Stress and phase purity analyses of diamond films deposited through laser-assisted combustion synthesis.

Diamond films were deposited on silicon and tungsten carbide substrates in open air through laser-assisted combustion synthesis. Laser-induced resonant excitation of ethylene molecules was achieved in the combustion process to promote diamond growth rate. In addition to microstructure study by scanning electron microscopy, Raman spectroscopy was used to analyze the phase purity and residual stress of the diamond films. High-purity diamond films were obtained through laser-assisted combustion synthesis. The levels of residual stress were in agreement with corresponding thermal expansion coefficients of diamond, silicon, and tungsten carbide. Diamond-film purity increases while residual stress decreases with an increasing film thickness. Diamond films deposited on silicon substrates exhibit higher purity and lower residual stress than those deposited on tungsten carbide substrates.

Assessment of real-time PCR for quantification of Legionella spp. in spa water.

AIMS: Legionella bacteria ubiquitously colonize natural freshwater and are responsible for legionellosis in humans. Several cases of legionellosis have been associated in particular with the use of whirlpool spas. The objective of this study was to verify whether real-time PCR is applicable for the quantification of Legionella spp. in spa water. METHODS AND RESULTS: The study compared concentrations obtained by real-time PCR vs that obtained by conventional culture for 101 spa water samples. For the culture method, Legionella spp. were detected and quantified in 14 of 101 samples with measured concentrations ranging from 250 to 3.5 × 10(5) CFU l(-1). With the real-time PCR method, Legionella spp. were detected and quantified in 42 of 101 samples with concentrations ranging from 1000 to 6.1 × 10(7) GU l(-1). Results revealed a significant but weak correlation (r(2) = 0.1867) between the two methods. The positive predictive value (35%) of the PCR method compared to conventional culture herein was low. In contrast, the negative predictive value was excellent, reaching 93%. CONCLUSIONS: Real-time PCR could be used as a screening tool to rapidly ascertain the absence of Legionella spp. in spa water. However, a positive result involves the need to resort to conventional culture. SIGNIFICANCE AND IMPACT OF THE STUDY: Data of this study highlighted the pros and cons of quantification of Legionella spp. in spa water with real-time PCR using a commercial quantitative PCR kit in a routine laboratory, when compared to conventional culture.