The soft magnetic properties and electrical resistivity of Fe-Mg-O films prepared by an rf magnetron sputtering technique were studied for high-frequency (e.g., 100 MHz) soft magnetic materials. Soft magnetic Fe-Mg-O films have a heterogeneous structure containing nanometer sized Fe-grains.
A high saturation magnetization of 10-18 kG and a high electrical resistivity of 100-1000 μΩcm were achieved for Fe-Mg-O films with an Fe content of 40 to 80 at%. The relative permeability of an Fe₆₀Mg₁₇O₂₃ film was about 2000, and was almost constant up to 200 MHz.

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NiFeP films were electrodeposited based on the FeP film in order to decrease their saturation magnetostriction (λ_s) and increase their resistivity (ρ). Ni₁₁Fe₆₅P₂₄ films with low λ_s (= 8.2 × 10^-6) were obtained, because they contained 11 at%Ni. The films have suitable soft magnetic properties and thermal stability after annealing at under 250°C in vacuum. In order to increase the resistivity of Ni₁₁Fe₆₅P₂₄ film, an organic additive such as diethylenetriamine (DET) was added to the plating bath. A new type of soft magnetic NiFeP film with a higher resistivity of 170μΩcm was developed from a bath containing DET, because of the 0.2 at% carbon content of the deposited film.

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The magnetic properties and resistivity of electroplated FeNiP film were investigated. The resistivity of FeNiP film increased and its magnetic flux density decreased with the addition of phosphorus. The optimum Fe₂₉Ni₆₄P₇ film showed higher resistivity (85μΩcm) than Fe₅₅Ni₄₅ film (45 μΩcm). The magnetic flux density, saturation magnetostriction, anisotropic field, and coercivity of Fe₂₉Ni₆₄P₇ film were about 1.0T, 50×10^-7, 15 Oe, and lower than 1.0 Oe, respectively. The frequency characteristic and thermal stability of FeNiP film were also investigated. The permeability of FeNiP film began to decrease in a higher-frequency region than that of FeNi film. The resistivity of FeNiP film decreased as a result of annealing at 200°C, where as that of FeNi film was unchanged after annealing at temperatures up to 300°C.

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Fe₈₃Gd₁₇-O granular soft magnetic films with high electrical resistivity were successfully prepared at a rather high rate (∼90 nm/min) by the reactive evaporation method, in which an O₂ molecular beam was used. The films with good properties showed a coercivity of ∼2 Oe, 4πM_s of ∼8000 G, a uniaxial anisotropy field of ∼20 Oe, and a resistivity of ∼500μΩcm. The easy axis of the inplane anisotropy was found to be generated in the direction normal to the plane of O₂ beam incidence. After annealing at 250°C for 2 hours, the 4πM_s of as-deposited films increased to values of over 10000 G.

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When the stress applied to ferromagnetic materials after demagnetization is changed, the magnetic susceptibilities of their initial magnetization curves increase more than those without any stress change after demagnetization. This phenomenon is called the demagnetization-stress effect The demagnetization-stress effects on grain-oriented Si−Fe sheets cut parallel (L-sample) and perpendicular (T-sample) to the specimen‘s rolling direction were investigated. Observation of the stress effect in the L-sample showed that its magnetization increment ratio was up to 130%. Hardly any demagnetization-stress effects was observed in the T-sample. However, when a biasing tensile stress of 10 MPa was applied to the sample, the demagnetization-stress effect was observed in the T-sample. The differences between the properties of the sample in these conditions can be explained by taking account of their domain structures during their magnetization process.

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One of the main factors in the acoustic noise of power transformers is thought to be magnetostriction of the cores, because the magnetic flux deviates from the easy axes at the corners of the cores. Therefore, we measured the magnetostriction and observed the domain structure in single crystals of (100) Si-Fe sheets when the easy axes deviated from the exciting direction. Complicated behaviors involving shrinkage and expansion were observed in the measured magnetostriction. In the demagnetized state, 180° domain walls parallel to the [001] direction were observed. When a small field was applied, a [010] domain was generated at the edge of the sample. The [001] and the [010] domains are partitioned by a 90° domain wall, whose movement caused large shrinkage. In a larger field, rotation of the magnetization caused large expansion. Thus, it became clear that large vibrations with magnetostriction were generated at the corners of the core, even if the cube-textured Si-Fe was used as the core's material.

