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Owing to the inappropriate use of antimicrobial agents and the process of natural selection of microorganisms, antibiotic resistance has become a serious problem that challenges the health of human beings. Integrating two different bactericidal agents into one matrix is a feasible approach to enhance antibacterial efficiency. This study synthesized an efficient antibacterial nanocomposite material by conjugating polydopamine-modified silver nanoparticles (PDA@Ag) with amoxicillin (AMOX). The structure of PDA@Ag-AMOX (PAA) was characterized using TEM, UV-Vis, and FT-IR. Compared to PDA@Ag, PAA showed an increased inhibition rate of 33.3% against Escherichia coli, 31.3% against Bacillus subtilis, and 28.6% against Salmonella. It was speculated that the antimicrobial mechanism involved the reaction of Ag+ derived from PAA with functional groups of vital enzymes and proteins and the inhibitory effect of AMOX on the synthesis of bacterial cell walls and carboxypeptidase activity of binding proteins. PAA has both good coordinated antibacterial activity and high biocompatibility, which lays the foundation for the future combination and the exploration of more collaborative treatment plans among antibacterial agents. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of the narrow gap groove on the arc shape in the narrow gap swing arc welding process, magnetohydrodynamics theory was used to establish the three-dimensional symmetric mathematical model of the welding sidewall of the narrow gap welding arc based on the actual welding process. The numerical calculation of narrow gap welding arc was realized through the secondary development of the FLUENT user-defined-function (UDF), and the calculated arc shape was in good agreement with the experimental results. The distribution the flow field and temperature field of the narrow-gap welding arc were obtained. The results show that the magnetic induction intensity of the arc far away from the sidewall is greater than that near the sidewall. The plasma flow field, pressure field and temperature field are deflected toward the sidewall. The plasma at the bottom of the arc moves along the tangent of the molten pool to the bottom of the concave surface of the weld due to the influence of the narrow gap weld morphology, which affects the distribution of the current density and temperature field above the molten pool. [ABSTRACT FROM AUTHOR]