Extent and flux density of static magnetic fields generated by orthodontic samarium-cobalt magnets

Static magnetic fields (SMFs) and time-varying electromagnetic fields exposure is necessary to obtain the diagnostic information regarding the structure of patient's tissues, by the use of magnetic resonance imaging (MRI) scanners. A diagnostic procedure may also include the administration of pharmaceuticals called contrast, which are to be applied to a patient during the examination. The nurses involved in administering contrast into a patient during the pause in examination are approaching permanently active magnets of MRI scanners and are exposed to SMF. There were performed measurements of spatial distribution of SMF in the vicinity of MRI magnets and parameters of personal exposure of nurses (i.e. individual exposimetric profiles of variability in time of SMF affecting the nurse who is performing tasks in the vicinity of magnet, characterized by statistical parameters of recorded magnetic flux density affecting the nurse). The SMF exposure in the vicinity of various MRI magnets depends on both magnetic flux density of the main field B 0 (applicable to a patient) and the construction of the scanner, but the most important factor determining the workers' exposure is the work practice. In the course of a patient's routine examination in scanners of B 0 = 1.5 T, the nurses are present over ∼0.4–2.9 min in SMF exceeding 0.03% of B 0 (i.e. 0.5 mT), but only sometimes they are present in SMF exceeding 5% of B 0 (i.e. 75 mT). When patients need more attention because of their health status/condition, the nurses' exposure may be significantly longer – it may even exceed 10 min and 30% of B 0 (i.e. 500 mT). We have found that the level of exposure of nurses to SMF may vary from < 5% of the main field (a median value: 0.5–1.5%; inter-quartile range: 0.04–8.8%; max value: 1.3–12% of B 0) when a patient is moved from the magnets bore before contrast administration, up to the main field level (B 0) when a patient stays in the magnets bore and nurse is crawling into the bore.

A mechanical strain caused by shearing, drilling, and punching stresses that occur during the processing of the electrical steel sheets will cause a deterioration of the magnetic characteristics/properties of the material. The variation of localized magnetic flux density distribution is measured and monitored with the help of a search coil located at 45 ∘ angle with respect to the center of different hole shapes such as circular, elliptical, triangular, and square. The localized flux density and magnetic field strength, in laser-cut non-oriented electrical steels, were measured at different peak flux densities with values between 0 and 0.5 T in a frequency range from 50 to 400 Hz. The maximum flux density was obtained in the case of the sample, which has an ellipsoidal hole at the same value of the field strength, whereas the minimum flux density was measured for the triangular hole at 50 Hz.

The biological effects of static magnetic fields (MFs) with intensity of 6 mT were investigated in lymphocytes and U937 cells in the presence or absence of apoptosis-inducing drugs by transmission (TEM) and scanning (SEM) electron microscopy. Lectin cytochemistry of ConA-FITC conjugates was used to analyze plasma membrane structural modifications. Static MFs modified cell shape, plasma membrane and increased the level of intracellular [Ca++] which plays an antiapoptotic role in both cell types. Modifications induced by the exposure to static MFs were irrespective of the presence or absence of apoptotic drugs or the cell type. Abundant lamellar-shaped microvilli were observed upon 24 hrs of continuous exposure to static MFs in contrast to the normally rough surface of U937 cells having numerous short microvilli. Conversely, lymphocytes lost their round shape and became irregularly elongated; lamellar shaped microvilli were found when cells were simultaneously exposed to static MFs and apoptosis-inducing drugs. In our experiments, static MFs reduced the smoothness of the cell surface and partially impeded changes in distribution of cell surface glycans, both features being typical of apoptotic cells. Cell shape and plasma membrane structure modifications upon static MFs exposure were time-dependent. Lamellar microvilli were clearly observed before the distortion of cell shape, which was found at long times of exposure. MFs exposure promoted the rearrangement of F-actin filaments which, in turn, could be responsible for the cell surface modifications. Here we report data that support biological effects of static MFs on U937 cells and human lymphocytes. However, the involvement of these modifications in the onset of diseases needs to be further elucidated.

