The Terahertz Scattering Analysis of Rough Metallic and Dielectric Targets

The terahertz scattering characteristics of metallic and dielectric rough targets is important for the investigation of the terahertz radar targets properties. According to the stationary phase theory and scalar approximation, if the radius of curvature at any point of the surface is much larger than the incident wavelength, and the wavelength is also much longer than the surface height function and Root-Mean-Square (RMS) surface slope, the coherent and incoherent scattering Radar Cross Section (RCS) of rough metallic and dielectric targets can be obtained. Based on the stationary phase approximation, the coherent RCS of rough conductors, smooth dielectric targets and rough dielectric targets can be easily deputed. The scattering characteristics of electrically large smooth Al and painted spheres are investigated in this paper, and the calculated RCS are verified by Mie scattering theory, the error is less than 0.1 dBm2. Based on lambert theory, it is demonstrated that the incoherent RCS is analyzed with better precision if the rough surfaces are divided into much more facets. In this paper, the coherent and incoherent scattering of rough Al and painted spheres are numerically observed, and the effects of surface roughness and materials are analyzed. The conclusions provide theoretical foundation for the terahertz scattering characteristics of electrically large rough targets

Acute Hypoxia Stress-Induced Apoptosis in Gill of Japanese Flounder (Paralichthys olivaceus) by Modulating the Epas1/Bad Pathway

The physiological responses and molecular mechanisms of apoptosis in Japanese flounder under hypoxic stress remain unclear. In the present study, we performed acute hypoxia stress on Japanese flounder (2.39 ± 0.84 mg/L) and detected gills responses in histomorphology and molecular mechanisms. The results showed that the volume of the interlamellar cell mass decreased and the gill lamellae prolonged, indicating the expansion of the respiratory surface area. Additionally, the fluorescence signal of apoptosis increased under hypoxic stress. In addition, the expression of two genes (EPAS1 and Bad) related to apoptosis increased about four-fold and two-fold, respectively, at 6 h of hypoxia. Meanwhile, the result of the dual-luciferase reporter assay showed that EPAS1 is a transcription factor, which could regulate (p < 0.05) the expression of the Bad gene, and we identified the binding site of EPAS1 was the AATGGAAAC sequence located near −766. DNA methylation assay showed that hypoxia affected the methylation status of CpG islands of EPAS1 and Bad genes. All results indicated that hypoxia could activate the EPAS1/Bad signal pathway to induce gill apoptosis of Japanese flounder. Our study provides new light on understanding the molecular mechanism of hypoxia-induced apoptosis in Japanese flounder