RESUMO
In recent decades, to reduce electromagnetic pollution, scientists focus on finding new microwave absorbers with effective performance, thin thickness, and broad bandwidth. In this work, the nanoparticles of NiFe2O4, X-doped g-C3N4 (M = S, P, and O), and MTiO3 (M = Fe, Mg, and Zn) were successfully synthesized using co-precipitation, specific heat program, and semi-wet sol-gel methods, respectively. The synthesized nanoparticles were utilized as absorption agents and polyester resin as the matrix. Morphology, particle size, crystal structure, and chemical composition of the prepared nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and energy dispersive X-Ray analysis (EDX), respectively. The microwave absorption performance of the coatings was also investigated by a vector network analyzer (VNA). Moreover, the effect of different parameters on the performance of absorbent coatings was studied by the Taguchi method and optimized to achieve an optimal absorbent. The results showed that the optimal nanocomposite has the reflectance loss (RL) less than - 30 dB (equal to absorption > 99%) at a high-frequency range (8-12 GHz) and 1 mm thickness. Furthermore, the addition of such novel nanoparticles to absorbents resulted in high values of attenuation constant (more than 200 dB/m) at the X-band. Therefore, the polyester coating filled with ZnTiO3, O-doped g-C3N4, and NiFe2O4 nanofillers can be considered a high-efficiency and low-density absorber.
RESUMO
BACKGROUND: Testosterone may be an important factor causing depression in the elderly men. The purpose of this study was to determine the relationship between testosterone levels and depressive symptoms in older men in Amirkola, Iran. METHODS: This cross- sectional study is a part of the Amirkola Health and Aging Project (AHAP) that involves people aged 60 and above living in Amirkola, a small town in northern Iran. The testosterone levels were measured using ELISA on morning blood samples (ngr / ml) and depressive symptoms were identified using Geriatric Depression Scale (GDS). The data were collected and analyzed. RESULTS: Eight hundred thirty elderly men with the mean age of 70.02±7.7 years were included. On the basis of GDS criteria, 593 individuals had no depressive symptoms and 237 had at least one of these symptoms. The mean serum testosterone level in men without symptoms of depression (4.94±4.22) ngr/ml and was higher than in those with such symptoms (4.19±3.65) ngr/ml (P=0.011). Also, there was a significant inverse correlation between the testosterone levels and number of depressive symptoms (P=0.015, r=-0.084). After adjusting with age and educational levels, and living alone (OR=2.6, 95% CI: 1.17-5.82, P=0.02), testosterone levels (OR=1.67, 95% CI: 1.03-2.72, P=0.038) had the greatest impact on the development of depression. CONCLUSION: The results of this study showed a significant inverse relationship between serum testosterone levels and depressive symptoms in elderly men.
