Hz Magnetic Fields Research Articles

The Effect of The Shape of Magnetic Field on the Viability of Endothelial Cells

Purpose: Magnetic field is one of the effective and non-invasive modalities on biology and angiogenesis. Studies on the effects of magnetic fields on angiogenesis showed that the shape of the magnetic field could potentially affect angiogenesis. Therefore, this study aimed to control the frequency, intensity, and duration of exposure of magnetic field while investigating the effect of the shape of the magnetic field on the viability of Human Umbilical Vein Endothelial Cells (HUVECs). Materials and Methods: The HUVECs were exposed to various shapes of 50 and 60 Hz magnetic fields with intensities of 0.5 and 1 mT in acute and chronic exposure regimes. The viability of HUVECs was assessed via MTT assay. Results: Results showed that the sin type 50 and 60 Hz magnetic fields are more effective in decreasing the viability. The rectified 100 and 120 Hz with 1 and 0.5 mT could increase and decrease the viability compared with 50 and 60 Hz, respectively. Conclusion: It can be concluded that the shape of the magnetic field can be an effective factor in biology and must be controlled to have a reliable response.

Change in H+ Transport across Thylakoid Membrane as Potential Mechanism of 14.3 Hz Magnetic Field Impact on Photosynthetic Light Reactions in Seedlings of Wheat (Triticum aestivum L.).

Natural and artificial extremely low-frequency magnetic fields (ELFMFs) are important factors influencing physiological processes in living organisms including terrestrial plants. Earlier, it was experimentally shown that short-term and long-term treatments by ELFMFs with Schumann resonance frequencies (7.8, 14.3, and 20.8 Hz) influenced parameters of photosynthetic light reactions in wheat leaves. The current work is devoted to an analysis of potential ways of this ELFMF influence on the light reactions. Only a short-term wheat treatment by 14.3 Hz ELFMF was used in the analysis. First, it was experimentally shown that ELFMF-induced changes (an increase in the effective quantum yield of photosystem II, a decrease in the non-photochemical quenching of chlorophyll fluorescence, a decrease in time of changes in these parameters, etc.) were observed under the action of ELFMF with widely ranging magnitudes (from 3 to 180 µT). In contrast, the potential quantum yield of photosystem II and time of relaxation of the energy-dependent component of the non-photochemical quenching were not significantly influenced by ELFMF. Second, it was shown that the ELFMF treatment decreased the proton gradient across the thylakoid membrane. In contrast, the H+ conductivity increased under this treatment. Third, an analysis of the simplest mathematical model of an H+ transport across the thylakoid membrane, which was developed in this work, showed that changes in H+ fluxes related to activities of the photosynthetic electron transport chain and the H+-ATP synthase were not likely a mechanism of the ELFMF influence. In contrast, changes induced by an increase in an additional H+ flux (probably, through the proton leakage and/or through the H+/Ca2+ antiporter activity in the thylakoid membrane) were in good accordance with experimental results. Thus, we hypothesized that this increase is the mechanism of the 14.3 Hz ELFMF influence (and, maybe, influences of other low frequencies) on photosynthetic light reactions in wheat.

Power Frequency Еlectromagnetic Fields of Electrical Installations in Buildings

Introduction: All components of the power supply system are sources of electric and magnetic fields of industrial frequency of 50 Hz, both posing risks to human health. Estimation of predicted magnetic field levels from switchboards and transformers inside buildings is challenging and implies the importance of full-scale measurements of electromagnetic fields from built-in electrical equipment. Objectives: To establish the levels of 50 Hz electromagnetic fields during operation of built-in electrical installations in industrial, public, and residential premises. Materials and methods: We studied 50 Hz electromagnetic fields generated by electrical installations located in buildings. EMF levels were measured near transformers, switchboards, and switchgear. The electromagnetic situation in the rooms above the electrical equipment was investigated. The assessment of EMF levels was carried out in accordance with the current hygienic standards. Results: The intensity of electric fields near the equipment and in the surveyed premises was significantly lower than that of magnetic fields. The excess of maximum permissible levels at workplaces of operators servicing EMF sources in residential buildings was not detected. In the rooms of public buildings located above electrical installations, measured values of magnetic field induction ranged from 0.18 to 31 µT. The intensity of magnetic fields depended on the current load and the distance from EMF sources. Discussion: Electromagnetic field intensity depends on specifications of equipment, current loads, and distances from the sources of electromagnetic fields. Induction of 50 Hz magnetic fields in adjacent rooms may exceed hygienic standards set for residential and public buildings. Additional adverse factors include instability of magnetic fields caused by current load changes and significant magnetic field gradients in premises.