The present work was a comparative study of the bio-effects induced by exposure to 6 mT static magnetic field (MF) on several primary cultures and cell lines. Particular attention was dedicated to apoptosis. Cell viability, proliferation, intracellular Ca(2+) concentration and morphology were also examined. Primary cultures of human lymphocytes, mice thymocytes and cultures of 3DO, U937, HeLa, HepG2 and FRTL-5 cells were grown in the presence of 6 mT static MF and different apoptosis-inducing agents (cycloheximide, H(2)O(2), puromycin, heat shock, etoposide). Biological effects of static MF exposure were found in all the different cells examined. They were cell type-dependent but apoptotic inducer-independent. A common effect of the exposure to static MF was the promotion of apoptosis and mitosis, but not of necrosis or modifications of the cell shape. Increase of the intracellular levels of Ca(2+) ions were also observed. When pro-apoptotic drugs were combined with static MF, the majority of cell types rescued from apoptosis. To the contrary, apoptosis of 3DO cells was significantly increased under simultaneous exposure to static MF and incubation with pro-apoptotic drugs. From these data we conclude that 6 mT static MF exposure interfered with apoptosis in a cell type- and exposure time-dependent manner, while the effects of static MF exposure on the apoptotic program were independent of the drugs used.

This study was designed to directly quantify the effect of localized static magnetic field (SMF) exposure on the diameter of microvessels in adult rat skeletal muscle in vivo. Microvascular networks in the exteriorized rat spinotrapezius microvasculature were exposed to a localized, uniform 70 mT SMF for 15 min. Arteriolar vessel diameters were measured; and the extent of vessel contraction, microvascular tone, was calculated before exposure, immediately after exposure, and 15 and 30 min after removal of the field. A calculated value of high tone corresponds to vessels that are vasoconstricted and a calculated value of low tone refers to vessels that are vasodilated. Vessels with initial tone <15% showed an increasing trend in tone and, conversely, vessels with initial tone >15% showed a significant (P < 0.05) decrease in tone 15 and 30 min following application, respectively. Further classification of the data with regards to the initial vessel diameter demonstrated that vessels with initial diameters <30 microm and initial tone <15%, smaller diameter vessels that are initially vasodilated, showed significant (P < 0.05) increase in tone immediately, 15 and 30 min following SMF exposure. Additionally, <30 microm vessels with >15% initial tone, smaller diameter vessels that are initially vasoconstricted, demonstrated a significant (P < 0.05) decrease in tone 30 min after SMF exposure. Vessels with initial diameters >30 microm had no significant response to the SMF. These results imply that SMF exposure influences arteriolar diameters, and therefore microvascular tone, in a restorative fashion acting to normalize the tone to the median tone value of 15% following exposure. Because this response occurs primarily in the resistance arterioles, which significantly influence tissue perfusion, SMF application could be efficacious for the treatment of both ischemic and edematous tissue disorders involving compromised microvascular function.

Power losses of electrical iron sheets have been measured under controlled magnetizing conditions in which a waveform of magnetic flux density was controlled to be trapezoidal and symmetrical. The magnetizing frequency was varied from 200 Hz to 50 Hz by varying the time duration of the maximum flux density from 0 to 7.5 ms while keeping the time for flux change at 2.5 ms. The result shows that losses per magnetizing cycle increase with the duration of the pause time at the maximum flux density and that this increase of losses may be attributed to several magnetic relaxation phenomena and reversal of magnetizing direction. >

Magnetotactic bacteria (MTB) can use their unique intracellular magnetosome organelles to swim along the Earth's magnetic field. They play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have shown that the applied magnetic fields could affect the magnetosome formation and antioxidant defense systems in MTB. However, the molecular mechanisms by which magnetic fields affect MTB cells remain unclear. We aim to better understand the dark at 28°C-29°C for 20 h, as shownthe interactions between magnetic fields and cells, and the mechanism of MTB adaptation to magnetic field at molecular levels. We performed microbiological, transcriptomic, and genetic experiments to analyze the effects of a weak static magnetic field (SMF) exposure on the cell growth and magnetosome formation in the MTB strain Magnetospirillum magneticum AMB-1. The results showed that a 1.5 mT SMF significantly promoted the cell growth but reduced magnetosome formation in AMB-1, compared to the geomagnetic field. Transcriptomic analysis revealed decreased expression of genes primarily involved in the sulfate reduction pathway. Consistently, knockout mutant lacking adenylyl-sulfate kinase CysC did no more react to the SMF and the differences in growth and Cmag disappeared. Together with experimental findings of increased reactive oxidative species in the SMF-treated wild-type strain, we proposed that cysC, as a key gene, can participate in the cell growth and mineralization in AMB-1 by SMF regulation. This study suggests that the magnetic field exposure can trigger a bacterial oxidative stress response involved in AMB-1 growth and magnetosome mineralization by regulating the sulfur metabolism pathway. CysC may serve as a pivotal enzyme in mediating sulfur metabolism to synchronize the impact of SMF on both growth and magnetization of AMB-1.

