Patients who have had one oral cancer are at increased risk of developing a semi-malignant tumour. The detecting of oral cancer is made difficult (and is often delayed) by the unknown appearance of the early oral lesion. A technique that could reliably detect early cancers would be useful to the oral and dental health specialist. One possible technique is the use of a photosensitiser that may be preferentially taken up by cancerous cells. 5-aminolaevulinic acid (ALA) is one such drug that is converted to Protoporphyrin IX (PpIX) and fluoresces at 636nm when illuminated with light of wavelength 405nm. It has been hypothesized that cell inclined towards malignant change would have a higher metabolic rate, and thus convert more ALA into its metabolite PpIX. These drugs can then be detected using a technique called Photodynamic detection, through the analysis of their fluorescence spectra. We describe a pilot study that used a compact spectroscopic instrument designed to excite and measure fluorescence in the oral cavity. Some Inter-subject variation in PpIX time course characteristics may be evident in our volunteers, as has been reported by other researchers. The obtained data would suggest that this instrument may be a valuable tool for detecting early oral cancers. However, further studies are required, not least to ensure that these data are due to detection of ALA metabolite in cancer and not some other systemic effect.
We present a device designed to measure laser output wavelength and based on Wollaston prisms and Barium borate (BBO) crystal polarizers. The arrangement generates a localized fringe plane perpendicular to the optic axis at which a CCD array is placed; consequently, good spatial coherence of the light is not a critical requirement for effective operation of the device. The interferogram is recorded with a digital camera allowing complete pixel registration, which results in improved accuracy. After calibration of the arrangement, the wavelength can then be measured with a precision of better than 1 part in 105, and has been shown to track changes in the output wavelength of the laser sources used. In addition, the calibrated wavelength meter was found to be able to measure the absolute value of a series of defined laser lines to an accuracy of 0.18% (+/- 0.86nm).
In this paper in-fiber Bragg gratings (IFBGs) were embedded in epoxy resin carbon fiber composite coupons, and these coupons were subjected to transient events such as impacts. The IFBGs were demodulated using a fiber Fabry-Perot interferometer and an interference filter. In addition to the IFBGs, two other types of sensors were used. These were a force transducer mounted in the impact rig, and resistive foil strain gauges mounted on the surface of the test coupons. Comparisons of the data obtained using these sensors have been made. The IFBGs have successfully survived the impacts and have been used to record strain transients that characterize typical fracture events.
In-fiber Bragg gratings (IFBGs) and dielectric sensors have been embedded in the same carbon fiber epoxy composite and have been used together during the curing process to make in- situ measurements of two cure parameters, namely internal strain and conductivity. This was performed using an automated acquisition system, part of which could use real-time measurements to estimate and predict cure parameters. The IFBGs were demodulated using a scanning fiber Fabry-Perot interferometer. The results obtained using this combined cure monitoring system demonstrate that it is possible to monitor the strain levels in the optical fiber resulting from the onset of liquification, gelation, and vitrification within the surrounding resin matrix.
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