Combined effect of co-exposure to di (2-ethylhexyl) phthalates and 50-Hz magnetic-fields on promoting human amniotic cells proliferation

Di (2-ethylhexyl) phthalate (DEHP) and extremely low-frequency electromagnetic fields (ELF-EMFs) exist far and wide in our surroundings. Studies have reported that both of DEHP and ELF-EMFs could promote cell proliferation which is related with adverse bioeffects. In this study, we investigated whether there is the combined effect between DEHP and 50-Hz magnetic fields (MFs) on cell proliferation in human amniotic (FL) cells. Results revealed that the low-concentration DEHP (1 μM) could promote FL cell proliferation, whereas the high-dose DEHP (100 μM) inhibited cell proliferation. When FL cells were treated jointly by a 50-Hz, 0.2-mT MF and 0.1 μM DEHP, the proliferation rate of cells was significantly higher than that of single factor exposure. Additionally, co-exposure to under-threshold MF and DEHP could cooperatively activate protein kinase B (Akt), sphingosine kinase 1 (SphK1) and extracellular signal regulated kinase (ERK) in a cascade manner, and finally mediate cell proliferation. Taken together, the findings of this study indicated that the co-exposure to under-threshold MF and DEHP could jointly promote cell proliferation through activating proliferation-related signal pathway, which warned us that it should be cautious about assessing the underlying health hazards of co-exposure to MFs and DEHP at under-threshold levels.

Effect of 50-Hz Magnetic Fields on Argyrophilic Nucleolar Organizer Regions in Bone Marrow Cells

Background: Exposure to an increasing amount of extremely low-frequency magnetic fields (MFs) causes some adverse effects. Considering a direct association between the sizes and numbers of argyrophilic nucleolar organizer regions (AgNORs) and cell proliferation, this study was conducted to evaluate the effect of 50-Hz MFs on the AgNORs of bone marrow (BM) cells. Methods: Eighty male rats were randomly divided into four exposed groups and one control group. The exposed groups received 50-Hz MFs with magnetic flux densities of 1, 100, 500, and 2000 µT two hours a day for two months. BM cells were aspirated from sacrificed rats’ femoral bones, smeared on glass slides, and then stained with silver nitrate for AgNORs. The area (AA), length (AL), and number (AN) of AgNORs were calculated by a microscope equipped with a camera and Scion Image software in 100 BM cells of each rat. The mean of AA, AL, and AN was computed for each group. Results: AA, AL, and AN significantly reduced in the 1 µT group compared with 2000 µT and control groups. Eventually, there was a nonlinear relationship between the effect of 50-Hz MFs and magnetic flux densities. Conclusion: Overall, 50-Hz MFs with a magnetic flux density of 1 µT reduced AgNORs in BM cells. However, 100, 500, and 2000 µT did not affect AgNORs. Therefore, 50-Hz MFs with low density may suppress BM cell proliferation.

Exposure to 60 Hz magnetic field can affect membrane proteins and membrane potential in human cancer cells