The safety of electric power cables is dependent in part upon the maximum electrostatic flux density in the dielectric. The core loss in revolving machinery is, in part, a pole-face loss, dependent on variations in the magnetic flux density. Alternators work best in parallel, and give less interference with communication circuits, if of a good wave form, of flux density. These fields of electrostatic and magnetic flux are often too irregular to lend themselves to an accurate comaputation, and hence experimental methods of study are needed. The writers have improved a method suggested by F. W. Carter, and the results obtained give promise of a field for useful study. The method itself may be briefly described as measuring an electric model of the field to be studied cut out of sheet metal. By the use of a contact-making device, with two contacts, held at a fixed distance apart, but movable to any part of the edge of the metal sheet, voltage gradients may be measured upon a galvanometer. From these measurements, the flux densities may be calculated. The paper describes the method in detail and also gives some results of study on the three problems mentioned. It is shown how this method of test can be used to improve pole-shoe design. The importance of pole-shoe design is pointed out. An appendix is included, showing that correct pole-shoe design is needed to eliminate the so-called ``tooth ripples.''

Transdermal drug delivery systems of indapamide have been formulated by using solvent casting method. Monolithic systems were prepared by using hydroxy propyl methyl cellulose (HPMC) and ethyl cellulose (EC) polymers by incorporating glycerine and dibutyl phthalate as plasticizers, respectively. All the patches were uniform with respect to physicochemical and scanning electron microscopy (SEM) evaluation. Th e in vitro drug release studies indicated that HPMC containing fi lms have shown better release than that of EC containing fi lms without any permeation enhancer. A total of eight monolithic systems were prepared by using a drug polymer ratio of 1:4 and incorporated diff erent vegetable oils as permeation enhancers in diff erent concentrations. Th e prepared systems released the drug in the following order: F3 > F4 > F7 > F5 > F8 > F6 > F1 > F2. Th e various permeation parameters such as fl ux, permeability coeffi cient, enhancement ratio and diff usion rate constants were determined for all the formulations. Th e maximum fl ux of 9.08 × 102 mg/ cm2 h was observed with HPMC monolithic system containing 30% w/w olive oil. A signifi cant improvement of fl ux was observed in the following order: olive oil > linseed oil > sunfl ower oil > cottonseed oil > coconut oil > castor oil. Further improvement of fl ux was observed, when 30% w/w olive oil was applied directly onto the skin prior to the studies. Th e in vitro release studies revealed that the release was sustained up to 24 h and it follows zero-order kinetics. All the fi lms were found to be stable at 37°C and 45°C with respect to their physical parameters and drug content. Key words: EC, HPMC, linseed oil, olive oil, permeation enhancers, sunfl ower oil, transdermal

Osteogenic differentiation of MC3T3-E1 cells on poly(L-lactide)/Fe3O4 nanofibers with static magnetic field exposure.

Evapotranspiration （ET） is an important component of ecosystem water and energy balances, and subtropical evergreen and deciduous broadleaf forests play an important role in regional water cycles and budgets. To enhance prediction of climate change impact on the terrestrial ecosystem an improved understanding of the water and energy fluxes between vegetation and the atmosphere is needed. In Mount Tianmu area of Zhejiang Province, a subtropical evergreen and deciduous broadleaf mixed forest observation tower was set up in December 2012 with a three dimensional ultrasonic anemometer, a H2O/CO2 infrared analyzer, and conventional meteorological instruments for measuring a multi-layer gradient of temperature and humidity, windspeed, and radiation. Based on data observed from July 2013 to June 2014, water vapor flux features of the ecosystem were analyzed, and the net radiation responses to water vapor flux were determined. Results showed that annual water vapor flux was positive with distinct diurnal and seasonal variations. The maximum monthly water vapor flux occurred in July with a maximum daily 0.115 gm－2s－1; the lowest was in January with a maximum of only 0.029 gm－2s－1. The maximum quarterly water vapor flux occurred in summer, and the lowest was in January. The annual total ET was 721.25 mm （about 51.5% of the annual precipitation）. The annual net radiation （Rn） for this ecosystem was 3 305.65 MJm－2. Also, Rn was the main driving force of ET and was a key factor in energy balance. Thus, water vapor flux being positive meant that the ecosystem was the source of water vapor. ［Ch, 6 fig. 2 tab. 28 ref.］