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Methods for improving the magnetic properties of 3% non-oriented silicon steel were investigated. The thickness of samples was reduced to 0.1 mm by cold-rolling, and they were subsequently annealed in an argon gas atmosphere under various annealing conditions (annealing temperature, holding time, heating rate, and cooling rate). The obtained minimum iron loss was W_15/50 = 2.38 W/kg, the coercive force was H_c=38 A/m, and the magnetic induction at 800 A/m was B₈ = 1.69 T. The sample annealed under the optimum annealing conditions showed a dual-axis-like torque curve and had a high proportion of (100) plane texture.

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We found that in the three-stage rolling method, control of the intermediate annealing temperatures improves the [001] orientation and makes it possible to reduce the iron loss in silicon steels. The measured iron loss W_13/50 for an applied tensile strength of 2 kg/mm² was 0.28 W/kg, which is about 50% less than that of conventional (300-μm) grain-oriented silicon steels.

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The effects of tensile stress and strain on magnetization and magnetic domains in grain-oriented silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. The magnetization increased with decreasing strain and, after reaching a peak value, decreased with decreasing strain. We observed Lancet domains in a sample after removing stress applied to a plastic deformation region. This phenomenon can be explained by changes in the domain structures, which were partly observed. The results obtained in this investigation can be applied to the nondestructive detection of fatigue in metallic magnetic materials.

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The microstructure of Mn-Zn ferrite on MoO₃ addition was studied. It was found that although MoO₃ addition expanded the diameters of crystalline grains, it also promoted porosity, thereby impeding grain growth. When the amount of MoO₃ was increased, the grain diameter expanded, peaked, and then gradually declined under the influence of the porosity. It is important to note that it forms a fine microstructure that has large grains and a low level of porosity. We studied the effect of the sintering parameters−sintering time, heating rate, and oxygen partial pressure−on the microstructure of the ferrite. As a result, we obtained a high-initial-permeability Mn-Zn ferrite with μ_iac = 24,400.

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The effect of the composition of MnZn ferrites on the loss characteristics at 1 MHz and 50 mT has been studied. An increase of the iron content in the system of Fe_0.53+xMn_0.44-xZn_0.03 reduced the core loss. Hysteresis, eddy current, and residual losses were all reduced because of the decrease in H_c, the increase in resistivity, and the upward shift of the resonance frequency at the minimum temperature of core loss, respectively. Magnetizing at 100 mT, however, increased the core loss. Chemical analysis results of Fe²⁺/Fe and Mn³⁺/Mn decreased by magnetizing. Moreover, low partial pressure of oxygen during firing, cation defects and the change of the core loss decreased.

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Fe-Al-O films with high electrical resistivities were prepared on polyimide substrates by reactive dc magnetron sputtering in Ar + O₂ gases and by RF co-sputtering of Fe and Al₂O₃. The relationship between the magnetic properties and resistivities of the films was investigated. The films prepared by RF co-sputtering exibited soft magnetic properties together with high resistivities of more than 10³μΩcm. After annealing at 380°C for 1 hour under a field of 1 kOe, a coercivity of 1.5 Oe, a resistivity of 2600μΩcm, an anisotropy field of 6 Oe and a saturation magnetization of 10 kG were obtained. These results are considered to be same values as the nano-granular structure reported on Fe-Al-O films prepared on glass substrates. On the other hand, the films prepared by reactive dc magnetron sputtering did not exibit such soft magnetic properties, because the nano-granular structure was disturbed by the presence of excess oxygen during film deposition.

