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The influence of a surface electric charge on the character and properties of wave motion along the free surface of a viscous homogeneous fluid is investigated by analytical asymptotic methods. Expressions describing the dispersion relations of the wave-motion components are obtained. The phase and group velocities of the structures forming wave motion are determined. [ABSTRACT FROM AUTHOR]

The influence of a surface electric charge on the character and properties of wave motion along the free surface of a viscous homogeneous fluid is investigated by analytical asymptotic methods. Expressions describing the dispersion relations of the wave-motion components are obtained. The phase and group velocities of the structures forming wave motion are determined. [ABSTRACT FROM AUTHOR]

Cancer is a public health problem throughout the world as incidence and mortality rates are increasing year after year. Although conventional therapies such as chemotherapy and radiation show favorable results against this disease, the side effects it causes throughout the body reduce the quality of life of the patient. Therefore, nanomedicine offers us new promising tools to attack cancer through the innovation of nanodrugs, to increase the therapeutic response, reduce dosage, and without generating as many side effects as conventional therapies. For the design of nanodrugs, it is essential to know the biological barriers of the organism and the cancer barriers faced by nanodrugs, such as cell membrane openings, the solubility of the drugs to be transported, and surface electric charge and the protein corona. Due to the aforementioned, the purpose of this review article is to delve into the long journey that nanodrugs undertake from the moment they are administered until they are internalized in tumor cells, taking into account some of the biological and molecular challenges that they defy to reach to its final destination, to observe a desired therapeutic response in the cancer patient. [ABSTRACT FROM AUTHOR]

Within the framework of the thermodynamic theory of equilibrium two-component adsorption from a liquid on a flat solid surface, taking into account its deformation and the presence of an electric charge on it, two equations of the isotherm of such adsorption are derived at small deformations containing two unknown functions independent of the electric potential of the solid phase. It is shown that the problem of finding the conditions for the single-phase nature of the adsorption layer is reduced to the same problem, but posed for an undeformed surface. [ABSTRACT FROM AUTHOR]

Herein, the surface charge characteristics of a tri‐post insulator in a ± 500 kV direct current gas‐insulated transmission lines (DC‐GIL) filled with SF6 are thoroughly studied. The influences of volume and surface conductivity of the insulator on the surface charge and consequent electric field distribution are discussed. An improved method is introduced to obtain the distribution of surface charge with considerable accuracy and efficiency for the calculation. It is found that with increasing the volume conductivity, the dominative conduction mechanism changes from surface conduction to bulk conduction, while the inverse variation appears with increasing the surface conductivity. During the variation of electric conductivity, obvious effect of surface charge accumulation is found on the electric field distribution involving the variation of peak electric field strength and its location. Besides, high charge density usually appears along with low peak field strength during this variation. It can be concluded that the surface charge accumulation should be paid special attention when analysing the insulation characteristics of tri‐post insulators. The variation of volume and surface electric conductivity should be thoroughly considered. [ABSTRACT FROM AUTHOR]

The gas–solid interface of high-voltage insulating equipment is a weaker part of insulating equipment insulation, and preventing the occurrence of discharge along the surface of insulating equipment is a critical problem for high-voltage insulation. This article investigates the discharge characteristics and charge movement characteristics of insulating media under an airflow environment. The surface discharge characteristics of the insulating medium in the airflow environment were obtained by using a high-velocity airflow test platform, and the surface discharge voltage characteristics, discharge path characteristics, and force conditions of the discharge process were analyzed. The surface charge motion characteristics of the insulating medium in the high-velocity airflow environment were also tested, and the distribution characteristics, dissipation characteristics and conduction mechanism of the surface charge of the insulating medium in the high-velocity airflow environment were revealed. The research results showed that: the discharge voltage along the insulating medium surface gradually increases with the increasing velocity of airflow; the discharge path along the surface of the insulating medium gradually shifts backward under the action of airflow; under the action of airflow, the charge on the insulating medium surface is blown away, thus reducing the charge concentration on the insulating medium surface; the trap level center of the insulating medium gradually decreases under the action of airflow, which provides the conditions for the charge blowing effect on the insulating medium surface. This investigation supplies the theory support for the protection of insulation equipment in an airflow environment and technical guidance for the insulation design of insulating equipment in an airflow environment to ensure the secure and steady running of insulating equipment in high-speed trains and high-voltage transmission lines. [ABSTRACT FROM AUTHOR]

