In this paper, the terahertz (THz) radiation generated by mixing two Cosh–Gaussian laser beams (decentered Gaussian beams) in collisional magnetized plasma has been studied in the presence of a helical magnetostatic wiggler. Equations governing the THz radiation generation of laser beams and the efficiency of emitted radiation for both left- and right-hand circular polarizations have been derived. The effects of the wiggler strengths and the decentered parameter on the THz field amplitude and laser electric field magnitude have been investigated. Numerical results indicate that the amplitude of THz electric field radiation increases when the wiggler frequency increases, and consequently the THz radiation becomes stronger. Moreover, it is seen that normalized laser efficiency has a decreasing trend with increasing normalized collision frequency for different wiggler magnetic field strengths. Furthermore, it is found that the efficiency increases with an increase in the values of the wiggler frequencies. Finally, by adjusting the decentered parameter and wiggler magnetic field strength, the peak intensity of lasers can be shifted and a significant change is found in the THz field amplitude and its conversion efficiency.

The present study reports a significant combined antibacterial activity ofCichorium intybusL. (known asChicory) natural extract with cold atmospheric-pressure argon plasma treatment against multi-drug resistant (MDR) Gram-negative bacteria. To detect reactive species that are generated in the argon plasma, optical emission spectra were recorded. The molecular bands were allocated to the hydroxyl radicals (OH) and neutral nitrogen molecules (N₂). Moreover, the atomic lines form the emitted spectra were determined to argon atoms (Ar) and the oxygen atoms (O), respectively. The results revealed thatChicoryextract treatment at a concentration of 0.043 g/ml reduced the metabolic activity ofP. aeruginosacells by 42%, while, a reduced metabolic activity of 50.6% was found forE. colibiofilms. Moreover, the combination ofChicoryextract with 3 min Ar-plasma introduced a synergistic effect, so that it exhibited a significantly reduced metabolic activity ofP. aeruginosato 84.1%, andE. coliones to 86.7%, respectively. The relationship between cell viability and membrane integrity ofP. aeruginosaandE. colibiofilms treated withChicoryextract and argon plasma jet were also analyzed by CLSM. It was found that after the combined treatment, a noticeable membrane disruption was formed. Besides, it was concluded thatE. colibiofilms showed a higher sensitivity to Ar-plasma thanP. aeruginosabiofilm at longer plasma exposure times. This study suggests that the anti-biofilm therapy based on a combined effect ofChicoryextract and cold argon plasma treatment can serve as a considerable green method for treatment of antimicrobial MDR bacteria.

An advanced incremental scheme for generating tunable coherent radiation in a free-electron laser has been presented: the basic concept is the use of a relativistic electron beam propagating through a magnetized dusty plasma channel where dust helicon, dust Alfven and coupled dust cyclotron-Alfven waves can play a role as a low-frequency wiggler, triggering coherent emissions. The wiggler wavelength at the sub-mm level allows one to reach the wavelength range from a few nm down to a few Å with moderately relativistic electrons of kinetic energies of a few tens/hundreds of MeV. The laser gain and the effects of beam self-electric and self-magnetic fields on the gain have been estimated and compared with findings of the helical magnetic and electromagnetic wigglers in vacuum. To study the chaotic regions of the electron motion in the dusty plasma wave wiggler, a time independent Hamiltonian has been obtained. The Poincare surface of a section map has been used numerically to analyze the nonintegrable system where chaotic regions in phase-space emerge. This concept opens a path toward a new generation of synchrotron sources based on compact plasma structures.