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YIG ferrite is widely used for microwave applications such as isolators and circulators. This paper studies the origin of intermodulation distortion (IMD) in microwave isolators in terms of the influence of the ferromagnetic resonance linewidth (ΔH), which is a material property of YIG ferrites. ΔH is affected by the non-uniformity of the spin direction under a dc field, which results from crystal anisotropy and the demagnetizing field around pores. The IMD was decreased by minimizing ΔH, which in turn was achieved by minimizing these two contributions separately. It also appeared that the input power dependence of IMD was increased by using low-anisotropy YIG ferrites.

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A highly sensitive linear strain gauge using a pair of amorphous CoSiB wires fixed to a plastic cantilever beam combined with a CMOS IC multivibrator circuit is presented. The wires are magnetized with a sharp pulse current to generate the stress impedance (SI) effect, showing a gauge factor of about 2000 in the CMOS IC circuit The linear strain gauge shows a resolution of about 2.5 mg for weight detection with high linearity in the range of −0.75∼1.25 g. The mechanism of the SI characteristics in the CoSiB wire is analyzed using a magnetization rotation model. Pulsation of fingertip blood vessels was stably detected by using the SI gauge stress sensor.

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This paper describes a long-scale displacement sensor using a magnetostrictive wire with a measurement range of over 10 m. Since the sensor is a non-contact type that measures the propagation time of the elastic wave transmitted in the wire, it is thought to be suitable as a displacement sensor for transportation systems. However, no sensor of this type with a range of over 5 m has been reported in practical use hitherto. In order to develop a long-scale displacement sensor, it was considered that two detection methods should be compared experimentally: One using an AE sensor, and the other using a detection coil. The experimental results showed that the method using a detection coil is more stable and has a lower attenuation coefficient of the elastic wave detection voltage versus distance than the method using an AE sensor.

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Temperature-sensitive magnetic bulk cores and thick films have been fabricated for thermal sensors. These magnetic substances are used in large size instruments, but cannot be adapted for miniaturization. The authors have previously been proposed a temperature-sensitive magnetic thin film annealed in oxygen atmosphere, but the saturation magnetization is below 1/5 of a bulk core. Then a temperature-sensitive Mn-Zn ferrite thin film sensor device (TMS) was prepared by sputtering and annealing in argon atmosphere. TMS's saturation magnetization is nearly equal to that of an Mn-Zn bulk ferrite. The magnetization has a marked temperature dependence like that of a bulk core or a thick film. A TMS with a small heat capacitor responds sharply to a minute temperature variation, and is therefore expected to be applicable in pyromagnetic photosensors, photo pattern sensors, and enzyme sensors.

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In recent years, sensors have come to require high resolution and accuracy because of the progress of control technology. Magnetic encoders are widely used in servo motors in factory automation, because of their suitability for use in difficult environments. Research on efficiency tends to favor the use of a magnetic simulation method. However, this requires complex calculations and much time. Therefore, a simplified simulation method has been developed and used. In this paper, to obtain an ideal index phase signal, a new magnetization pattern is proposed and calculated by using the developed simulation method, named the superposed magnetizing method. The experimental results showed that by expanding the detection gap it is possible to obtain a highly accurate index phase signal.

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Torque was detected in a steel shaft with a ring-shaped surface by using a magneto-impedance effect sensor. The hysteresis of torque detection was removed by summing the output of two magmeto-impedance effect sensors whose heads were placed on the two edges of a gutter in the ring-shaped surface. The hysteresis removal was done utilizing two different shapes of the hysteresis of torque detection at the two edges. A large pulse current was a priori applied through the shaft to induce circumferential magnetic anisotropy in order to remove the magnetic poles at the gutter edge for zero torque.

