Both left and right sartorius muscle preparations with or without sciatic nerve were isolated from the bullfrog, Rana catesbeiana, and were mounted in the chambers. Left side of the preparation was exposed to a static magnetic field, 0.65T, for several hours and the right side preparation was used as a control. The muscle tension was induced by the nerve or muscle stimulation electrically, with the intervais of 40ms; 100 Pulses, every 30min. The latency and the maximal rate-of rise of muscle tension were measured and the obtained values from the exposed muscle were compared with those from the control muscle. The results showed that the latency was shortened approximately 20% in case of muscle stimulation and about 15% in nerve stimulation, within 3 hours when the preparation was exposed to the magnetic field, although the time courses were different between the two. The maximal rate of rise of the tension became faster by about 10 to 15% in case of the muscle stimulation. However, the maximal rate of rise was changed little when the tension was induced by the nerve stimulation within 3-hr exposure. It was discussed that the differences between the results obtained by the muscle stimulation and those obtained by the nerve stimulation would mean that the transmission mechanisms on the neuro-muscular junction were influenced by the magnetic field.

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A non-invasive method of magnetic stimulation of the spinal roots was designed. The basic idea is to concentrate induced eddy currents in a target by a pair of opposing pulsed magnetic fields. A figure-eight coil was positioned a little laterally from the median line of the back so that time-varying magnetic fields could pass through the body in the opposite directions around the target. Magnetic stimulation of the spinal roots was carried out in the human and rabbit. Each spine level was stimulated selectively with electromyographic (EMG) waves related to both the H-reflex and M-wave. Our results indicate that the M-wave can be produced by currents flowing either in the rostral or caudal direction, whereas the H-reflex is only generated by curents flowing in the caudal direction. The H-reflex elicited by magnetic stimulation of the nerve in the vicinity of the spine could provide a new tool in diagnosis of intra-and infraspinal neuro-muscular diseases.

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Functional maps of the human motor cortex related to the hand and foot areas have been obtained by a method of focal magnetic stimulation of the brain. We have obtained that an optimal direction exists for currents to flow in order to produce neural excitation in all functional areas of the cortex examined. We also observed that the functional maps of the brain vary according to the orientation of the stimulating currents. This study focuses on the mechanism which is responsible for producing this anisotropic response to brain stimulation. We investigate how optimal directions of stimulating current vectors change at different points in each fuctional area in the cortex and develope a model of neural excitation elicited by magnetic stimulation. The model is based on the assumption that a nerve axon is mostly excited when the magnetically induced eddy currents flow in the direction in parallel to the nerve axon. The validity of the model is verified by experiments using peripheral nerve-muscle systems in humans and frogs. The model explains our observation that the orientation of the induced current vectors reflect both the functional and anatomical organization of neural fibers in the brain.

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Seeds of a corn with a primary root were exposed to static and alternating magnetic field. Positions of roots were accurately measured by a microscope before and after exposure of field, and growth of the roots during the exposure was calculated. The calculated values were compared to those of a control group by means of Kolmogolov-Smirnov test. We discussed growth of the roots in the field and tropism to magnetic poles.
Judging from the results, growth of a primary root of the corn was restrained in alternating field of 200 (gauss) -10(Hz). Under static field, however, was not. Tropism of the roots for the gravity was also restrained in 100 (gauss) -20(Hz).

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It is important to know whether or not static magnetic fields give influence on biological systems. It has been reported that some of biological materials such as fibrin and sickle cells orient to the direction of strong magnetic fields. In this study, magnetic orientation of fibrin is observed under a 6.34T magnetic field. Ferri-magnetic materials γ-Fe₂O₃(0.3μm×0.03μm) are mixed into fibrinogen, and the gelling process of the mixture is exposed to a 0.5T magnetic field. Magnetic orientation of fibrin is enhanced. Magnetic orientation of gelatin is detected by birefringence measurements under a 1.6T magnetic field. Magnetic orientation of gelatin mixed with γ-Fe₂O₃ is also demonstrated. It is observed that giant fibers which orient to the direction of magnetic field are produced. These fibers consist of ferri-magnetic material and polymer chains.

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Totally implantable artificial heart actuated electrically is in the process of development now. For energy transmission it is considered to transport electrical energy through the skin by means of the two coils. The flexible transformer utilizing amorphous magnetic fiber transmitts the electrical energy of 20 Watts through the gap of 5mm. The thickneses of each coil is 1.5mm.
Using the circuit constants yielded from the measurement, the primary and the secondary current density, the primary counter electromotive force are calculated. Temperature properties of the transformer are also discussed.

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Recently local hyperthermia has become a topic of broad interest. In hyperthermia measurement of temperature distribution inside a body is important to avoid occurrence of a hot spot. At present, the temperatures inside the body are measured as sampled data using invasive tools.
Soft heating method using temperature-sensitive ferrite rod is applied for hyperthermia as a cancer treatment. The heating element developed generates sufficient heat which causes the temperature of a tumor up to 44°C. As an animal experiment, Wistar rats and Walker carcinosarcoma 256 are prepared. The Carcinosarcoma was transplanted into the right femoral regions of the rats. Heating operation was performed twice a week. A necrotic mass formed by a heating device was approximately ellipsoidal. Tumors whose volume were less than 1cm³ vanished almost completely. The method may also be suitable for deep-seated small brain tumor.

