Investigation of Serum Zinc Level in Patients with Hearing Loss and its Association with Tinnitus

Introduction: This study aims to determine the serum zinc level in patients with hearing loss and its relation with tinnitus.  Materials & Methods: In this Cross-Sectional study, 110 patients older than 20 years old with Complaining of hearing loss and tinnitus were involved. Participating patients were first visited by an ear, nose, and throat specialist with a history and physical examination, and were assessed for standard hearing loss as well as the intensity and frequency of tinnitus by standard audiometric tests. Then, fasting blood samples were taken to check serum zinc levels. Results:The mean serum level was 85.32 ± 27 27.62, and the mean frequency of tinnitus was 4.94 ± 2.76, both of which had significant differences between different groups (P = 0.001). The mean intensity of tinnitus was 7.77 ± 4.56, and there was no significant difference between different groups (P = 0.677). Serum zinc level and tinnitus frequency were associated with a correlation coefficient of 0.205 (P = 0.032), and serum zinc level and tinnitus severity were associated with a correlation coefficient of 0.249 (P = 0.009). Conclusion: According to the present study results, the positive effect of serum zinc levels on the severity and frequency of tinnitus has been determined so that with decreasing serum zinc levels, tinnitus occurs at lower frequencies.

Effect of grain size on ultrasonic softening of pure aluminum

The objective of this paper is to reveal the main cause of volume effects of ultrasonic vibrations on the plastic behavior of pure aluminum specimens. For this purpose, specimens with different grain sizes were made by ECAP. An experimental tensile test system was designed and made, in which the specimens could be excited by ultrasonic vibrations with a frequency of 20 kHz and amplitude of 5 μm. Five specimens with grain sizes of 109, 38, 15, 7 and 0.97 μm were prepared. Tensile tests of the specimens were performed at room temperature and at constant speed of 0.2 mm/min under static load and superimposed ultrasonic excitations. It was found that ultrasonic vibrations had a remarkable influence on the plastic behavior of pure aluminum and after applying ultrasonic vibrations, flow stress of the all specimens reduced. Reduction of flow stress was dependent on grain size. The specimens with the largest grain size of 109 μm showed a flow stress reduction of 66% while finest grain size of 0.97 μm, a reduction of 11.3% was observed. The result of the current study can help to understand the underlying mechanisms of ultrasonic softening.