ABSTRACT The experimental data support the hypothesis that extremely low frequency magnetic field (ELF-MF) can affect cell membranes. Since our previous studies suggested that MF changes the permeability of cell membrane, in this study we focused on the cell membrane and investigated the effect of 60 Hz, 50 mT MF on the membrane potential and membrane proteins. The membrane potentials of three cultured human cancer cell lines, A549, MES-SA, and MES-SA/Dx5, were increased by exposure to ELF-MF. When exposed to MF and an anticancer drug, changes in the membrane potentials were detected in A549 and MES-SA cells, but not in the multi drug-resistant cells, MES-SA/Dx5. We examined whether MF has an influence on the membrane proteins extracted from cultured A549 cells, using DiBAC4(3) dye enhanced fluorescence binding to a hydrophobic site. The increase in fluorescence observed following MF exposure for 10 min indicated that the structure of the hydrophobic site on the membrane proteins changed and became more likely to bind the probe dye. A decrease in fluorescence was detected following exposure to MF for 240 min. These results indicated that 60 Hz, 50 mT MF causes changes in the membrane potential of cultured cancer cells and the conformation of membrane proteins extracted from cultured cancer cells, and has different effects depending on the exposure time.

A 50 Hz magnetic field affects hemodynamics, ECG and vascular endothelial function in healthy adults: A pilot randomized controlled trial.

Application of exposure to 50/60 Hz magnetic fields (MFs) has been conducted in the treatment of muscle pain and fatigue mainly in Japan. However, whether MFs could increase blood flow leading to muscle fatigue recovery has not been sufficiently tested. We investigated the acute effects of a 50 Hz sinusoidal MF at Bmax 180 mT on hemodynamics, electrocardiogram, and vascular endothelial function in healthy young men. Three types of regional exposures to a 50 Hz MF, i.e., forearm, upper arm, or neck exposure to MF were performed. Participants who received three types of real MF exposures had significantly increased ulnar arterial blood flow velocity compared to the sham exposures. Furthermore, after muscle loading exercise, MF exposure recovered hemoglobin oxygenation index values faster and higher than sham exposure from the loading condition. Moreover, participants who received real MF exposure in the neck region had significantly increased parasympathetic high-frequency activity relative to the sham exposure. The MF exposure in the upper arm region significantly increased the brachial artery flow-mediated dilation compared to the sham exposure. Computer simulations of induced in situ electric fields indicated that the order-of-magnitude estimates of the peak values were 100-500 mV/m, depending on the exposure conditions. This study provides the first evidence that a 50 Hz MF can activate parasympathetic activity and thereby lead to increase vasodilation and blood flow via a nitric oxide-dependent mechanism. Trial registration: UMIN Clinical Trial Registry (CTR) UMIN000038834. The authors confirm that all ongoing and related trials for this drug/intervention are registered.

The duration of exposure to 50 Hz magnetic fields: Influence on circadian genes and DNA damage responses in murine hematopoietic FDC-P1 cells.

We investigated the effects of 50 Hz extremely low-frequency magnetic fields (MFs) on gene expression related to the circadian rhythm or DNA damage signaling and whether these fields modify DNA damage repair rate after bleomycin treatment. Murine FDC-P1 hematopoietic cells were exposed for different durations (15 min, 2 h, 12 h, and 24 h) to either 200 μT MFs or sham-exposures. Cells were then collected for comet assay or real-time PCR to determine immediate DNA damage level and circadian rhythm gene expression, respectively. To assess DNA-damage signaling and DNA repair rate, the cells were subsequently treated with 20 μg/mL bleomycin for 1 h and then either assayed immediately or allowed to repair their DNA for 1 or 2 h. We found that circadian rhythm-related genes were upregulated after 12 h of MF exposure and downregulated after 24 h of MF exposure, but none of the affected genes were core genes controlling the circadian rhythm. In addition, we found that the repair rate for bleomycin-induced damage was only decreased after MF exposure for 24 h. In conclusion, our findings suggest that the effects of MFs are duration-dependent; they were observed predominantly after long exposures.

Appreciable-tuned ferrite/austenite phase balance in the fusion zone of GTAW welds via an assisted magnetic field

In the present paper, a transverse magnetic field was applied to gas tungsten arc welding (GTAW) for 2205 DSS in order to regulate the weld microstructure, which has not been investigated so far. The results indicated that the application of magnetic field not only can increase the austenite/ferrite phase ratio of the welds, but also refine the ferrite grains, and a magnetic field with a frequency of 1 Hz worked best. Both of the above can be attributed to the slower cooling rate of the welding pool with arc oscillation. Hardness test showed that the arc oscillation exerted a significant influence on hardness distribution. Under the effect of a low frequency (1 Hz) magnetic field, the hardness level of the weld metal was close to that of the base material. However, when no magnetic field was applied, the hardness level of the weld increased.

