AC High Field Research Articles

Synergistic Photothermal-Chemotherapy Based on the Use of Biomimetic Magnetic Nanoparticles.

MamC-mediated biomimetic magnetic nanoparticles (BMNPs) have emerged as one of the most promising nanomaterials due to their magnetic features (superparamagnetic character and large magnetic moment per particle), their novel surface properties determined by MamC, their biocompatibility and their ability as magnetic hyperthermia agents. However, the current clinical application of magnetic hyperthermia is limited due to the fact that, in order to be able to reach an effective temperature at the target site, relatively high nanoparticle concentration, as well as high magnetic field strength and/or AC frequency are needed. In the present study, the potential of BMNPs to increase the temperature upon irradiation of a laser beam in the near infrared, at a wavelength at which tissues become partially transparent, is explored. Moreover, our results also demonstrate the synergy between photothermia and chemotherapy in terms of drug release and cytotoxicity, by using BMNPs functionalized with doxorubicin, and the effectiveness of this combination therapy against tumor cells in in vitro experiments. Therefore, the findings of the present study open the possibility of a novel, alternative approach to fight localized tumors.

The effect of silica content to partial discharge characteristic of low-density polyethene and natural rubber blend as the electrical insulator

The dielectric properties of low-density polyethylene natural rubber (LDPE-NR) biopolymeric insulating materials can be improved by adding the silica nanoparticles in a certain percentage of weight (w%). In the present study, four types of bio-nano polymeric samples were prepared. To each sample, the nanosilica particles with wt% 1.5%, 3%, 4.5% and 6%. As one characteristic of dielectric, the partial discharge (PD) characteristics, each sample has been tested for 1 hour under AC high voltage field, and the pulses were counted for each sample and grouped into positive and negative pulses. The PD pattern was also plotted based on X-Y axes, namely Φ-q-n pattern. It was found that the number of positive and negative partial discharge (PD) pulses for each silica sample after 60 minutes of testing varied for all samples. It is also found that samples with a higher percentage of nanosilica had fewer PD pulses. The PD pattern in lower w% of silica was identified in the 90 degrees mostly in containing This indicates that w% of nanosilica particles can improve the PD resistance or the insulation quality of LDPE-NR insulation materials.

Exploring the potential of the dynamic hysteresis loops via high field, high frequency and temperature adjustable AC magnetometer for magnetic hyperthermia characterization

Aim The Specific Absorption Rate (SAR) is the key parameter to optimize the effectiveness of magnetic nanoparticles in magnetic hyperthermia. AC magnetometry arises as a powerful technique to quantify the SAR by computing the hysteresis loops' area. However, currently available devices produce quite limited magnetic field intensities, below 45mT, which are often insufficient to obtain major hysteresis loops and so a more complete and understandable magneticcharacterization. This limitation leads to a lack of information concerning some basic properties, like the maximum attainable (SAR) as a function of particles' size and excitation frequencies, or the role of the mechanical rotation in liquid samples. Methods To fill this gap, we have developed a versatile high field AC magnetometer, capable of working at a wide range of magnetic hyperthermia frequencies (100 kHz – 1MHz) and up to field intensities of 90mT. Additionally, our device incorporates a variable temperature system for continuous measurements between 220 and 380 K. We have optimized the geometrical properties of the induction coil that maximize the generated magnetic field intensity. Results To illustrate the potency of our device, we present and model a series of measurements performed in liquid and frozen solutions of magnetic particles with sizes ranging from 16 to 29 nm. Conclusion We show that AC magnetometry becomes a very reliable technique to determine the effective anisotropy constant of single domains, to study the impact of the mechanical orientation in the SAR and to choose the optimal excitation parameters to maximize heating production under human safety limits.

