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We perform fully relativistic band-structure calculations for cubic SrTiO3, which are used to obtain carrier effective masses and the frequency behavior of its complex dielectric function ε(ω). The obtained values and anisotropy of the carrier effective masses are shown to be highly influenced by the relativistic contributions. In order to evaluate the static dielectric constant, the low-frequency behavior of ε(ω) is obtained by taking into account also the optical phonon contributions to the imaginary part of ε(ω), adopting a simplified classical oscillator dispersion model. It is found that the phonon contribution leads to about 240 times (at T=85 K) the value of the bare electronic contribution to the dielectric constant. The calculated temperature dependence of the dielectric constant is shown to be consistent with that observed in bulk SrTiO3 static permittivity measurements.

In this work the time resolved thermal lens spectrometry was applied to measure the absolute values of the thermo-optical properties of low silica calcium aluminosilicate and soda lime glasses at low temperatures, in the range between 20 and 300 K. The thermal relaxation calorimetry was used as a complementary technique to determine the specific heat. The results showed a marked decrease of the thermal diffusivity with the temperature rise, with a dependence similar to that of the mean free path ͑ϳT −1 ͒ in the interval between 20 and 70 K, while in the range between 70 and 300 K the dependence was T −͑0.33±0.02͒. The marked variation of the temperature coefficient of the optical path length change with the temperature rise was attributed to the increase in the coefficient of the electronic polarizability. The results also showed that for the aluminosilicate glass the excess in the specific heat correlated to the so-called boson peak occurred at about 17 K, higher than that of soda lime, which occurs at about 12 K. In conclusion, our results showed the ability of the time resolved thermal lens to determine the thermo-optical properties of glasses at low temperatures, bringing possibilities for experiments in a wide range of optical materials.

In this work, we assessed the use of confocal Raman microscopy and artificial neural network as a practical method to assess and quantify adulteration of fluid milk by addition of whey. Milk samples with added whey (from 0 to 100%) were prepared, simulating different levels of fraudulent adulteration. All analyses were carried out by direct inspection at the light microscope after depositing drops from each sample on a microscope slide and drying them at room temperature. No pre- or posttreatment (e.g., sample preparation or spectral correction) was required in the analyses. Quantitative determination of adulteration was performed through a feed-forward artificial neural network (ANN). Different ANN configurations were evaluated based on their coefficient of determination (R2) and root mean square error values, which were criteria for selecting the best predictor model. In the selected model, we observed that data from both training and validation subsets presented R2>99.99%, indicating that the combination of confocal Raman microscopy and ANN is a rapid, simple, and efficient method to quantify milk adulteration by whey. Because sample preparation and postprocessing of spectra were not required, the method has potential applications in health surveillance and food quality monitoring.

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