Increase Of Electric Field Intensity Research Articles

Vertical optical antennas integrated with spiral ring gratings for large local electric field enhancement and directional radiation

We propose a device for reproducible achievement of enormous enhancement of local electric field intensities. In each device, a metallic spiral ring grating is employed for efficient excitation of local surface plasmon resonance in the tiny gap of a vertically oriented optical antenna. Radiation from the optical antenna is collimated by the ring grating which facilitates efficient collection. As a numerical example, for a gold nanosphere placed one nanometer above the center of a gold spiral ring grating, our simulations predict an increase in local electric field intensity of up to seven orders of magnitude compared to planewave illumination, and collection efficiencies of up to 68% by an objective with a numerical aperture of 0.7. Single molecule SERS application is discussed.

Effect of external electric field excitation on titanium monoxide

The present paper is devoted to the calculating of transition wavelengths, oscillator strength, Einstein An0 and B0ncoefficients of titanium monoxide molecule from ground state to the first six different excited states by employing the density function theory BLYP and the single substitute configuration interaction approach with basis set 6-311 + + G **. The excited states of titanium monoxide molecule under different external electric fields are also investigated. It is shown that the α HOMO-LUMO gaps become smaller and the electrons of the occupied orbital tend to the virtual orbital as the external electric field intensity increases, and the β HOMO-LOMO gaps become bigger, while the variation in excitation wavelength of high-excited states turns more complicated than that of low-excited states, and the coupling strengths of excited states increase with external electric field increasing.

Effects of energy controllable steep pulses on intracellular calcium concentration and cell membrane potential

Our previous experiments showed that steep pulses could kill tumor cells, but the mechanism is unclear. This study was to probe the effects of different dosages of energy controllable steep pulses (ECSP) on intracellular concentration of dissociative calcium ion ([Ca2+]i) and cell membrane potential. The breast carcinoma MDA-MB-231 cells were divided into control group and five ECSP (different dosages) groups. Ca2+ was labeled by Fluo-3/AM and cell membrane potential was labeled by DiBAC4(3). The mean fluorescence intensity in MDA-MB-231 cells was observed by laser confocal microscopy after ECSP treatment. The changes of calcium concentration and cell membrane potential after ECSP treatment were analyzed. The changes of intracellular [Ca2+]i after ECSP treatment were also observed either with or without Ca2+ outside of the cells. Ca2+ outflow was observed when the cells were treated with lower dosage of pulse in quiet state; the outflow was enhanced with the dosage increase. In real-time kinetic detection, intracellular Ca2+ concentration was increased with the increase of pulse electric field intensity when cells were treated with lower dosages of ECSP. When the voltage was 285 V, frequency was 100 Hz, [Ca2+]i decreased obviously. The intracellular Ca2+ concentration was obviously lower in the cells without outside Ca2+ than in cells with outside Ca2+, but it still increased gradually. Low dosage of ECSP induced the increase of cell membrane potential, indicating the depolarization of cell membrane. With increase of the dosage, cell membrane potential was attenuated, indicating the superpolarization of cell membrane. Lower dosage of ECSP can induce the depolarization of cell membrane and the inflow of outside Ca2+; higher dosage of ECSP can directly destroy the cell membrane and induce the superpolarization of cell membrane, then induce the outflow of intracellular Ca2+ which causes the necrosis of tumor cells.

Enhanced photocurrent efficiency of a carbon nanotube p–n junction electromagnetically coupled to a photonic structure

We present photocurrent power-enhancement calculations of a carbon nanotube p–n junction electromagnetically coupled to a highly efficient photonic structure. Particular attention is paid to a GaAs photonic structure specifically modified to increase the intensity of infrared light onto the nanotube region for effective energy conversion. Using finite-difference time-domain calculations, we compute a significant increase in electric field intensity in the nanotube region which enables an estimation of power efficiency. These results demonstrate the potential of using a photonic structure to couple large-scale infrared sources with carbon nanotubes while still retaining all the unique optoelectronic properties found at the nanoscale.