Introduction: The current understanding of the biological impacts of a static magnetic field (SMF) is restricted to the direct interactions of the magnetic field with biological membranes. The electrokinetic (zeta) potential is an electrochemical property of erythrocyte surfaces which was negatively charged in physiological media after SMF exposure (0.1‒2.0 T).Methods: The novel data about electrokinetic parameters of the erythrocytes is determined by microelectrophoresis after SMF-exposure in norm and heterozygous β-thalassemia. The methods of light scattering, lipid peroxidation, fluorescence microscopy are used.Results: The electrokinetic potential of erythrocytes in norm is increased after SMF intensities due to enhanced negatively exposed charges on the outer surface of the membrane accompanied by an increase in light scattering where changes in cell morphology are observed. Conversely, a decrease in the zeta potential of β-thalassemia erythrocytes upon SMF-treatment was determined because of the reduction in the surface electrical charge of the membranes, where a significant decrease in light scattering at 1.5 T and 2.0 T was recorded. Exposure to SMF (0.5–2.0 T) was associated with an increase in the malondialdehyde content in erythrocytes. Biophysical studies regarding the influence of SMF on the electrostatic free energy of cells shows an increase in negative values in healthy erythrocytes, which corresponds to the implementation of a spontaneous process. This is also the process in β-thalassemia cells after SMF exposure with lower negative values of free electrostatic energy than erythrocytes in norm.Discussion: The effect of static magnetic field (SMF 0.1–2.0 T) on the electrokinetic and morphological characteristics of erythrocytes in norm and β-thalassemia is determined and correlated with the increase/reduction in surface charge and shrinkage/swelling of the cells, respectively. Lipid peroxidation of healthy and β-thalassemia erythrocytes caused an enhancement of lipid peroxidation because of the higher concentrations of TBARS products in cellular suspension. SMF (0.1‒2.0 T) altered the spontaneous chemical processes with negative values of electrostatic free energy of erythrocytes in norm and β-thalassemia accompanied by a lower FITC-Concanavalin A binding affinity to membrane receptors (SMF 2.0 T). The electrokinetic properties of human erythrocytes in norm and β-thalassemia upon SMF treatment and their interrelationship with the structural-functional state of the membrane were reported. The presented work would have future fundamental applications in biomedicine.

Static magnetic field (SMF) interacts with mammal skeletal muscle; however, SMF effects on skeletal muscle cells are poorly investigated. The myogenic cell line L6, an in vitro model of muscle development, was used to investigate the effect of a 80 +/- mT SMF generated by a custom-made magnet. SMF promoted myogenic cell differentiation and hypertrophy, i.e., increased accumulation of actin and myosin and formation of large multinucleated myotubes. The elevated number of nuclei per myotube was derived from increased cell fusion efficiency, with no changes in cell proliferation upon SMF exposure. No alterations in myogenin expression, a modulator of myogenesis, occurred upon SMF exposure. SMF induced cells to align in parallel bundles, an orientation conserved throughout differentiation. SMF stimulated formation of actin stress-fiber like structures. SMF rescued muscle differentiation in the presence of TNF, a muscle differentiation inhibitor. We believe this is the first report showing that SMF promotes myogenic differentiation and cell alignment, in the absence of any invasive manipulation. SMF-enhanced parallel orientation of myotubes is relevant to tissue engineering of a highly organized tissue such as skeletal muscle. SMF rescue of muscle differentiation in the presence of TNF may have important therapeutic implications.

The maximum flux density of a gyrosynchrotron radiation spectrum in a magnetic diploe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrotron spectrum increases with increasing low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing angle, and with decreasing energy spectral index of energetic electrons, number density and temperature of thermal electrons. It is found that there are linear correlations between the logarithms of the maximum flux density and the above eight parameters with correlation coefficients higher than 0.91 and fit accuracies better than 10%. The maximum flux density could be a good indicator of the changes of these source parameters. In addition, we find that there are very good positive linear correlations between the logarithms of the maximum flux density and peak frequency when the above former five parameters vary respectively. Their linear correlation coefficients are higher than 0.90 and the fit accuracies are better than 0.5%.

Effect of static magnetic field on the molten pool dynamics during laser powder bed fusion of Inconel 718 superalloy