What is wrong with Chinese COVID-19 statistics?

The media is reporting tens of millions of new daily Covid-19 cases in China in the final days of 2022. However, official statistics have recorded in mainland China only 1.9 million cases since the start of the pandemic and stopped providing data after December 21, 2022. Results of SIR simulations showed that daily numbers of new cases stated to decline in December 2022. The contradictions in statistics and estimations are discussed. Millions of new daily cases in China look very unlikely

Shape of Slender Axisymmetric Ventilated Supercavities

The integral-differential equation was obtained to simulate unsteady evolutions of the slender axisymmetric ventilated supercavity with the use of one-dimensional inviscid flow of the incompressible gas in the channel between the cavity surface and the body of revolution. For small ventilation rates, the solution of this equation was expressed as asymptotic series. In the steady case the nonlinear differential equation and its solutions were obtained. It was shown that the ventilation can increase and diminish the supercavity dimensions. Examples of calculations for different hull shapes are presented. At some critical values of the gas injection rate the cavity dimensions can become unbounded. Stability of steady and pulsating gas cavities was investigated in the case of the low gas injection rate.</jats:p

RusTitW: Russian Language Text Dataset for Visual Text in-the-Wild Recognition

Information surrounds people in modern life. Text is a very efficient type of information that people use for communication for centuries. However, automated text-in-the-wild recognition remains a challenging problem. The major limitation for a DL system is the lack of training data. For the competitive performance, training set must contain many samples that replicate the real-world cases. While there are many high-quality datasets for English text recognition; there are no available datasets for Russian language. In this paper, we present a large-scale human-labeled dataset for Russian text recognition in-the-wild. We also publish a synthetic dataset and code to reproduce the generation processComment: 5 pages, 6 figures, 2 table

Optimal Body Masses for Different Olympic Sports

Background. The weight of the best athletes at different distances and in different sports can be very different. It is known that rowers, as a rule, are very massive. In order to give a chance to athletes with a small mass, the rowing federation was introduced a special category with the weight restrictions. These facts are connected with the peculiarities of the aerobic and un-aerobic activities, drag and propulsion characteristics. Objective. In this paper, we don’t try to explain the body mass differences. We will only fix them for different sports: running, swimming (free style), skiing, skating, cycling, and rowing and for different Olympic distances. Methods. A significant amount of data on the velocity and body mass of the best athletes professionals (both female and male) in Olympic sports (running, swimming, skiing, skating, cycling and rowing) was collected and analyzed. Since the weights of the best athletes only are taken into consideration, the expected results can be treated as the most suitable (optimal) body masses for different sports and distances. In order to check, how the values of body mass and average speed on the distance fit the linear dependence, the equation of the linear regression was used. The regression coefficient and two parameters of the straight line were calculated. In order to check that the velocity of skating doesn’t depend on the athlete mass, the Fisher test was used. Results. The optimal masses of athletes for different distances and sports were calculated. In general, for the short distances, the large masses of athletes are optimal and they decrease for long distances. Exception is the results for female swimming and running, where the largest masses of athletes correspond to the medium distances. For longer distances, results show that the most performing athletes are characterized by a lower body mass, except for skating. For a fixed distance, the optimal weights of female athletes are 79.5 ± 3.1% of the weight of male athletes, at the same time they develop 89.4 ± 1.8% of the speed of men. Conclusions. The presented statistical analysis indicates that within one distance there is no significant dependence of speed on the mass (the exception is only rowing). For each distance there are their optimal masses of athletes, which are different for different sports. The revealed facts can be used in athlete selection and training. They need also further investigations with the use of the metabolic and propulsion peculiarities

A New Algorithm to Analyze the Video Data of Cell Contractions in Microfluidic Platforms

Проблематика. Одним из быстро развивающихся направлений в науке является тканевая инженерия с использованием технологии “лаборатория на микрочипе”. Для оценки механических сокращений клеток используются оптическая микроскопия и анализ видеоданных. Однако известные методы регистрируют только факт сокращения клеток и существенно искажают форму и амплитуду полезного сигнала. Поэтому задачи корректного количественного анализа таких видеоизображений являются актуальными. Цель. Целью работы является разработка алгоритма анализа видеоданных механических сокращений кардиомиоцитов на микрочипе для определения их функциональных и структурных свойств на тканевом уровне. Методика реализации. Разработанный алгоритм анализа видеоизображений реализован программным кодом Matlab 2016. Для апробации предложенного метода были проанализированы данные о сокращения клеток кардиомиоцитов, выращенных в микрочипе. Исследовались три группы клеток: выращенные без стимуляции, а также клетки, которые стимулировались электрическими полями 5 и 25 В/см. Форма стимулирующих импульсов – прямоугольная, частота – 1 Гц. Результаты. Предложенный алгоритм анализа видеоданных, позволяет оценить скорость сокращения клеток в микрометрах за секунду. Кроме того, он позволяет разложить механические колебания клеток на компоненты. Алгоритм использовался для оценки изменения скорости сокращения кардиомиоцитов в зависимости от интенсивности напряжения и частоты возбуждения. Выводы. Предложенный метод анализа видеоданных сокращений клеток кардиомиоцитов на микрочипе не требует каких-либо вспомогательных биомаркеров или сред. Анализ видеоизображений позволяет оценить амплитуду и скорость колебаний, форму сигнала, пространственно- неоднородное распределение механической активности клеток. Показано, что импульсное электрическое поле в диапазоне 5–25 В/см на частоте 1 Гц при культивировании клеток оказывает отрицательное влияние на сократительную способность кардиомиоцитов

Shapes of the fastest fish and optimal underwater and floating hulls

A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern. The fastest fish have a very sharp convex nose (rostrum), the purpose of which remains unclear. The bodies of revolution similar to their shapes are analyzed in steady underwater and floating motion. The sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water surface. It was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface elevation. These fact allow diminishing the maximum pressure on the surface and wave drag. Special shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls