Ultrasonic characterization of alumina/silicone-rubber composites for acoustical applications

ICSV28 Local Committee in Singapore, July 24-28, 2022Silicone rubber has been used commonly as a material for an acoustic lens in medical ultrasonic probes. In order to achieve the desired properties for an acoustic lens, i.e., acoustic impedance close that of, and wave velocity lower than that of, human body, different materials have been considered as fillers or dopants to be dispersed in silicone rubber. A micromechanics-based analysis has revealed that silicone-rubber composites can have the desired acoustical properties with a certainamount of dispersed alumina particles. In this study, the ultrasonic wave propagation characteristics of alumina-particle-dispersed silicone-rubber composites fabricated with different particle concentrations and average particle radii were investigated experimentally. Namely, the velocity and attenuation coefficient of longitudinal wave in the alumina/silicone-rubber composites were evaluated at the frequency of 5 MHz by the spectral analysis of the reflected waves obtained in the immersion measurement. The experimental results have shown that the acoustic impedance and the wave velocity desired for an acoustic lens can be achieved by the alumina particle concentration as predicted by the micromechanics-based analysis. The influence of the particle radius on the acoustical properties of the composite has also been examined

Urine Levels of Defensin α1 Reflect Kidney Injury in Leptospirosis Patients

Leptospirosis is a zoonotic disease whose severe forms are often accompanied by kidney dysfunction. In the present study, urinary markers were studied for potential prediction of disease severity. Urine samples from 135 patients with or without leptospirosis at San Lazaro Hospital, the Philippines, were analyzed. Urine levels of defensin 1 (uDA1) were compared with those of neutrophil gelatinase-associated lipocalin (uNGAL) and N-acetyl- -D-glucosidase (uNAG). Serum creatinine (Cr) was used as a marker of kidney injury. The levels of uDA1/Cr, uNGAL/Cr, and uNAG/Cr were positive in 46%, 90%, and 80% of leptospirosis patients, and 69%, 70%, and 70% of non-leptospirosis patients, respectively. In leptospirosis patients, the correlation of uDA1/Cr, uNGAL/Cr and uNAG/Cr levels with serum Cr were r = 0.3 (p < 0.01), r = 0.29 (p < 0.01), and r = 0.02 (p = 0.81), respectively. uDA1/Cr levels were correlated with uNGAL/Cr levels (r = 0.49, p < 0.01) and uNAG/Cr levels (r = 0.47, p < 0.0001) in leptospirosis patients. These findings suggest that uDA1, uNGAL, and uNAG were elevated in leptospirosis patients and reflected various types of kidney damage. uDA1 and uNGAL can be used to track kidney injury in leptospirosis patients because of their correlation with the serum Cr level