CHARACTERIZATION OF ELECTRO-RHEOLOGCIAL FLUIDS UNDER HIGH SHEAR RATE IN PARALLEL DUCTS

Electro-rheological (ER) fluid is a smart suspension which can be changed promptly from Newtonian to Bingham plastic material when subjected to a high-intensity electric field. This property of ER fluid makes it possible to be applied in adaptive energy absorbers. As the impact velocity encountered in applications could be very large, it is necessary to characterize the ERF under high shear rate. In this study, a capillary rheo-meter with parallel duct was designed and manufactured which is capable of producing a shear rate as high as 5000(1/s). Two giant ER fluids with mass concentration C = 51% and 44.5% and a commercial density-matched ER fluid with C = 37.5% were characterized. The experimental results show that when the ER fluids are free of electric field (E = 0 kV / mm ), they are Newtonian. However, for the former two ER fluids, the deposition effect is very remarkable and stirring has to be made continuously to keep the suspension stable. With the increase of the electric field intensity, the yield shear stresses of ER fluids increase exponentially but their viscosities do not change much. It is also found that within the parallel duct, the flow of ER fluids exhibits notable fluctuations, whose period increases with the increase of electric field intensity and is independent of the shear rate.

Instability analysis of an inner-driving coaxial jet inside a coaxial electrode for the non-equipotential case

In this paper, the temporal linear stability analysis of a coaxial jet with two coflowing immiscible liquids inside a coaxial electrode is carried out to investigate the non-equipotential case of the inner-driving coaxial electrospray. Accordingly the outer liquid is assumed to be insulating and the inner liquid as the driving medium with finite conductivity. However, the current due to conduction is assumed to be much smaller than that due to convection so that charge is transported mainly by means of convection. In this case, free charge seems to be “frozen” on the interface between two liquids. The analytical dimensionless dispersion relation is derived straightforwardly through theoretical analysis. In order to study the jet instability, the complex frequencies are solved using numerical approach. According to the calculation results, three different unstable modes, i.e. the para-varicose mode, the para-sinuous mode and the transitional mode, are found in the Rayleigh regime. It is also found that the non-dimensional electrostatic force and the Weber number have the similar effects on the unstable modes. In particular, these two parameters both stabilize the para-sinuous mode for relatively long wavelengths and destabilize it for relatively short wavelengths. Moreover, the unstable regions are extended into the wind-induced regime as the electric field intensity or liquid velocity increases, or surface tension decreases. It is predicted that the non-equipotential case closes to the equipotential one when the inner-driving liquid has sufficiently large electrical permittivity. Conversely, if the permittivity of the inner liquid is considerably small, the non-equipotential case is much less unstable than the equipotential case. In addition, the permittivity of the outer insulating liquid shows an unexplainable non-monotonical effect on the jet instability. As a summary, a general dispersion relation expression is given for all the four involved models, according to equipotential and non-equipotential, as well as inner and outer driving. And the essence of the effect of the electric field on the jet instability is outlined for these cases.

Enhanced Half-Metallicity in Edge-Oxidized Zigzag Graphene Nanoribbons

We present a comprehensive theoretical study of the electronic properties and relative stabilities of edge-oxidized zigzag graphene nanoribbons. The oxidation schemes considered include hydroxyl, lactone, ketone, and ether groups. Using screened exchange density functional theory, we show that these oxidized ribbons are more stable than hydrogen-terminated nanoribbons except for the case of the etheric groups. The stable oxidized configurations maintain a spin-polarized ground state with antiferromagnetic ordering localized at the edges, similar to the fully hydrogenated counterparts. More important, edge oxidation is found to lower the onset electric field required to induce half-metallic behavior and extend the overall field range at which the systems remain half-metallic. Once the half-metallic state is reached, further increase of the external electric field intensity produces a rapid decrease in the spin magnetization up to a point where the magnetization is quenched completely. Finally, we find that oxygen-containing edge groups have a minor effect on the energy difference between the antiferromagnetic ground state and the above-lying ferromagnetic state.

Gibbs free energy calculation of Al–Cu–Li alloy with the effect of electric field from electron level

Based on Thomas–Fermi model, the calculation method of Gibbs free energy for atom cluster with electric field had been found. The change trend of Gibbs free energy of Al–Cu–Li alloy under the effect of electric field had been calculated systemically and quantitatively. And following results had been given: near the zero electric field and the side of positive electric field, the Gibbs free energy of Cu 4LiAl 7 compound at aging temperature 460 K was higher than that of Gibbs free energy at solid solution temperature 725 K, but once the negative electric field increased to a certain degree there would be an opposite result. The Gibbs free energy of binary solid solution was increased with the addition of third element lithium or copper, and with the increase of electric field intensity the Gibbs free energy margin of two kinds of solid solution became bigger.