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Magneto-electric (ME) elements were constructed by combining piezoelectric materials and magnetostrictive films. The fundamental properties of elements were studied, to determine whether the elements exhibit any considerable ME effect at room temperature. The elements had a hybrid structure, in which thin soft glass substrates with highly magnetostrictive amorphous FeCoSiB films were bonded on PZT piezoelectric substrates. When a dc voltage was applied to an element, large changes in the magnetic properties of the FeCoSiB film were observed: for example, when a dc voltage of between -200 V and +200 V was applied, the change in magnetic permeability of the film reached more than 1680%. These unique characteristics of the present ME elements are considered to be very attractive for constructing novel types of micromagnetic devices.

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When a built-in resolver is incorporated into a motor shaft, there is sometimes a problem of an eccentricity error caused by mounting misalignment and tilting. This eccentricity error affects the sensing accuracy of the resolver and causes an angular error. A short-circuit winding applied in quadrature to the exciting winding helps to reduce the angular error due to the shaft eccentricity if the internal impedance of the short-circuit winding is optimally designed. This paper (1) analyzes the mechanism whereby the angular error leads to an error equation, (2) analyzes how the short-circuit winding reduces the magnetic flux in the quadrature axis, which acts to induce the angular error, and (3) clarifies the conditions for realizing a resolver error of under 10' at an eccentric rate (δ/g×100%) of under 50%.

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We developed a thin-film current sensor using a flux-saturable ring core. The sensor consists of a transformer unit composed of a saturable core, primary and secondary coils, and a load coil surrounding the transformer unit. The sensor is suitable for use in a fail-safe system. The chip size is 4mm × 4mm. A transmission efficiency of 60% was obtained when the carrier signal was a 3 V_pp-1 MHz sine wave. The secondary voltage of the sensor dropped by 90% when a 100-mA load current was applied to a 20-turn load coil.

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The ratios of core losses to material iron losses were investigated with the following results: (1) The ratios of iron losses are influenced by the core shape. (2) It is possible to find the most suitable conditions (Si content and grain size) of non-oriented electrical steel sheets for reducing the hysteresis loss ratios. Electrical steel sheets with higher Si content and larger grain size have lower eddy current loss ratios. (3) The ratios of hysteresis losses and eddy current losses increase with increasing flux densities. These results are explained by the flux distribution due to magnetic non-linearity and saturation, the phase difference between inner and outer fluxes, and the distortion of the flux waveform.

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Local magnetic flux in the T-joint model of three-phase stacked transformers was examined by a stylus probe method. The distribution of the rotational loss in the T-joint part was determined by two-dimensional SST measurement. The deterioration of the iron loss in the form of the iron loss in the T-joint model to the iron loss in the material was calculated. The deterioration caused by the rotational flux decreased as the excitation magnetic flux density increased, whereas the deterioration caused by the distortion of the wave form of the local magnetic flux increased. Therefore the penetration of the magnetic flux into the limb and the yoke was determined to be the major cause of the increase in the iron loss of transformers at higher inductions.

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A micro parametric transformer previously proposed by authors has various desirable features, including voltage regulation, overload protection, and noise rejection. This paper analyzes the performance of the transformer and validates the magnetic circuit model of the transformer used for the analysis. The performance characteristics of the transformer are analyzed by solving the nonlinear differential equation obtained from the parametric oscillation circuit. The equation is solved by the harmonic balance method. The calculated characteristics of the transformer agreed approximately with the experimental ones. The validity of the proposed magnetic circuit model was confirmed.

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This paper deals with a method for controlling instability in a two-phase nonlinear power device. The instability consists of nonperiodic oscillations such as quasi-periodic or chaotic oscillations and interruptions in the operation of the device. The authors previously reported that the instability depends on circuit factors, namely, the sharpness of the saturation curves of the reactor used in the device, and the resistances of the supply side.
This paper shows that a very effective way of controlling the instability is to introduce inductances into the primary side of the device. The inductances suppress not only the nonperiodic oscillations, but also the interruption of the operation. The analysis is supported by experiments.

