Biorheology - Volume 19, issue 1-2

Authors: Fukada, Eiichi

Article Type: Introduction

DOI: 10.3233/BIR-1982-191-211

Citation: Biorheology, vol. 19, no. 1-2, pp. 103-103, 1982

Authors: Wayland, Harold

Article Type: Introduction

DOI: 10.3233/BIR-1982-191-212

Citation: Biorheology, vol. 19, no. 1-2, pp. 105-108, 1982

Authors: Oka, Syoten

Article Type: Other

DOI: 10.3233/BIR-1982-191-213

Citation: Biorheology, vol. 19, no. 1-2, pp. 109-110, 1982

Authors: Silberberg, A.

Article Type: Research Article

Abstract: Steady flow of a multicomponent, incompressible fluid through a connected, solid-like network is considered. ’The network acquires a finite deformation, bears the extra stresses required for mechanical balance, but does not flow. It constitutes at least one thermodynamic component and, in terms of the thermodynamics of irreversible processes, the simplest case of the flow of a binary solution through the network creates a three-component system with three independent cross-coefficients to be determined. The number of coefficients to be determined in the case of more than three components tends to become prohibitive. Hence, the formalism, developed for three components, is often …applied, justifiably and unjustifiably, to practical problems in biology, where the system is much more complex. The conditions under which this is permissible are given and discussed. For such a case, the questions of volume and separation flows is also considered. Relationships are given in terms of the friction coefficients between the components. The important biorheological and thermodynamic role of the matrix is stressed throughout. Show more

Keywords: Poiseuille equation, extra stress in tissue, tissue pressure, separation flow, friction coefficients, reflection coefficient, permeability, diffusion coefficient

DOI: 10.3233/BIR-1982-191-214

Citation: Biorheology, vol. 19, no. 1-2, pp. 111-127, 1982

Authors: Niimi, Hideyuki | Sugihara, Masako

Article Type: Research Article

Abstract: Blood rheology at a stagnation point is studied in views of microhemorheology. Special emphasis is put on the effect of both non-Newtonian and unhomogeneous properties of blood on the fine structure of blood flow impinging on the wall. It is shown that “non-flow” region exists just at the stagnation point due to the non-Newtonian viscosity when its yield stress is large enough, compared with the viscous stress far from the wall. When the yield stress becomes negligibly small, RBC and plasma behave individually near the stagnation point; RBC is deviated from the plasma streamline and impinges on the wall. Finally, …a microhemorheological factor of legional metabolic disorder is discussed on basis of the fine structure near a stagnation point. Show more

Keywords: Microhemorheology, Non-Newtonian viscosity, RBC suspension, Stagnation-point flow

DOI: 10.3233/BIR-1982-191-215

Citation: Biorheology, vol. 19, no. 1-2, pp. 129-136, 1982

Authors: Pai, Bipin K.

Article Type: Research Article

Abstract: The principle of minimum energy of deformation is used to determine the shapes of red cells during micropipette aspiration. Both bending and shear stresses are included in the analysis. The red cell shapes are described by equations with adjustable parameters. The parameters are then used to satisfy the geometrical and mechanical constraints. The geometrical constraints are that the surface area and volume have specific values. The mechanical constraint is that the red cell satisfy the equilibrium criterion that the total energy of deformation is a minimum. A numerical procedure is used to find a variety of shapes satisfying the geometrical …constraints. The total energy of deformation, which is the sum of bending and shear energies, is calculated for each of these shapes. An optimization procedure is then used to determine the shape which has the least energy of deformation. Show more

Keywords: Red blood cells, erythrocytes, micropipette aspiration, red cell membrane, microcirculation