PHASE TRANSITIONS OF POLY(VINYLIDENE FLUORIDE) UNDER ELECTRIC FIELDS

ABSTRACT The electric poling behavior of poly(vinylidene fluoride) (PVDF) films was investigated by Fourier transition infrared spectrum (FT-IR), ferroelectric and piezoelectric effect test in this paper. PVDF undergoes a structural evolution under electric fields over a wide range of electric fields from 0 to 180 MV/m. The phase transitions were characterized as α phase to β phase via middle δ phase with increase of poled electric field intensity. According to ferroelectric hysteresis performance of PVDF films, it could be found that the trend of piezoelectric coefficient d33 which increased with poled electric field intensity was coincident with Boltzmann distributing function. And the results indicated that the range of the poled electric field intensity which brought the maximal remnant polarization was 100–125 MV/m, the maximal piezoelectric coefficient d33 for β phase of PVDF films was achieved 28 pC/N.

High-Intensity Pulsed Electric Field Variables Affecting Staphylococcus aureus Inoculated in Milk

Staphylococcus aureus is an important milk-related pathogen that is inactivated by high-intensity pulsed electric fields (HIPEF). In this study, inactivation of Staph. aureus suspended in milk by HIPEF was studied using a response surface methodology, in which electric field intensity, pulse number, pulse width, pulse polarity, and the fat content of milk were the controlled variables. It was found that the fat content of milk did not significantly affect the microbial inactivation of Staph. aureus. A maximum value of 4.5 log reductions was obtained by applying 150 bipolar pulses of 8μs each at 35 kV/cm. Bipolar pulses were more effective than those applied in the monopolar mode. An increase in electric field intensity, pulse number, or pulse width resulted in a drop in the survival fraction of Staph. aureus. Pulse widths close to 6.7μs lead to greater microbial death with a minimum number of applied pulses. At a constant treatment time, a greater number of shorter pulses achieved better inactivation than those treatments performed at a lower number of longer pulses. The combined action of pulse number and electric field intensity followed a similar pattern, indicating that the same fraction of microbial death can be reached with different combinations of the variables. The behavior and relationship among the electrical variables suggest that the energy input of HIPEF processing might be optimized without decreasing the microbial death.

Linearly polarized terahertz radiation in uniaxially deformed Ge(Ga) upon the electric breakdown of an impurity

The polarization spectra of spontaneous terahertz radiation in uniaxially deformed germanium have been measured upon the electric breakdown of shallow acceptors. Lines with various degrees of polarization with respect to the compression axis have been observed in the radiation spectrum. These lines are associated with the optical transitions of holes between the excited and ground states of the acceptor, as well as with the transitions of holes from the valence band to the ground state of the impurity. At a pressure of about 3 ± 0.3 kbar in the [111] direction near the impurity breakdown, the linear polarization degree reaches ∼80–90% in the main lines of terahertz radiation. As the electric field intensity increases, the depolarization of radiation is observed, which is caused by the heating of nonequilibrium holes by the electric field.

Dielectric and Ferroelectric Properties of [(CH3)2NH2]3CuCl5 Single Crystal

The detailed studies of dielectric properties of [(CH3)2NH2]3CuCl5 single crystal were performed. Distinct anomalies of permittivity along three crystallographic direction were observed at 277.5 K and 252.7 K on cooling. The observed permittivity behaviour evidenced the first order character of both phase transitions. The hysteresis loops characteristic of a ferroelectric phase were observed in the range of temperature 277.5–252.7 K. An appearance and disappearance of spontaneous polarization confirms the first order phase transitions in this crystal. The permittivity measured along the ferroelectric a-axis under influence of external electric field in paraelectric phase showed clearly a nonlinear increase with increase of electric field intensity applied to the crystalline sample.

Influence of Electric Fields on the Fracture Behavior of Ferroelectric Ceramics under Combined Electromechanical Loading

In this paper, fracture behavior of ferroelectric ceramics under combined electromechanical loading was investigated using moiré interferometry. It is found that the influence of electric field on fracture toughness is not very larger in the case that the directions of the poling, electric field and crack extension are perpendicular to each other. When the poling direction is parallel to the crack extension direction and both are perpendicular to the electric field direction, the normal strain measured reduced faster than that calculated by FEM with and without electrical loading as the distance away from the crack tip increases. Fracture toughness decreases obviously as the electric-field intensity increases.

