Wyniki wyszukiwania - BazTech

1

Non-uniform viscosity caused by red blood cell aggregation may affect NO concentration in the microvasculature

Qiao H., Zhao H., Jaron D.

Biocybernetics and Biomedical Engineering

|

2017

|

Vol. 37, no. 3

341--346

EN

Aggregation of red blood cells in the micro vasculature may affect blood viscosity in the vessel. The purpose of this study was to investigate the potential effect of non-uniform viscosity caused by red blood cell (RBC) aggregation on nitric oxide (NO) concentration and distribution. A 3-D multi-physics model was established to simulate the production, transport and consumption of NO. Two non-uniform viscosity models caused by RBC aggregation were investigated: one assuming a linear and the other a step hematocrit distribution. In addition, the effect of the thickness of the plasma layer was tested. Simulation results demonstrate that non-uniform viscosity caused by RBCs aggregation influences NO concen-tration distribution. Compared with the uniform viscosity model, NO concentration using non-uniform viscosity is lower than that using uniform viscosity. Moreover, NO concentration calculated from the step hematocrit model is higher than that calculated from the linear hematocrit model. NO concentrations in the endothelium and the vascular wall decrease with the decline of the thickness of the plasma layer. The relative decrease differs between the linear and the step model. Our results suggest that non-uniform viscosity caused by red blood cell aggregation affects nitric oxide distribution in the micro vasculature. If uniform viscosity is assumed when performing numerical simulations, NO concentration values may be overestimated.

2

Fåhræus effect revisited

Herczyński R.

Archives of Mechanics

|

2016

|

Vol. 68, nr 1

81--93

EN

A consistent hydrodynamic analysis of blood flow through capillaries is proposed. The approach, while suggested by empirical observations, is based solely on the properties of Newtonian fluids and suspensions. Blood flow is divided into three phases: the first is a thin erythrocyte-free layer near the wall, the second a core flow of constant hematocrit and the third an intermediate layer wherein the hematocrit varies. Based on the observation that viscosity depends exponentially on the local hematocrit, blood flow velocity profiles are obtained and the direct connection between the Fåhræus and the Fåhræus-Lindqvist effects is established.

3

Analiza wpływu równoczesnego oddziaływania pola magnetycznego i światła podczerwonego na właściwości reologiczne krwi w warunkach in vitro

Marcinkowska-Gapińska A., Nawrocka-Bogusz H.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

|

2016

|

Vol. 22, nr 4

261--266

PL

Własności reologiczne krwi warunkują przepływ krwi w naczyniach krwionośnych. Głównymi czynnikami wpływającymi na przepływ krwi w naczyniach krwionośnych są: lepkość krwi pełnej, lepkość osocza, odkształcalność erytrocytów i zdolność erytrocytów do agregacji. W niniejszej pracy badano wpływ metod wykorzystywanych w fizykoterapii takich jak światło podczerwone (855 nm) i pole magnetyczne (44,5 μT) niskich częstotliwości wykorzystywane w magnetostymulacji na własności reologiczne krwi w warunkach in vitro. Krew wykorzystywana do badań pobierana była od osób zdrowych zgłaszających się do Stacji Krwiodawstwa i Krwiolecznictwa w Poznaniu. Łącznie badaniom poddano 14 próbek krwi. Dla każdej próbki przeprowadzano pomiar wartości hematokrytu oraz dwukrotnie lepkości krwi pełnej i osocza (przed i po równoczesnej aplikacji pola magnetycznego i światła podczerwonego). Analiza uzyskanych wyników wskazuje na wpływ łącznego działania światła podczerwonego i pola magnetycznego na lepkość krwi i osocza oraz zdolność erytrocytów do deformacji i agregacji.

EN

Blood flow is determined by the properties of the circulatory system and by physico-chemical properties of blood: blood viscosity, plasma viscosity, red cells aggregability and deformability. The aim of this work was to analyze the influence of combined magnetic field and infrared light illumination on rheological properties of blood in in vitro conditions. Samples of blood were obtained from Regional Center of Blood and Blood Treatment in Poznań. The study was performed on blood samples coming from 14 donors. The measurement were taken twice for each sample: before and after simultaneous irradiation and magnetostimulation. The analysis shows the influence of IR light and magnetic field on rheological properties of blood.

4

The biomechanics of atherosclerosis development

Makinde O. D., Acho T. M., Sibanda P., Lungu E. M.

Computer Assisted Mechanics and Engineering Sciences

|

2003

|

Vol. 10, No. 1

23-31

EN

In this paper, we investigate the bio-mechanics of atherosclerosis development in human physiology. Blood is modelled as an incompressible fluid of variable viscosity flowing in a slightly diverging channel (i.e. large artery) of small aspect ratio [1]. The hypothetical viewpoint in this work is the existence of relationship between the atherosclerosis development, blood viscosity, flow separation and turning points in the flow field. The problem is tackled by asymptotic approximation and the graphical results are discussed quantitatively.