The dynamics of ionization waves (IWs) in atmospheric pressure discharges is fundamentally determined by the electric polarity (positive or negative) at which they are generated and by the presence of memory effects, i.e. leftover charges and reactive species that influence subsequent IWs. This work examines and compares positive and negative IWs in pulsed plasma jets (1 μ s on-time), showing the difference in their nature and the different resulting interaction with a dielectric BSO target. For the first time, it is shown that a surface charging memory effect is produced, i.e. that a significant amount of surface charges and electric field remain in the target in between discharge pulses (200 μ s off-time). This memory effect directly impacts IW dynamics and is especially important when using negative electric polarity. The results suggest that the remainder of surface charges is due to the lack of charged particles in the plasma near the target, which avoids a full neutralization of the target. This demonstration and the quantification of the memory effect are possible for the first time by using an unique approach, assessing the electric field inside a dielectric material through the combination of an advanced experimental technique called Mueller polarimetry and state-of-the-art numerical simulations. [ABSTRACT FROM AUTHOR]

Surface charge accumulation subjected to direct current (DC) voltages poses hazardous effects on the surface insulation performance of the involved insulators. It is of great significance to investigate surface charge regulation methods applicable to industrialized spacers. In this study, we propose a graded conductivity coating method, with excellent adhesion strength consisting of TiO2/epoxy composites with different TiO2 contents, realizing a gradually decreased conductivity distribution on the spacer surface from high voltage (HV) to grounded (GND) electrodes. Surface charging behavior and flashover performance under DC voltages on this kind of spacer is obtained. A simulation model for surface charge computation is constructed for the sake of better understanding the surface charging mechanism on spacers with graded conductivity coating. The results indicate that the randomly distributed surface charges are obviously suppressed by this coating manner and the ring-shaped homo-charges adjacent to HV and GND electrode dominate surface charge patterns. The main cause lies in the fact that surface charge dominant mechanism changes from the bulk conductivity model to the surface conductivity model, where surface leakage current becomes the primary sources of surface charges, with the increase in coating conductivity. DC flashover performance is enhanced as well due to the improvement of surface charge accumulation and electric field distribution. This study supplies an important reference for designing DC gas insulated transmission line spacers of high reliability as well as inspires novel ideas in surface charge regulation. [ABSTRACT FROM AUTHOR]

In honor of Igor Dzyaloshinskii on his 90th birthday, we revisit his pioneering work on the linear magnetoelectric effect in light of the modern theory of ferroelectric polarization. We show that the surface magnetic dipole moment associated with magnetoelectric materials is analogous to the bound surface charge in ferroelectrics, in that it can be conveniently described in terms of a bulk magnetoelectric multipolization that is analogous to the ferroelectric polarization. We define the intrinsic surface magnetization to be this surface magnetic dipole moment per unit area, and provide a convenient recipe for extracting it for any surface plane, from knowledge of the bulk magnetic order. We demonstrate the procedure for the prototypical magnetoelectric material, Cr2O3, in which Dzyaloshinskii first identified the linear magnetoelectric effect, and compare the value of the intrinsic surface magnetization to recent experimental measurements. Finally, we argue that non-magnetoelectric antiferromagnets whose multipolization lattices do not contain zero should have an intrinsic surface magnetization, in the same way that non-polar insulators whose polarization lattices do not contain zero have an intrinsic surface charge. [ABSTRACT FROM AUTHOR]

The accumulation of surface charges is a crucial challenge, especially for HVDC components. Accumulated surface charges can change the electric field distribution and generate weak points, especially in case of superimposed transient voltages and, therefore lower the performance e.g. of insulators. Hence, an accurate measurement of the surface potential and so the surface charges is necessary to optimize these components. Commonly, the surface potential is measured with an electrostatic voltmeter. In this study a procedure for determining the spatial impulse response of a compensating electrostatic voltmeter depending on only the surface to probe distance is presented. Based on the performed measurements a mathematical model is developed to describe the capacitive influence and significance of the local surface potential on the measurement result. The actual measurement value is a weighted and averaged value given by the actual position and its surrounding, which is also confirmed by numerical simulations. The performed procedure enables high accuracy of the measurement of surface potentials and so of surface charges using different types of electrostatic voltmeters and shows the limitation of the measurement procedure. This knowledge increases the possibility to design optimized components for HVDC systems. [ABSTRACT FROM AUTHOR]

When designing spacecraft with electric propulsion (EP) devices, it is important to assess spacecraft integration to ensure that the important components are not subject to significant sputtering by high-energy ions. In addition to the EP device and its plume, surface charging of spacecraft has to be modeled properly, as surface potential can directly affect the sputtering rate. Three surface charging models are incorporated into the spacecraft module of the numerical simulation framework–Thermophysics Universal Research Framework (TURF), and these include: 1) dielectric; 2) conductive; and 3) charge propagation models. The charge propagation model has been upgraded to solve the surface charge distribution implicitly, allowing a wide range of electrical conductivity values without causing the simulation to become unstable. Each of the charging models is verified against a simple problem where an analytical solution can be determined. Then, the coupling of the surface charging model and a hybrid particle/fluid model is tested in a more complex problem, where the floating potential on a sphere immersed in plasma is to be obtained. Finally, the surface charging model in an EP plume simulation is demonstrated. These problems are multiscale in that the charging model has to resolve an electron timescale (i.e., plasma oscillation) while the particle time step has to be orders of magnitude larger than the electron timescale in order to maintain a long enough sampling window for the ion current to effectively reduce the statistical noise. Therefore, two separate time steps are introduced for a stable convergence of the coupled models. [ABSTRACT FROM AUTHOR]

