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NaNbO3:SrTiO3 interface nanolayers are studied by combining first-principles modeling and experimental approach. The nature of NaNbO3:SrTiO3 interface is investigated using density-functional theory calculations. Interface parameters are experimentally estimated using analysis of the dielectric response of SrTiO3 and NaNbO3 epitaxial films and NaNbO3:SrTiO3 superlattices. It is shown that NaNbO3:SrTiO3 interfaces can be approximated by dielectric nanolayers with thickness 1-2 nm and with temperature independent permittivity 25-55. Mechanism responsible for the nanolayer formation is the ionic charge mismatch between constituents. [ABSTRACT FROM AUTHOR]

Our aim was to develop a signal analysis method for revealing interrelationships between heart rate and blood pressure and for displaying the influence of autonomic nervous control on these signals in a chronic lamb model. A chronically instrumented neonatal lamb model was made to record ECG and direct arterial blood pressure (N = 15). Continuous two-minute recordings of blood pressure (BP) and ECG were digitised. The instantaneous heart rate signal (IHR) was derived from the ECG. The IHR and BP signals were bandpass filtered. Autospectra, cross-spectra, coherence spectra and phase spectra for the signals were computed to study the relative magnitudes and inter-relationships of the cardiovascular signals under normal conditions and during beta-adrenergic blockade. It was noted that both in the BP and IHR there were oscillations at the frequency of less than 0.1 Hz and also at the respiratory rate around 0.6 Hz. Beta-blockade reduced the oscillations of the IHR in less than 30-day-old lambs. It did not affect the coherence spectra or the phase lag between the signals. During quiet sleep the variability of blood pressure was decreased. In over-30-day-old-lambs the beta-blockade did not affect the variabilities of the cardiovascular parameters. These findings indicate that in neonatal lambs the sympathetic control system is a major regulator of cardiovascular interactions. [ABSTRACT FROM AUTHOR]