RESUMO
The use of photoacoustic spectroscopy and mid-infrared quantum-cascade lasers (QCLs) for the detection of hexamethyldisilazane (HMDS) is reported. A detection limit of 200 parts in 10(9) is found using a Fabry-Perot QCL operated at 8.4 microm in pulsed mode and a photoacoustic cell equipped with four electret microphones. The laser multimode spectrum matches the range of the N-H bending absorption band of HMDS. Further improvements to reach lower detection limits are discussed.
Assuntos
Lasers , Compostos de Organossilício/química , Teoria Quântica , Fotometria , Espectroscopia de Infravermelho com Transformada de Fourier , VolatilizaçãoRESUMO
An optical sensor for real-time monitoring of laser welding based on a spectroscopic study of the optical emission of plasma plumes has been developed. The welding plasma's electron temperature was contemporarily monitored for three of the chemical species that constitute the plasma plume by use of related emission lines. The evolution of electron temperature was recorded and analyzed during several welding procedures carried out under various operating conditions. A clear correlation between the mean value and the standard deviation of the plasma's electron temperature and the quality of the welded joint has been found. We used this information to find optimal welding parameters and for real-time detection of weld defects such as crater formation, lack of penetration, weld disruptions, and seam oxidation.
RESUMO
The optical oxymetry methods based on light transmission or diffuse reflectance of living tissues are discussed. The experimental techniques now under test are highlighted.
Assuntos
Oximetria/métodos , Oxigênio/análise , Monitorização Transcutânea dos Gases Sanguíneos/métodos , Humanos , Luz , Modelos Biológicos , Fluxo Pulsátil , Espalhamento de RadiaçãoRESUMO
Near-infrared spectroscopy (NIRS) is a noninvasive technique to measure the tissue oxygenation in real time. This optical method has many advantages over the invasive analysis currently used for clinical tests. Among the possible applications of near-infrared oxymetry, we report three protocols (exercise, venous occlusion and tilting table) in conjunction with NIRS, and discuss their applicability in the diagnosis of peripheral vascular disease (PVD).
