As regenerative medicine becomes more active, the need for international transportation of regenerative medical products such as stem cells is increasing. Currently, international transport is mainly by air, but there are concerns about the effects of exposure to X-rays during security inspections at airports and cosmic radiation. Although the probability of cosmic radiation hitting cell nuclei during a single international flight to/from Japan is not high, it is necessary to minimize not only cell death and malignant transformation, but also the effects on the differentiation potential required of stem cells. Therefore, it is necessary to study the effects of low-dose radiation exposure during air transport and to develop transport containers and systems that can effectively shield cells from space radiation.

We decommissioned the Nishina Memorial Cyclotron Center that was mainly used for PET/PIXE study until 2019. The main body of the cyclotron and peripheral equipment were separated as radioactive waste. For the concrete in the accelerator room building, radioactivity analysis of concrete core samples using a Ge detector, dose measurement of concrete surface using a CsI scintillation survey meter with a lead shield, and activation calculation using PHITS code were performed. The PHITS calculation with detailed modeling well reproduced the measurement result. The activated part was evaluated to have a depth of 21 to 41 cm, and the scraped concrete was treated as radioactive waste. All the work took 22 months. A practical procedure is proposed for the estimation of activated part of the concrete.

Sodium (Na) exclusion is vital for plants to cope with salt stress, and the plasma membrane Na⁺/H⁺ antiporter, SALT OVERLY SENSITIVE 1 (SOS1), has been known to play a central role in this process although the function of this molecule is not completely understood. In this study, we performed ²²Na⁺ radiotracer experiments to investigate the function of SOS1 in the mature root zone. Arabidopsis thaliana seedlings were placed on the gel medium, which had air gaps to separate the medium at the mature root zone from that at the root apex zone. Then, ²²Na⁺ was added to the root apex zone for 4 h, and the radioactivity in the mature root zone with 5 mm in length and in the mature root zone gel was measured. As a result, we found that knock-out of SOS1 caused ²²Na⁺ accumulation in the mature root zone and reduction of ²²Na⁺ exclusion to the gel, demonstrating that Na⁺ delivered via the xylem is excluded to the rhizosphere by SOS1 in the mature root zone.