Effects Of Time-varying Magnetic Fields Research Articles

Role of Time-Varying Magnetic Field on QGP Equation of State

The phase diagram of quantum chromodynamics (QCD) and its associated thermodynamic properties of quark-gluon plasma (QGP) are studied in the presence of time-dependent magnetic field. The study plays a pivotal role in the field of cosmology, astrophysics, and heavy-ion collisions. In order to explore the structure of quark-gluon plasma to deal with the dynamics of quarks and gluons, we investigate the equation of state (EoS) not only in the environment of static magnetic field but also in the presence of time-varying magnetic fields. So, for determining the equation of state of QGP at nonzero magnetic fields, we revisited our earlier model where the effect of time-varying magnetic field was not taken into consideration. Using the phenomenological model, some appealing features are noticed depending upon the three different scales: effective mass of quark, temperature, and time-independent and time-dependent magnetic fields. Earlier the effective mass of quark was incorporated in our calculations, and in the current work, it is modified for static and time-varying magnetic fields. Thermodynamic observables including pressure, energy density, and entropy are calculated for a wide range of temperature- and time-dependent as well as time-independent magnetic fields. Finally, we claim that the EoS are highly affected in the presence of a magnetic field. Our results are notable compared to other approaches and found to be advantageous for the measurement of QGP equation of state. These crucial findings with and without time-varying magnetic field could have phenomenological implications in various sectors of high-energy physics.

Effect of time-varying magnetic field on metal droplet profiles

A nonmagnetic metal droplet with dynamic interfaces under a time-varying magnetic field was considered. Considering that the thermal effect of the magnetic field and the droplet evaporation were disregarded, we obtained the magnetically augmented Young–Laplace equation theoretically according to the normal stress balance principles. The droplet contact angle was further determined according to the droplet volume conservation. According to the curvature and contact angle, the droplet profile was mathematically determined. Results showed that a downward magnetic force caused droplet contraction and an upward force caused expansion. The increase in surface tension hindered the droplet spreading without affecting the change trend of droplet shape parameters. The increase in angular frequency (ω) decreased the variation amplitude of the droplet curvature and contact angle, and the increase in damping factor (τ) slowed down the decay of the droplet curvature and contact angle.

The Effect of Pulsed Magnetic Field on the Molecular Uptake and Medium Conductivity of Leukemia Cell

The cell membrane acts as a barrier that hinders free entrance of most hydrophilic molecules into the cell. Owing to the numerous applications, the introduction of non-permeate molecules into biologic cells has drawn considerable attention in the past years. The aim of our study was to investigate the effect of time-varying magnetic field on transmembrane molecular transport by measuring bleomycin cytotoxicity and conductivity modifying in K562 cells. The cells were exposed to magnetic pulses of 2.2 T strength peak and about 250-μs duration via Magstim stimulator and double 70-mm coil. Three different frequencies of 0.25, 1, and 10 Hz pulses for 56,112, and 28 numbers of pulses, respectively, were applied (nine experimental groups) and uptake and conductivity was measured in each group. Our results show that time-varying magnetic field increase transmembrane molecular transport and media conductivity; this enhancement is greater for 28 pulses with 1 Hz frequency. The observed uptake enhancement due to magnetic exposure is considerable.

Lucifer Yellow uptake by CHO cells exposed to magnetic and electric pulses

BackgroundThe cell membrane acts as a barrier that hinders free entrance of most hydrophilic molecules into the cell. Due to numerous applications in medicine, biology and biotechnology, the introduction of impermeant molecules into biological cells has drawn considerable attention in the past years. One of the most famous methods in this field is electroporation, in which electric pulses with high intensity and short duration are applied to the cells. The aim of our study was to investigate the effect of time-varying magnetic field with different parameters on transmembrane molecular transport.Materials and methods.‘Moreover, a comparison was made between the uptake results due to magnetic pulse exposure and electroporation mediated uptake.’ at the end of Background part. The Chinese hamster ovary (CHO) cells were exposed to magnetic pulses of 2.2 T peak strength and 250 μs duration delivered by Magstim stimulator and double 70 mm coil. Three different frequencies of 0.25, 1 and 10 Hz pulses with 112, 56 and 28 number of pulses were applied (altogether nine experimental groups) and Lucifer Yellow uptake was measured in each group. Moreover, maximum uptake of Lucifer Yellow obtained by magnetic pulses was compared to the measured uptake due to electroporation with typical parameters of 8 pulses of 100 μs, repetition frequency of 1 Hz and electric field intensities of 200 to 600 V/cm.Results and conclusions.Our results show that time-varying magnetic field exposure increases transmembrane molecular transport and this uptake is greater for lower frequencies and larger number of pulses. Besides, the comparison shows that electroporation is more effective than pulsed magnetic field, but the observed uptake enhancement due to magnetic exposure is still considerable.