Surface charge accumulation on epoxy based nanocomposites under DC stress with and without the presence of a magnetic field was investigated in this work. Two mm-thick sheet samples were prepared by adding 60 nm-Al 2 O 3 particles into epoxy with filler content of 1 to 5 wt%. A pair of finger-shaped electrodes was employed to introduce electric charges onto the sample surface under DC stress of ±5 and ±10 kV. The magnetic field was established by using a pair of permanent magnets, by which a magnetic flux density of 100 and 180 mT was achieved. Surface charge between the electrodes was measured by means of a Kelvin type electrostatic voltmeter, and the influence of nano-filler content and magnetic flux density on charge distribution as well as charge density was estimated. The results indicate that increasing nano-filler content from 0 to 5 wt%, the average charge density increased initially then decreased. The presence of a magnetic field results in a deflection of charge profile as compared with that formed without a magnetic field. The charge density increased as the magnetic flux density increased from 0 to 180 mT. It is suggested that the charge trajectory close to high voltage electrode varies by the combined electric-magnetic force, by which electric field recovery in such a region is facilitated thus more charges are encouraged to accumulate on the surface. [ABSTRACT FROM AUTHOR]

Surface charge accumulation of polymer insulating materials is harmful to the safe operation of electrical equipment, especially under DC electric field excitation. In order to ensure the safety and stable operation of HVDC power system such as Gas-insulated transmission line, it is necessary to understand the influence of the surface charge on the flashover and improve the surface charge dynamic characteristics. In this paper, Epoxy resin (EP) is deposited by SiOx thin films with different plasma treatment conditions. The flashover voltages are measured with and without surface charges. The results show that the flashover occurs at lower voltage due to the accumulated charges on the EP surface. In particular, the surface charge with the same polarity of flashover discharge can reduce the surface flashover voltage significantly. Moreover, the charge decay rate is increased up to 90% by plasma treatment of 3 min, corresponding flashover voltage is increased. In addition, the flashover voltages of samples during the surface charge dissipation are obtained. Both static impact index I and dynamic impact index S are introduced to estimate effect of surface charge on dielectric surface flashover. [ABSTRACT FROM AUTHOR]

• Preparation of charge impregnated surface using triboelectrification is studied. • Charge density profile is estimated from drop impact on pillared surface. • Drop translation over surface with charge density gradient has been established. • Higher charge gradient accelerates drop transport. • Velocity rises faster in case of higher surface contact angle. Though different methodologies like thermal and magnetic fields have been tried to control a droplet's mobility in biochemical and medical applications, charge imprinted super-amphiphobic surface is the recent and promising development in which droplets can be transported through any predefined path over the surface. Such surfaces are electrified by impacting water droplets from varying release heights through triboelectrification. Impacting droplets on pillared surface dynamics of the same have been analyzed to understand the nature of electrostatic charge distribution generated. Further to this, droplet actuation on such surfaces with surface charge gradient has been simulated. Charge separation inside the liquid droplet and charge accumulation near the interface has been visualized to understand the phenomenon. Asymmetry in droplet shape and charge distribution has been analyzed as the reason behind the droplet actuation. The effect of different charge density gradients and surface wettability over droplet mobility has also been studied. [ABSTRACT FROM AUTHOR]

Surface charges are ubiquitous in nature and their existence is in many forms. Due to an unbalanced electrical force induced by surface charge gradient, the droplet self-propels towards the direction of larger surface charge density. In 2008, Liu and Bard [11] reported the surface charge on the dielectric material can be used as a redox reagent to drive chemical reaction. [Extracted from the article]

Electrically-insulating samples placed on the grounded sample tray in ionization detectors perturb the electric field within the detector. The resulting alpha particle emissivity of the samples is reduced depending on the magnitude and polarity of the surface voltage. Data are shown for samples with positive and negative surface charge, as well as methods to both measure and eliminate the effects of the surface charge. [ABSTRACT FROM PUBLISHER]

In this paper, a comparison of different techniques for SiC high-voltage devices is performed using numerical simulations. In particular, the method of counter doping (CD) introduced in the junction termination extension (JTE) region to create a multizone termination effect is investigated. Simulation shows that compared with the other edge termination techniques, CD-JTE greatly reduces the sensitivity of breakdown voltage (BV) to JTE doses and surface charges. The multizone CD-JTE with outer rings shows that for a 30- \mu m thick epi-layer, 90% of the theoretical BV is achievable with a wide tolerance of 11\,\times \,10^{\mathrm {12}} /cm ^{2} to the JTE dose and 85% of the theoretical BV with an increased tolerance of 6.19\times 10^\mathrm 12 /cm ^2 to the positive surface charges, both superior to other JTE structures investigated in this paper. [ABSTRACT FROM AUTHOR]

