ABSTRACT
High-resolution absorption measurements of CO(2) were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO(2) combustion diagnostic based on a distributed-feedback diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H(2)O and CO(2) were used to find candidate transitions for CO(2) detection, and the R(50) transition at 1.997 mum (the nu(1) + 2nu(2) + nu(3) band) was selected on the basis of its line strength and its isolation from interfering high-temperature water absorption. Measurements of spectroscopic parameters such as the line strength, the self-broadening coefficient, and the line position were made for the R(50) transition, and an improved value for the line strength is reported. The combustion-product populations of CO(2) in the combustion region above a flat-flame burner were determined in situ to verify the measured spectroscopic parameters and to demonstrate the feasibility of the diode-laser sensor.
ABSTRACT
Line-of-sight diode-laser absorption techniques have been extended to enable temperature measurements in nonuniform-property flows. The sensing strategy for such flows exploits the broad wavelength-scanning abilities (>1.7 nm approximately 30 cm(-1)) of a vertical cavity surface-emitting laser (VCSEL) to interrogate multiple absorption transitions along a single line of sight. To demonstrate the strategy, a VCSEL-based sensor for oxygen gas temperature distributions was developed. A VCSEL beam was directed through paths containing atmospheric-pressure air with known (and relatively simple) temperature distributions in the 200-700 K range. The VCSEL was scanned over ten transitions in the R branch of the oxygen A band near 760 nm and optionally over six transitions in the P branch. Temperature distribution information can be inferred from these scans because the line strength of each probed transition has a unique temperature dependence; the measurement accuracy and resolution depend on the details of this temperature dependence and on the total number of lines scanned. The performance of the sensing strategy can be optimized and predicted theoretically. Because the sensor exhibits a fast time response (~30 ms) and can be adapted to probe a variety of species over a range of temperatures and pressures, it shows promise for industrial application.
ABSTRACT
Enhanced wavelength tuning of a distributed-feedback InGaAsP diode laser is demonstrated by use of rapid temperature cycling. The laser-active region is cycled from -10 to +50 degrees C (scanning the output from 1399 to 1403 nm) at kilohertz rates by pulsed heating with an auxiliary 532-nm laser. Such 4-nm scans represent a ten-fold increase in the wavelength-scanning range offered by standard current-tuning techniques and thus extend the capabilities of scan-wavelength sensors and systems. As an example application, we demonstrate absorption spectroscopy of H(2)O vapor at a pressure of 10 atm.
ABSTRACT
OBJECTIVE: To determine the factors related to undesired effects of chloral hydrate in young children undergoing echocardiogram. Undesired effects studied were reaction to chloral hydrate before to sedation (ataxia, excitement), delayed sedation, light sleep during sedation, and behavioral changes after sedation. DESIGN: Descriptive, correlational design. SETTING: Echocardiography laboratory in a pediatric teaching hospital. SUBJECTS: 140 children aged 0 to 36 months who were undergoing diagnostic echocardiography. Severity of cardiac disease ranged from benign murmur to uncorrectable lesion. Thirty children (21%) had cyanotic cardiac disease. Children were sedated with chloral hydrate per routine (mean dose 87 mg/kg) and observed from time of sedation throughout the examination. Data were collected on child's age, food ingested before sedation, transcutaneous oxygen saturation, and daytime nap schedule. OUTCOME MEASURES: Incidence of paradoxical excitement before sedation, length of time until child reached deep sedation, depth of sleep during the examination, and behavioral changes after sedation. RESULTS: Paradoxical excitement before sedation occurred in 25 children (18%). Length of time until child reached deep sedation averaged 25 minutes. Three children never fell asleep. Proximity of sedation to naptime was positively correlated to the speed of sedation. Deep sedation was achieved in 131 children (94%). Depth of sleep during the examination was related to child's age, proximity of sedation to nap time, and recent food ingestions. Older children, who were due for a nap and who had refrained from eating before the examination were most likely to remain soundly asleep throughout the examination. Children with cyanotic defects were not adversely affected by deep sedation with chloral hydrate. Most children experienced motor and affective changes after sedation. CONCLUSIONS: In this sample, chloral hydrate was an effective and safe sedative. Implications for nursing include changes in scheduling practices, limiting food ingestion before sedation, and information to provide parents about chloral hydrate sedation.
