Free-space measurement of bi-axial anisotropic materials
This paper presents an extension of the free-space method for measurement of bi-axial anisotropic material at microwave frequencies. In this method, four complex transverse constitutive parameters are directly computed from the reflection and transmission coefficients of a planar sample in free space for a normally incident plane wave with two polarizations. By using the measured amplitudes of the reflection and transmission coefficients of a planar sample at six incident angles with two polarizations, two complex longitudinal constitutive parameters are obtained by finding the solution to minimize the properly designed objective function under the suitable judging criterion. The numerical trials are carried out for a high-loss material by joining random errors to simulate the real measurement condition, which verifies the validity of this method.
A new free-wave method for ferrite measurement at millimeter wavelengths
It is shown that by measurement of the complex Fresnel reflection coefficients of a thick slab of ferrite for both parallel and perpendicular polarization, the complex permittivity and permeability of the ferrite can be found. In case the reflection coefficients are too small to be measured accurately, it is also shown that a slab of arbitrary but known thickness, backed by a metal plate, may be used. The necessary formulas are given for both cases. They are simple and explicit and do not involve the solution of transcendental equations, as might have been expected in the case of the second method proposed.
X-rays and photocarcinogenesis in hairless mice
It is well known that excessive X-ray radiation can cause non-melanoma skin cancers. With the increased incidence of sun-related skin cancer there is a need to investigate the combination of sunlight and X-rays. Immunocompetent C3.Cg/TifBomTac mice (n = 298) were divided into 12 groups. Mice were irradiated with 12, 29 or 50 kV X-rays. The mice received a total dose of 45 Gy. They were irradiated with 3 SED simulated solar radiation (SSR) either before or after irradiation with X-rays. The groups irradiated with X-rays alone, 0, 3, 9 and 10 mice (0, 12, 29 and 50 kV, respectively) developed squamous cell carcinoma. In the groups irradiated with SSR after X-rays the development of tumours was significantly faster in the 50 kV group than in the corresponding control group (175 vs. 194 days, p < 0.001). In the groups irradiated with SSR prior to the X-ray radiation the development of tumours was significantly faster in the 29 and the 50 kV groups than in the corresponding control group (175 vs. 202 days, p < 0.001 and 158 vs. 202 days, p < 0.001, respectively). In conclusion, X-ray radiation alone is a weak carcinogen in hairless mice. There is an added carcinogenic effect if X-ray radiation is given on prior sun-exposed skin or if the skin is sun-exposed after X-rays. We still believe that X-ray radiation is a safe and effective therapy for various dermatological diseases but caution should be observed if a patient has severely sun-damaged skin or has a high-risk sun behaviour.