High Frequency Electric Field Research Articles

Interaction of Two-Dimensional Extremely Short Optical Pulses in a Zig-Zag Carbon Nanotubes in the Presence of a High-Frequency Electric Field

Interaction of Two-Dimensional Extremely Short Optical Pulses in a Zig-Zag Carbon Nanotubes in the Presence of a High-Frequency Electric Field

Effect of cooling fluids on high frequency electric and magnetic fields in microelectronic systems with integrated TSVs

A fully 3D conjugate numerical analysis was performed to reveal the effects of air, R134a refrigerant and water on electromagnetic fields of electronic cooling designs made of arrays of micro pin-fins with integrated Through-Silicon-Vias (TSVs). The integrated TSV cooling configuration included 8 cylindrical TSVs with 150µm diameter each and 200µm height. The external dimensions of the silicon substrate were 900×700×280µm. Each TSV encapsulated four equally spaced copper vias each having a diameter of 40µm. The impacts of the presence of the stationary cooling fluids without heat transfer on TSVs electric and magnetic fields were examined for five different frequencies; 100MHz, 500MHz, 1GHz, 5GHz and 10GHz. Then, separately, the effects of moving cooling water with temperature-dependent physical properties were studied while exposing the cooled micro pin-fin array to a uniform heat flux of 500Wcm−2. For the case of stagnant and moving cooling fluids it was found that water influences the electric field twice as much as either R134a or air and that this influence decreases only negligibly with the increase in frequency of the electric current passing through the TSVs. The influence of the presence of the stagnant and moving cooling fluids on the magnetic field is orders of magnitude smaller and reduces rapidly with the increased frequency.

Determining of the electric field strength using high frequency broadband measurements

Exposure of humans to electromagnetic fields of high frequency (above 100 kHz), i.e. radiofrequency radiation from the modern wireless systems, today inevitable is. The purpose of this paper is to highlight the importance of broadband measurements of the electric field of high frequency in order to fast and reliable assessment of human exposure. A practical method of ‘in situ’ measurement the electric field intensity which is related to the frequency range of 3 MHz to 18 GHz, is provided.

Yolk/Shell Colloidal Crystals Incorporating Movable Cores with Their Motion Controlled by an External Electric Field.

Yolk/shell particles composed of a submicrometer-sized movable core and a silica shell are promising building blocks for novel optical colloidal crystals, because the locations of cores in the shell compartment can be reversibly changed by using external stimuli. Two dimensional arrays of yolk/shell particles incorporating movable cores were prepared by a self-assembly method. The movable cores of colloidal crystals in water could be observed with an optical microscope under application of external electric field. The motions of inner silica cores depended on the electric field strength and frequency and were categorized into three cases: (1) Random Brownian motion, (2) anisotropic motion of cores moving in a direction orthogonal to a field, and (3) suppressed motion fixed in the center of shell compartment. Random Brownian motion of cores was scarcely affected by field strength when a high frequency (in the MHz range) electric field was applied. On the other hand, an increase in field strength at low-frequency fields (kHz) transiently changed the core motion from (1) to (2) and a further increase in field strength changed it from (2) to (3). When the silica core was incorporated in a large void a stronger electric field was needed to suppress its motion than when it was in a small void. The high responsivity to electric fields in a low-frequency range indicated the importance of electric double layer (EDL) interaction between core and inner shell in controlling the core location in yolk/shell colloidal crystals. It was also shown that movable titania cores in yolk/shell particles required a low-frequency field with a high strength to change from the random to anisotropic motion. The result suggested that the electrostatic interaction between EDLs of the silica core and the inner silica wall could be stronger than that between EDLs of the titania core and the silica shell.

Switchable Fresnel lens based on hybrid photo-aligned dual frequency nematic liquid crystal

In this article we disclose a method to fabricate a polarization independent dual frequency liquid crystal (DFLC) Fresnel lens (FL) with relatively high efficiency. The switchable FL is based on a patterned hybrid photo-aligned nematic (HPAN) DFLC cell assembled by one substrate providing the homeotropic anchoring and the other one providing the in-plane patterned alignment, with mutually orthogonal easy axis in the neighboring alignment domains, which has been prepared by means of two-step photo-alignment technique. Due to the electro-optical properties of dual frequency LC, the proposed HPAN DFLC FL, which manifests relatively high diffraction efficiency of 38.5% and low driving voltage, has the possibility of achieving a fast response by alternatively switching between high frequency and low frequency electric fields. Thus, with an excellent rewritable performance leading to the alternative focus/defocus switch, the HPAN DFLC FL would definitely be practical and promising in many modern devices.

