Activity of an enzyme immobilized on superparamagnetic particles in a rotational magnetic field

We immobilize α-amylase extracted from Bacillus Iicheniformis on the surfaces of superparamagnetic particles and investigate the effect of a rotational magnetic field on the enzyme’s activity. We find that the activity of the enzyme molecules immobilized on superparamagnetic particles increases in the rotational magnetic field and reaches maximum at a certain frequency. We clarify the effect of the cluster structures formed by the superparamagnetic particles on the activity. Enzyme reactions are enhanced even in a tiny volume of solution using the present method, which is very important for the development of efficient micro reactors and micro total analysis systems (μ-TAS).     

Effect of an external RF field on the beam-plasma discharge in a magnetic field

The effect of an RF field on a steady-state beam-plasma discharge with a plane electrode placed parallel to a sheetlike electron beam is studied experimentally. The plasma parameters were measured by a single probe, and the electron distribution function was determined with the use of an electrostatic analyzer. The energy and current of the electron beam were E _B=2.5 keV and J _B=0.05–1.5 A, respectively. The working pressure was p=2×10^?5–10^?3 torr. The frequency of the external RF field was 13.56 MHz. Both the steady-state regimes in which the RF field had no effect on the plasma parameters and regimes with a pronounced effect of the RF field were observed. The experiments show that the regime of the discharge depends strongly on the plasma density and the magnetic field. The parametric instability is studied theoretically in the weak-turbulence approximation. It is shown that, due to the decay nature of the spectrum of plasma oscillations, the onset of instability is accompanied by the transfer of the energy of fluctuations over the spectrum, from the pump frequency toward its harmonics.     

Effect of viscosity on the plasma decay in a magnetic field

The effect of viscosity on the evolution of an axisymmetric plasma column in a longitudinal magnetic field is considered. It is found that, under the action of viscosity, the plasma density profile tends to become Gaussian.     

Effect of the magnetic field curvature on magnetic islands in tokamaks

The effect of the magnetic field curvature on magnetic islands in a tokamak is analyzed. It is demonstrated that the original investigation of this effect by Kotschenreuther et al. (1985) is inconsistent: on the one hand, the authors made the correct assumption that this is an ideal effect and, on the other hand, they described it in terms of the parameters characteristic of the “resistive ordering” approach, which is incompatible with the ideal approximation. More recent studies of the magnetic curvature effect have produced further ambiguities; as a result, a branch of the theory of magnetic islands has arisen that is based on the supposition that the effect under discussion can be described in terms of the Glasser-Greene-Johnson parameter D_R. This branch is shown to be erroneous, because the parameter D_R describes the plasma response to magnetic field perturbations on spatial scales of about the dimension of the linear resistive layer, while the characteristic spatial scale of the magnetic islands is much longer. It is concluded that the correct theory developed here for the magnetic curvature effect makes more optimistic predictions about its stabilizing role.     

Effect of a permanent magnetic field on the formation of lipid bilayers

Effect of the constant magnetic field (MF) by the induction of 1.1 T on formation kinetics of bilayer lipid membranes (BLM) from egg lecithin in decane was discovered. Under the effect of MF oriented in parallel to the lipid film place the rate of BLM formation decreases, while at its perpendicular orientation it is accelerated. The stationary value of BLM capacity decreases under MF effect at both orientations. The discovered changes in the rate of BLM formation under MF effect seem to be related to the effect of MF on liquid crystalline structure of colour lipid film.     

Effect of a 60 Hz magnetic field on the behavior of Paramecium

Paramecium multimicronucleatum was used as a model cell to study the effects of 60 Hz magnetic fields on swimming behavior. When exposed to a vertical field of 0.6 T, the cells accumulated at the upper end of the cuvette. An analysis of the swimming behavior revealed that the exposure to the field increased the number of cells swimming upwards maximally at 1 min after onset of the exposure. This effect of the magnetic field was transient, disappearing within a few minutes during the exposure. It is suggested that the magnetic field may amplify to a large extent the negative gravitaxis of Paramecium. Effects of an induced electric field on the swimming behavior are also discussed.     