果汁製造ラインへの交流高電界殺菌技術の実用化

果汁製造ラインへの交流高電界殺菌技術の実用化

Nonlinear distortion of AC dissipation current waveform and space charge in EVA film

AC dissipation current waveform shows nonlinear distortion at AC high field, and this nonlinear distortion is supposed to be related to the behavior of space charge under AC field (AC space charge). We investigated the relationship between the nonlinear distortion of AC dissipation current waveform and AC space charge formation in ethylene–vinyl acetate copolymer film (EVA film). At low field, the capacitive current component was subtracted from the output signal of AC current, and then, the AC dissipation current waveform was obtained with the increase of applied AC field. As the result, the AC dissipation current waveform of EVA film showed nonlinear distortion at high field. In addition, the AC dissipation current waveform has a phase advanced from the phase of the applied AC field. The phase advance is considered to be caused by the increase of the capacitive current component due to space charge injection. We suggested that the nonlinear distortion and the phase advance of AC dissipation current waveform of EVA film were affected by the space charge injection. In addition, we developed a new evaluation method of the AC space charge injection layer based on the phase advance and the nonlinear deformation of the AC dissipation current waveform. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Study on the Malfunction Characteristics of Mobile Device by AC High Electric Field

Due to the development of technology, core technologies and information leakage of companies through mobile devices are increasing. Therefore, Various researches on electronic devices and IC elements protection technologies have been conducted. In the case of high frequency electromagnetic waves, it is harmful to the human body and damages electronic devices, making it difficult to apply them to real life. In this study, we investigated the characteristics of malfunction of shooting and recording function of smartphone near 20kHz which is audible frequency, not electromagnetic wave of high frequency band. Experimental results show that the camera is touched arbitrarily or the focus of the camera is changed. It can be applied to various industrial technology fields in the future.

The Functions of AC and DC Field Components in the Toner Transfer Technique Using AC High Field

A novel transfer technique using AC high fields, which are composed of high AC components having peak electric fields around the discharge limit and lower DC components than those used in conventional printers, has been developed, and the functions of each component on toner transfer have been studied by observations of the toner behavior and the discharge. From the observations of the toner behavior, it has been revealed that the high AC components generate reciprocating motions of toner particles in recessed portions of papers, and reduce the toner adhesion by repeatedly providing mechanical and electrical interactions among toner particles. Furthermore, from the observations of the discharge, it is indicated that by using the low DC components, toner particles, whose adhesions are reduced by the high AC components, are transferred onto paper without discharge generation. Due to the functions of the AC and DC field components, uniform images can be realized even on heavily textured papers which have over 100 μm height difference between the highest and lowest points of the surface.

Piezoelectric and pyroelectric properties of Sr-doped PZT (PSZT) with minor manganese additions

A systematic study was performed to see the effect of Manganese addition and temperature gradient on the electrical properties of PSZT. Pb0.96 Sr0.04 (Zr0.52Ti0.48) O3 (PSZT) containing 0.3%, 0.5%, and 1% Mn was prepared by the sol gel method in order to ensure good stoichiometry and enhanced purity. The powders were calcined at 550 °C and sintered at 1200 °C to achieve 98% of the theoretical density. High field ac study was performed by (P-E) hysteresis measurements at different temperatures (RT, 60, 90, 120 and 150 °C) using an electric field up to 3 kV/mm. It was observed that for a lower Mn concentration P-E loops are pinched at the center while this constriction is found to decrease for greater concentrations. The optimized results were obtained for the 1 mol% of Mn content with 4 mol% of Sr. The values of Qm, k, d33 and tanδ were measured as 756, 0.38, 257 and 0.002 respectively. Higher temperatures coupled with a gradual increase of the electric field resulted in a shift of the hysteresis loops along electric field axis, indicating the presence of an internal bias field. Dependence of pyroelectric properties on applied electric field was also investigated. The value of pyroelectric coefficient was found maximum 6.25 × 10−4 (C/m2K) at 3 kV/mm.

New Effect of AC High Field on Toner Transfer

The effect of ac high fields on toner transfer in electrophotography has been studied. It has been revealed that the high ac components generate the reciprocating motions of toner particles in recessed portions of papers, and reduce the toner adhesions by repeatedly providing the physical and the electrical interactions among toner particles. Therefore, since toner particles can be transferred onto papers by low dc components, uniform images are realized even on heavily textured papers without discharge generation.

The Effect of Doping on the Magnetic Properties in ${\rm Ba}{({\rm Fe}_{1-x}{\rm Co}_{x})}_{2}{\hbox {As}}_{2}$ Polycrystalline Samples

We performed an extensive characterization of Co-doped polycrystalline 122 iron pnictide samples, Ba(Fe1-xCox)2As2 with x=0.07, 0.09, 0.1, 0.12, by means of high-field dc magnetization and ac 1st and 3rd harmonic susceptibility response measurements. From M(H) loops through the Bean model formula both the magnetic field and T dependences of the Jc are derived. From the 3rd harmonic response of the ac susceptibility as a function of the dc magnetic field up to 10 T recorded at different temperatures, we determined the irreversibility line, using the onset criterion. From these analyses, 7% and 9% of Co-doped samples showed the best Jc performances.

