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Biomedical subjects

Robert F Curl

Publications and source records attributed to Robert F Curl.

8 recordsLinked to original sources
PubMed2005

Color-blind fluorescence detection for four-color DNA sequencing.

We present an approach called pulsed multiline excitation (PME) for measurements of multicomponent, fluorescence species and demonstrate its application in capillary electrophoresis for DNA sequencing. To fully demonstrate the advantages of PME, a fluorescent dye set has been developed whose absorption maxima span virtually the entire visible spectrum. Unlike emission wavelength-dependent approaches for identifying fluorescent species, the removal of the spectral component in PME confers a number of advantages including higher and normalized signals from all dyes present in the assay, the elimination of spectral cross-talk between dyes, and higher signal collection efficiency. Base-calling is unambiguously determined once dye mobility corrections are made. These advantages translate into significantly enhanced signal quality as illustrated in the primary DNA sequencing data and provide a means for achieving accurate base-calling at lower reagent concentrations.

Base Sequence↗
PubMed2004

Pulsed quantum-cascade laser-based sensor for trace-gas detection of carbonyl sulfide.

Simultaneous exhaled carbonyl sulfide (OCS) and carbon dioxide concentration measurements in human breath are demonstrated with a compact pulsed quantum-cascade laser-based gas sensor. We achieved a noise-equivalent sensitivity (1sigma) of 1.2 parts per billion by measuring a well-isolated OCS P(11) absorption line in the v3 band at 2057.6 cm(-1) using an astigmatic Herriott cell of 36-m optical path length and 0.4-s acquisition time.

Journal Article↗
PubMed2004

Monitoring of ethylene by a pulsed quantum cascade laser.

We report on the development and performance of a gas sensor based on a quantum cascade laser operating at a wavelength of approximately 10 microns to measure ethylene (C2H4) concentrations by use of a rotational component of the fundamental nu 7 band. The laser is thermoelectrically cooled and operates in a pulsed mode. The influence of pulse-to-pulse fluctuations is minimized by use of a reference beam and a single detector with time discriminating electronics. Gas absorption is recorded in a 100-m optical path-length astigmatic Herriott cell. With a 10-kHz pulse repetition rate and an 80-s total acquisition time, a noise equivalent sensitivity of 30 parts per billion has been demonstrated. The sensor has been applied to monitor C2H4 in vehicle exhaust as well as in air collected in a high-traffic urban tunnel.

Journal Article↗
PubMed2004

Mid-infrared quantum cascade laser based off-axis integrated cavity output spectroscopy for biogenic nitric oxide detection.

Tunable-laser absorption spectroscopy in the mid-IR spectral region is a sensitive analytical technique for trace-gas quantification. The detection of nitric oxide (NO) in exhaled breath is of particular interest in the diagnosis of lower-airway inflammation associated with a number of lung diseases and illnesses. A gas analyzer based on a continuous-wave mid-IR quantum cascade laser operating at approximately 5.2 microm and on off-axis integrated cavity output spectroscopy (ICOS) has been developed to measure NO concentrations in human breath. A compact sample cell, 5.3 cm in length and with a volume of < 80 cm3, that is suitable for on-line and off-line measurements during a single breath cycle, has been designed and tested. A noise-equivalent (signal-to-noise ratio of 1) sensitivity of 10 parts in 10(9) by volume (ppbv) of NO was achieved. The combination of ICOS with wavelength modulation resulted in a 2-ppbv noise-equivalent sensitivity. The total data acquisition and averaging time was 15 s in both cases. The feasibility of detecting NO in expired human breath as a potential noninvasive medical diagnostic tool is discussed.

Exhalation↗
PubMed2004

Atmospheric formaldehyde monitoring in the Greater Houston area in 2002.

A laser spectrometer based on difference frequency generation (DFG) was deployed for real-time long-term monitoring of HCHO concentrations at an environmental monitoring site located at Deer Park, Texas, in the Greater Houston area. Three HCHO concentration measurements were made during the periods of July 20-31 (period I), August 2-14 (period II), and August 24-September 25 (period III), 2002. In periods I and II, differences in HCHO concentrations are apparent between day and night measurements, with elevated concentrations during daylight hours. Most of the HCHO peak values are less than 20 ppbV except for two intense peaks on August 02 (approximately 25 ppbV) and August 04 (approximately 30 ppbV). The formaldehyde concentration levels in ambient air at the measurement site are produced mainly by the photochemical oxidation of volatile organic compounds (VOCs) caused by intense sunlight during periods I and II. This observation was made based on a comparison with the ozone concentration, solar radiation, temperature, relative humidity, and wind speed data obtained from the Texas Commission on Environmental Quality (TCEQ). During period III, data collected by a time-integrating wet-chemical technique are compared to the data collected by the spectroscopic instrument.

Journal Article↗
PubMed2002

Transportable automated ammonia sensor based on a pulsed thermoelectrically cooled quantum-cascade distributed feedback laser.

A compact ammonia sensor based on a 10-microm single-frequency, thermoelectrically cooled, pulsed quantum-cascade laser with an embedded distributed feedback structure has been developed. To measure NH3 concentrations, we scanned the laser over two absorption lines of its fundamental v2 band. A sensitivity of better than 0.3 parts per million was achieved with just a 1-m optical path length. The sensor is computer controlled and automated to monitor NH3 concentrations continuously for extended periods of time and to store data in the computer memory.

Ammonia↗