Formation of circularly polarized wave by impedance wire dipole located over square screen
For a radiating system consisting of a resonant half-wave impedance oblique wire dipole and a rectangular perfectly conducting screen the conditions guaranteeing formation of a circularly polarized wave with extremely achievable field amplitude in the set directions of the main observation planes are investigated. Computation of the far field components is based on the asymptotic solution of 3D vector problem of diffraction of the field of electric dipole on the ideally conducting rectangular screen, obtained by the method of uniform geometric diffraction theory. To define a wire dipole's slope angle guaranteeing equality of the amplitudes of the orthogonal field components, the technique with account of diffraction effects on edges of the finite size screen is developed. It is shown that in defined interval of the observation angles the circularly polarized wave with extremely achievable field amplitude may be formed by a choice of appropriate wire dipole's slope angle and removal from a screen.
Directional and polarization radiation characteristics of a horizontal impedance vibrator located above a rectangular screen
An algorithm of calculation of the directivity, energy, and polarization radiation characteristics of an arbitrarily oriented thin impedance vibrator located above a rectangular screen is developed on the basis of the asymptotic solution to the 3D problem of diffraction of the field of the electric vibrator by a perfectly conducting rectangular screen. The asymptotic expressions for the current of an impedance vibrator having the electric length 0.4 ≤2l/λ ≤ 0.6 are applied. The asymptotic solution is obtained on the basis of the method of the uniform geometric diffraction theory. The aforementioned characteristics are studied in the whole observation space in the far zone. The effects of the thickness and length of the vibrators and the effects of the distances from the screen on the resonance values of the distributed surface impedance and the corresponding radiation characteristics are shown. The resonance vibrator’s radiation characteristics that depend on the screen dimensions are analyzed. The amplitude and polarization patterns of a horizontal vibrator located above a square screen having optimal dimensions are calculated.
Morphological characterization of Eustrongylides sp. larvae (Nematoda, Dioctophymatoidea) parasite of Rhinella marina (Amphibia: Bufonidae) from Eastern Amazonia.
Absctract Eustrongylides spp. nematodes have birds as final hosts and uses other vertebrates as intermediate/paratenic host (fish, amphibians and reptiles) and have zoonotic potential. In amphibians, the larvae may be located in the subcutaneous tissues, liver and mesentery, between the muscle fibres, especially in the lower limbs. Rhinella marina, which is widely observed in Brazil, has exhibited complex diversity in its helminth fauna, reflecting the unique habitat of the Amazon biome. For the first time, this study describes the morphological aspects of third-stage larvae of Eustrongylides sp. in Rhinella marina from Santa Cruz do Ararí, Marajó Archipelago, Eastern Amazonia, using light and scanning electron microscopy.