Published papers

Based on a questionnaire survey of approximately 1,500 child-rearing people living in Fukushima Prefecture, we developed a prototype of a new radiation visualization system required by citizens. The demonstration test results confirm that the system works properly in high-dose areas in Fukushima Prefecture. The system is expected to provide local residents with a quantitative monitoring of natural decay and decontamination results and reassurance that they can return to their original land and live in peace.

We measured ambient dose rates in a mountainous area in the evacuation zone (Namie town, Fukushima prefecture, Japan) to predict ambient dose rates several decades ahead based on collected data. The survey was conducted on a ridge in a mountainous area that had not been previously decontaminated. Future ambient dose rate projections based on observed dose rates suggest a faster dose rate decline than those based on the physical decay of radiocesium. Specifically, the projections based on observed data indicate that the Japanese decontamination threshold in the area would be reached 15 years earlier than predicted based on physical decay.

Here we report an improved μTAS based on electrochemical measurements and microbeads sorting for screening of NAD(P)-dependent oxidoreductases. By using this system, we measured the activity of model enzymes immobilized on microbeads by detection of NADH with a boron-doped diamond (BDD) electrode in each compartment (∼30 nL) of the microfluidic system. Then, we recovered the magnetic microbeads or the droplets containing genes of enzymes with higher activity by magnetophoretic or dielectrophoretic sorting, respectively. Our μTAS should be useful for directed evolution of various NAD(P)-dependent oxidoreductases with high activity and stability in the future.

© 2018 The Authors. Published by FEBS Press and John Wiley & Sons Ltd. Proper determination of the cell division axis is essential during development. Wnt3a is a known regulator of the cell division axis; however, the sensitivity of cells to Wnt3a signalling and its role in determining the cell division axis have not been measured to date. To address this gap, we took advantage of the asymmetric distribution of outer dense fibre 2 (ODF2/cenexin) proteins on centrosomes in dividing cells. To precisely quantify the sensitivity of cells to Wnt3a signalling, we developed a microfluidic cell culture device, which can produce a quantitative gradient of signalling molecules. We confirmed that mitotic SH-SY5Y neuroblastoma cells could detect a 2.5 ~ 5 × 10−3 nm·μm−1 Wnt3a concentration gradient and demonstrated that this gradient is sufficient to affect the determination of the pole-to-pole axis of cell division during the later stages of mitosis.

Here we report the development of a flow injection analysis system based on electrochemical measurements and dielectrophoresis for screening of NAD(P)-dependent oxidoreductases. In this system, the activity of enzyme which is immobilized on microbeads together with its encoding DNA can be measured with a boron-doped diamond (BDD) electrode in each compartment (~30 nL) of the microfluidic system, and the large droplets (~30 nL) containing genes of enzymes with higher activity can be recovered by dielectrophoretic sorting.

We report the development of a micro total analysis system (μTAS) based on electrochemical measurements and dielectrophoretic sorting for screening of NAD(P)-dependent oxidoreductases. In this system, the activity of enzymes immobilized on microbeads, together with their encoding DNA, can be measured with a boron-doped diamond (BDD) electrode in each compartment (∼30 nL) of the microfluidic system. The 30 nL droplets containing microbead-displayed genes of enzymes with higher activity can then be recovered by dielectrophoretic sorting. Previously, we developed the NAD(P)H-measuring device containing the BDD electrode for high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. In this study, we fabricated an encapsulating device and a droplet-sorting device for nanoliter-size droplets, for the first time, and then combined these three devices to construct a μTAS for directed evolution of NAD(P)-dependent oxidoreductases. We confirmed that this system works by proof-of-principle experiments and successfully applied this system for screening of randomized libraries of NAD-dependent dehydrogenases.

This study analyzed radiation dose data to observe the annual decline in ambient radiation doses and assess the factors contributing to fluctuations in reconstructed areas of the Fukushima prefecture. Utilizing a novel mobile monitoring system installed on a community minibus, the study employed a cost-effective sensor, namely, Pocket Geiger which was integrated with a microcontroller and telecommunication system for data transfer, access, visualization, and accumulation. The study area included the region between Okuma and Tomioka towns. The ambient dose rate recorded along the minibus route was depicted on a map, averaged within a 1 × 1 km mesh created with the Quantum Geographic Information System. To ensure accuracy, the shielding factor of the minibus material is determined to adjust the dose readings. A significant decrease (p < 0.001) in the radiation dose ranges from 2022 to 2023 was observed. The land use classification by the Advanced Land Observation Satellite revealed an ecological half-life ranging from 2.41 years to 1 year, suggesting a rapid radiation decay across all land types. This underscores the close connection between radiation attenuation and environmental factors, as well as decontamination efforts across diverse land categories.