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Introduction. Currently, there is a deterioration trend in the health of the younger generation, in particular, an increasing number of persons with functional disorders of the cardiovascular system. Regarding this it is important to develop an comprehensive approach to the study of the circulatory indices in the young age with informative clinical diagnostic techniques and new ways to analyze the data. Material and methods. Heart rate variability (HRV) indices in 200 students at rest and during exercise were studied. For a more complete assessment of the functional reserves of cardiovascular system after the load the index of the normal heart rhythm restoration (SDNN) was calculated. Moreover, we built logistic models and curves of the operating characteristics. Results. At rest, no significant differences in indices of both HRV and autonomic regulation of heart rate have been identified between boys and girls aged of 16-18 years. Students of the different gender, aged of 19-22 years showed significant differences in spectral parameters of HRV, there was noted the dominance of the sympathetic component of heart rate regulation in boys and parasympathetic - in girls. In terms of physical activity in undergraduate students there is observed mainly the activation of vagal influences on the heart, in senior students the vegetative balance shifted to the direction of the increased activity of mechanisms of the sympathetic regulation. The revealed decrease of NHRR reflects the low level of the reserve capacity of the cardiovascular system in 41% out of observed students. Part of students with an increased probability of the reduction of functional cardiac disorders accounted for 42% of boys and 39% of girls among students aged 16-18 years and 36% of boys and 44% of girls among students aged of 19-22 years. Conclusion. There is a change in the nature of autonomous regulation of heart rate in students of different gender and ages from 16-18 to 19-22 years. The optimal cardiac response to stress test is observed at low baseline values of heart rate and the prevalence of the parasympathetic part of the autonomic regulation of the heart rate at rest. To assess the functional reserve of the cardiovascular system in HRV indices we recommend the calculation of NHRR and the analysis of the SDNN coefficient for the effective prediction of heart rate recovery rate after exercise testing.

The study object is a “wheel - rail” system. The subject is the computer simulation of the system elements wear. The work objective is to investigate the wheel and rail wear dependence on the kinetic performance parameters. The problems solved here are analysis of the earlier proposed mathematical functions describing the kinetic performance for the presence of extremes, the functional behavior (growth, decrease, monotonicity, and unimodality, etc.) in various parameter ranges; implementation of the computer simulation of the wheelpair movement by rail with the quantitative estimation of the wheel and rail wear with various kinetic performance parameters; to determine qualitative influence patterns of the kinetic wear performance. The simulation is fulfilled by the software package “Universal Mechanism”. As a result, values of various characteristics related to wear (power, total and specific friction work) under different conditions of the kinetic friction performance are obtained. The conclusions are as follows. The kinetic friction performance parameters must be considered as they can significantly affect the wear within the range of the actual operating conditions in the course of the computer simulation. Under some conditions, there are cases when an increase in the friction coefficient is accompanied by a decrease in depreciation. It is proposed to continue the research in two main areas: determining the influence patterns on the kinetic friction performance and wear of the multiple actual factors, and studying the dynamic (at variable slip velocity) feature of friction effect on the parameter wear through the same procedure.

Rapid-onset obesity with hypoventilation, hypothalamic, autonomic dysregulation, electrolyte disorders like a hypernatriemia, and neural tumor (ROHHADNET) is a newly described syndrome that can cause cardioresperitory arrests and death. It mimics several endocrine disorders or genetic obesity syndromes during early childhood and is associated with various forms of hypothalamic-pituitary endocrine dysfunctions that have not yet been fully investigated. The article describes the clinical case of a 4-year old patient.