Based on Fick's second law the problem of drug diffusion into a membrane was solved. Spatial and time dependent distribution of the drug in the membrane was described analytically. Comparison of obtained solution with experimental results from infrared attenuated total reflectance studies of dithranol diffusion into the dodecanol-collodion membrane confirmed correctness of the theory. Based on a model describing the concentration of diffusing matter it was possible to calculate numerically the photoacoustic signal arising when the membrane was illuminated by modulated light. Detailed numerical analysis showed that photoacoustic spectroscopy (PAS) can be used in experimental investigation of diffusion, but some limitations connected with optical parameters of diffusing matter and the membrane must be taken into account. Proposed mathematical model was used for interpretation of experimental data from "classical" PAS measurement in UV range and step-scan Fourier-transform infrared PAS. Experiments were carried out for diffusion of: dithranol, ketoconazole and methoxalen. Using a multiparameter fitting procedure one has determined diffusion coefficient of enumerated drugs in dodecanol-collodion membrane. Obtained results confirmed usability of PAS technique for studies of diffusion processes.
An experimental setup with well defined boundary conditions is proposed for photothermal measurement of thermal parameters of opaque, plate-like samples. One dimension mode of temperature field in layered structure and simple-single ray description of photodeflection detection is used for theoretical description of experimental results.
Basing on a 1D model of heat propagation in gas-sample-gas structure, a method for determining thermal properties of plat-like samples is proposed. The method assumes photodeflection detection of photothermal signal. In the method, a signal frequency dependence is measured. It is shown that in high frequency limit, the signal depends only on thermal properties of gas. Excluding the gas contribution to the measured dependence a signal part connected with the sample can be calculated. Fitting theoretical curves to obtained data, one can estimate thermal diffusivity of the sample. Methods for determining thermal diffusivity of gas and distance between a probe beam and the sample surface are also proposed. A good agreemnt between theory and experiment is obtained.
In the report an experimental apparatus for photoacoustic imaging is described. Results of testing measurements and investigation of ion-implanted silicon wafer were presented. Obtained results show possibilities of photoacoustic imaging of ion-implanted regions in semiconductors with good resolution. Strong dependence of the resolution on frequency was demonstrated.
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