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Objective. Brain-computer interfaces (BCIs) using electrocorticographic (ECoG) signals have been developed to restore the communication function of severely paralyzed patients. However, the limited amount of information derived from ECoG signals hinders their clinical applications. We aimed to develop a method to decode ECoG signals using spatiotemporal patterns characterizing movement types to increase the amount of information gained from these signals. Approach. Previous studies have demonstrated that motor information could be decoded using powers of specific frequency bands of the ECoG signals estimated by fast Fourier transform (FFT) or wavelet analysis. However, because FFT is evaluated for each channel, the temporal and spatial patterns among channels are difficult to evaluate. Here, we used dynamic mode decomposition (DMD) to evaluate the spatiotemporal pattern of ECoG signals and evaluated the accuracy of motor decoding with the DMD modes. We used ECoG signals during three types of hand movements, which were recorded from 11 patients implanted with subdural electrodes. From the signals at the time of the movements, the modes and powers were evaluated by DMD and FFT and were decoded using support vector machine. We used the Grassmann kernel to evaluate the distance between modes estimated by DMD (DMD mode). In addition, we decoded the DMD modes, in which the phase components were shuffled, to compare the classification accuracy. Main results. The decoding accuracy using DMD modes was significantly better than that using FFT powers. The accuracy significantly decreased when the phases of the DMD mode were shuffled. Among the frequency bands, the DMD mode at approximately 100 Hz demonstrated the highest classification accuracy. Significance. DMD successfully captured the spatiotemporal patterns characterizing the movement types and contributed to improving the decoding accuracy. This method can be applied to improve BCIs to help severely paralyzed patients communicate.

The characteristic distribution of radioactive fallout 90Sr and 137Cs absorbed into a Satsuma orange fruit was investigated. After peeling, the so-called edible part of the fruit was divided into two parts by use of an autojuicer. One was juice including interior cells of vesicle and a part of vesicle, the other was residue including the vesicle, vascular bundle and carpet wall. The ratio of 90Sr concentration in juice to that in risidue part was found to be three vs. seven, while this ratio was seven vs. three for 137Cs concentration. When expressed in Sr unit, the values (266-422pCi/g Ca) of the residue part were about six times as much as the juice part and about two to three times as much as the rind part. When expressed in Cs unit, the values (88-133pCi/g K) of the rind part was about five times as much as the residue part or the juice part, and the residue and the juice part had almost the same value. For practical purpose, it is more convenient to express 90Sr or 137Cs concentration in orange fruit by content of the nuclide in juice per unit weight of fresh fruit than by the nuclide content per unit weight of so-called edible part of fresh sample.

From 1961 through 1971, the distribution of fallout 137Cs in the skin, juice and residue part of the mature fruit of Satsuma orange trees grown on soils under clean, mulch and sod systems of soil management was investigated to compare its annual change with that of 90Sr.Due to a great dependency on the fallout rate the level of this nuclide in each of the fruit parts showed a high concentration during the period of heavy fallout deposition followed by a sharp decrease. After this, a slow exponential decrease was observed with almost the same half-time as that of the replaceable 137Cs content in soil during the period of very little fallout deposition. The ratio of the 137Cs contribution due to direct (surface) absorption, root absorption and translocation from leaves was 95:4:1 for skin, 44:45:11 for juice and 34:53:13 for residue in 1963 with heavy fallout deposition. The ratio of 137Cs/K in plant tissues to replaceable 137Cs/K in soil and the ratio of 137Cs to 90Sr in plant tissues were also discussed.

Cesium-137 concentration in Japanese beer was determined for the samples of 1959 through 1967. It was found that the level of this nuclide in beer depends on the fallout rate to a great extent and the peak value in beer appears about 1.5 years after the period of the highest rate of 137Cs fallout. The results on certain samples of beer, raw materials (malt, side materials and hops) and the spent residues indicated that almost all 137Cs and K contained in raw materials were transferred to beer during its manufacturing process.

The majority of radioactive self-luminous paint produced in Japan uses 147Pm. The characteristics of the radiation from a 147Pm-activated self-luminous plate which had a luminous area of 12×8 cm2 and radioactivity of 12.5 mCi were examined. Bremsstrahlung was produced from the luminous plate absorbing the 220 keV β-particles of 147Pm. The energy of the bremsstrahlung was analyzed with use of both NaI scintillation and Ge solid state detectors: the spectrum obtained showed a peak at around 50 keV and also a small peak due to γ-rays emitted from the 147Pm at 121 keV. Measurements of the bremsstrahlung made with Lauritsen electroscope, film badges, fluoroglass dosimeters and thermoluminescent dosimeters gave estimated exposure rates of at most only 0.5 and 0.3 mR/hr respectively at distances from the plate of 3 and 7 cm.

Since 1961 through 1971, the replaceable 137Cs content in the same surface soil of the same area under clean, mulch and sod systems of soil management at a citrus orchard with that described in the previous paper1) was determined in order to compare its annual change with that of replaceable 90Sr. The relation of humus content in surface soils classified as clean < sod < mulch closely related to half-time for an exponential decrease of replaceable 137Cs from 1963 through 1971 and with distribution coefficient1) for the downward distribution of replaceable 137Cs in, surface soil. Both half-times of approximately 8.5, 45.2 and 30.7 years and distribution coefficient of 0.094—0.111, 0.142—0.165 and 0.129—0.140 for clean, mulch and sod, respectively, are larger than those of 90Sr. The ratios of replaceable 137Cs to 90Sr of 0.92—1.13 in surface soil found for the year from 1961 through 1967 followed by a slight increase afterwards and reached 1.24—1.36 in 1971. It was found that 137Cs is fixed much more strongly than 90Sr in the surface soil of a citrus orchard.