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In power system applications to limit the flow of enormously strong fault currents during faults, sudden short-circuits, and other such abnormal conditions, it has become essential to use some kind of current limiter. The development of a current limiter based on passive magnetic components (a permanent magnet and ferrite core) has already been reported by the authors. The geometry and characteristics of the materials are very important for the proper functioning of a fault current limiter (FCL). This paper characterizes the parameters of a passive fault current limiter. Simulated results for various values of permeability of the ferrite core and various thicknesses of the permanent magnet (PM) are reported.

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Switching a transformer primary with a perfectly demagnetized core brings down the possibility of high inrush current. This paper gives a method for transient solution of a scheme which can demagnetize the core after the primary of the transformer is switched off. A transient hysteresis model has been utilized to properly deal with the residual magnetism which has to decay for demagnetization. The method is expected to help the design of such a scheme by quick calculation of the transient current and voltages in the circuit.

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This paper describes the development of an orthogonal-core-type variable reactor. The variable reactor is used in an automatic voltage regulator (AVR), which stabilizes the distribution line voltage by controlling the reactive power. The structure of the orthogonal core, consisting of copper and iron, gives it high endurance and reliability, and it is therefore expected to be used in power systems. We previously presented the dc-ac converter and the Var compensator, which have an orthogonal core. However, this orthogonal core distorts the current because of its non-linear characteristic in a magnetic circuit, making it necessary to reduce the current, before the core can be used in a high-capacity apparatus in a power system. In this paper, we report that we reduced the current by partly reforming the orthogonal core, and developed a variable reactor that incorporates this improvement.

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This paper describes the equivalent circuit analysis of a noise-reduction transformer. The optimum design and quantitative analysis of noise-reduction transformers have not yet been clarified. To determine a method for realizing the optimum design of noise-reduction transformers we discuss the noise attenuation characteristics of the noise-reduction transformer. On the basis of experiments and equivalent circuit analysis. The circuit parameters of the equivalent circuit are dependent variables, but in the equivalent circuit analysis, the parameters are independent variables. We also discuss the dependence of the noise attenuation on the circuit parameters.

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We propose the use of an electric double-layer capacitor (EDLC) as an emergency power source for a totally implantable medical device. Hitherto, only chemical batteries, such as Ni-MH and Li-ion batteries, have been considered as power sources. EDLCs need no control circuits to prevent excess charge and discharge. Furthermore, they can be cycled many times. In these respects, they are superior to batteries.

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A transcutaneous signal-transmission system is discussed. We propose the use of cross coils as signal-transmitting coils. A pair of cross coils is placed between power-transmitting pancake coils that transmit power from outside the body to implantable devices, such as ventricular assist devices. Cross coils can cancel the effect of the power-transmitting magnetic fields and transmit signals at the same time. By examining actual-signal transmission, we were able to draw up a guideline on the design of cross coils.

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Environmental magnetic noises changing with time influences biomagnetic meaurements. Trains, movements of elevators and cars, and fan-pumps of air conditioners and computer servers are thought to be the main causes. The influence is significant when biomagnetic measurement is performed without a magnetically shielded room. In this paper, the variation of environmental magnetic noise was measured in two places, Kagoshima University and Tokyo Denki University. The origin of magnetic field noise is discussed with respect to magnetic field generated by electric trains and streetcars. The magnetic noise at Kagoshima University is larger than that at Tokyo Denki University. As a result of the current measurements, it was confirmed that the magnetic noise at Kagoshima University is affected by streetcars.

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We measured the auditory and visual evoked magnetic fields of rats, using a high-resolution dc-SQUID magnetometer with 12 channels. The specifications of our system are as follows: pick-up coils 5 mm in diameter located on a 7.5-mm grid, 15-mm base-line of the gradiometer, one-turn pick-up coil, 5-mm distance between the pick-up coil and the outside surface of the dewar, and 100-fT/√Hz field resolution. The rats, responses to auditory and visual stimulation were observed. Auditory signals appeared at 34 ms, and the intensities of the magnetic fields were approximately 500 fT. Visual signals appeared at 60 ms, and their intensities were about 1 pT. Consequently, the system used in this study is useful for physiological studies of small animals.

