We report the development of a versatile microfluidic (MF) reactor with multiple analytical probes, which can be used for (i) quantitative characterisation of molecular vibrational signatures of reactants or products, (ii) the localised real-time monitoring of temperature and (iii) site-specific measurements of pH of the reaction system. The analytical probes utilised for in situ reaction analysis include an ATR-FTIR probe, a temperature probe, and a pH probe. We demonstrate the applications of the MF reactor with integrated probes for the parallel monitoring of multiple variables in acid/base neutralisation reaction, of changes in buffer pH, temperature, and vibrational absorption bands, and for monitoring the kinetics of the reaction between CO(2) and a buffer system with therapeutic applications.

An experimental technique for the measurement of thermal properties of air at low pressures using a photopyroelectric (PPE) thermal-wave cavity (TWC) was developed. In addition, two theoretical approaches, a conventional one-dimensional thermal-wave model and a three-dimensional theory based on the Hankel integral, were applied to interpret the thermal-wave field in the thermal-wave cavity. The importance of radiation heat transfer mechanisms in a TWC was also investigated. Radiation components were added to the purely conductive model by linearizing the radiation heat transfer component at the cavity boundary. The experimental results indicate that the three-dimensional model is necessary to describe the PPE signal, especially at low frequencies where thermal diffusion length is large and sideways propagation of the thermal-wave field becomes significant. Radiation is found to be the dominant contributor of the PPE signal at high frequencies and large cavity lengths, where heat conduction across the TWC length is relatively weak. The three-dimensional theory and the Downhill Simplex algorithm were used to fit the experimental data and extract the thermal diffusivity of air and the heat transfer coefficient in a wide range of pressures from 760 to 2.6 Torr. It was shown that judicious adjustments of cavity length and computational best fits to frequency-scanned data using three-dimensional photopyroelectric theory lead to optimally accurate value measurements of thermal diffusivity and heat transfer coefficient at various pressures.

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The technique of modulated luminescence of bones was developed experimentally and theoretically and was subsequently used to interpret measurements performed on the cortical layer of human skull bones. The photophysical theory is based on the optical excitation and decay rate equations of the fluorescent endogenous chromophore and on the molecular interaction parameter with the photon field density in the matrix of the bone. An effective mean relaxation lifetime, tau(M), of skull cortical bone was derived theoretically and was found to depend on the endogenous chromophore decay lifetime, tau(2), in the upper energy state, on the generated luminescence field density through its dependence on the incident photon field density and on the thickness of the bone. A linear dependence of tau(M) on laser beam intensity, I0, was found and sensitivity of the value of tau(M) to bone thickness, L, was observed for L < or = 6.2 mm. Both experimental dependencies of tau(M) on I0 and L were in excellent agreement with the theoretical model. The unusually long relaxation luminescence lifetime was accounted for theoretically by means of an excited-state manifold invoking intersystem crossing to a forbidden state followed by decay to the ground state of the chromophore. Best fits to the data were able to yield measurements of the following chromophore and photon field parameters: tau(2)=19.7 ms , optical scattering coefficient mu(s)(659 nm)=44,340 m(-1), optical absorption coefficient mu(a)(659 nm)=13 m(-1), and coupling coefficient B(21)= 1.6 x 10(4) m(3) J(-1) s(-1), the decay coupling coefficient of the endogenous chromophore participating in the optical interaction in the form of stimulated luminescence emission mediated by the luminescence photon field between the long-lived excited state E2 and the lower (ground) state E1. The method of modulated luminescence can be used to measure photophysical properties of the chromophore in cortical skull bones, being a sensitive marker of bone diseases, namely, osteoporosis and cancer.

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