Electric Fields

The differentiation and proliferation of neural stem/progenitor cells (NPCs) depend on various in vivo environmental factors or cues, which may include an endogenous electrical field (EF), as observed during nervous system development and repair. In this study, we investigate the morphologic, phenotypic, and mitotic alterations of adult hippocampal NPCs that occur when exposed to two EFs of estimated endogenous strengths. NPCs treated with a 437 mV/mm direct current (DC) EF aligned perpendicularly to the EF vector and had a greater tendency to differentiate into neurons, but not into oligodendrocytes or astrocytes, compared to controls. Furthermore, NPC process growth was promoted perpendicularly and inhibited anodally in the 437 mV/mm DC EF. Yet fewer cells were observed in the DC EF, which in part was due to a decrease in cell viability. The other EF applied was a 46 mV/mm alternating current (AC) EF. However, the 46 mV/mm AC EF showed no major differences in alignment or differentiation, compared to control conditions. For both EF treatments, the percent of mitotic cells during the last 14 h of the experiment were statistically similar to controls. Reported here, to our knowledge, is the first evidence of adult NPC differentiation affected in an EF in vitro. Further investigation and application of EFs on stem cells is warranted to elucidate the utility of EFs to control phenotypic behavior. With progress, the use of EFs may be engineered to control differentiation and target the growth of transplanted cells in a stem cell-based therapy to treat nervous system disorders.

Real-time holographic interferometry and shadowgraph visualization are used to study convection in the fluid between two concentric spheres when two distinct buoyancy forces are applied to the fluid. The heated inner sphere has a constant temperature that is greater than the constant temperature of the outer sphere by ΔT. In addition to the usual gravitational buoyancy from temperature induced density differences, another radial buoyancy is imposed by applying an a.c. voltage difference, ΔV between the inner and outer spheres. The resulting electric field gradient in this spherical capacitor produces a central polarization force. The temperature dependence of the dielectric constant results in the second buoyancy force that is especially large near the inner sphere. The normal buoyancy is always present and, within the parameter range explored in our experiment, always results in a large-scale cell that is axisymmetric about the vertical. We have found that this flow becomes unstabl...

A simulation based comparative study of the polarization hysteresis of the ferroelectric capacitor using various ferroelectric models is presented. A 2-dimensional finite element device-level model was implemented using SILVACO's ATLAS device simulator to generate the polarization hysteresis characteristics for Au/Poly(vinylidene fluoride-trifluoroethylene)/Au metal-insulator-metal (MIM) device. Landau free energy expression for electric field in terms of polarization is also implemented in the MATLAB to produce the polarization hysteresis curve of polycrystalline ferroelectrics. The main drawback of these models was their inability to predict polarization saturation at the same electric field limits for which the experimental device was saturating. A new model for ferroelectric hysteresis based on curve fitting algorithm is derived that forces the polarization to be saturated at desired electric field. The MATLAB simulation of this model and the experimental hysteresis is compared which shows an excellent level of agreement.

the pattern of partial discharge (PD) occurrence at a defect site within a solid dielectric material is influenced by the conditions of the defect site. This is because the defect conditions, mainly its size and location determine the electric field distributions at the defect site which influence the patterns of PD occurrence. A model for a spherical cavity within a homogeneous dielectric material has been developed by using Finite Element Analysis (FEA) software. the model is used to study the influence of different conditions of the cavity on the electric field distribution in the cavity and the PD activity. in addition, experimental measurements of PD in spherical cavities of different size within a dielectric material have been undertaken. the obtained results show that PD activity depends on the size of the cavity within the dielectric material. © 2009 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5252384

High voltage cable terminations are widely used in power system networks. A proper design of cable termination is essential in reducing the electric field distribution around the end of high voltage cable. However, if there are defects exist at cable termination structure, the electric field can be enhanced significantly and can be the source of electrical discharges. Therefore, it is important to understand the effect of defects on the electric field distribution at cable terminations. In this work, a 132 kV XLPE outdoor cable termination has been modelled using finite element analysis (FEA) method. The model has been used to simulate the electric field distribution in the cable termination in the presence of defects. Defects that have been considered are void defect in porcelain, stress cone and fluid, sharp pin on the porcelain surface and delamination defect between the insulator and the stress cone. The effect of different void location, material dielectric constant and porcelain radius on the electric field magnitude at cable termination have also been investigated. From the results obtained in this work, a better understanding of the electric field distribution at the cable termination with defects can be attained. © 2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6416254