Influence of electric field intensity on the copper catalyst-mediated crystallization of amorphous silicon

The effects of electric field intensity on the crystallization of amorphous silicon (a-Si) using the field-aided lateral crystallization (FALC) process have been studied in the range of 0–180 V∕cm. The crystallization velocity increases as the electric field intensity increases. Moreover, the better quality of polycrystalline silicon resulted in the films that crystallized faster. The activation energy of the metal-induced lateral crystallization process calculated from the Arrhenius plot is 1.79 eV (±0.03 eV), whereas that of the FALC process is 1.65 eV (±0.04 eV) regardless of the electric field intensities. It is also shown that the electric field affects both the enhancement of the preexponential factor in the Arrhenius equation and the decrease in the energy barrier height for the crystallization. In particular, the effect is almost the same in the temperature range of 400–500 °C. The increase in the crystallization velocity is attributed to the field-enhanced diffusion of copper ions in the Cu3Si crystallization mediator and the amorphous Si.

Study on fracture behavior of ferroelectric ceramics under combined electromechanical loading by using a moiré interferometry technique

This paper discusses an in situ observation of fracture behavior around a crack tip in ferroelectric ceramics under combined electromechanical loading by use of a moire interferometry technique. The deformation field induced by the electric field and the stress concentration near the crack tip in three-points bending experiments was measured. By analysis of the moire images it is found that under a constant mechanical load, the electric field almost has no effect on the crack extension in the case that the directions of the poling, electric field and crack extension are perpendicular to each other. When the poling direction is parallel to the crack extension direction and perpendicular to the electric field, the strain decreases faster than that calculated by FEM with and without electrical loading as one goes away from the crack tip. In addition, as the electric field intensity increases, the strain near the crack tip increases, and the strain concentration becomes more significant.

Change of ionospheric plasma parameters under the influence of electric field which has lithospheric origin and due to radon emanation

A mechanism of electric-photochemistry channel of seismo-ionospheric coupling is investigated. In particular, the penetration of electric field from the lithospheric source into the ionosphere and effect of this field on the photochemistry coefficient and ionospheric parameters in the altitude range in the lower D region are modeled numerically. It is shown that observable effects can be expected when lithospheric electric source strength is of the order of 1.5 kV/m. In this case, variations of electron temperature and electron concentration will be of the order of (40–60)% and (25–40)% respectively at the range of altitudes 60–70 km. An increase of near-ground conductivity (caused by increasing humidity and/or radon emanation) by ∼2.3 times can cause increase of electric field intensity by ∼2 times in altitude ranges of 60–70 km. Corresponding relative change of T e increases up to ∼50%, as compared with the case of lower near-ground temperature. Spatial shapes of relative distribution of electron temperature and the ratio of negative ion–electron concentration map the spatial shape of the lithospheric electric field distribution. Spatial shapes of electron concentration distribution and electric field strength distribution of the lithospheric source are “opposite” to each other.

Fluorescence imaging in the millisecond time range of membrane electropermeabilisation of single cells using a rapid ultra-low-light intensifying detection system

A fast and sensitive fluorescence image acquisition system is described which uses an ultra-low-light intensifying camera able to acquire digitised fluorescence images with a time resolution of 3.33 ms/image. Two modes of recording were employed. The synchronisation mode allowed acquisition of six successive 3.33 ms-images synchronised with an external trigger, while the memorisation mode allowed acquisition of twelve successive 3.33 ms images starting after a 20 ms-time lag from the external trigger. Interaction of ethidium bromide (EB) with the membrane of electropermeabilised living cells was studied using this imaging system. We observed enhanced fluorescence of the dye when associated with electropermeabilised cells. Using single cells, 3.33 ms-images of the fluorescence interaction patterns of ethidium bromide showed well-defined membrane labelling. The enhanced fluorescence patterns were shown to represent the electropermeabilised area of the cell membrane. The average level of fluorescence associated with the labelled part of the cell membrane increased linearly during and immediately (less than 7 ms) after the electropermeabilisation pulse. Steady-state EB interaction with the membrane was achieved in a maximum 20 ms-time lag after electropermeabilisation. The membrane labelled parts were always observed in the cell regions facing the electrodes. They were present only when the electric field strength was higher than a threshold value which was different for the two cell sides. An increase in electric field intensity led to an increase in the dimensions of the labelled cell region.