Role of insulin/glucagon ratio and cell redox state in the hyperglycaemia induced by exposure to a 60-Hz magnetic field in rats

The exposure to extremely low-frequency electromagnetic fields (EMFs) could adversely affect the endocrine system and cellular proliferative response. Nonetheless, the use of 60-Hz EMFs in the form of magneto-therapy exerts beneficial actions on human health but can also induce hyperglycaemia. Therefore, the present study was aimed to search for metabolic responses of fed or fasted male rats to a single EMF exposure. We performed a 15 min-single exposure to 60-Hz (3.8 mT, intensity) EMF, and determined serum levels of glucose, lipids, and indicators of cellular redox state and energy parameters. A single exposure to a 60-Hz EMF induced hyperglycaemia in both animal groups, and an attenuated second serum insulin peak. The 60-Hz EMF also decreased free fatty acids and lactate serum levels, oppositely increasing pyruvate and acetoacetate levels. Significant increases in blood glucose level and rat’s glucose metabolism were related to a more oxidized cellular redox state and variations in insulin and glucagon secretion. The 60-Hz EMF’s effects were not modified in animals previously subjected to chronic EMFs exposure (14 days). In conclusion, increased serum glucose levels and glucose metabolism induced by a single 60-Hz EMF exposure were closely related to the cellular redox state and the insulin/glucagon ratio.

Exploring the Inhibitory Effect of Low-frequency Magnetic Fields on Epileptiform Discharges in Juvenile Rat Hippocampus

Stimulation with a low frequency electromagnetic field (LF-EMF) has proven to represent a powerful method for the suppression of seizures, as demonstrated in select clinical and laboratory studies. However, the mechanism by which LF-EMF suppresses seizures remains unclear. The purpose of the present study was to explore the modulatory effect of LF-EMF on epileptiform discharges (EDs) using rat hippocampal slices and investigate the underlying mechanisms that mediate these effects. EDs in hippocampal slices was induced by magnesium-free (zero-Mg2+) artificial cerebrospinal fluid (ACSF) and recorded using an in vitro micro-electrode array (MEA). A small sub-decimeter coil was designed and incorporated in a flexible magnetic stimulation device that allowed electromagnetic fields with different parameters to be delivered to slices. After a stable ED event was recorded, magnetic fields of 0.5 Hz (30 min) with a magnetic intensity of 0.13 mT (5 Vpp voltage input) and 0.25 mT (20 Vpp voltage input) were applied. The results indicated that a high-amplitude 0.5 Hz magnetic field could lead to persistent suppression of ictal discharges (IDs), while low-amplitude magnetic fields did not influence IDs. The persistent suppression of complex ED was prevented if the magnetic fields were applied in the presence of 10 μmol/L bicuculline (BIC), a γ-aminobutyric acid type A (GABAA) receptor antagonist, while the application of BIC subsequent to a magnetic field application led to the reappearance of ID. The addition of BIC resulted in EDs that had previously been inhibited by magnetic fields, reappearing. Low-frequency magnetic stimulation was able to inhibit the conversion from interictal discharges (IIDs) or preictal discharges (PIDs) to IDs. This suppression was attributed to the modulation of GABAA receptor activity.

