Moderate Strength Magnetic Field Research Articles

Thin-layer chromatography in moderate strength magnetic fields

Magnetic field can influence some processes taking part in the solid-liquid interphase area. An excellent tool for the investigation of this phenomenon is thin-layer chromatography. In this experiment, the influence of magnetic field parallel with chromatogram development direction on retention and system efficiency was investigated. The application of superconducting magnet allowed for generating the adjustable magnetic field up to about 2 T and allowed for investigation on dependence between inductivity of the field and retention changes of the chosen polyaromatic hydrocarbons. The obtained results show that the presence of magnetic field alternates the interactions among all components of a chromatographic system. Thus, in order to predict substance retention and system efficiency changes induced by the presence of the field, more parameters than the force acting on chromatographed molecule must be taken into account.

Stimulation of Chondrogenic Differentiation of Adult Human Bone Marrow-Derived Stromal Cells by a Moderate-Strength Static Magnetic Field

Tissue-engineering strategies for the treatment of osteoarthritis would benefit from the ability to induce chondrogenesis in precursor cells. One such cell source is bone marrow-derived stromal cells (BMSCs). Here, we examined the effects of moderate-strength static magnetic fields (SMFs) on chondrogenic differentiation in human BMSCs in vitro. Cells were cultured in pellet form and exposed to several strengths of SMFs for various durations. mRNA transcript levels of the early chondrogenic transcription factor SOX9 and the late marker genes ACAN and COL2A1 were determined by reverse transcription-polymerase chain reaction, and production of the cartilage-specific macromolecules sGAG, collage type 2 (Col2), and proteoglycans was determined both biochemically and histologically. The role of the transforming growth factor (TGF)-β signaling pathway was also examined. Results showed that a 0.4 T magnetic field applied for 14 days elicited a strong chondrogenic differentiation response in cultured BMSCs, so long as TGF-β3 was also present, that is, a synergistic response of a SMF and TGF-β3 on BMSC chondrogenic differentiation was observed. Further, SMF alone caused TGF-β secretion in culture, and the effects of SMF could be abrogated by the TGF-β receptor blocker SB-431542. These data show that moderate-strength magnetic fields can induce chondrogenesis in BMSCs through a TGF-β-dependent pathway. This finding has potentially important applications in cartilage tissue-engineering strategies.

Simulation of flow behavior of particles in liquid–solid fluidized bed with uniform magnetic field

Abstract Flow behavior of solid phases is simulated by means of DEM–CFD in a liquid–solid fluidized bed with magnetization of preliminarily fluidized bed (LAST) mode along an axial uniform magnetic field. By changing the magnetic field strength, the distribution of particles is studied within the bed. The distributions of velocity and concentration of ferromagnetic particles are analyzed at the different magnetic field intensities. When the magnetic field strength is increased to a value at which the fluidization of strings starts, the particles are found to form straight-chain aggregates along the direction of the magnetic field. At very high magnetic field strengths, the defluidization is observed at which particles are fixed in the bed. Simulations indicate that the granular temperature of particles increases, reaches a maximum, and then decreases with the increase of magnetic-flux density. The moderate strength magnetic field gives a high fluctuation of particles. The predicted solid pressure increases with the increase of concentration of particles.

Shockwave–turbulent boundary layer interaction control using magnetically driven surface discharges

This study demonstrates the potential for shockwave–turbulent boundary layer interaction control in air using low current DC constricted surface discharges forced by moderate strength magnetic fields. An analytical model describing the physics of magnetic field forced discharge interaction with boundary layer flow is developed and compared to experiments. Experiments are conducted in a Mach 2.6 indraft air tunnel with discharge currents up to 300 mA and magnetic field strengths up to 5 Tesla. Separation- and non-separation-inducing shocks are generated with diamond-shaped shockwave generators located on the wall opposite to the surface electrodes, and flow properties are measured with schlieren imaging, static wall pressure probes and acetone flow visualization. The effect of plasma control on boundary layer separation depends on the direction of the Lorentz force (j × B). It is observed that by using a Lorentz force that pushes the discharge upstream, separation can be induced or further strengthened even with discharge currents as low as 30 mA in a 3-Tesla magnetic field. If shock-induced separation is present, it is observed that by using Lorentz force that pushes the discharge downstream, separation can be suppressed, but this required higher currents, greater than 80 mA. Acetone planar laser scattering is used to image the flow structure in the test section and the reduction in the size of recirculation bubble and its elimination are observed experimentally as a function of actuation current and magnetic field strength.