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Particle accumulations in the lungs can be detected because of their external magnetic characteristics. With this principle as a basis, equipment for measuring the magnetic field emanating from the lungs was developed that is capable of ascertaining the quantity and distribution of particles lodged in the lungs. However, because there are some errors of measurement, accurately determining the amount and distribution of particles is still difficult. We previously reported results obtained in a model test. We conclude here that the quantity and distribution of particles lodged in the lungs from the surface to the inner region can be ascertained by performing a surface elimination of magnetism.

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We carried out a 3D vector measurement of magnetocar-diograms (MCGs) of a subject with myocardial infarction and three normal subjects, using a 3D second-order gradiometer connected to three rf-SQUIDs, which can detect the magnetic field component perpendicular to the chest wall (B_z) and tangential to the chest wall (B_x, B_y) simultaneously. We introduced principal component analysis in order to compare the frequency characteristic in the MCG waveform of myocardial infarction with that of normal subjects. The results showed that the frequencies in the MCG waveform of myocardial infarction were dominated by lower frequencies (less that 10 Hz) than in normal MCG, and that the score proportion characteristic of B_x was different from that of B_z and B_y.

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This paper presents a new method of multiple source estimation using a combination of eigenvalue analysis and measurement of the tangential magnetic field component in a 3D vector magnetoencephalogram (MEG). Time series of magnetic data for simulating MEGs were calculated by using a single and/or two alternating current dipoles on a homogeneous sphere head model (of 10 cm radius). The alternating current dipole is a sine wave of 10 Hz with an intensity of 30 nAm. By using these source models, we examined the possibility of estimating multiple sources by combining eigenvalue analysis and measurement of 3D MEG components (B_r, B_θ, B_φ). It was found that the eigenvalues obtained from the tangential magnetic components (B_θ, B_φ) give the number of sources with more accuracy than those obtained from the radial magnetic component (B_r). This proposed method is useful for finding the constraint condition for calculating multiple sources in MEGs, which has hitherto been difficult.

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The strength and spread of MEG / EEG sources were studied. In a previous study, the current dipoles were estimated as electrical sources in the brain. However, the dipole model does not include information about the sources‘ spread. In this study, source models were proposed to describe the strength and the spread of the sources. Since MEG is better for source estimation than EEG, the source estimation of MEG was investigated first. The simulated results show that the strength and spread cannot be estimated by using only MEG information. New methods using both MEG and EEG were therefore designed.

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The weighted minimum-norm estimation (wMNE) is a popular method for obtaining the current distribution in the human brain from magnetic field measurement (magnetoencephalography: MEG) if detailed information about the generator profile is not available. However, because the conventional wMNE method deals only with instantaneous distribution of MEG data, the reconstructed current can be seriously distorted when the method is applied to noisy data. To reduce the distortion of the reconstructed current, a method is proposed for including temporal information from MEG data in the wMNE method, using MUSIC-like pre-scanning. Computer simulations of the proposed method and a comparison with the conventional wMNE method were performed. The results demonstrate that the proposed method is more effective than the conventional wMNE method for reconstructing the current distribution from noisy data.

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A mental rotation process requires rotation and matching of a pair of mental images. We measured MEG signals during mental rotation processes and estimated their source distributions, using the MUSIC (Multiple Signal Classification) algorithm. After being shown a pair of simple line-drawings, the subjects were required to discriminate a rotation-symmetric pair from a mirror-reversed pair. Activation of the right lateral posterior temporal region at a time about 200 ms after the onset of mental rotation stimuli was observed in three of the five subjects.

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To investigate the characteristics of short-term memory in the human brain, magnetoencephalograms (MEGs) evoked by a delayed paired comparison task were recorded. A visual stimulus, a circle with a different color in each quadrant, was presented. In the memory task, subjects were requested to move the index finger when the second stimulus (TEST) was identical to the first stimulus (SAMPLE), and the middle finger when it was not identical. In the control task, the subjects were instructed not to pay attention to the SAMPLE, and to move the index and middle fingers alternately. A slow magnetic activity was observed for between 900 and 1500 ms during the memory task in the occipital region of all subjects. Sources for this slow activity were localized in either the visual cortex and/or the posterior temporal region. The results suggest that these areas may be responsible for retaining the stimulus in visual short-term memory.

