[en] Cerium oxide nanoparticles (CeO₂ NPs) are widely used in industries and have caused environmental problems. However, the phytotoxicity induced by CeO₂ NPs lacks detailed information on phytotoxicity. In this research, the effect of CeO₂ NPs on soybean plants (Glycine max) was studied. Scanning electron microscopy with the energy dispersion spectroscopy was used to characterize the NPs form in soybean. The growth of the root was increased, whereas the growth of shoot was inhibited. Besides, Chlorophyll Fluorescence Imager (CF Imager) showed that chlorophyll synthesis was inhibited: the maximum quantum yield of Photosystem II complex (PSII) (Fv/Fm) and photochemical quenching (qP) decreased. Moreover, transmission electron microscopy revealed that the chloroplast thylakoid structure was changed, and thus reduced the energy conversion in the Calvin cycle from C5 to C3. Our work suggests that CeO₂ NPs will cause growth changes as well as irreversible damage to soybean plants. Our findings will provide evidence for estimation of plant toxicity induced by CeO₂ NPs.

[en] [Background] China Spallation Neutron Source (CSNS) based on the spallation reaction is a large multi-principle research platform, which has been completed and began commissioning since August 2018. Experimental muon source (EMuS) is one of important research platforms constructed at CSNS in the future. [Purpose] This study aims to design a simplified EMuS according to the multiple-stage construction plan. [Methods] First of all, the processes of a high energy proton beam bombarding on a carbon target were simulated by employing FLUKA code based on Monte Carlo method. Then, the disposition of abandoned proton beam, energy deposition in target, muon production were analysed in details, background and whole target radiation and shielding scheme were investigated by simulation. [Result and Conclusion] The aluminum alloy is determined to be target chamber material according to the simulation. The residual radiation dose can be controlled to below 2.5 μSv · h^-1 with optimal geometry structure, providing a low-radiation environment for the maintenance. (authors)