Neurophysiological and behavioral effects of a 60 Hz, 1,800 μT magnetic field in humans

The effects of time-varying magnetic fields (MF) on humans have been actively investigated for the past three decades. One important unanswered question is the potential for MF exposure to have acute effects on human biology. Different strategies have been used to tackle this question using various physiological, neurophysiological and behavioral indicators. For example, researchers investigating electroencephalography (EEG) have reported that extremely low frequency (ELF, <300 Hz) MF can increase resting occipital alpha rhythm (8-12 Hz). Interestingly, other studies have demonstrated that human motricity can be modulated by ELF MF: a reduction of anteroposterior standing balance or a decrease of physiological tremor intensity have been reported as consequences of exposure. However, the main limitation in this domain lies in the lack of results replication, possibly originating from the large variety of experimental approaches employed. Therefore, the present study aimed to investigate the effects of a 60 Hz, 1,800 μT MF exposure on neurophysiological (EEG) and neuromotor (standing balance, voluntary motor function, and physiological tremor) aspects in humans using a single experimental procedure. Though results from this study suggest a reduction of human standing balance with MF exposure, as well as an increase of physiological tremor amplitude within the frequency range associated with central nervous system contribution, no exposure effect appeared on other investigated parameters (e.g., EEG or voluntary motor control). These results suggest that 1 h of 60 Hz, 1,800 μT MF exposure may modulate human involuntary motor control without being detected in the cortical electrical activity.

Simulating the effects of time-varying magnetic fields with a realistic simulated scanner

Transient magnetic fields induce changes in magnetic resonance (MR) images ranging from small, visually undetectable effects (caused, for instance, by neuronal currents) to more significant ones, such as those created by the gradient fields and eddy currents. Accurately simulating these effects may assist in correcting or optimising MR imaging for many applications (e.g., diffusion imaging, current density imaging, use of magnetic contrast agents, neuronal current imaging, etc.). Here we have extended an existing MR simulator (POSSUM) with a model for changing magnetic fields at a very high-resolution time-scale. This simulator captures a realistic range of scanner and physiological artifacts by modeling the scanner environment, pulse sequence details and subject properties (e.g., brain geometry and air-tissue boundaries). The simulations were validated by using previously published experimental data sets. In the first dataset a transient magnetic field was produced by a single conducting wire with varying current amplitude (between 17 μA and 765 μA). The second was identical except that current amplitude was fixed (at 7.8 mA) and current timing varied. A very close match between simulated images and experimental data was observed. In addition, these validation results led to the observation that the current-induced effects included ringing in the image, which extended away from the conductor, primarily in the phase-encode direction. This effect had previously not been noticed in the noisy, experimentally-acquired images, demonstrating one way in which simulated images can provide potential insight into imaging experiments.

Effects of Time-Varying Magnetic Fields on Transient increase in Intracellular Ca2+Concentration of Cultured Cells.

We tested the effects of some kinds of time-varying magnetic fields (0-1.2T) on neurotransmitter-induced transient increases in intracellular Ca2+concentration ([Ca2+]) of cultured chromaffin and HeLa cells. After these cells were exposed for 2 hours to these magnetic fields, transient increases in [Ca2+]i by addition of acetylcholine or histamine were measured. In control cells, after addition of these neurotransmitters [Ca2+]i was increased immediately and then decreased with time in both cells. But, addition of these drugs to the magnetic fields exposed cells increased [Ca2+]i to a level similar to that for control cells. These results suggest that the transient increases in [Ca2+]i were not significantly influenced by the magnetic fields used in this experiment.