Measurement and theoretical investigation of arc sensor sensitivity in dynamic state during gas metal arc welding

This paper shows the experimental and the theoretically predicted results of the sensitivity characteristics of the arc sensor in a dynamic state during gas metal arc welding. First, a mathematical model of the sensor for theoretical prediction was introduced, and then the rationality of the model was confirmed by a series of corresponding experiments. Finally, simulation analyses were made in order to clarify how the welding system and welding conditions affect the sensitivity characteristics of the arc sensor. It is shown that the frequency of torch height variation (the sensor's input) significantly affects the sensitivities of the welding current and the welding voltage (the sensor's outputs). The current sensitivity is highest when the frequency of torch height variation is ∼5 Hz, but the voltage sensitivity simply increases with the increase of torch height variation frequency. It is also clarified that a decrease in the welding loop's inductance and/or the equivalent output resistance of the welding power source improves the sensor's current sensitivity but decreases voltage sensitivity. Decreasing the electrical resistance, but with an increase in electric field intensity of the arc column, or using a shorter setting electrode extension are useful ways of increasing the current and voltage sensitivities of the sensor.

Deformation on normal and fused haematopoietic blasts in ac electric fields

Changes in the physical properties of a cell plasma membrane following electrically induced cell fusion have been studied alongside changes in the mechanical properties of the system. This allows direct comparison of the experimental results with the theory of the electromechanical stresses produced in the plasma membrane by electric fields. The geometrical deformation of K-562 cells (Ph+ haematopoietic blasts) and their fusates (produced by electric fusion of 2 or 3 K-562 cells) in ac electric fields has been investigated. For electric fields in the range 0–270000 V/m (at a frequency of 370 kHz) the eccentricity of both cells and fusates increased with field strength asymptotically. The effect of field strength on eccentricity was similar for cells and fusates. There was an almost linear relationship between the ratio of the major to the minor semi-axes of cells and fusates and the field strength. Smaller cells underwent larger deformations in an electric field. An increase in electric field intensity caused an increase in the surface area of cells and fusates while the volume of cells and fusates was independent of the field. For a given field strength, cell and fusate deformation increased with excitation frequency over the range 100–450 kHz, with a broad peak in the region 350–450 kHz, and was almost constant at higher frequencies. A time constant of approximately 15 s was obtained for deformation of K-562 cells and two- and three-nuclei fusates. The dynamics of cell and fusate deformation indicates that 50 s after exposure to an electric field no additional changes in geometrical deformation occurred. For small deformations the restoring stress is probably dominated by the mechanical stress set up in the membrane. Employing Maxwell's tensor for the distorting force ensures consistency between theory and the experimental results.

Deformation on normal and fused haematopoietic blasts in ac electric fields

Changes in the physical properties of a cell plasma membrane following electrically induced cell fusion have been studied alongside changes in the mechanical properties of the system. This allows direct comparison of the experimental results with the theory of the electromechanical stresses produced in the plasma membrane by electric fields. The geometrical deformation of K-562 cells (Ph + haematopoietic blasts) and their fusates (produced by electric fusion of 2 or 3 K-562 cells) in ac electric fields has been investigated. For electric fields in the range 0–270000 V/m (at a frequency of 370 kHz) the eccentricity of both cells and fusates increased with field strength asymptotically. The effect of field strength on eccentricity was similar for cells and fusates. There was an almost linear relationship between the ratio of the major to the minor semi-axes of cells and fusates and the field strength. Smaller cells underwent larger deformations in an electric field. An increase in electric field intensity caused an increase in the surface area of cells and fusates while the volume of cells and fusates was independent of the field. For a given field strength, cell and fusate deformation increased with excitation frequency over the range 100–450 kHz, with a broad peak in the region 350–450 kHz, and was almost constant at higher frequencies. A time constant of approximately 15 s was obtained for deformation of K-562 cells and two- and three-nuclei fusates. The dynamics of cell and fusate deformation indicates that 50 s after exposure to an electric field no additional changes in geometrical deformation occurred. For small deformations the restoring stress is probably dominated by the mechanical stress set up in the membrane. Employing Maxwell's tensor for the distorting force ensures consistency between theory and the experimental results.