Numerical simulation of particle motion in a gradient magnetically assisted fluidized bed

Flow behavior of magnetizable particles is simulated in a two-dimensional gradient magnetically assisted bubbling fluidized bed. The motion of particles is simulated by discrete element method (DEM) with the consideration of external magnetic forces at a constant gradient magnetic field along bed height. The distributions of velocity and concentration of magnetizable particles are analyzed at the different magnetic field intensities. The simulations show a significant effect on the motion of particles with vertical magnetic-fields applied. When the magnetic field strength is increased to a value at which the fluidization of strings starts, the particles are found to form straight-chain aggregates in the direction of the magnetic field. At very high magnetic field strengths, defluidization is observed. Gas pressure drop of bed decreases with the increase of magnetic-flux densities. The granular temperature of particles increases, reaches a maximum, and then decreases with the increase of magnetic-flux density. Through the analysis of the motion of particles, it is concluded that the moderate strength magnetic field gives a high fluctuation of particles and distribute gas more evenly in the bed.

Elastic modulus of viscoelastic magnetic silicone gel body

AbstractThis paper describes various viscoelastic magnetic silicone gel bodies developed to create a new type of viscoelastic magnetic material. This material is capable of undergoing substantial changes in mechanical properties due to the large deformation caused by magnetic traction force under the application of a moderate strength magnetic field. This study performed tensile tests for various viscoelastic magnetic silicone gel bodies under a uniform steady magnetic field. The elastic moduli of the gel bodies were measured under different controlled experimental conditions. The experimental results showed that, under the applied magnetic field, the elastic moduli of the viscoelastic magnetic silicone gel bodies increased and were largely dependent upon the magnetic properties of the magnetic particles. The magnetic particle size and the material properties of the dispersant and the silicone gel also had significant effects on the moduli of the gel bodies. This paper also discusses the most appropriate combination of the materials used in this study from the standpoint of gaining a large magnetic traction force. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

Use of mucolytics to enhance magnetic particle retention at a model airway surface

A previous study has shown that retention of magnetic particles at a model airway surface requires prohibitively strong magnetic fields. As mucus viscoelasticity is the most significant factor contributing to clearance of magnetic particles from the airway surface, mucolytics are considered in this study to reduce mucus viscoelasticity and enable particle retention with moderate strength magnetic fields. The excised frog palate model was used to simulate the airway surface. Two mucolytics, N-acetylcysteine (NAC) and dextran sulfate (DS) were tested. NAC was found to enable retention at moderate field values (148 mT with a gradient of 10.2 T/m), whereas DS was found to be effective only for sufficiently large particle concentrations at the airway surface. The possible mechanisms for the observed behavior with different mucolytics are also discussed based on aggregate formation and the loading of cilia.

Magnetic field perturbations as a tool for controlling enzyme-regulated and oscillatory biochemical reactions

The feasibility of magnetic field perturbations as a tool for controlling enzyme-regulated and oscillatory biochemical reactions is studied. Our approach is based on recent experimental results that revealed magnetic field effects on the in vitro activity of enzyme systems in accordance with the radical pair mechanism. A minimum model consisting of two coupled enzyme-regulated reactions is discussed that combines, in a self-consistent manner, magnetic field-sensitive enzyme kinetics with non-linear dynamical principles. Furthermore, a simple detector mechanism is described that is capable of responding to an oscillatory input. Results reveal that moderate-strength magnetic fields ( B=1–100 mT) may effectively alter the dynamics of the system. In particular, a response behavior is observed that depends on: (1) the combination of static and time-varying magnetic fields; (2) the field amplitude; and (3) the field frequency in a non-linear fashion. The specific response behavior is critically determined by the biochemical boundary conditions as defined by the kinetic properties of the system. We propose an experimental implementation of the results based on the oscillatory peroxidase–oxidase reaction controlled by the enzyme horseradish peroxidase.

Tests for Human Perception of 60 Hz Moderate Strength Magnetic Fields

After preliminary experiments that pointed out the extreme cleverness with which perceptive individuals unintentionally used subtle auxiliary clues to develop impressive records of apparent magnetic field detection, we developed a heavy, tightly sealed subject chamber to provide extreme isolation against such false detection. A large number of individuals were tested in this isolation system with computer randomized sequences of 150 trials to determine whether they could detect when they were, and when they were not, in a moderate (7.5-15 gauss rms) alternating magnetic field, or could learn to detect such fields by biofeedback training. In a total of over 30,000 trials on more than 200 persons, no significantly perceptive individuals were found, and the group performance was compatible, at the 0.5 probability level, with the hypothesis that no real perception occurred.