Magnetical effect to enzyme activity of immobilized catalase or peroxidase was examined by an electrochemical method. In buffer solution contained 10mM H₂0₂, oxidation current on an enzyme-immobilized-electrode (φ=0.1mm platinum-black electrode) was monitored under static strong magnetic fields. We observed increase of current with catalase-immobilized-electrode under 8 T. It means that immobilized-catalase-activity was disturbed magnetically. On the other hand, magnetical disturbance of immobilized-peroxidase-activity was extremely small under 14 T. From these results, we conclude that a catalase differs from a peroxidase in magnetical disturbance of immobilized-enzyme-activity.

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We are developing a new diagnosis algorithm to detect cardiac diseases from MCG by using the spatial frequency analysis. This analysis method is effective for analyzing cardiac activity, which has the widespread signal source. By this method, we can get the spectra of the phase & the amplitude of the data. The phase spectrum suggests the moving speed & the direction of the excited wave front, & the amplitude spectrum suggests the spread of the signal source. In this paper, simulation with cubic-shape cardiac models is used to examine whether this method can detect the features of the necrosis on the model, such as the position or the extent of the necrosis. In results, eight patterns of necrotic cardiac models can be distinguished from each other with this method, using both the phase & the amplitude spectrum. It suggests that the position & the extent of the real necrosis of a human heart can be estimated by this method.

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Most recently, magnetic stimulation has been used for many studies. However, because electric fields are influenced by inhomogenous soft tissue, it is difficult to find the region of nerve excitation. It is, however, different to clarify the region of nerve exicitation by magnetic stimulation, because electric field is affected by the conductivity or the stracture of living body. We investigated character of nerve excitation for each direction of induced current in homogenous or inhomogenous model. Moreover, we calculated induced electric fields of these models by finite element method. To compare these results is able to clarify the character of nerve excitation in inhomogenous tissue by pulsed magnetic stimulation.

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In biomagnetic measurements, such as magnetoencephalography (MEG) & magnetocardiography (MCG), very weak magnetic fields are measured. Therefore, biomagnetic measurements are mostly carried out inside a walk-in relatively high performance magnetically shielded room (MSR). Generally speaking, the amplitude of MCG signals is higher than that of MEG's signals by about one order, so the rooms for MCG can be designed with lower performance, & constructed cheaply and light enough for any floor in a building. A trial MSR we developed incorporated active compensation combined with a simplified MSR of one permalloy layer & one pair of cancellation coils to enable moderate performance at low cost mainly for MCG. A 3-D magnetic field analysis of the simplified MSR was carried out to obtain a guide for designing the system, & the results compared with a system consisting of only one pair of cancellation coils. We found that firstly, the distribution of the magnetic noise generated by a line current source was diminished & rendered uniform by the MSR compared with the case without the MSR, enabling the distance between reference & measuring sensors were to be larger. Secondly, the magnetic field distributions were made more uniform when the cancellation coils were outside the MSR than when inside it. The phase shift when the cancellation coils were inside the MSR was lower than when outside it. Thirdly, the phase shift by measurements when the cancellation coils were inside the MSR was found to be less than that when they were outside, as predicted, but that when inside was greater than 10 degrees although shifts of less than this had been predicted.

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We investigated whether exposure to high frequency electromagnetic fields causes DNA damage in cells, using the alkaline Comet assay. The exposure device made for this study used a TE₀₁ circular waveguide operating at a frequency of 2.45GHz. Cells of the human brain tumor-derived MO54 cell line were exposed to an electromagnetic field (input power: 7.8W, average SAR in the middle well of an annular culture plate: CW 50W/kg) for 2 hours & the tail moments of the cells in the inner, middle & outer wells of the plate were compared with those of sham-exposed cells. There was no significant difference between the high frequency electromagnetic field-exposed groups & the sham-exposed groups. Three studies performed under the same conditions gave similar results. Next, cells were exposed to a stronger electromagnetic field (input power: 13W, average SAR in the middle well: CW 100W/kg) for 2 hours & compared with sham-exposed cells. There was also no significant difference in the tail moments of cells in the inner, middle & outer wells of the plate in the high frequency electromagnetic field-exposed groups and the sham-exposed groups. These findings suggest that a high frequency electromagnetic field does not cause direct DNA damage, & does not induce DNA strand breaks, even at a SAR of 100 W/kg.