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Auditory evoked magnetic fields were measured to investigate the reaction of the auditory cortex to a train of sounds. Auditory stimuli, 1000-Hz tone bursts (percentage of appearance: 90%), and 2000-Hz tone bursts (percentage of appearance: 10%) were presented sequentially. The stimuli were presented with the stilmulus onset asynchronies (SOAs) within one trial fixed at either 380 ms, 480 ms, 580 ms, 1080 ms, 1580 ms, or 2080 ms. Nlm amplitudes of 2000-Hz tone bursts, 1000-Hz tone bursts 1 position before, 1 position after, 2 positions after, and 3 positions after the 2000-Hz tone bursts, were investigated. As a result, (1) the amplitudes of Nlm of 2000-Hz tone bursts were significantly larger than those of 1000-Hz tone bursts except for SOA of 2080 ms, (2) the amplitudes of Nlm increased as the SOA increased except for 380 ms and 480 ms, (3) the Nlm amplitude ratios of 1000-Hz tone bursts to 2000-Hz tone bursts increased as the SOA increased, (4) no significant effects of serial position on Nlm amplitude of 1000-Hz tone bursts were observed.

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The effects of dc magnetic fields on animals and plants have been studied for a long time. In particular, many studies of the effects on plants have been reported, because of the ease with which experiments can be controlled. However, it is still not clear whether dc magnetic fields have any influence on plants. This study shows the effects of both horizontal and vertical dc magnetic fields on the growth of Japanese radishes. A dc magnetic field plays a role in restricting the initial growth of radishes, and the growth and root hair are also affected by the direction of the magnetic field.

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The present study focuses on the effects of magnetic fields on the formation of thrombus under a flow condition. We carried out a blood flow experiment, using a fluidic circuit with plastic tubing passed through the bore of a superconducting magnet. The blood flow in the fluidic circuit passed through a filter-tube in the magnetic fields. The blood coagulation started by the injection of thrombin into the blood suspension. We measured the weight of dried thrombus taken out from the filter-tube. The weight of the thrombus formed in the blood with 5.0 mg/ml of fibrinogen decreased under a magnetic field of 14 T. For the second time, we measured the viscosity of the samples outside of magnetic fields. The change in the viscosity of the blood suspension and fibrinogen solution that passed through magnetic fields of up to 14 T increased and decreased, respectively.

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We investigated the possible effects of magnetic fields on the oxidation and deoxidation of hemoglobin in red blood cells. We observed a change in the oxidation rate of a red blood cell solution by measuring the change in the absorbance of red blood cells at 560 nm in both, an equilibrium state and a nonequilibrium state, the change in the absorbance of hemoglobin in an equilibrium state under a 14-T magnetic field was not significant. However, we obtained a minute change in the absorbance of hemoglobin in an equilibrium state during magnetic field exposure. When the red blood cell solution was not in contact with air, the the absorbance did not change. The influence of contact with open air was significant, especially in a nonequilibrium state. We concluded that the oxidation of hemoglobin in a blood cell solution was enhanced by the change in the composition of the atmosphere surrounding the optical cell, and by convection caused by gradient magnetic fields. The possibility of a 14-T magnetic field affecting the oxidation of a blood cell itself was also suggested.

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In this study, a new method is proposed for detecting the effect of a pulsed magnetic field without a loss of temporal information. The strength of exposed magnetic field was 0.1 T. Trains of 10 pulses of the magnetic fields at intervals of 0.05 s were applied at 1 Hz. Physarum polycepharum is an amoeba that moves in search of food, and its trace forms net-shaped patterns. Fractal analysis was performed, and the fractal dimension of the patterns was determined by the box-counting method. The value of the fractal dimension was about 1.7 in both exposed and control groups after 4 hours of exposure. After 8 hours of exposure, the value for the control group was 1.72 and that for the exposed group was 1.77. The results indicate that longer time exposure affects the complexity of the patterns of P. polycepharum.

