fluid forces in a microfluidic vessel bifurcation model.

Previous in vitro studies have reported on the use of direct current electric fields (DC-EFs) to regulate vascular endothelial permeability, which is important for tissue regeneration and wound healing. However, these studies have primarily used static 2D culture models that lack the fluid mechanical forces associated with blood flow experienced by endothelial cells (ECs) in vivo. Hence, the effect of DC-EF on ECs under physiologically relevant fluid forces is yet to be systematically evaluated. Using a 3D microfluidic model of a bifurcating vessel, we report the role of DC-EF on regulating endothelial permeability when co-applied with physiologically relevant fluid forces that arise at the vessel bifurcation. The application of a 70 V m-1 DC-EF simultaneously with 1 μL min-1 low perfusion rate (generating 3.8 dyn cm-2 stagnation pressure at the bifurcation point and 0.3 dyn cm-2 laminar shear stress in the branched vessel) increased the endothelial permeability 7-fold compared to the static control condition (i.e., without flow and DC-EF). When the perfusion rate was increased to 10 μL min-1 (generating 38 dyn cm-2 stagnation pressure at the bifurcation point and 3 dyn cm-2 laminar shear stress in the branched vessel) while maintaining the same electrical stimulation, a 4-fold increase in endothelial permeability compared to the static control was observed. The lower increase in endothelial permeability for the higher fluid forces but the same DC-EF suggests a competing role between fluid forces and the applied DC-EF. Moreover, the observed increase in endothelial permeability due to combined DC-EF and flow was transient and dependent on the Akt signalling pathway. Collectively, these findings provide significant new insights into how the endothelium serves as an electro-mechanical interface for regulating vessel permeability.

Electrokinetic effects on the interaction of phenanthrene with geo-sorbents.

Interactions with solid matrices control the persistence and (bio-)degradability of hydrophobic organic chemicals (HOC). Approaches influencing the rate or extent of HOC interactions with matrices are thus longed for. When a direct current (DC) electric field is applied to a matrix immersed in an ionic solution, it invokes transport processes including electromigration, electrophoresis, and electroosmotic flow (EOF). EOF is the surface charge-induced movement of pore fluids. It has the potential to mobilize uncharged organic contaminants and, hence, to influence their interactions with sorbing geo-matrices (i.e. geo-sorbents). Here, we assessed the effects of weak DC electric fields on sorption and desorption of phenanthrene (PHE) in various mineral and carbonaceous geo-sorbents. We found that DC fields significantly changed the rates and extent of PHE sorption and desorption as compared to DC-free controls. A distinct correlation between the Gibbs free energy change (ΔG°) and electrokinetic effects such as the EOF velocity was observed; in case of mineral sorbents EOF limited (or even inhibited) PHE sorption and increased its desorption. In strongly sorbing carbonaceous geo-sorbents, however, EOF significantly increased the rates of PHE sorption and reduced PHE desorption by > 99% for both activated charcoal and exfoliated graphite. Based on our findings, an approach linking ΔG° and EOF velocity was developed to estimate DC-induced PHE sorption and desorption benefits on mineral and carbonaceous sorbents. We conclude that such kinetic regulation gives rise to future technical applications that may allow modulating sorption processes e.g. in response to fluctuating sorbate concentrations in contaminated water streams.

The Suppression of transformation of γ-FeOOH to α-FeOOH accelerating the steel corrosion in simulated industrial atmospheric environment with a DC electric field interference

ABSTRACTThe initial corrosion of steels exposed to the simulated industrial atmospheric environment with a direct current (DC) electric field for 30 days was investigated using weight loss, electrochemical and characterisation methods. The results show that the steel weight loss increased with the increase in DC electric field intensity. The steels exposed to the DC electric field interference exhibited a higher corrosion rate than the blank samples during the exposure. The microstructural studies reveal that the existence of the DC electric field favours the growth of the γ-FeOOH, while suppresses the transformation of γ-FeOOH into α-FeOOH during the 30 days’ exposure, as a result of decreasing the protective ability and stable property of the rust layer. The amount of porous γ-FeOOH enhances the transmission of oxygen and conductivity of the whole rust layer. All these induce an accelerated effect of DC electric field on the initial steel corrosion in simulated industrial environment.