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We examined the effect of extremely low frequency magnetic fields at 5mT on point mutations & chromosomal aberrations, using the mouse lymphoma assay with L5178Y (tk^+/-) cells. Cells were exposed for 3h or 24h to mitomycin C (MMC), ethylmethanesulfonate (EMS), a magnetic field (5mT), & a combination of magnetic field exposure & MMC or EMS. A decreased survival rate, an increased point mutation frequency & an increased occurrence of chromosomal aberrations were caused by MMC & EMS. However, there was no difference between the groups treated with the chemical agents alone & the groups treated with a combination of exposure to the magnetic field & chemical agents. Consequently, exposure to a 5mT magnetic field is not considered, in itself, to induce chromosomal aberrations or point mutations, or to modify mutations induced by treatment with chemical agents in L5178Y cells.

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We have developed a magnetometer system using high-Tc SQUIDs, aiming to use in a basic physiological study of cardiac functions of small experimental animals. A cryostat was prepared to have a spacing of 3mm between the air & nitrogen at the bottom, where the capacity of liquid nitrogen was about 4L. Two direct-coupled SQUIDs were located within the cryostat in such a manner that a reference SQUID that detected environmental field noise was placed 8.5cm above a sensing SQUID. The feedback current of the reference SQUID was also supplied to the same type of coil at the sensing SQUID, to form a gradiometer at the level of signal detection. The whole system was operated within a magnetically shielded room having an attenuation of 50dB at low frequencies. The effect of the direct-feedback gradiometer to reduce external field noises was confirmed, where more than 20dB attenuation was obtained for the largest 50Hz noise in the shielded room. MCG signals of anesthetized rats were measured in a wide bandwidth of 0.5-200Hz.

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Partial discharge is one of the causes of deterioration of insulating polymer materials subjected to high voltages.In this case, the deterioration that is caused by partial discharges in gaps, such as voids inside an insulator is of particular importance.In this study, the prediction of tree initiation due to partial discharge occurring in void is considered. New tree initiation diagnostic methods are proposed by measuring discharge magnitude & discharge luminescence in each phase angie section of the applied voltage.It is noted that some samples revealed different time dependence of partial discharge patterns even under the same measurement condition. These patterns were the case of occurrence of swarming pulsive microdischarge(SPMD)before tree initiation & nooccurrence of SPMD. The prediction of tree initiation by using moving average of the discharge magnitude is discussed. We propose the parameters to reflect apre-tree initiation mode and also evaluate their usefulness for the prediction of tree initiation by using moving average analysis.

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Polyimide (PI) has been widely used for insulation in electrical apparatus, but it is easily corroded by water & alkali chemicals. In the present paper, the electrical properties of API (all-aromatic polyimide) & TPI (thermoplastic polyimide) soaked in H₂O or KOH are reported. The peak value of the recovery voltage in API or the one in TPI increases with the soaking time in H₂O. The dielectric constant of the sample also increases by soaking in H₂O. The increase in the peak value of recovery voltage is explained theoretically by the change of the dielectric constant. In the case of KOH, the peak value of the recovery voltage in API or the one in TPI is highest when the soaking time is zero. The peak value decreases, then increases, & finally decreases with an increase in the soaking time. The change in the peak value of the recovery voltage in soaked API is higher than that measured in the soaked TPI. It is thought that weakness of API to alkali is responsible for this result.

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A mean rate controllable random pulser to use for a random pulse train simulator is presented in this paper. The control of the men rate is practiced with a personal computer by referring to the look-up table of time-variant rate. The random pulser with present design can be used as a model to simulate the random pulses delivered from detectors being exposed to a source which provides time-variant events. In practice an attempt was exercised to the partial discharge detection system which was used to predict the electrical breakdown of an insulator.

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The profile optimization of an insulator such as a spacer is very important for reducing the cost of power equipment. This paper describes the profile optimization of a post-type spacer utilized in coaxial cylindrical power equipment such as a gas insulated transmission line, which needs a three-dimensional electric field calculation.
We have developed new techniques for analyzing electric fields in three-dimensional arrangements, which utilize elliptical charges in the Charge Simulation Method. One of the techniques is to numerically integrate the potential & the electric field of elliptical charges which are defined by spline functions. The other uses segmented line charges to approximate elliptical charges. In an arrangement of a spheroid under a uniform field, the difference of the maximum electric field strength was less than 1% between the segmented line approximation and the analytical solution.
The optimization is to make the electric field distribution as uniform as possible on the surface of a spacer. The Marquardt method was used as an optimization technique. In the optimization of a total electric field, the field strength decreased to about 68% of the maximum value in the corresponding coaxial cylindrical arrangement without a spacer.

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