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In this study, Escherichia coli mutant IM303 was used to detect the effect of pulsed magnetic fields through reactive oxygen species. IM303 is a mutant defective in the superoxide dismutases Fe-SOD and Mn-SOD. The strength of the exposed magnetic field was 0.06, 0.1, or 0.13 T. Trains of 10 or 5 pulses of magnetic field at intervals of 0.05 s were applied at 1 Hz. The growth of the mutant was detected by measuring the light absorbance at 600 nm every hour. After six hours of exposure, cell were centrifuged and two-dimensional gel electrophoresis of the proteins in E. coli was performed. Two-dimensional gel electrophoresis data revealed lost protein in the exposed samples of IM303. Their growth rate did not change with exposure. The results of this study indicate that the synthesis of proteins that do not change the cell cycle length has been altered. However, lethal damage to IM303 did not occur.

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In this study, we focused on the biological effects of repetitive-pulsed magnetic stimulation. Using the Swiss mouse embryo-derived fibroblast cell line (NIH3T3) and ret-II (a colon cancer-derived oncogene)-transformed cells (Ret-II) as a model of normal and malignant cells, changes in the expression of heat shock protein 70 (HSP70) were investigated by Western-blotting analysis. The cells were exposed to train-pulsed magnetic fields at 50 Hz, and the waveform of each pulsed field was a biphasic shape with a 200 μs duration. The magnetic field intensity was 17 mT. As a result, the expression of HSP70 in both NIH3T3 and Ret-II cells did not change at 37°C, but at 40°C, the expression in both cells increased after stimulation for 3 h and 6h but decreased after stimulation for 12 h. When incubated at 42°C, an increase in the expression of HSP70 due to the increase in temperature was observed. It is concluded that, under normal conditions, cells are not affected by magnetic stimulation, but under adequate stress, magnetic stimulation is also a stressful stimulus.

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This paper describes eddy current analysis and magnetic stimulation of organic tissues such as brain tumor cells (RGC-6). First, eddy current analysis was performed, both by calculation and experiment ally, to confirm whether a constant gradient distribution of the induced electric field (IEF) generated by a magnetic field could be obtained in a sample area in which circular glass vessels filled with saline water were located. The calculated IEF was agreed with the measured value within an average error of 4.3%. Next, promotion of DNA synthesis was experimentally observed by applying pulsed magnetic stimulation (2.0 mT, 200 Hz) to RGC-6. A decrease in RGC-6 was observed as a result of combined application of an anticancer agent and a pulsed magnetic field.

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A calculation model is proposed for the induced electric fields and the activating function in inhomogeneous volume conductors during magnetic stimulation. On the basis of the proposed model, the finite element method (FEM) is used to perform numeric calculation for the induced electric fields in an inhomogeneous volume conductor. In order to study the influence of inhomogeneities on nerve excitation, the spatial distribution of the activating function was also calculated. In a comparison of the results with a homogeneous case, the interface between conductors of different conductivities appears to affect markedly the nerve excitation elicited by magnetic stimulation. Theoretical explanations are given for this simulation result.

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The process of oxygen concentration in water was examined in the presence of a magnetic field. The equilibrium concentration of oxygen was found to remain the same whether the field was present or absent, in accordance with the prediction of the laws of thermodynamics. However, it was found that the rate of oxygen dissolution in water was significantly enhanced in a magnetic field. The degree of enhancement of the dissolution rate depended on the magnetic force (x/μ₀)·B· (dB/dx) showing a minimum at the position in which the magnetic field was strongest. The phenomenon was explained by assuming that liquid-phase convection is caused by the gradient distribution of dissolved oxygen in water, which in turn raises the gradient of the magnetic susceptibility in a direction perpendicular to the magnetic field gradient.

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