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In non-invasive hyperthermia, it is usually difficult to heat deep and selected region in a body. This paper describes a new inductive heating method, in which a large ferrite core in troidal shape and water bolus are used, and which has been proposed in our previous paper. In this method, if the eddy current which passes through the surface of the body is cut by an insulating film between the body and the bolus or by the bolus in a special shape, we can expect to heat the selected region. We have developed our computation code of the finite element method which analyzes 3-D eddy current and 3-D spatial temperature distributions, in order to study characteristics of selective heating. At first, this computation code is applied to a cylindrical model. And we examine an effect of selective heating by cutting the eddy current path by the finite element analysis of SAR and temperature distribution, and the experimental data. Furthermore an effect which this heating method made on the human body, was studied by 3-D analysis.

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We have made simulation measurements of the neuromagnetic field generated by a current dipole electrode, that was located at different depths in the human cranium phantom fille with the saline, and the localization of the current dipole. The multichannel measurement was simulated by measuring the normal field so that a single detection coil moved on a spherical surface over the phantom. The error in the computed location of the dipole source from the measured magnetic field data increased with the source depth, indicating the effect of the volume current within the non-spherical conductor. As a conductor model in the source localization, the sphere that was fitted to the local inner shape of the cranium was suited. Further, this spherical conductor model can be eliminated if we choose a sphere with a radius close to that of the skull as the measurement surface of the multidetection coils.

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Recently, magnetic stimulations of living body by using time-varying magnetic field have been investigated with respect to stimulator and its effect. The authors have been developing the more focal magnetic stimulator which is effective for stimulating tissue of human body. In this developing process, the density distribution of the eddy current induced in saline tank by magnetic stimulator coils has been measured with a current probe in order to examine the effectiveness of the coils. The probe is made of ultra-mini coaxial cable and detects the eddy current signal of 20kHz sinusoidal wave with the current density resolution of about 0.2μA/mm² and with the half angular resolution of about 40 degrees. The probe is set in the current stream at a measuring point, and the picked-up current as the current density signal is transmitted to a measuring instrument with inductive interference suppressed. The measured values at the lattice points on a horizontal plane make up the arrow map of the current distribution.
Experiments are made by combining several coils and tanks. The experiment in the semi-infinite volume shows that the measured distribution agrees well with the computed distribution. The other experiments in the tank simulating human limb show the difference of concentration due to the effect of boundary.

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The electrochemical, optical and magnetic properties in poly(p-phenylene vinylene), PPV, during electrochemical p-type doping have been investigated by cyclic voltammetry, optical absorption spectrum and electron spin resonance (ESR) measurements. The band gap of PPV was evaluated to be about 2.7eV. The evolution of localized states is evidenced by the spectral change with electrochemical doping. The spin susceptibility (χ) increased by about three orders of magnitude from 2.6×10^-8 to 2.5×10^-5 emu/mol up to a dopant concentration of about 2.4mol%. With further increasing dopant concentration, χ decreases slightly. The spin density evaluated from χ was consistent with the polaron density assumed to be formed by dopants of 2.4mol%. The ESR linewidth decreases by doping from about 9.5 to 0.4G and then again increases slightly with increasing dopant concentration. The g value of 2.0038 at the neutral state shifts upon doping to the smaller value of 2.0030. These results are discussed in terms of polaron and/or bi-polaron models. Thermally stimulated current (TSC) measurements have been performed on undoped stretched PPV. Two TSC peaks P1 and P2 are observed and become smaller as the stretching ratio (l/l0) was gradually increased. Especially, peak. P2 is markedly suppressed on stretching. The trap depths are evaluated from the initial increasing part of each separated peak by the thermal cleaning method to be-about 0.36 and 0.55eV for peaks P1 and P2, respectively, regardless of l/l0. Peak P1 is interpreted as originating from electron traps formed by impurities such as Br₂ or SO₃ which were not eliminated by heat treatment. In contrast, peak P2 was confirmed to be based on defects already existing in the amorphous parts of PPV since the crystallinity in PPV increases and χ evaluated by ESR spectra in stretched PPV decreases on increasing l/l0.

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A series of electrical breakdown by impulse voltage in a sphere gap arrangement shows that the breakdown voltages are scattered in a certain range of voltage and the sparks are not always along the central axis line. A nearly circular distribution of spark points is formed and centered on the axis of the gap. To make these phenomena clear, the distribution of electrical breakdown voltages and breakdown points in the sphere gap is analyzed by alculating the breakdown voltage along electric field lines by integrating the effective ionization coefficient and also calculating the probability of breakdown by initial electron emitted from the cathode surface.

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