Electron heating and particle fluxes in dual frequency atmospheric-pressure helium capacitive discharge

In this letter, a 1D fluid model has been used to study the electron heating and particle transport in dual frequency atmospheric-pressure helium capacitive discharge with a high-frequency (HF) voltage of 10 MHz and a low-frequency (LF) voltage of 1 MHz. The electric field is decoupled to three components: the HF, the LF and the direct current (DC) ones, and they have much different effects on the plasmas. The eletrons in plasma bulk are mainly heated by the HF electric field, while in plasma sheath they are heated and cooled by the LF and DC electric fields, respectively. With a fixed total input power, the increase of LF power leads to great enhancement of the electrode fluxes of electrons and ions, especially for the energetic electrons of Te > 2 eV, because more power is dissipated in the vicinity of electrodes and the inelastic collision is more pronounced. Therefore, the particle transport on the treated sample can be greatly enhanced without additional gas heating in dual frequency plasmas, which meets the application requirements more compared to the single frequency plasmas.

Effects of the Ultra-High-Frequency Electrical Field Radiofrequency Device on Mouse Skin: A Histologic and Molecular Study.

Radiofrequency technology is one of the most recently developed methods for noninvasive skin tightening and facial contouring, and works by generating thermal energy in the deep dermis. Although clinical improvements have been reported using radiofrequency devices, there are few histologic and molecular studies about the mechanisms of dermal collagen remodeling. The authors investigated the histologic effects of an ultra-high-frequency electrical field (40.68 MHz) radiofrequency device (Polargen) on collagen remodeling in hairless mouse skin and evaluated its relative molecular mechanism. The radiofrequency was applied to the dorsal skin of hairless mice three times per week for 2 weeks. At 21 days after initial treatment, treated skin and nontreated control skin samples were excised for semiquantitative analysis of histologic features, including collagen. The authors also checked the mRNA expression levels of collagen type 1, transforming growth factor (TGF)-β, matrix metalloproteinase-1, vascular endothelial growth factor, tumor necrosis factor-α, and interleukin-1. Histologic examination revealed epidermal hyperplasia, increased collagen staining, and fat atrophy in treated skin area compared with the nontreated skin area. In addition, mRNA expression of collagen type І, TGF-β, and vascular endothelial growth factor in radiofrequency-treated areas was significantly increased compared with that in untreated control areas (p < 0.05, p < 0.05, and p < 0.01, respectively). These results suggest that the device may facilitate replacement of subcutaneous fat tissue with new collagen in association with the increased mRNA levels in TGF-β and vascular endothelial growth factor. Therefore, this device may effectively reduce adipose tissue and achieve facial contouring in addition to skin tightening.

Detection of flashing areas attributed to the frog cardiac function in the vagosympathetic trunk placed into a high frequency electric field.

In a high frequency electric field, two flashing areas were observed during each contraction of the heart in the vagosympathetic trunk of a paralyzed frog with an intact brain. One area with a higher diameter was moving along the nerve from the heart at a speed of 16.6 ± 0.2 m/s. It was identified as afferent. Another area with a smaller diameter was spreading along the nerve towards the venous sinus of the frog heart at a speed of 5.6 ± 0.3 m/s, and it was efferent.

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

The effect of high frequency (HF) electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP) ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO4)3 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

Frequency-Dependent Modulation of Dopamine Release by Nicotine and Dopamine D1 Receptor Ligands: An In Vitro Fast Cyclic Voltammetry Study in Rat Striatum.

Nicotine is a highly addictive drug and exerts this effect partially through the modulation of dopamine release and increasing extracellular dopamine in regions such as the brain reward systems. Nicotine acts in these regions on nicotinic acetylcholine receptors. The effect of nicotine on the frequency dependent modulation of dopamine release is well established and the purpose of this study was to investigate whether dopamine D1 receptor (D1R) ligands have an influence on this. Using fast cyclic voltammetry and rat corticostriatal slices, we show that D1R ligands are able to modulate the effect of nicotine on dopamine release. Nicotine (500nM) induced a decrease in dopamine efflux at low frequency (single pulse or five pulses at 10Hz) and an increase at high frequency (100Hz) electrical field stimulation. The D1R agonist SKF-38393, whilst having no effect on dopamine release on its own or on the effect of nicotine upon multiple pulse evoked dopamine release, did significantly prevent and reverse the effect of nicotine on single pulse dopamine release. Interestingly similar results were obtained with the D1R antagonist SCH-23390. In this study we have demonstrated that the modulation of dopamine release by nicotine can be altered by D1R ligands, but only when evoked by single pulse stimulation, and are likely working via cholinergic interneuron driven dopamine release.

INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval’s axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

High frequency electric field levels: An example of determination of measurement uncertainty for broadband measurements

Determining high frequency electromagnetic field levels in urban areas represents a very complex task, having in mind the exponential growth of the number of sources embodied in public cellular telephony systems in the past twenty years. The main goal of this paper is a representation of a practical solution in the evaluation of measurement uncertainty for in-situ measurements in the case of spatial averaging. An example of the estimation of the uncertainty for electric field strength broadband measurements in the frequency range from 3 MHz to 18 GHz is presented.

Subthreshold High-Frequency Electrical Field Stimulation Induces VEGF Expression in Cardiomyocytes.

Subthreshold electrical stimulation (SES) has been shown to induce an improvement of angiogenesis in ischemic and nonischemic skeletal muscles, mediated by increased VEGF expression. VEGF plays a key role in physiological and pathological angiogenesis. Cardiomyocytes possess the ability to synthesize and secrete VEGF. Thus, we thought to investigate the effect of SES on VEGF regulation in cultured neonatal rat ventricular myocytes (NRVMs), in the aim to reveal new techniques for therapeutic angiogenesis in ischemic heart disease. Cell cultures of NRVMs were electrically stimulated with field strengths below the myocyte depolarization threshold (0.5 V/cm with 1 ms bipolar impulse duration). Frequencies ranging from 5 Hz up to 25, 50, and 99 Hz were applied over a period of 48 h. The expression of VEGF and its receptor KDR was determined with Western blot and ELISA. To reveal the biological activity of the secreted VEGF amount, cultured human coronary artery endothelial cells (HCAECs) were treated with the cell culture supernatant of NRVMs exposed to SES. A dominant effect of SES was observed at 25 Hz. Within this particular frequency the VEGF protein amount in the cytoplasm as well as in the cell culture supernatant increased significantly. In parallel, the protein expression of the KDR receptor decreased in a significant manner. Moreover, cell culture supernatant of NRVMs exposed to SES augmented the growth of HCAECs. Cardiomyocytes respond to SES with an increase in biologically active VEGF expression that promotes cell proliferation of HCAECs. This mechanism may provide new approaches to develop therapeutic angiogenesis in the ischemic heart.

The influence of low frequency of external electric field on nucleation enhancement of hen egg-white lysozyme (HEWL)

Protein crystal nucleation processes are drawing increasing interests in both academic and industrial communities. Electric field is a promising means, due to its versatility and easy application, among various external fields that may lead to controllable desired protein crystal nucleation. Different from literature reported experimental and theoretical studies that examined the effects of high frequency electric fields; this work was focused on the low frequency range. For this purpose, Hen-White Lysozyme crystal nucleation from its aqueous solution was used as the model system. We found by experiments that the nucleation rate is non-monotonously dependent on electric field frequency less than 1kHz, which may be ascribed to the mutual orientation modification between neighbor protein molecules induced by the external low frequency, and is different from the case of high frequencies that influence the intermolecular interactions.

SMN deficiency disrupts gastrointestinal and enteric nervous system function in mice

The 2007 Consensus Statement for Standard of Care in Spinal Muscular Atrophy (SMA) notes that patients suffer from gastroesophageal reflux, constipation and delayed gastric emptying. We used two mouse models of SMA to determine whether functional GI complications are a direct consequence of or are secondary to survival motor neuron (Smn) deficiency. Our results show that despite normal activity levels and food and water intake, Smn deficiency caused constipation, delayed gastric emptying, slow intestinal transit and reduced colonic motility without gross anatomical or histopathological abnormalities. These changes indicate alterations to the intrinsic neural control of gut functions mediated by the enteric nervous system (ENS). Indeed, Smn deficiency led to disrupted ENS signaling to the smooth muscle of the colon but did not cause enteric neuron loss. High-frequency electrical field stimulation (EFS) of distal colon segments produced up to a 10-fold greater contractile response in Smn deficient tissues. EFS responses were not corrected by the addition of a neuronal nitric oxide synthase inhibitor indicating that the increased contractility was due to hyperexcitability and not disinhibition of the circuitry. The GI symptoms observed in mice are similar to those reported in SMA patients. Together these data suggest that ENS cells are susceptible to Smn deficiency and may underlie the patient GI symptoms.