The effects of AC electric field on wine maturation

Abstract A pilot plant scale innovative technique applying AC high voltage electric field to accelerate wine aging of Young Cabernet Sauvignon is reported in this paper. The design principles, equipment configuration and its effect on wine taste and flavour are presented. Results from a sensory evaluation group demonstrated that there were various effects on the wine quality under different conditions, some positive while others negative. An optimum treatment, with electric field 600 V/cm and treatment time 3 min, was identified to accelerate wine aging, which made the harsh and pungent raw wine become harmonious and dainty. HPLC and GC/MS combined with routine chemical analysis methods were used to identify the differences between the treated and untreated samples. It was found that the contents of higher alcohols as well as aldehydes in volatile compounds decreased to a large number, meanwhile, the contents of esters and free amino acids slightly increased while others remained unchanged through all treatments. The results of this study show that the technology of accelerating wine aging by high voltage electric field is a feasible method to shorten wine maturing process times and to improve the quality of a young wine, if favourable process conditions are chosen. Industrial relevance The application of physical treatment methods other than heat, such as electric field, magnetic field, ultrasonic wave and microwave, etc., for green processing of foods, is becoming popular. AC electric current is of continuous wave form, thus being seldom used in food processing. However, numerous previous studies about the effect and mechanisms of accelerating wine aging with high voltage AC electric field have been conducted in the Laboratory of South China University of Technology. This manuscript presents the effect of high intensity AC electric field on young wine’s physicochemical properties and sensory quality. The results presented in this paper show that it is a promising and novel technology to shorten the young wine’s aging period. Recently, a few of the Chinese winery companies have already started to set up the plant scale equipment.

Inactivation of Various Microorganism Spores by High Electric Field AC Treatment in Saline

Inactivation of Various Microorganism Spores by High Electric Field AC Treatment in Saline

Octahedral tilt-suppression of ferroelectric domain wall dynamics and the associated piezoelectric activity inPb(Zr,Ti)O3

The $R3m\text{\ensuremath{-}}R3c$ transition is in a limited phase field in the $\mathrm{Pb}({\mathrm{Zr}}_{1\ensuremath{-}x},{\mathrm{Ti}}_{x}){\mathrm{O}}_{3}$ (PZT) phase diagram and is a ferroelectric-ferroelectric phase transition that involves the coupling of a secondary displacive ferroelastic phase transition, associated with a structural rotation of the octahedra about the polar threefold axis. Through systematic temperature-dependent piezoelectric characterization under resonance conditions and high-field unipolar ac drive the influence of the aforementioned transition on piezoelectric and electromechanical properties is noted for two compositions $x=0.30$ and $x=0.40\phantom{\rule{0.3em}{0ex}}\mathrm{mol}$ fraction lead titanate. Applying Rayleigh law analysis to access the relative extrinsic domain wall contributions to the nonlinear permittivity and converse piezoelectric properties, we observe significant differences in the nonlinear response between the $R3m$ and $R3c$ phases and note a discontinuity at the transition for both PZT compositions. A complementary study was conducted through diffraction contrast transmission electron microscopy to access structure property relations. Diffraction contrast imaging reveals that antiphase boundaries (APB's) associated with octahedral tilt may coincide with non-180\ifmmode^\circ\else\textdegree\fi{} ferroelectric domain walls. This microstructural evidence suggests that APB's suppress the motion of non-180\ifmmode^\circ\else\textdegree\fi{} ferroelectric domain walls, leading to reduced extrinsic contributions to the piezoelectric and dielectric response in the low-temperature phase $(R3c)$. The implications of these observations are discussed in relation to both the PZT system and other perovskite-based systems such as $\mathrm{Bi}\mathrm{M}{\mathrm{O}}_{3}\text{\ensuremath{-}}\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3}$ systems.

Field-induced transitions in a single crystal of ErZn2

Temperature dependence of DC and AC magnetic susceptibility and high field magnetization are studied for a single crystal of ErZn2. The results indicate ErZn2to be an antiferromagnet and show an anisotropic and complicated field induced magnetic transitions.