• Interaction energy between tumour cells. • Zeta potential. • Surface free energy. The surface electrical charge of cells is conditioned by the ionic medium in which they are immersed. This charge is specific for each cell type and is especially important in tumour cells because it determines their state of aggregation and their adhesion in the different organs. This study analyses the variations in surface charge of cells when pH, electrolytes, and their concentration are modified. The modification of these factors leads to changes in the surface charge of tumour cells; therefore, their states of aggregation and behaviour can be modified. This may even have a use in the prognosis and treatment of various tumours. Some studies conclude that the activity associated with the glycolysis process is accompanied by a change in the surface charge of cells. Notably, there is a high rate of glycolysis in tumours. Our results show that surface charge of cells strongly depends on nature of ionic medium in which they are found, with the valence of the majority ion being the most important factor. When ionic strength was high, the charge decreased dramatically. On the other hand, charge becomes zero or positive in an acidic pH, while in a basic pH, the negative charge increases. [ABSTRACT FROM AUTHOR]

Polymeric insulating materials exposed to pulse voltage with a nanosecond rise time in pulsed power have drawn increasing attention. Surface charge accumulation and decay on the charged polymers are very important parameters related to discharge. Nanocomposite technology has been used to improve the electrical properties of polymeric insulating materials. Therefore, it must be confirmed whether the nanosecond rise time of pulse voltage on the dynamic behaviour of surface charge on polymeric nanocomposites is different from that without nanoparticles. In this paper, we attempted to clarify the effect of the rise time on the electrical properties of epoxy/TiO2 nanocomposites focusing on surface charge accumulation and decay. Samples were prepared by dispersing nano-scale TiO2 particles into epoxy (EX) by mixing with shear force. Corona charging tests were performed at room temperature with a relative humidity of ~ 40%. The charge distribution was measured by means of an electrostatic voltmeter. The results show that the rise time plays an important role in the accumulating charge as well as the charge decay rate and varies with the concentration of nanoparticles and charge polarity. It is suggested that charge dynamics are dependent upon the rise time. [ABSTRACT FROM AUTHOR]

Most studies on corona-charged nonwoven filters have used grounded electrodes during charging and surface potential measurements but not during filtration experiments. This study was focused on the investigation of a grounded metal grid effect on the filtration efficiency. The results showed that the filtration outcome strongly depends on the filter–grid distance. Moreover, the electric charge was maintained for a considerably long duration when the ground electrode was used, which led to an increase in the filtration efficiency. The efficiency exceeded 90% at a voltage of 10 kV with the grid and was <70% at 30 kV without the grid. • Potential decay and filtration performance of corona charged filters were investigated. • The effect of a grounded metal grid on the filtration efficiency was investigated. • The "filter–grid" distance affects both potential decay and filtration efficiency. • Electric charges are kept longer on the filter surface with the grid electrode. • The filtration performance was significantly improved with the grid electrode. [ABSTRACT FROM AUTHOR]

To clarify the importance of the surface charge for the formation of polyelectrolyte multilayers, layer-by-layer (LbL) assemblies of polydiallyldimethylammonium chloride (pDADMAC) and polystyrenesulfonate (PSS) have been investigated on cellulose films with different carboxylic acid contents (20, 350, 870, and 1200 μmol/g) regenerated from oxidized cellulose. The wet cellulose films were thoroughly characterized prior to multilayer deposition using quantitative nanomechanical mapping (QNM), which showed that the mechanical properties were greatly affected by the degree of oxidation of the cellulose. Atomic force microscopy (AFM) force measurements were used to determine the surface potential of the cellulose films by fitting the force data to the DLVO theory. With the exception of the 1200 μmol/g film, the force measurements showed a second-order polynomial increase in surface potential with increasing degree of oxidation. The low surface potential for the 1200 μmol/g film was attributed to the low degree of regenerationof the cellulose film in aqueous media due to increasing solubility with increasing charge. The multilayer formation was characterized using a quartz crystal microbalance with dissipation (QCM-D) and stagnation-point adsorption reflectometry (SPAR). Extensive deswelling was observed for the charged films when pDADMAC was adsorbed due to the reduced osmotic pressure when ions inside the film were released, and the 1:1 charge compensation showed that all the charges in the films were reached by the pDADMAC. The multilayer formation was not significantly affected by the charge density above 350 μmol/g due to interlayer repulsions, but it was strongly affected by the salt concentration during the layer build-up. [ABSTRACT FROM AUTHOR]