Frequency response of alternating currents through the Staphylococcus aureus α‐hemolysin ion channel†

AbstractAlternating currents were measured through transmembrane ion channels formed by Staphylococcus aureus α‐hemolysin proteins in planar bilayer membranes as part of an investigation to determine the channel's frequency response and the appropriateness of an equivalent circuit commonly used to model electrical interactions at the surface of cells. The experimental approach includes a novel method for separating the alternating current through one or more channels, which is conductive in nature, from the capacitively coupled current through the membrane. Separation of the conductive and capacitive alternating currents made it possible to measure the frequency response of the α‐hemolysin channels. The results of the study are consistent with an equivalent circuit of a membrane capacitor in parallel with one or more channel resistors over the frequency range 30–120 Hz. The possible usefulness of frequency response data for ion channels in cell membranes during investigations of biological effects of time‐varying magnetic fields is briefly discussed. Bioelectromagnetics 22:487–493, 2001. Published 2001 Wiley‐Liss, Inc.

Frequency response of alternating currents through the Staphylococcus aureus alpha-hemolysin ion channel.

Alternating currents were measured through transmembrane ion channels formed by Staphylococcus aureus alpha-hemolysin proteins in planar bilayer membranes as part of an investigation to determine the channel's frequency response and the appropriateness of an equivalent circuit commonly used to model electrical interactions at the surface of cells. The experimental approach includes a novel method for separating the alternating current through one or more channels, which is conductive in nature, from the capacitively coupled current through the membrane. Separation of the conductive and capacitive alternating currents made it possible to measure the frequency response of the alpha-hemolysin channels. The results of the study are consistent with an equivalent circuit of a membrane capacitor in parallel with one or more channel resistors over the frequency range 30-120 Hz. The possible usefulness of frequency response data for ion channels in cell membranes during investigations of biological effects of time-varying magnetic fields is briefly discussed.

Time-varying magnetic fields increase cytosolic free Ca2+ in HL-60 cells

Electromagnetic fields have been reported to cause a variety of biological effects. It has been hypothesized that many of these phenomena are mediated by a primary effect on the concentration of cytosolic free calcium ([Ca2+]i). We investigated the effects of exposure to electromagnetic fields on [Ca2+]i in HL-60 cells using the Ca2(+)-sensitive fluorescent indicator indo-1. Indo-1-loaded cell samples were exposed to a radiofrequency electromagnetic field, a static magnetic field, and a time-varying magnetic field, which were generated by a magnetic resonance imaging (MRI) unit. We found that a 23-min exposure to all three fields, in combination, induced a significant increase in [Ca2+]i of 31 +/- 8 (SE) nM (P less than 0.01, n = 13) from a basal level of 121 +/- 8 nM. Also, cells exposed to only the time-varying magnetic field had a mean [Ca2+]i that was 34 +/- 10 nM (P less than 0.01, n = 11) higher than parallel control samples. Separate exposure to the radio-frequency (6.25 MHz) or static field (0.15 T) had no detectable effects. These results demonstrate that time-varying magnetic fields alter [Ca2+]i and suggest that at least some of the reported biological effects of time-varying magnetic fields may arise from elevation of [Ca2+]i.

The effects of time varying magnetic fields on biological materials

The author reviews the mechanism by which time-varying magnetic fields affect biological systems and calculates some of the numbers which put these values in perspective with respect to both natural body currents and other sources. The author also reviews a very small fraction of the literature on observed bioeffects at low levels with an emphasis on those papers which are often cited in lawsuits. Selected data from some of the most frequently cited experiments on the biological effects of time-varying magnetic fields at low frequencies are presented, and their possible relevance as health hazards is discussed. >

Effects of time-varying magnetic fields on fibroblast growth.

L929 mouse fibroblasts were exposed to sinusoidally varying magnetic fields. Compared with controls the exposed cells showed differences in morphology, clustering and orientation with respect to the magnetic fields and an increased mitotic rate. These effects are time dependent, but occurred at frequencies of 10 and 27 MHz.