The chelation mechanism of neonicotinoid insecticides influencing cadmium transport and accumulation in rice at different growth stage.

The combined exposure of heavy metals and organic contaminates can influence the transport and accumulation of heavy metals within the soil-rice system. However, the underlying mechanisms of this process remain largely unknown. Herein, this study investigated the influence of three neonicotinoid insecticides (NIs), including imidacloprid (IMI), clothianidin (CLO), and thiamethoxam (THI), on the Cd transport and accumulation in rice (Oryza sativa) at different growth stages. Particular focus lied on their complex interaction and key genes expression involved in Cd transport. Results showed that the interaction between Cd and NIs was the dominant factor affecting Cd transport and accumulation in rice exposed to NIs. All three NIs chelated with Cd with nitrogen (N) on the IMI and THI nitro groups, and the N on the CLO nitro guanidine group. Interestingly, this chelation behavior varied between the tillering stage and the filling/ripening stages, resulting in diverse patterns of Cd accumulation in rice tissues. During the tillering stage, all three NIs considerably inhibited Cd bioavailability and transport to the above-ground part, lowering Cd content in the stem and leaf. The inhibition was increased with stronger chelation ability in the order of IMI (-0.46 eV) > CLO (-0.41 eV) > THI (-0.11 eV), with IMI exhibiting the highest binding energy for Cd and reducing Cd transfers from root to stem by an impressive 94.49 % during the tillering stage. Conversely, during the filling/ripening stages, NIs facilitated Cd accumulation in rice roots, stems, leaves, and grains. This was mainly attributed to the generation of nitrate ions and the release of Cd2+ during the chelation between Cd and NIs under drainage condition. These findings provide theoretical basis for the treatment of combined contamination in field and deep insights into understanding the interaction of organic contaminants with heavy metals in rice culture process.

Equal-intensity beam splitter realization by wire grid polarizers for passive laser speckle reduction.

A method to realize an equal-intensity beam splitter (EIBS) using wire grid polarizers (WGPs) is proposed. The EIBS consists of WGPs with predetermined orientations and high-reflectivity mirrors. We demonstrated the generation of three laser sub-beams (LSBs) with equivalent intensities using EIBS. The three LSBs were incoherent by introducing optical path differences larger than the laser coherence length. The LSBs were used to reduce speckle passively, where the objective speckle contrast was reduced from 0.82 to 0.5 when all three LSBs were used. The feasibility of EIBS in speckle reduction was studied using a simplified laser projection system. The structure of the EIBS implemented by WGPs is simpler than EIBSs obtained by other methods.