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Purpose of the work is to identify the directional coupling between the structures of the brain and the autonomic control of the heart rate variability, to analyze the changes in these coupling in sleep and in wakefulness. Infra-slow oscillations of the electroencephalograms potential and low-frequency components (0.04-0.15 Hz) of the interbeat intervals signal where analyzed using a sensitive method for identifying the directional coupling. The technique, based on modeling the dynamics of instantaneous phases of oscillations, made it possible to reveal the presence and quantify the directional couplings between the structures of the brain and the autonomic control of the heart rate variability. It was shown that the coupling coefficients in the frequency band of 0.04-0.15 Hz (associated mainly with sympathetic control of blood circulation), on average, decrease with falling asleep. We have also shown the asymmetry of coupling. At the same time, stronger connections were revealed in the direction from the autonomic control of the heart rate variability to the brain structures than in the opposite direction. It has been shown that the strength of such couplings decreases with increasing of sleep depth.

this study presents the results of the spectral analysis of the photoplethysmographic signals obtained from the healthy subjects and the patients with early pre-clinical stages of arterial hypertension, coronary artery disease, and aortic valve stenosis patients. The normalized power density of the low-frequency (LF%) oscillations is significantly higher in the cardiovascular patients, while the normalized power density of the high-frequency (HF%) oscillations and the LF/HF ratio are significantly lower in comparison to the healthy subjects. Aging had no significant effect on the spectral indexes. It was shown that the spectral analysis of the photoplethysmographic signals can be used to diagnose the dysfunction of the autonomic control even at early pre-clinical stages of cardiovascular diseases.

An original method for reconstruction of time-delay systems parameters from time-series was tested on a radiophysical chaotic generator with quadratic nonlinearity and on a periodic radiophysical model of baroreflectory control of the mean arterial pressure. The method in question is based on analysis of synchronous response of the driven system. It was shown that parameters of chaotic generator can be reconstructed (the error is less than 1%) from a time-series which length was less than 2 delay times. The parameters of the periodic model were reconstructed from a time-series which length was 10 delay times.

In many cases, cancers are detected only after they have become untreatable due to development of deadly metastasis. Most treatment is more effective at early cancer stages. We explore early cancer diagnosis at singe cell levels by their irradiation with short laser pulses followed by time-resolved detection of laser-induced acoustic waves. We explored the viability of correlation analysis for analysis of acoustic responses. It was estimated that correlation between cancer cells responses is 0.86±0.06, while correlation between cancer cells responses and responses from human blood is - 0.05±0.06.

In this paper, we studied the features of the autonomic regulatory system of the heart rate and the tone of the arteries in newborns. During the experiment, we obtained 15 records of synchronous electrocardiograms and photoplethysmograms of newborns. A spectral analysis was conducted, the results of which revealed a number of features, including the presence of an LF peak at a lower frequency than is common in adult subjects. Based on these results, we have chosen new parameters to assess the degree of synchronization of the autonomic regulatory contours of the blood circulation in newborns, which contribute to the greater significance of the results.

We proposed a method of experimental observation of the Arnold tongues in the study of the synchronization of the contours of autonomic regulation of the heart rate with a characteristic frequency of about 0.1 Hz and respiration. The formulation of a special active experiment made it possible to determine the boundaries of synchronization tongues in 3 subjects. The method allows noninvasive research. The basic idea is to influence the contours of heart rate regulation with a respiratory signal, which has respiratory frequency varying linearly about 0.1 Hz according to the sound signal generated by a special device. The amplitude of the breath is changed by the subjects at the command of the researcher. The study is important for understanding the features of complex multichannel systems of biological nature and their mathematical modeling.

The features of the individual dynamics and interaction of the elements of the autonomous regulation of blood circulation and blood flow fluctuations in the microvasculature of the skin were investigated. Phase synchronization of the laser Doppler flowmetry signal with processes of autonomic regulation is revealed. This may indicate the effect of vegetative regulation on the myogenic range of laser Doppler flowmetry.