A remote radiation imaging system comprising a lightweight Compton camera and a multicopter drone was developed to remotely and quickly measure radioactive contamination inside the buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). The drone system is used for measuring detailed radiation distributions in narrow areas, which have been difficult to gauge with conventional aircraft monitoring using helicopters. A measurement of radiation distributions in outdoor environments in the coastal areas of Fukushima, Japan, was performed. The drone system with the Compton camera succeeded in remote observations of dense hotspots from the sky over a contaminated area near the FDNPS. The time required for image reconstruction is approximately 550 s in the case of a 9-m flight altitude for the hotspots with a surface dose rate of several tens of µSv/h. This drone system will be used inside the buildings of the FDNPS for remote measurement of radioactive contamination.

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A: The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the large tsunami caused by the Great East Japan Earthquake of March 11, 2011. Very large amounts of radionuclides were released from the damaged plant. Radiation distribution measurements inside FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We have developed a compact Compton camera to measure the distribution of radioactive contamination inside the FDNPS buildings threedimensionally (3D). The total weight of the Compton camera is lower than 1.0 kg. The gamma-ray sensor of the Compton camera employs Ce-doped GAGG (Gd 3 Al 2 Ga 3 O 12 ) scintillators coupled with a multi-pixel photon counter. Angular correction of the detection efficiency of the Compton camera was conducted. Moreover, we developed a 3D back-projection method using the multi-angle data measured with the Compton camera. We successfully observed 3D radiation images resulting from the two 137 Cs radioactive sources, and the image of the 9.2 MBq source appeared stronger than that of the 2.7 MBq source.

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Telomeres, which consist of single-, double-and four-stranded DNA, shorten after each round of cell division. The repeated telomeric DNA sequence 5′-TTAGGG-3′ does not encode genetic information and is not replicated completely. We performed molecular dynamics (MD) simulations of telomeric single-stranded DNA (ssDNA) and protection of telomere 1 (POT1) for 100 ns. We calculated the distance between C α (POT1) and O5' (telomeric ssDNA) to verify the binding system for 100 ns MD. We then calculated the distance between the bases of the telomeric DNA ends and the root-mean-square deviation and gyration radius in the single and binding states. Moreover, we compared the root-mean-square fluctuations (RMSFs) between the single and binding states and calculated the number of hydrogen bonds between POT1 and telomeric DNA. There are many hydrogen bonds between Gln94 and the first guanine of the closest 5′-TTAGGG-3′ sequence in telomeric single-stranded DNA, and the RMSF between the single and binding states has a large difference between Gln94 and guanine. Overall, we found that Gln94 and guanine are important components of the binding system and are related to the stability of this system.