Capacitive power transfer (CPT) is one of the technologies in the field of wireless power transfer (WPT). A CPT
system is much similar to an inductive power transfer (IPT) system. The CPT technology based on the electric field
coupling has addressed many limitations of an IPT technology, such as low electromagnetic interference (EMI), low
eddy current losses, and ability to transfer power through the metal barriers. Firstly, the CPT systems were utilized
for low power transfer applications through small air-gaps, because the development of unsafe voltages across the
conductive plates, However, the utilizing of new compensation circuit topologies have enabled the systems that
use this technology to be utilized for small, medium and long air-gaps applications. Currently, the CPT technology
can be used in many applications, such as charging mobile phones, laptop, and electric vehicles (EVs) batteries.
This paper presents a comprehensive review of the current patterns and trends of the CPT technology usage in a
wireless battery charging. The principal of operation, capacitive coupler structures, equivalent circuits modelling,
plates configurations, resonance circuit topologies, challenges and limitations are actively described in this paper.
A hybrid wireless power transfer (HWPT) technology which is a combination of IPT and CPT technologies is also
presented.

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of ...

This paper reviews the current understanding of electrocoalescence of water droplets in oil, highlighting particularly the mechanisms proposed for droplet–droplet and droplet–interface coalescence under the influence of an applied electric field, as well as various factors influencing the ...

1. Dos pequeñas esferas cada una de 1 gramo de masa están suspendidas por cuerdas ligeras de 8 de longitud. Un campo eléctrico uniforme se aplica en la dirección horizontal, sobre las esferas las cuales poseen cargas de-70 y +70. Determine la intensidad de campo eléctrico para que las dos esferas se mantengan en equilibrio cuando = 10°. 2. En los vértices de un cuadrado, cuyo lado es 2 , se encuentran cuatro cargas puntuales, con cargas + y-, como se muestra en la figura (a). Determine el vector campo eléctrico y su intensidad, en un punto que está a la distancia z y se sitúa simétricamente respecto a los vértices del mismo, como lo indica la figura (b). 3. Una distribución lineal de carga positiva tiene la forma de un semicírculo de radio R, como se muestra en la figura. La carga total sobre el semicírculo es Q, con densidad de carga lineal = cos. Determine el campo eléctrico en el centro del semicírculo 4. Un disco de radio R uniformemente cargado con una carga total Q se encuentra en el plano xy, centrado en el origen de coordenada como se ve en la figura. Determine el campo eléctrico en el punto P, a lo largo del eje z y que pasa a través del centro del disco perpendicular al plano. Discutir el caso límite cuando R >> z. Dos barras de longitudes iguales = 1 , transportan densidades de carga uniformes 1 = 25 μ y 2 = 30 , respectivamente, y se encuentran ubicadas como lo indica la figura. Encuentre el campo eléctrico en el origen del sistema coordenado.-+ +-(a) (b)

A simple design to compute accurate resonant frequencies and the electric fields of rectangular microstrip antennas using artificial neural networks (ANN) is proposed. The ANN is developed to calculate the frequency and antenna's field. ANN is designed using multilayer perceptron networks (MLP). The results that were obtained accord the trained and tested data of ANN models. As a result, the ANN model is presented as a substitutional method to the detailed electromagnetic design of rectangular microstrip antenna.

This report describes the results of a theoretical investigation into the nonlinear optical response of granular composites. In particular, we have investigated the degree to which the cubic nonlinear response can be enhanced in such composites, relative to the same response in pure materials. Cubic nonlinear response is potentially of great practical importance in developing novel materials with a strongly intensity-dependent transmission coefficient, index of refraction, etc. We find that there are many types of composite geometries which give rise to such strong enhancements. These include composites near the percolation threshold, composites in which one of the components is arranged in the form of a fractal cluster, and nonlinear coatings (such as dyes) adsorbed onto the surface of particles which have a resonant optical response at an appropriate frequency. We have carried out this investigation using both analytical approximations and a variety of approximate numerical techniques, including large-scale computer simulations. Finally, we briefly describe some work in progress, in which a composite composed of materials with a purely guardratic response can exhibit an enhanced curbic response.