Magnetic field-induced Ca2+ intake by mesenchymal stem cells is mediated by intracellular Zn2+ and accompanied by a Zn2+ influx

Chronic exposure to magnetic fields (MFs) has a diverse range of effects on biological systems but definitive molecular mechanisms of the interaction remain largely unknown. One of the most frequently reported effects of MF exposure is an elevated concentration of intracellular Ca2+ through disputed pathways. Other prominent effects include increased oxidative stress and upregulation of neural markers through EGFR activation in stem cells. Further characterization of cascades triggered by MF exposure is hindered by the phenotype diversity of biological models used in the literature. In an attempt to reveal more mechanistic data in this field, we combined the most commonly used biological model and MF parameters with the most commonly reported effects of MFs.Based on clues from the pathways previously defined as sensitive to MFs (EGFR and Zn2+-binding enzymes), the roles of different types of channels (voltage gated Ca2+ channels, NMDA receptors, TRP channels) were inquired in the effects of 50 Hz MFs on bone marrow-derived mesenchymal stem cells. We report that, an influx of Zn2+ accompanies MF-induced Ca2+ intake, which is only attenuated by the broad-range inhibitor of TRP channels and store-operated Ca2+ entry (SOCE), 2-Aminoethoxydiphenyl borate (2-APB) among other blockers (memantine, nifedipine, ethosuximide and gabapentin). Interestingly, cation influx completely disappears when intracellular Zn2+ is chelated. Our results rule out voltage gated Ca2+ channels as a gateway to MF-induced Ca2+ intake and suggest Zn2+-related channels as a new focus in the field.

Endocytosis induction by high-pulsed magnetic fields to overcome cell membrane barrier and improve chemotherapy efficiency

ABSTRACT Cell membrane acts as a barrier to the entry of impermeable drugs into cells. Recent studies have suggested that using magnetic fields can enable molecules to overcome the cell membrane barrier. However, the mechanism of membrane permeabilization remains unclear. Therefore, we evaluated the increases in bleomycin (CT) uptake, a non-permanent chemotherapy agent, using high-pulsed magnetic fields and investigated whether endocytosis was involved in the process. This study exposed MCF-7 cells to magnetic fields (2.2 T strength, different number of 28 and 56 pulses, and frequency of 1 and 10 Hz) in order to investigate whether this approach could promote the cell-killing efficiency of bleomycin. The involvement of endocytosis as a possible mechanism was tested by exposing cells to three endocytosis inhibitors, namely chlorpromazine, genistein, and amiloride. Our results illustrated that magnetic fields, depending on their conditions, could induce different endocytosis pathways. In such conditions as 10 Hz-28 pulses, 10 Hz-56 pulses, and 1 Hz-56 pulse, clathrin-mediated endocytosis was observed. Moreover, macropinocytosis was induced by the 10 Hz magnetic field and caveolae-mediated endocytosis occurred in all the magnetic field conditions. The findings imply that high-pulsed magnetic fields generate different endocytosis pathways in the MCF-7 cells, thus increasing the efficiency of chemotherapy agents.

Remote Performance Modulation of Ultrafiltration Membranes by Magnetically and Thermally Responsive Polymer Chains.

Ultrafiltration membranes, that respond to an external magnetic field and local temperature have been developed. Surface-initiated activator-generated electron transfer (AGET) atom transfer radical polymerization (ATRP) has been used to graft poly(N-isopropylacrylamide) (PNIPAm) from the surface of 300 kDa regenerated cellulose membranes. The polymerization initiator was selectively attached to the entire membrane surface, only the outer membrane surface or only the inner pore surface. A superparamagnetic nanoparticle was attached to the end of the polymer chain. The DI water flux as well as the flux and rejection of bovine serum albumin were investigated in the absence and presence of a 20 and 1000 Hz oscillating magnetic field. In an oscillating magnetic field, the tethered superparamagnetic nanoparticles can cause movement of the PNIPAm chains or induce heating. A 20 Hz magnetic field maximizes movement of the chains. A 1000 Hz magnetic field leads to greater induced heating. PNIPAm displays a lower critical solution temperature at 32 °C. Heating leads to collapse of the PNIPAm chains above their Lower Critical Solution Temperature (LCST). This work highlights the versatility of selectively grafting polymer chains containing a superparamagnetic nanoparticle from specific membrane locations. Depending on the frequency of the oscillating external magnetic field, membrane properties may be tuned.

Enhancement of Energy-Harvesting Performance of Magneto-Mechano-Electric Generators through Optimization of the Interfacial Layer.

