The Numerical and Experimental Investigation of Particle Size Distribution Produced by an Electrical Discharge Process.

The vague influence of thermal action of electrical discharge on size distribution of metallic powders hinders the adjustability of powder quality. Due to the small gap, short discharge on-time, uncertain discharge point, and strong light interference, direct observation of preparation is difficult to carry out. Herein, the multi-physics coupling finite element method (FEM) was applied to numerically investigate the relationship between size distribution and thermal action. Through modeling of thermal transformation and heat distribution on the surface of electrode, temperature of the electrode is found to be decided by the latent heat and the distribution of heat point obeys the normal distribution, which corresponds with experimental results. Finally, the vapor film to droplet fragmentation theory was proposed to explain the phenomenon of normal distribution. The research results provide theoretical support for the preparation of metallic powder by electrical discharge, and also play a guiding role in optimizing the process parameters in the actual preparation process to tune the size distribution.

Fenoxaprop-P-ethyl resistance conferred by cytochrome P450s and target site mutation in Alopecurus japonicus.

BACKGROUND: Alopecurus japonicus is a serious grass weed species in wheat fields in eastern Asia, and has evolved strong resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Although target-site resistance (TSR) to ACCase inhibitors in A. japonicus has been reported, non-target site resistance (NTSR) has not. This study investigated both TSR and NTSR in a fenoxaprop-P-ethyl-resistant A. japonicus population (AHFD-3), which was collected in Feidong County, Anhui Province, China. RESULTS: We found that AHFD-3 exhibited high resistance to fenoxaprop-P-ethyl and low resistance to flucarbazone-sodium. The sensitivity of AHFD-3 to fenoxaprop-P-ethyl increased significantly after treatment with cytochrome P450 (P450) inhibitors; however, such synergies between P450 inhibitors and fenoxaprop-P-ethyl were not found in two control populations. Sequences of the entire carboxyltransferase domain of A. japonicus ACCase were obtained, and AHFD-3 plants showed an Asp-2078-Gly substitution in the ACCase. With the derived cleaved amplified polymorphic sequence (dCAPS) method, we found that 85.4% of the plants of AHFD-3 carried this mutation. The P450 content in AHFD-3 plants was significantly higher than those of the two control populations after treatment with fenoxaprop-P-ethyl. Ten partial sequences of P450 genes in A. japonicus were cloned. Three P450 genes were up-regulated 12 h after fenoxaprop-P-ethyl treatment, which were all from the P450 subfamily CYP72A. Moreover, a P450 gene from the P450 family CYP81 was up-regulated after fenoxaprop-P-ethyl treatment in all populations studied. CONCLUSION: Fenoxaprop-P-ethyl resistance in AHFD-3 plants was conferred by up-regulation of cytochrome P450s in the CYP72A subfamily and target site mutation of the ACCase gene. © 2018 Society of Chemical Industry.