This paper aims to study the path oscillations of single, spherical water droplets levitated in a wind tunnel to better comprehend the mechanical motion of small raindrops. The observations were carried out in the Mainz vertical wind tunnel. The discrete, fast Fourier transform was used to determine the oscillatory frequencies of the droplet paths, and the Hilbert transform was applied to analyze their instantaneous frequency stability. Both transversal and streamwise components of the path oscillations are described with typical frequencies of several tens of Hertz. The studied oscillations elongate the paths, reduce the terminal velocity of the smallest droplets, and make the rain droplet fall in a non-uniform motion even after reaching terminal velocity. The terminal velocity can be considered as physically having been reached if our proposed practical criterion is satisfied. From a fluid mechanics perspective, the paper fills an experimental gap in the studies of the paths oscillations of single, liquid spheres of microscopic sizes at low Bond numbers <1 and relatively low Reynolds numbers ~10².

Цель исследования — в течение проспективного (годового) наблюдения изучить хронофизиологические особенности ритмов артериального давления (АД) у нормотензивных лиц и определить их прогностическую значимость в развитии артериальной гипертензии (АГ) в условиях вахты на Крайнем Севере. Материалы и методы. В течение проспективного годового наблюдения в условиях вахтового режима труда в Заполярье обследованы 173 мужчины с нормальным АД и с отрицательным анамнезом по АГ, средний возраст 40,2 ± 4,1 года; северный стаж 16,5 ± 6,8 года; стаж работы вахтой — 11,2 ± 3,8 года; офисное систолическое/диастолическое АД 123,4 ± 7,5 / 80,5 ± 5,5 мм рт. ст. Всем пациентам 1 раз в 3 месяца выполнено суточное мониторирование АД (СМАД) и индивидуальный косинор-анализ данных с определением хронотипов (ХТП) суточных ритмов АД. Результаты. Результаты проспективного годичного изучения хронобиологических параметров выявили высокую распространенность атипичных ХТП суточных ритмов АД у нормотензивных лиц в условиях вахты на Крайнем Севере. Прогностическое значение нарушений суточного ритма АД заключается в высокой частоте трансформации атипичных нормотензивных ХТП в гипертензивные. В условиях заполярной вахты хронобиологический подход в сравнении со стандартным анализом СМАД показал более высокие диагностические чувствительность, специфичность и эффективность выявления АГ у нормотензивных лиц по результату проспективного (годичного) наблюдения. Выводы. Метод логистической регрессии выявил прогностическую значимость нормотензивных атипичных ХТП АД в развитии АГ в сравнении с основными факторами риска: курение, низкая физическая активность, избыточная масса тела, дислипидемия, возраст, длительность северного и вахтового стажа, режим и тип вахты. С помощью мультивариантного анализа получена модель, позволяющая определить диагностический показатель, прогнозирующий риск развития АГ в течение года у нормотензивных лиц в условиях вахты на Крайнем Севере.

Aim. The aim of the study was to select, based on mathematical apparatus of artificial neural networks (ANN), the most sen- sitive parameters for creating an ANN model aimed at prediction of atrial fibrillation (AF) in men with coronary artery disease (CАD).Material and Methods. The study focused on data of men from the register of coronary angiography with angiographically proven coronary artery disease: the main group comprised 180 men with AF; the comparison group comprised 713 men of comparable age without AF. The ANN mathematical model, a multilayer perceptron with one hidden layer, was used to assess the risk of AF. The initial group of patients was divided into three samples: the training, test, and control samples.Results. Patients with AF were significantly less likely to be employed in budget organizations (55.0% vs 63.7%, p = 0.040) and more often showed higher (III–IV) heart failure NYHA classes (49.2% vs 21.1%, p < 0.001), higher body mass index (BMI) (30.2 [27.4; 33.2] kg/m² vs 29.0 [26.1; 32.3] kg/m², p = 0.002), and higher echocardiographic indices of the left ventricular (LV) myocardial mass (163.7 [144.5; 192.4] g/m² vs 143.9 [126.1; 169.0] g/m², p < 0.001), left (25.8 [24.1; 29.1] mm/m² vs 25.6 [23.9; 27.5] mm/m², p = 0.020) and right ventricular dimensions, and the left atrial diameter (23.6 [21.7; 25.7] mm/m² vs 21.1 [19.7; 22.7] mm/m², p < 0.001). The group of AF patients had higher rate of hemodynamically significant mitral regurgitation (48.2% vs 14.1%, p < 0.001). In this group of patients, the index of aortic root dimensions (7.7 [16.4; 19.0] mm/m² vs 18.3 [17.8; 20.0] mm/m², р = 0.002) and LV ejection fraction (EF) were lower (49 [42; 56]% vs 56 [47; 60]%, p < 0.001); coronary calcification (23.2% vs 15.7%, p = 0.024 ) and proximal lesions of the right coronary artery (RCA) (28.3% vs 22.7%, p = 0.025) were detected more often. The final model, which included 10 parameters, had the diagnostic accuracy of 85%, sensitivity of 85%, and specificity of 86%.Conclusion. Atrial fibrillation in men with coronary artery disease can be predicted by ANN model that takes into account the presence of significant mitral regurgitation, extra-budgetary employment, severity of heart failure, coronary calcification, proximal lesion of RCA, BMI, echocardiographic indexes of left heart, aortic root dimensions, and LV EF.

Aim. To assess the relationship between the prolonged PR interval (≥200 ms) and the long-term survival of patients undergoing cardiac resynchronization therapy (CRT).Material and methods. A total of 85 patients (mean age — 55,1Ѓ}9,9 years; men — 81,2%) with NYHA class II-IV heart failure (HF) were examined. The mean follow-up was 34,0Ѓ}21,2 months. Patients with PR<200 ms (n=52) made up group I, with PR≥200 ms (n=33) — group II. Then the patients were divided into subgroups depending on the QRS duration: ≥150 ms (n=33 in group I and n=14 in group II, respectively) <150 ms (n=19 in group I and n=19 in group II, respectively).Results. In patients of group II, a history of myocardial infarction (MI) was more often registered (p=0,005), left ventricular ejection fraction (LVEF) was lower (p=0,032). In a multivariate analysis, MI (OR 3,217; CI 95% 1,188-8,712; p=0,022) and LVEF value (OR 0,869; CI 95% 0,780-0,968; p=0,011) had a significant relationship with the PR interval prolongation (≥200 ms). The survival of patients of group I was 59,6%, group II — 18,2% (Log-rank test p<0,001). According to Cox regression model, the initial left ventricle end-systolic volume (OR 1,012; 95% CI 1,006-1,017; p<0,001), inferior wall MI (OR 1,690; 95% CI 1,131-2,527; p=0,011) and PR interval ≥200 ms (OR 2,179; 95% CI 1,213–3,915; p=0,009) were associated with long-term mortality. In patients with PR≥200 ms, survival rate was low, regardless of the QRS duration (21,4% in patients with QRS≥150 ms, 15,8% in patients with QRS<150 ms; Log-rank test p=0,698) In patients with PR<200 ms, the survival rate of patients with QRS≥150 ms was 72,7%, and for patients with QRS<150 ms — 36,8% (Log-rank test p=0,031).Conclusion. In HF patients, PR interval prolongation (≥200 ms) is associated with long-term mortality increase. The highest survival rates were observed in patients with PR<200 ms and QRS≥150 ms. In patients with QRS≥150 ms, the presence of PR≥200 ms should be considered as an additional criterion for CRT.

Взаимосвязь сосудистой и сердечной ригидности у больных артериальной гипертензией в условиях вахты в Арктическом регионе