No abstract

The paper reports results of preliminary experiments on a continuous curing carbon fibre reinforced epoxy composite, designed to achieve simultaneous characterizations of the state of cure of the resin and the development of strain in the reinforcing fibres. The measurements were carried out using embedded dielectric microsensors and in-fibre Bragg gratings (IFBGs) to follow changes in the conductivity of the matrix resin and in the internal strain in the embedded optical fibre respectively. This was performed using an automated data acquisition system, part of which uses real-time dielectric measurements to follow the industrially relevant parameters of curing. The system can multiplex several sensors and could be used in a quasi-distributed system. The IFBG sensors were demodulated using a scanning fibre Fabry-Pérot interferometer. The results obtained with this combined cure monitoring system show that it is possible to monitor the strain levels in the optical fibre resulting from the onsets of liquification, gelation and vitrification within the surrounding resin matrix. The combined measurements constitute a first step towards a scientific study of the development of internal residual stresses in a cured composite, which will be crucial to the ultimate elimination of warpage and `spring-back' in large composite structures.

Marked inter- and intra-subject variation in ALA-induced PpIX fluorescence occurs in normal human skin. ALA application time, body site and the state of the stratum corneum are all determinants of PpIX fluorescence within subjects and these factors need to be taken into account in optimization of PDT regimes.

Sulphur speciation in volcanic gases acts as a major redox buffer, and H2S/SO2 ratios represent a valuable indicator of magmatic conditions and interactions between magmatic and hydrothermal fluids. However, measurement of H2S/SO2 even by direct sampling techniques, is not straightforward. We7 report here on application of a small ultraviolet spectrometer for real‐time field measurement of H2S and SO2 concentrations, using open‐path and extractive configurations. The device was tested at fumaroles on Solfatara and Vulcano, Italy, in November 2002. H2S concentrations of up to 220 ppmm (400 ppmv) were measured directly above the Bocca Grande fumarole at Solfatara, and H2S/SO2 molar ratios of 2 and 2.4, respectively, were determined for the ‘F11’ and ‘F0’ fumaroles at Vulcano. In comparison with other optical techniques capable of multiple volcanic gas measurements, such as laser and FTIR spectroscopy, this approach is considerably simpler and cheaper, with the potential for autonomous, sustained high‐time resolution operation.

Comparison of the photobleaching rates suggests that a blue light intensity of 5 mW/cm(2) gives the same rate of photobleaching as the typical red light PDT intensity of 100 mW/cm(2). Further investigation of the correlation between PpIX photobleaching and PDT effect would be beneficial in interpreting the clinical significance of our findings.