Among various energy harvester paradigms, the simple cantilever-structured magneto-mechano-electric (MME) energy generator comprises a piezoelectric material laminated on a magnetostrictive metal plate and permanent magnets as proof mass, exhibiting excellent magnetic energy-harvesting performance. The current challenge in using MME energy harvesters is the mechano-electric coupling at the interface between the piezoelectric material and magnetostrictive metal layer, which depends significantly on the mechanical properties of the interfacial adhesive layer. In this study, the effects of four types of adhesive interfacial layers on the output power and environmental and fatigue resistances of MME harvesters are systematically investigated. An optimized MME energy generator with an adhesive interfacial layer of 18.8 μm thickness and elastic modulus of 3.1 GPa achieves colossal enhancement (∼300%) with a maximum output power density of 0.92 mW/cm2, while a 10 Oe (=10 G = 1 mT in air; 60 Hz) magnetic field is applied. In addition, the generator exhibits a robust endurance of continuous 108 fatigue cycles and excellent temperature stability in the range of -30 to 70 °C. The presented MME generator, which harvests stray magnetic energy reliably, is promising as a low-cost and efficient autonomous power source for Internet of Things devices, wireless sensor networks, and so on.

Аддитивное воздействие электрических и магнитных полей на электротехнический персонал

The article is devoted to the formation of a safe working environment at the industrial enterprises. Conducted experimental studies allowed to reveal not only the presence of electric and magnetic fields of 50 Hz, but also the spectrum of higher harmonic components at the workplaces of electrical personnel. Similar situation is observed in the electric (freight) alternating current locomotives of the railway transport. This is due to the specific features of electrical installations of two-pole and single-phase traction power supply. The important problem was solved related to the assessment of the additive effects of electric and magnetic fields with their simultaneous effect on the personnel. The new method is proposed for calculating and standardizing electric and magnetic fields of 50 Hz based on consideration of their dose energy characteristics at their simultaneous harmful effects on the personnel. The standardization is proposed to be carried out on the basis of the current maximum permissible levels of the parameters of 50 Hz electric and magnetic fields but in the form of the field energy characteristics based on the definition of the Poynting vector. The additivity of the effect of electric and magnetic fields on the personnel is proposed to be assessed by the additivity coefficient in the form of a quantitative measure of the combined harmful effect of the field strengths components. At the additive standardization of simultaneously two harmful factors of the electric and magnetic field strengths, the standardized indicators of magnetic and electric strengths required for assessing the total energy maximum safe level are reduced by 2 times. Based on the maximum permissible levels of electric and magnetic fields, a graph was built for the changes in the energy load of these fields versus the length of exposure. Technical device was developed that measures the level of energy load of the electric and magnetic fields. Using this device, it is possible to minimize the total effect of harmful factors on the electrical personnel with the help of protective means.

Microstructure and tribological behavior of in situ ZrB2/A356 composites prepared under magnetic field

A356-3 wt% ZrB2 composite was prepared by in-situ magnetochemical reaction at x Hz(x = 0, 5, 10, 15) magnetic field frequency, and its dry sliding friction and wear properties were studied. XRD results show that the composite is composed of ZrB2 and aluminum phase. SEM analysis showed that the size and distribution of ZrB2 particles improved with the increase of frequency. The size of ZrB2 particles in the cluster is about 20–100 nm. The hardness test results showed that with the increase of frequency, the hardness of the composite increased to 235.72 Hv. The friction and wear test results show that the friction coefficient and wear rate of the composite material under 10 N load are lower than that under 5 N load, and the lowest values are 0.28112 and 0.50875, respectively. With the increase of frequency, the wear mechanism changes from adhesive wear to abrasive wear. The effect of magnetic field on in-situ reaction is discussed.

