Biomedical subjects

Nigel Langford

Publications and source records attributed to Nigel Langford.

6 recordsLinked to original sources

PubMed2005

Real-time trace-level detection of carbon dioxide and ethylene in car exhaust gases.

A direct-absorption spectrometer, based on a pulsed, distributed feedback, quantum cascade laser with a 10.26-microm wavelength and an astigmatic Herriott cell with a 66-m path length, has been developed for high-resolution IR spectroscopy. This spectrometer utilizes the intrapulse method, an example of sweep integration, in which the almost linear wavelength up-chirp obtained from a distributed feedback, quantum cascade laser yields a spectral microwindow of as many as 2.5 wave numbers/cm(-1). Within this spectral microwindow, molecular fingerprints can be monitored and recorded in real time. This system allows both the detection of carbon dioxide and ethylene and the real-time observation of the evolution of these gases in the exhaust by-products from several cars.

Air Pollutants↗

PubMed2005

Quantum cascade semiconductor infrared and far-infrared lasers: from trace gas sensing to non-linear optics.

The Quantum cascade (QC) laser is an entirely new type of semiconductor device in which the laser wavelength depends on the band-gap engineering. It can be made to operate over a much larger range than lead salt lasers, covering significant parts of both the infrared and submillimetre regions, and with higher output power. In this tutorial review we survey some of the applications of these new lasers, which range from trace gas detection for atmospheric or medical purposes to sub-Doppler and time dependent non-linear spectroscopy.

Gases↗

PubMed2005

The use of levomepromazine in Hyperemesis Gravidarum resistant to drug therapy--a case series.

Hyperemesis Gravidarum (HG) is a potentially serious complication of early pregnancy, which may rarely be severe enough to warrant termination of pregnancy. HG requires prompt treatment with intravenous fluids, thiamine supplementation and appropriate anti-emetic therapy. Anti-histamines such as promethazine are favoured as first-line agents, with prochlorperazine being used as a second-line drug. However, there is no clear data as to the most appropriate drug if these are ineffective. A case series of six women who presented with HG resistant to drug treatment is described. In these cases, levomepromazine 6.25mg tds was used to control HG. Five pregnancies progressed leading to live born infants with no evidence of congenital anomaly. One pregnancy resulted in an intra-uterine death with no external or ultrasound evidence of congenital anomaly. The role of phenothiazines in the pharmacological management of HG is discussed.

Adolescent↗

PubMed2005

Efficient Raman shifting of high-energy picosecond pulses into the eye-safe 1.5-microm spectral region by use of a KGd(WO4)2 crystal.

We report an efficient transient stimulated Raman conversion of high-energy picosecond pulses at 1350 nm into the eye-safe 1500-nm wavelength range by use of a KGd(WO4)2 crystal. The conversion efficiency into either 1503- or 1537-nm radiation (767- or 901-cm(-1) Raman modes, respectively) is measured to be approximately 10% in a single-pass configuration. The transient Raman gain coefficient is found to be approximately 0.8 cm/GW. Simultaneous generation of multiple Raman lines is also observed.

Journal Article↗

PubMed2004

Coherent two-photon absorption spectroscopy of the Raman-active KGd(WO4)2 crystal.

We report on the systematic open-aperture Z-scan characterization of the two-photon absorption properties in one of the most efficient solid-state Raman frequency shifters, the crystal potassium gadolinium tungstate [KGd(WO4)2]. The two-photon absorption coefficient was determined in the 370-600-nm wavelength range, with the highest value found to be approximately 1.9 cm/GW at 370 nm. Nonlinear losses are crucial in determining the conversion efficiency of the stimulated Raman scattering process when it is excited with ultrashort laser pulses with photon energy exceeding half of the bandgap. In addition, the results were analyzed within the context of a simple two-parabolic-band theoretical model to yield an effective bandgap energy value for the crystal.

Journal Article↗

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