Monitoring Variations of Biological Impedances at Microwave Frequencies

Two interferometer systems for monitoring time-varying biological impedances at 915 MHz and 913 GHz were developed. The systems compare the phase of the signal scattered from a region of biological tissue to that of a reference signal, using a phase sensitive detector. The phase changes of the scattered signal are an indication of the net changes within the test region due to various physiological processes, for example, the displacements of blood vessels during the cardiac cycle. The systems were tested with simulation models and their detection characteristics were found to be a linear function of the phase changes for return losses within the test region as high as 60 dB. Because of the interference between the signal scattered from the test region and the signal reflected at the antenna-tissue interface, the maximum range of operation of the systems was limited to a fraction of a wavelength in the test medium. Copyrigh

Do radiofrequency radiation affect the auditory system of people with occupational exposure?

The present study intended to investigate whether radiofrequency (RF) affects auditory system of people who are occupationally exposed to RF in terms of noise-induced hearing loss (NIHL) or not. The study was carried out on 31 men from 26 to 53 years of age. All of them have been working in the Diyarbakir Radio Broadcasting Station. On the other hand, the control group was based on 30 unexposed voluntary and healthy men. The range of age for control group was the same as in the exposed group (experimental group). The results of the present study showed that the incidence of NIHL in the exposed group is more and more than that of the unexposed (control) group. The incidence of NIHL was approximately found 70 % for exposed group and 6% for unexposed group. The difference of the incidence of NIHL between exposed and unexposed groups were statistically found significant for right and left ears at “4 kHz notch” (p < 0.001). Hearing loss was not observed below 1 kHz. The percentage difference in the incidence of hearing loss (decibel) between control and experimental group was found insignificant for frequency below 1 kHz (p > 0.05). The experimental group was also divided to three subgroups of technicians, officers and men staying in the quarters of radio broadcasting station. Three subgroups were compared with one another statistically. The incidence of NIHL for the right ears of technicians was found higher than the officer (p < 0.05). The incidence of NIHL for the left ears of men staying in quarters was found higher than officers (p < 0.05). The other results of comparison were found insignificant (p > 0.05). In conclusion, the incidence of NIHL at “4 kHz Notch” in the experimental group was found more common than the control group