A Novel Approach to Identify Genes Related to FGID

To investigate novel genes involved in functional gastrointestinal disorders, we disrupted a master regulator of mRNA splicing, the survival motor neuron (SMN) protein. SMN disruption leads to widespread changes in gene expression but has not been evaluated for effects in the gastrointestinal (GI) tract. Mice with a Nestin‐cre transgene were crossed to cre reporter mice to analyze expression in the enteric nervous system (ENS). Gene expression was detected in excitatory and sensory neurons, interneurons, and intraganglionic glia throughout the myenteric plexus but not muscle. Next, nestin‐cre mice were crossed to mice with a floxed Smn allele on a SMNΔ7 background (SMN2+/+;SMNΔ7+/+;SmnF7/‐) to produce Nestin‐F7 mice. In organ baths, SMN reduction disrupted colon longitudinal muscle contraction during high frequency electrical field stimulation (EFS). Muscle relaxation was consistently greater in control tissue. The addition of L‐NAME had no effect on differences between control and Nestin‐F7 responses. Tissues showed no morphological changes or cell loss. Gastric emptying and intestinal transit were significantly slower in Nestin‐F7 mice compared to controls. Nestin‐F7 mice had dry, infrequent stool that corresponded to reduced colonic motility in the bead latency test. Collectively, these data suggest that SMN reduction results in impaired GI function. Future studies will identify specific enteric cell types sensitive to SMN reduction and evaluate mRNA expression in those cells.

Wall charging of a helicon antenna wrapped plasma filled dielectric tube

Dielectric wall charging of a cylindrical glass wall surrounded by a helicon antenna of 18 cm length is measured in a linear helicon plasma device with a diverging magnetic field. The ions because of their lesser mobility do not respond to the high frequency electric field and the electrons charge the wall to a negative DC potential also known as the DC self-bias. The wall potential in this device is characterized for different neutral pressure, magnetic field, and radio frequency (RF) power. Axial variation of wall potential shows higher self-bias potentials near the antenna rings. Ion magnetization in the source chamber increases both wall charging and plasma potential of the source due to confinement.

High-Frequency Electric Field Induced Nonlinear Electron Transport in Chiral Carbon Nanotubes

We investigate theoretically the high frequency complex conductivity in carbon nanotubes that are stimulated axially by a strong inhomogeneous electric field of the form E(t)=E0+E1cos(ωt). Using the kinetic approach based on Boltzmann’s transport equation with constant relaxation time approximation and the energy spectrum of the electron in the tight-binding approximation, together with Bhatnagar-Gross-Krook collision integral, we predict high-frequency nonlinear effects along the axial and the circumferential directions of the carbon nanotubes that may be useful for the generation of high frequency radiation in the carbon nanotubes.

Multiferroic oxide composites: synthesis, characterisation and applications

The nature of mechanical strain mediated electromagnetic coupling in multiferroic composites has been studied extensively in recent years. This review is on composites with ferromagnetic or ferrimagnetic oxides and ferroelectrics. Systems studied so far include samples with spinel ferrites, hexagonal ferrites or lanthanum manganites for the ferromagnetic phase and barium titanate, lead zirconate titanate (PZT), lead magnesium niobate–lead titanate (PMN-PT) or lead zinc niobate–lead titanate (PZN-PT) for the ferroelectric phase. Bilayer and multilayer heterostructures, bulk composites, core shell nanoparticles and core shell nanotubes and nanowires were investigated for their response to magnetic fields, termed direct magnetoelectric effect (DME). Several systems show a giant low frequency DME and resonance enhancement at bending and electromechanical resonance. The response of the composites to an electric field, called converse ME effect, is found to be strong in several ferrite–ferroelectric composites. The potential for use of the composites for pico-Tesla magnetic sensors and high frequency electric field tunable ferrite signal processing devices are also addressed in this review.

The effect of high frequency electric field on enhancement of chondrogenesis in human adipose-derived stem cells.

Osteoarthritis (OA) is globally one of the most common diseases from the middle age onwards. Cartilage is an avascular tissue therefore it cannot be repaired in the body. Conservative treatments have failed as a good remedy and cell therapy as a decisive cure is needed. One of the best and easily accessible cell sources for this purpose is adipose-derived stem cells which can be differentiated into chondrocytes by tissue engineering techniques. Chemical and physical inducers have a key role in stem cell - chondrocyte differentiation. We have tried to determine the role of electric fields (EF) in promoting this kind of chondrogenesis process. Human adipose derived stem cells (ADSCs) were extracted from subcutaneous abdominal adipose tissue during cesarean section. A high frequency (60 KHz) EF (20 mv/cm), as a physical inducer for chondrogenesis in a 3D micromass culture system of ADSCs was utilized. Also, MTT, ELISA, flow cytometry, and real-time PCR techniques were used for this study. We found that using physical electric fields leads to chondrogenesis. Furthermore, results show that using both physical (EF) and chemical (TGFβ3) inducers simultaneously, has best outcomes in chondrogenesis, and expression of SOX(9) and type II collagen genes. It also causes significant decreased expression of type I and X collagen genes in pure EF group compared with control group. The EF was found as a proper effective inducer in chondrogenic differentiation of human ADSCs micromass culture.