Effect of a constant magnetic field on biological systems]

The effect of magnetic field on biological systems is discussed. A number of existing theories are evaluated, and a conclusion is made that it is difficult to explain from the standpoint of physics, neglecting the specifies of the living cell, the effect of the constant magnetic field on biological systems at the microscopic level.     

Effect of the magnetic field on the resonant particle acceleration

The acceleration of charged particles trapped by a potential wave in a magnetic field is investigated as applied to the problem of the generation of fast particles in a laser plasma. The conditions for unlimited particle acceleration are determined, and the spectra of fast particles are found.     

Effect of a magnetic field on ascorbate system in mice.

The effect exerted on the ascorbate system due to the exposure of mice to the constant magnetic field associated with MRI methods has been examined. The mice were exposed to magnetic field 1.00 T strength for 0.2 h, 3 h, or 24 h. The ascorbyl free radical in tissues was measured in vitro, which in vivo corresponds to the level of ascorbic acid. Only in a group of mice where the ascorbyl free radical was measured 24 h following their exposure to magnetic field 1.00 T strength for 24 hours, was the level of free radical in tissues significantly decreased.     

Effect of a low intensity magnetic field on human motor behavior

Extremely low frequency (ELF) magnetic fields (MF) are omnipresent in our modern daily environment, but their effects on humans are still not clearly established. The aim of this study was to determine the effect of a 50 Hz, 1,000 microT MF centered at the level of the head on human index finger micro-displacements. Twenty-four men recruited among the personnel of the French company, Electricité de France (EDF), completed the experiment. Their postural and kinetic tremors were recorded under four "field-on" and four "field-off" conditions, each tested during a real and a sham sequence. Eight postural and four kinetic tremor characteristics were calculated on recorded time series and were used for statistical analysis. No effect of the MF was found for kinetic tremor. Concerning postural tremor, the proportion of oscillations at low frequencies (between 2 and 4 Hz) was higher during the real than during the sham exposure sequence (P<.05). It suggests that MF could have a subtle delayed effect on human behavior, which is clearly not pathological. These results should be taken into account for the establishment of new exposure limits.     

The trajectories of particles suspended in electrolytes under the influence of crossed electric and magnetic fields

We observed that particles, suspended in an electrolyte and brought into crossed magnetic and electric fields of low intensities, will deviate in the central part of the electrophoresis chamber of a standard Zeiss Cytopherometer with a component vertical to both fields. The direction and magnitude, however, were sharply at variance with what would be expected by the action of the Lorentz force (EMF) on the surface of the particles. The magnitude of the deviation depends upon the magnetic and electric field strength, the ion concentration of the suspension medium and the geometry of the chamber. The movement of the particles is due to streaming of the electrolyte which is mainly caused by inhomogeneities of the electric field in the electrophoresis chamber. The magnitude of the effect is high enough to occur under physiological conditions. Magneto-electrophoretic streaming might eventually act as a transducer mechanism which could explain the ability of some animals to orientate themselves in the geomagnetic field.     

Effect of relative humidity on the movement of rat vibrissae in a 60-Hz electric field

The snouts of rats were placed in a 60-Hz electric field at an unperturbed field strength of 50 kV/m. A count of the number of vibrissae that moved in the field was made on a series of rats over a number of days where the laboratory humidity varied from 25% to 48%. The number observed to vibrate fell from nine to zero or one at relative humidities between 25% and 39%, respectively.     

Effect of a single magnetic field pulse on the electric activity of mollusk neurons

The influence of a single impulse of magnetic field (MF) of triangular shape of neuron electrical activity (EA) of Limnaea stagnalis registered intracellulary was studied. The dependence of the neuron reaction on the MP speed changing has been found. The effective values of speeds of impulse fronts were within 0,1 to 10,0 mT/c range. The threshold amplitude of MF impulse for most neurons was between 0,1 and 1,0 mT. With increasing MF amplitude up to 10,0 mT the efficiency of the effect does not essentially increase.