Very high field magnetization and AC susceptibility of native horse spleen ferritin

The magnetization of native horse spleen ferritin protein is measured in pulsed magnetic fields to 55 T at T=1.52 K. The magnetization rises smoothly with negative curvature due to uncompensated Fe 3+ spins and with a large high field slope due to the underlying antiferromagnetic ferritin core. Even at highest fields the magnetic moment is only ∼4% of the saturation moment of the full complement of Fe 3+ in the ferritin molecule. The AC magnetic susceptibility, χ AC( T, f), responding to the uncompensated spins, reaches a maximum near the superparamagnetic blocking temperature with the temperature of the maximum, T M, varying with excitation frequency, T M −1 α log f for 10⩽ f⩽10 4 Hz.

AC susceptibilities of conducting cylinders and their applications in electromagnetic measurements

We present accurate calculations and tabulations of the volume and midplane-averaged complex ac susceptibilities of nonmagnetic conducting cylinders with aspect ratio ranging from 0.1 to 10 as functions of a dimensionless frequency. We discuss their features in terms of eddy-current demagnetizing effect. We explain their applications in high-sensitivity, low-temperature, and high-field ac susceptometers and contactless conductivity measurements.

The perpendicular low-frequency susceptibility of Bi-2223/Ag tapes

The low-frequency susceptibility of six Bi-2223/Ag superconducting tapes with the same 61 filaments but different cross-sectionalaspect ratios is measured at 77 K as a function of the amplitude of the perpendicularly applied field,Hm, using a carefully designed and calibrated high-field ac susceptometer with necessarysample-length corrections. The measured results are compared with two-dimensional calculationsperformed based on the critical state model with constant critical current density or the−1 internal susceptibility at low fields. It is shown that although the fill fraction is about 0.55for the filament-containing core, the measured low-field agrees well with the calculated critical state when the core is assumed to be completely superconducting, when the aspect ratio of thecore ranges from 13 to 32. This indicates a strong magnetostatic coupling among thefilaments. The same coupling is theoretically shown to reduce the field where maximum occurs, . However, the experimental is much higher than that even without coupling when the transport critical currentdensity is used for the model calculation. This suggests that ac magnetization arises fromall superconducting grains and the links between them, whereas the transport current islimited by the filament cross-section where grains are the worst linked, and thegreat discrepancy between magnetic and transport results is a consequence of thenon-uniformity of the superconducting structure of the tape. Therefore, transport criticalcurrent can be significantly improved by ensuring the uniformity of the grain links.

High-field ac susceptometer using Helmholtz coils as a magnetizer

An ac susceptometer is designed for measuring ac susceptibility of disc, film or tape samples of high-temperature superconductors at 77 K in an applied field as high and uniform as possible. It is equipped with a pair of magnetizing Helmholtz coils and a pair of coaxial concentric measuring–compensating coils. For this, the field uniformity and impedance of the magnetizing Helmholtz coils with square coil cross-section and the flux linkage in the measuring–compensating coils produced by the sample moment are systematically and accurately computed based on the analytical formulae for the mutual inductance between two loops and the self-inductance of a thin solenoid. Problems related to the susceptometer calibration and the susceptibility measurements are discussed.

Space charge behavior in polymer film based on increment of capacitance under AC high field

AbstractPolymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1. AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement.We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10018

Developing a new apparatus for inactivating Bacillus subtilis spore in orange juice with a high electric field AC under pressurized conditions

An electric inactivating apparatus of micro-organic spores was designed. A continuous AC electric field (20 kHz, 16.3 kV/cm) was applied to orange juice containing Bacillus subtilis spores in order to examine the inactivation effect of electrical equipment. Electrical treatment at 100 °C under atmospheric pressure has a poor ability to inactivate Bacillus subtilis spores. But electrical treatment at 121 °C under pressurized conditions to elevate the boiling point can reduce the viable Bacillus subtilis spores in orange juice four logarithmic orders in <1 s of treatment. 10% of the original ascorbic acid in the orange juice was destroyed after electric treatment. This value compares with 30% that was destroyed by heating in boiling water for 10 min. And the unpalatable flavor of heat-treated Satsuma mandarin juice was not developed in the electric treated juice.