Difference analysis in terahertz wave propagation in thermochemical nonequilibrium plasma sheath under different hypersonic vehicle shapes

Research on terahertz communication under different vehicles has important guiding significance for the design of future hypersonic vehicle and Radio Frequency(RF)blackout.In this paper,a joint simulation model of plasma flow under thermochemical nonequilibrium state and terahertz transmission is developed to investigate the differences in terahertz wave transmission characteristics under different vehicle shapes and the related mechanisms.By comparing the plasma sheath characteristics and terahertz transmission among HIFIRE-5b(Hypersonic International Flight Research Experimentation-5b),RAM C(Radio Attenuation Measurement C)and ARD(Atmospheric Reentry Demonstrator)vehicles,it is found that the sheath thickness and electron density of ARD vehicles is significantly larger than that of HIFIRE-5b and RAM C vehicles,resulting in greater terahertz wave attenuation.Collision absorption plays a major role in the terahertz attenuation of vehicles,and the contribution of reflection effects is only observed in the ARD vehicle due to its larger plasma sheath thickness and spatial structure variation.Based on the above comparison results,a shape design scheme of reducing the vehicle head and tail for mitigating RF blackout is proposed,and the scheme is proved by further analyzing the effects of different vehicle heads and tails on the terahertz communication.With the decrease of the head radius and tail width of hypersonic vehicle,the wave attenuation at the same terahertz frequency decreases,and the contribution of reflection effect to wave attenuation gradually disappears.Therefore,the shape design scheme of reducing the vehicle head and tail can effectively alleviate the RF blackout problem,which provides an important reference value for future hypersonic vehicle design.

Cold air plasma:A potential strategy for inducing apoptosis of rheumatoid arthritis fibroblast‐like synoviocytes

Rheumatoid arthritis(RA)is an autoimmune disease of the joints characterised by synovial hyperplasia and chronic inflammation.Rheumatoid arthritis fibroblast‐like synoviocytes(RA‐FLS)cells are the dominant cell type in the hyperplastic synovial membrane,which play a key role in the pathogenesis of RA.They can invade cartilage,cause inflammation,destroy joints,and show tumour‐like anti‐apoptosis characteristics.Thus,the purpose of this study is to investigate the effect of cold air plasma(CAP)on RA‐FLS cells.The results showed that CAP treatment for 120 s could significantly reduce the viability of RA‐FLS cells,increase the content of intracellular reactive ox-ygen species(ROS),and significantly down‐regulate the ratio of apoptosis‐related protein Bcl‐2 to Bax.In this study,a novel approach of inducing apoptosis in RA‐FLS cells using CAP was proposed,which may provide a new choice for joint tar-geting therapy of RA.