Comparison of two high-precision nondestructive measurement methods for evaluating thermal expansion differences in the 8.3-m ultralow-expansion Subaru primary mirror blank.
The building blocks for fabricating the 8.3-m Subaru primary mirror blank are ultralow-expansin solid hexagonal units that were subjected to rigorous ultrasonic examination to establish thermal expansion characterization as reported by Hagy [Appl. Opt. 12, 1440 (1973)]. Following assembly of the mirror by fusion and fine annealing, photoelastic analyses at hex-to-hex seals were used to calculate thermal expansion differences. These differences are found to be in excellent agreement with the ultrasonically established differences.
The Dependence of Ultrasonic Velocity in Ultra-Low Expansion Glass on Temperature
The coefficient of thermal expansion (CTE) is an important property of ultra-low expansion (ULE) glass, and the ultrasonic velocity method has shown excellent performance for the nondestructive measurement of CTE in large ULE glass. In this method, the accurate acquisition of the ultrasonic velocity in ULE glass is necessary. Herein, we present a correlation method to determine the ultrasonic TOF in ULE glass and to further obtain the ultrasonic longitudinal wave velocity (cL) indirectly. The performance of this method was verified by simulations. Considering the dependence of cL on temperature (T), we carried out the derivation of the analytical model between cL and T. Based on reasonable constant assumptions in the physical sense, a cL–T exponential model was produced, and some experimental results support this model. Additional experiments were carried out to validate the accuracy of the cL–T exponential model. The studies we conducted indicate that the cL–T exponential model can reliably predict the ultrasonic velocity in ULE glass at different temperatures, providing a means for the nondestructive CTE measurement of large ULE glass at a specified temperature.
Exopolysaccharide biosynthesis and related enzyme activities of the medicinal fungus, Ganoderma lucidum, grown on lactose in a bioreactor
Exopolysaccharide (EPS) production and biosynthesis were studied in Ganoderma lucidum, a fungus used in traditional Chinese medicine, grown with lactose in a bioreactor. β-Galactosidase activity, which implies the existence of a lactose permease system, was induced by lactose. Lactose feeding also increased α-phosphoglucomutase activity and EPS accumulation but decreased phosphoglucose isomerase activity and lactate concentration in the culture broth. A maximum cell density of 22 g l−1 and EPS at 1.25 g l−1 were obtained in fed-batch bioreactor culture.