Local Time Differences in the Ionospheric Electromagnetic Ion Cyclotron Waves during Storm Time

By using high-resolution (50 Hz) magnetic field observations from Swarm constellation, the temporal and spatial characteristics of Electromagnetic Ion Cyclotron (EMIC) waves in different local time sectors at mid-latitudes are investigated during the magnetic storm period of 16—25 March 2015. There are comparable number of EMIC wave events in the dawn and dusk sectors, while there are more EMIC wave events in the pre-noon sector than in the pre-midnight sector. The duskside preference is related to the plasmaspheric plume, while the dawnside preference is related to the enhanced solar wind dynamic pressure and dense cold plasma. The wave frequency in the dawn and pre-noon sectors is higher than that in the dusk and pre-midnight sectors, implying the local time difference in the source location and the ion composition. Most of the duskside events occur in the early recovery phase, while the dawnside events occur in the late recovery phase. The time difference comes from the time required for the westward drift of energetic ions and local time difference in the plasmapause position. H⁺ band waves are mainly found in the 06:00 MLT—10:00 MLT sector, while He⁺ band waves are mainly confined in the 18:00 MLT—22:00 MLT sector. There is no H⁺ band but a two band (He⁺ and O⁺) EMIC wave during the storm main phase, indicating the role of the dense oxygen ion in inhibiting the H⁺ band in the inner magnetosphere.

Assessment of the effects of exposure to extremely low-frequency magnetic fields on MDCK epithelial cell lines under a controlled environment.

To assess the effects of exposure to extremely low-frequency magnetic fields (ELF-MFs) on MDCK cell lines, experiments were performed in a chamber under controlled conditions (temperature, humidity and CO2). Therefore, the measured physicochemical and electrical changes in the cells are due solely to the magnetic field exposure and not to external factors. A developed sinusoidal magnetic field generator produced the ELF-MFs with a uniform magnetic field and adjustable intensity and frequency. Three experimental indicators were used: (i) transepithelial electrical impedance (TEEI); (ii) cell migration and proliferation; and (iii) expression of the proteins of the tight junctions, and changes in the area and shape of the cell nuclei. No significant effects on TEEI values were observed when 10 and 50 G 60 Hz magnetic fields were applied to confluent cell monolayers. There were no significant differences in migration and proliferation of the cell monolayer exposed to 60 Hz magnetic fields10 and 50 G , but a contact inhibition factor was observed. The expression of the CLDN-1 protein decreased by 90% compared with the control, while ZO-1 protein expression increased by 120%. No significant effects were observed in the area and shape of the cell nuclei. Experimentation in a controlled environment, under physiological conditions, ensures that the observed effects were strictly due to exposure to magnetic fields. Different exposure conditions are necessary to determine the impact on TEEI and cell migration–proliferation indicators.

Development and optimisation of low-power magnetic flux leakage inspection parameters for mild steel welds

Magnetic particle and other magnetic flux leakage (MFL)-based methods for the detection and evaluation of surfacebreaking flaws in ferromagnetic materials typically use high-strength (≥0.5 T RMS), low-frequency (≤50 Hz) magnetic fields. The rationale behind this is the ready availability of strong permanent magnets and mains power for high-strength electromagnets. This high field strength is needed to saturate the sample and compensate for the relatively low sensitivity of magnetic particle detection media, silicon Hall sensors, coils and other magnetic transducers used in such methods. Consequently, frequencies greater than 50 Hz and applied magnetic fields less than 100 mT strength have not been widely explored for MFL due to the lack of commercially available sensors capable of detecting the leakage fields (typically in the nT and μT range) with adequate versatility to cope with the variations in inspection parameters, such as changes in liftoff, material properties, etc, which are inherent to non-destructive testing and evaluation (NDT&E) settings. In this study, the MFL response of surface-breaking longitudinal cracks from a ground mild steel weld validation sample, within the DC to 1 kHz and 5 mT to 100 mT RMS applied magnetic field operating range, was explored. This was carried out to determine whether any optimal frequency response exists, better accommodating the inherent sample material properties (for example magnetic permeability and electrical conductivity) and MFL mechanism and attributing phenomena such as electromagnetic skin effect and eddy current contributions. Contrary to previous work published in Insight last year, this study found no particular optimal frequency within this operating range, with explanations to justify the disproval of previously reported conclusions about optimal frequencies within this range. Also, the iteratively developed quantitative analysis performed in this study can be used to help further understand the underlying mechanisms of AC MFL and provide best practice regarding the optimisation of MFL.