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The use of volatile production patterns produced by bacterial contaminants in urine samples were examined using electronic nose technology. In two experiments 25 and 45 samples from patients were analysed for specific bacterial contaminants using agar culture techniques and the major UTI bacterial species identified. These samples were also analysed by incubation in a volatile generation test tube system for 4-5 h. The volatile production patterns were then analysed using an electronic nose system with 14 conducting polymer sensors. In the first experiment analysis of the data using a neural network (NN) enabled identification of all but one of the samples correctly when compared to the culture information. Four groups could be distinguished, i.e. normal urine, Escherichia coli infected, Proteus spp. and Staphylococcus spp. In the second experiment it was again possible to use NN systems to examine the volatile production patterns and identify 18 of 19 unknown UTI cases. Only one normal patient sample was mis-identified as an E. coli infected sample. Discriminant function analysis also differentiated between normal urine samples, that infected with E. coli and with Staphylococcus spp. This study has shown the potential for early detection of microbial contaminants in urine samples using electronic nose technology for the first time. These findings will have implications for the development of rapid systems for use in clinical practice.

The degree of solid solubility between yttria and calcia was measured, in the yttria-rich region, over the temperature range 1200 to 2000°C. X-ray diffraction results indicate that as much as 12.4 mol% calcia can be dissolved in yttria at 2000°C. No solid solution between the two oxides was observed below 1400°C. In addition exsolution kinetics was measured. Kinetic data were compared to a number of solid state models with the three-dimensional nucleation model providing the best correlation. The Hulbert model was further used to characterize the growth mechanism. It suggested that growth is phase-boundary controlled between 1200 and 1500°C and that the nucleation rate either drops to zero or that growth becomes two-dimensional above 1600°C. Although undoped yttria is both a p- and n-type semiconductor, yttria-calcia solutions are ionic conductors below about 10−10 atm oxygen (ti>0.99) with no trace of n-type conductivity being observed. The activation energy for ionic conduction in yttria-5 mol% calcia is 125 kJ/mol.