Traumatic vessel injuries initiating hemostasis generate high shear conditions

Blood flow is a major regulator of hemostasis and arterial thrombosis. The current view is that low and intermediate flows occur in intact healthy vessels, whereas high shear levels (>2000 s−1) are reached in stenosed arteries, notably during thrombosis. To date, the shear rates occurring at the edge of a lesion in an otherwise healthy vessel are nevertheless unknown. The aim of this work was to measure the shear rates prevailing in wounds in a context relevant to hemostasis. Three models of vessel puncture and transection were developed and characterized for a study that was implemented in mice and humans. Doppler probe measurements supplemented by a computational model revealed that shear rates at the edge of a wound reached high values, with medians of 22 000 s−1, 25 000 s−1, and 7000 s−1 after puncture of the murine carotid artery, aorta, or saphenous vein, respectively. Similar shear levels were observed after transection of the mouse spermatic artery. These results were confirmed in a human venous puncture model, where shear rates in a catheter implanted in the cubital vein reached 2000 to 27 000 s−1. In all models, the high shear conditions were accompanied by elevated levels of elongational flow exceeding 1000 s−1. In the puncture model, the shear rates decreased steeply with increasing injury size. This phenomenon could be explained by the low hydrodynamic resistance of the injuries as compared with that of the downstream vessel network. These findings show that high shear rates (>3000 s−1) are relevant to hemostasis and not exclusive to arterial thrombosis

Mathematical Modeling of a Power Line–Electric Drive–Pump–Pipeline Power Technological Complex

Статья из журнала.Abstract: In this paper, a block diagram of a power line–electric drive–pump–pipeline system consisting of individual interconnected elements that makes it possible to use the structural method for mathematical modeling is presented. The results of the modeling confirm the viability of the proposed mathematical models. It is shown that, due to a considerable inertia of turbo mechanisms, the electromagnetic phenomena in the electric drive can be neglected so as to simplify significantly the structure of the studied system. Soft acceleration of the asynchronous motor by means of a soft starter makes it possible almost to eliminate the shock surges of the moment, which has a positive effect on the turbo mechanism operation. However, the high-frequency component of voltage, which emerges due to the soft starter operation, can affect the operation of other energy consumers. The applicability and efficiency of using polar coordinates to construct mathematical models of complex technical systems containing three-phase electromechanical energy transducers is confirmed. © 2020, Allerton Press, Inc

Mathematical Model of an Induction Machine in Polar Coordinates Taking into Account the Saturation Process of the Main Magnetic Circuit

Статья из журнала.Mathematical models of induction machine in polar coordinates taking into account the saturation process of the main magnetic circuit are presented. Software implementations of the proposed mathematical models and numerical investigations of the processe

Synthesis of information-reference systems of faculty

Дано определение информационно-справочной системы (ИСС), рассмотрены области применения, определены требования, которые должны быть выполнены при проектировании и разработки. Формализован процесс функционирования транзакций при создании ИСС факультета подготовки студентов (ФПС).Дано визначення інформаційно-довідкової системи (ІСС), розглянуті сфери застосування, визначені вимоги, які повинні бути виконані при проектуванні і розробки. Формалізований процес функціонування транзакцій при створенні ІДС факультету підготовки студентів (ФПС).The definition of information system, reviewed the application, identifies the requirements that must be met when designing and developing data systems. Describes the tools that are being implemented meet the requirements for establishing a reference system for the department of students

Analysis of microvascular thrombus mechanobiology with a novel particle-based model

Platelet accumulation at the site of a vascular injury is regulated by soluble platelet agonists, which induce various types of platelet responses, including integrin activation and granule secretion. The interplay between local biochemical cues, mechanical interactions between platelets and macroscopic thrombus dynamics is poorly understood. Here we describe a novel computational model of microvascular clot formation for the detailed analysis of thrombus mechanics. We adopt a previously developed two-dimensional particle-based model focused on the thrombus shell formation and revise it to introduce the platelet agonists. Blood flow is simulated via a computational fluid dynamics approach. In order to model soluble platelet activators, we apply Langevin dynamics to a large number of non-dimensional virtual particles. Taking advantage of the available data on platelet dense granule secretion kinetics, we model platelet degranulation as a stochastic agonist-dependent process. The new model qualitatively reproduces the enhanced thrombus formation due to dense granule secretion, in line with in vivo findings, and provides a mechanism for the thrombin confinement at the early stages of clot formation. Our calculations also predict that the release of platelet dense granules results in the additional mechanical stabilization of the inner layers of thrombus. Distribution of the inter-platelet forces throughout the aggregate reveals multiple weak spots in the outer regions of a thrombus, which are expected to result in the mechanical disruptions at the later stages of clot formation. © 2021 Elsevier Lt