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

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

Effect of direct-current electric field on the growth ofsubmerged macrophyte <i>Vallisneria natans</i>

沉水植物对维持湖泊生态系统平衡有重要作用，广泛应用在水体和沉积物污染修复领域.利用电场强化沉水植物修复过程是一种新的植物修复强化方法.本文研究了不同电压强度作用下沉水植物苦草的生长和生理响应，以期为应用电场强化沉水植物修复过程提供依据.结果表明：0.2～1.0 V电压可以促进苦草生长，而1.5～3.0 V电压则会抑制其生长.其中，0.5 V电压对苦草生长的促进效果最明显，生物量、平均株高、平均叶长、根尖数、新芽数和总叶绿素含量都比对照组显著增加；而3.0 V电压处理组的苦草在实验结束时出现萎蔫和凋亡，与对照组相比，叶绿素含量显著降低，丙二醛含量则极显著增加，表明苦草生长受到严重胁迫.系统上覆水的温度在不同处理组之间没有显著变化，上覆水的pH值在电压为1.0、1.5和3.0 V时显著下降，最终接近中性，上覆水的溶解氧浓度只在3.0 V电压处理组时表现显著下降；沉积物表层5 cm处的氧化还原电位随着电压增大显著下降，最终对苦草的生长形成胁迫.因此，本实验的结论是：0.2～1.0 V电压有助于沉水植物苦草的生长和强化植物修复过程，而1.5～3.0 V电压会破坏苦草组织，同时导致苦草生境变差，不利于沉水植物苦草的生长.;Submerged macrophytes play an important role in maintaining the ecosystem balance of lakes and are used widely in the remediation of contaminated water and sediment. Electric field provides a new technological approach to enhance the restoration of submerged plants. In this study, the growth performance and physiological response of Vallisneria natans under different voltage intensities were investigated. The results show that the voltage ranging from 0.2 to 1.0 V can stimulate the growth of Vallisnera natans, while the voltage ranging from 1.5 to 3.0 V can inhibit the growth. The obvious stimulation was observed under the voltage of 0.5 V. Compared with the control experiment, the obvious increase in the aspects of biomass, average stem length, average leaf length, the number of root tips, the number of buds and the content of total chlorophyll were observed. The plants grew worst under the voltage of 3.0 V, and some of them ended up wilting even death. The content of total chlorophyll in their leaves strikingly decreased but the content of MDA markedly increased, which showed the plants suffered serious stress. The temperature of overlying water did not change obviously among different voltages. The pH of overlying water dropped remarkably under the voltage of 1.0, 1.5 and 3.0 V, close to neutral. The content of dissolved oxygen decreased markedly under the voltage of 3.0 V. The redox potential of 5 cm under the sediment surface decreased sharply when the voltage was raised, and finally inhibited the growth of Vallisnera natans. Thus, these findings show that the voltage ranging from 0.2 to 1.0 V will contribute to the growth of Vallisnera natans and enhance the restoration of plants, while the voltage ranging from 1.5 to 3.0 V will damage the tissues of Vallisnera natans, resulting in worsening the living condition and inhabiting the growth of Vallisnera natans.

Effect of Direct-Current Electric Field on Enzymatic Activity and the Concentration of Laccase

This work investigates the effect of direct-current electric field on the extracellular enzymatic activity, concentration and other experimental parameters of laccase from Trametes versicolor. The results showed that laccase could significantly contribute to the change of pH at the end of graphite electrode. In addition, it increased the electrical conductivity of the water. In the experiment, the optimum pH and catalytic pH range for laccase activity were 3.0 and pH 2.5-4.0. The application of 6V direct current showed significant effects on the laccase enzyme activity. The activity of laccase was enhanced in the anodic region, but at the same time was strongly inhibited at the cathode. The electric charge characteristics of laccase were changed when exposed to electric field, and some laccases molecules moved to the anode, which produced a slight migration phenomenon. This study is the basis of combination of laccase and electrical technology, at the same time, providing a new direction of enhancing laccase activity. Compared to immobilization, using electric field is simple, no chemical additives, and great potential.

Effects of direct current electric-field using ITO plate on breast cancer cell migration.

BackgroundCell migration is an essential activity of the cells in various biological phenomena. The evidence that electrotaxis plays important roles in many physiological phenomena is accumulating. In electrotaxis, cells move with a directional tendency toward the anode or cathode under direct-current electric fields. Indium tin oxide, commonly referred to as ITO has high luminous transmittance, high infrared reflectance, good electrical conductivity, excellent substrate adherence, hardness and chemical inertness and hence, have been widely and intensively studied for many years. Because of these properties of ITO films, the electrotaxis using ITO plate was evaluated.ResultsUnder the 0 V/cm condition, MDA-MB-231 migrated randomly in all directions. When 1 V/cm of dc EF was applied, cells moved toward anode. The y forward migration index was -0.046 ± 0.357 under the 0 V/cm and was 0.273 ± 0.231 under direct-current electric field of 1 V/cm. However, the migration speed of breast cancer cell was not affected by direct-current electric field using ITO plate.ConclusionsIn this study, we designed a new electrotaxis system using an ITO coated glass and observed the migration of MDA-MB-231 on direct current electric-field of the ITO glass.

Soot Reduction Under DC Electric Fields in Counterflow Non-Premixed Laminar Ethylene Flames

The effects of DC electric fields on non-premixed ethylene flames in a counterflow burner were studied experimentally with a focus on the reduction of soot particles. The experiment was conducted by connecting a high voltage terminal and a ground terminal to a lower (fuel) and upper (oxidizer) nozzle, respectively. We applied direct current (DC) potentials in a range of -5 kV < Vdc < 5 kV. Uniform electric fields were then generated in the gap between the two nozzles. The experimental conditions were selected to cover both soot formation (SF) and soot formation oxidation (SFO) flames. The flames subjected to the negative electric fields moved toward the fuel nozzle because of an ionic wind due to the Lorentz force acting on the positive ions in the flames. In addition, the yellow luminosity significantly decreased, indicating changes in the sooting characteristics. To analyze the sooting characteristics under the electric fields, planar laser induced incandescence (PLII) and fluorescence (PLIF) techniques were used to visualize the soot, polycyclic aromatic hydrocarbons (PAHs), and OH radicals. The sooting limits in terms of the fuel and oxygen mole fractions were measured. No substantial soot formation due to the effects of the DC electric fields for the tested range of voltages and reactant mole fractions could be identified. The detailed flame behaviors and sooting characteristics under the DC electric fields are discussed.

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

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

The Effect of dcEFs on migration behavior of A549 cells and Integrin beta1 expression.

The effect of direct-current electric fields (dcEFs) on cells attracted extensive attention. Moreover the metastasis and its potential are considered to be related to dcEFs. The aim is to study the effect of dcEFs on migration behavior of A549 cells, Integrin beta1 and its signal pathways. According to exposure to 5 V/cm dcEFs or not and the time of exposure, the A549 cells were divided into 4 groups. Images were taken per 5 min within 2 h to recode the migration of the cells. The data of results were analyzed statistically. Most of A549cells exposed to the dcEFs aligned and elongated perpendicularly to the electric field lines and migrated to the cathode continually during 2 h. On the contrary, cells unexposed to dcEFs showed slightly random movements. Immunofluorescence showed that Integrin beta1 on plasma membrane polarized to the cathode of the dcEFs. Western blot showed that Integrin beta1 downstream signal pathways p-FAK and p-ERK were overexpressed in the dcEFs. A549 cells have a galvanotatic feature of cathodal directed migration while exposed to the dcEFs. The polarization of Integrin beta1 and the promotion of its downstream signal pathways may play an important roles in the galvanotaxis of A549 cells.

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

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

The effect of an external DC electric field on bipolar charged aerosol agglomeration

A direct-current (DC) electric field was exerted in a bench-scale electrostatic precipitator (ESP) to induce the agglomeration of bipolar charged aerosol particles. The test aerosol particles were generated from water with an atomizer and their average diameter was 7.71 μm. A phase doppler anemometer (PDA) was used to measure the size distribution and the number concentration of the particles. Systematic experiments were conducted to investigate the agglomeration efficiency of the system. The percentage decrease in number of sub-micron sized particles was found to be about 10.7%.

Effect of a high DC electric field on plant leaves reflectivity

The effect of a high direct current (DC) electric field viewed as an unfavorable environmental situation on intact plant leaf reflectivity was considered. Five genetic different corn spaces were exposed to a high DC electric field (14.4 KV/m). The reflectivity of the plant leaves at 550 nm and 682 nm was measured after 0, 1, 3, 7, 10, 14, 21, 28, 35 and 42 days. It was observed that the high DC electric field had a strong effect on plant leaves reflectivity. The leaf reflectivity changes nonlinearly with time for all investigated genetic types.

Liquid crystals as the stationary phase in gas chromatography: Adsorption phenomena caused by an electric field applied across the column

An investigation of the direct current electric field effect on capillary column gas chromatography, in which liquid crystals were used as the stationary phase, is described. When the electric field was applied across the column axis, the peak size was reduced, to an extent that depended on the configuration of the solute molecule, the field strength and the stationary phase employed. When the field strength was increased the amount adsorbed also increased. At every injection, the amount of sample adsorbed was constant, i.e. independent of sample size. This phenomenon was successfully exploited in qualitative and quantitative experiments.