The breath ammonia measurement of the hemodialysis with a QCM-NH3 sensor.

Recently, expired gases are analyzed non-invasively for monitoring the substances in the blood. Breath ammonia has been shown to correlate with BUN (blood urea nitrogen) and Cr (creatinine), both of which are indicators of solute removal in hemodialysis. In this study, breath ammonia concentration was continuously measured using a crystal oscillator QCM (quartz crystal microbalance) during the expiration of patients undergoing dialysis treatment. The results show that NH3 (ammonia) decreased gradually as the treatment proceeded. A strong correlation was observed between changes in the frequency of the QCM gas sensor and both the pre-dialysis BUN level (r=0.71, p<0.05) and the post-dialysis BUN level (r=0.90, p<0.05). NH3 was found to fall precipitously during dialysis. The differences were statistically significant. In addition, we found a statistically significant correlation between BUN and NH3 in expired gas. These results suggest that continuous measurement of NH3 is useful to assess the status of solute removal during hemodialysis.

Evaluation of blood access dysfunction based on a wavelet transform analysis of shunt murmurs.

We investigated shunt murmurs based on wavelet transform analysis as a new method for assessing vascular access function. In the present study, in patients with venous stenosis near an arteriovenous fistula (A-V fistula), a sensor was placed at different positions around the stenosis and shunt murmur signals obtained using a measurement system were subjected to time-frequency analysis based on wavelet transforms. The shunt murmurs obtained from the stenotic region closely represented some features of murmurs that are often referred to as "high-pitch" murmurs in the clinical setting. In contrast, shunt murmurs obtained about 5 cm downstream of the stenotic region closely represented some features of murmurs that are often referred to as "low-pitch" murmurs in the clinical setting. Furthermore, with the aim of extending the lifespan of arteriovenous grafts (A-V grafts) by detecting and treating stenotic lesions before the A-V graft becomes occluded, we evaluated the possibility of utilizing the present shunt murmur analysis for monitoring stenosis in such A-V grafts. When shunt murmurs from patients with A-V grafts were analyzed, the results suggested that the blood flow through the venous anastomosis of the graft was the most turbulent. This present method whereby blood flow in an A-V fistula is assessed based on the frequency distribution on a time-frequency plane by wavelet transform analysis is advantageous because findings are not markedly affected by sensor attachment. Furthermore, because the sensor is attached using an adhesive collar, measurements can be taken over a short period of time before each dialysis session.

Effect of defect size on fracture strength of dental low fusion porcelain.

Various grinding defects were produced on the surface of specimen dental low fusion porcelain in an attempt to establish the relationship between defect size and fracture strength. In addition, the applicability of the process zone size-fracture criterion in assessing the material properties of dental low fusion porcelain was examined. Super porcelain AAA E3 (Noritake Co., Japan) was used as dental low fusion porcelain. The bending strength and fracture toughness value were estimated by the three-point bending test. After glazing, grinding flaws were introduced by grinding the specimen with abrasive papers of various mesh sizes. In order to calculate the fracture toughness value of dental low fusion porcelain, we introduced a surface crack using a Vickers indenter. The results were discussed based on the process zone size-fracture criterion. The size of cracks caused by grinding was estimated with the process zone size-fracture criterion and Newman-Raju formula. As the defect size decreased, the fracture stress approached the strength for smooth specimen without defect. The K(c) value showed a tendency to approach the K(lc) value when the defect size increased. The relationship between the fracture stress, sigma(F), and the equivalent crack length, a(e), was in good agreement with the theoretical relations deduced from the criterion in dental low fusion porcelain.