DOI: 10.3233/BIR-1982-191-216

Citation: Biorheology, vol. 19, no. 1-2, pp. 137-141, 1982

Authors: Fukushima, Takayoshi | Azuma, Takehiko

Article Type: Research Article

Abstract: In order to elucidate the fluid dynamic feature of arterial blood flow, the present flow visualization study was carried out with various transparent blood vessel models having a protuberance, a bifurcation, or branchings. The observed flow patterns could be understood in terms of the occurrence of a secondary flow, named the horseshoe vortex. The mode of generation of the horseshoe vortex in a tube with a protuberance projecting into the boundary layer was explained as follows. A radial pressure gradient toward the tube wall was produced along the upstream surface of the protuberance because of the interaction between the viscous …sheared flow and the wall. This pressure gradient made fluid particles turn round downward directly before the obstacle. Then they curled round on themselves and formed a bound vortex tube, the horseshoe vortex, which in turn passed round the front of the protuberance in both directions. In a tube with a Y-shaped bifurcation or rectangular side branch, the flow divider at the branching site acted in place of the protuberance to produce a vortex tube similar in pattern to the horseshoe vortex. The vortex tube extended from the high pressure region, i.e. the apex of the flow divider, to the low pressure region, i.e. the lateral margin of the branch orifice, and generated swirling secondary flows in the main and branched tubes. These results suggested that the following mechanical factors might initiate or facilitate athero- and thrombogenesis: collision of blood cells captured by the horseshoe vortex with blood vessel walls, the interaction of the walls and blood cells due to turbulence, and the occurrence of localized high wall shear stresses. Show more

Keywords: flow visualization, shear stress, turbulence, atherogenesis, thrombogenesis

DOI: 10.3233/BIR-1982-191-217

Citation: Biorheology, vol. 19, no. 1-2, pp. 143-154, 1982

Authors: Matunobu, Y. | Takemitsu, N.

Article Type: Research Article

Abstract: Our previous work demonstrated the fact that the pulsatile flow impinglng on a fixed wall could give rise to enormous wall shear stress for large frequencies. Hence it can be inferred that if the arterial blood flow includes turbulent motion at the sites of bifurcation, stenosis and bend of the vessel, high-frequency velocity components may injure the endothelial lining of the vessel and may be a possible cause of the atherogenesis at these sites. However, the actual vessel wall is by no means a fixed one, but moves, more or less, compliantly according to the intraluminal blood pressure. The present …paper deals with this situation by solving the Navier-Stokes equation of motion, based on an idealized simple model, where two-dimensional pulsatile flow impinges obliquely on a plane wall oscillating normally to its own plane with common frequencies, First the solution for the unsteady flow induced by an oscillating plate on which steady flow is impinging is derived, Then, coordinate transformation of the result makes it possible to estimate the wall shear stress at the mean position of the stagnation point as a function of the common frequency, phase difference and ratio of the amplitudes of oscillation. The results are as follows: (a) The wall shear stress decreases monotonously and tends to the steady value as the frequency increases. This tendency is quite opposite to the case of an unmovable wall. (b) The wall shear stress increases monotonously with increasing phase difference and its amplitude attains a maximum at 180 degrees of difference. For 0 degree of difference which is the most compliant state, it attains a minimum. (c) The wall shear stress becomes larger as the ratio of the amplitudes of pulsating oncoming flow to oscillating wall increases. These conclusions have the physiological significance that the compliant motion of arterial walls may protect the endothelial cells from high-frequency components of turbulent motion. Show more

Keywords: Wall-shear-stress, relaxation, unsteady flow, arterial wall, turbulent motion, Wall shear stress, Stagnation-point flow, Turbulent motion of blood, Compliant motion of vessel wall

DOI: 10.3233/BIR-1982-191-218

Citation: Biorheology, vol. 19, no. 1-2, pp. 155-163, 1982

Authors: Singh, Megha | Vatsala, T.M.

Article Type: Research Article

Abstract: The erythrocyte sedimentation profiles under gravitational field, by scanning the sample holder along the height and width, containing the blood samples with normal and crenated erythrocytes, are determined. The normal shape of erythrocytes has been altered by the controlled He-Ne laser exposures and this change, as observed microscopically, is similar to that as produced by other methods. At low exposure the erythrocytes have normal appearance, whereas, at 400 mJ/cm2 , the percentage of crenated cells is 25 ± 5 percent. It is observed that the modification of the shape influences the sedimentation characteristics of the erythrocytes. The erythrocytes tend to …move faster after being exposed to lower exposure and slower after being exposed to higher exposure compared to that of normal erythrocytes. The possible mechanism associated with this change is discussed. Show more

Keywords: Erythrocytes sedimentation profiles, laser transmitted intensity, acanthocytes, aggregation

DOI: 10.3233/BIR-1982-191-219

Citation: Biorheology, vol. 19, no. 1-2, pp. 165-173, 1982

Authors: Whittington, R.B. | Harkness, J.

Article Type: Research Article

Abstract: The viscometers used were: (a) a proprietary rotational coaxial-cylinder instrument; and (b) a Harkness capillary-tube viscometer. In (a), the mean shear-rate is selected by the choice of rotational speed. In (b), the wall shear-stress is selected by the choice of driving-pressure. If the Viscosity is varied, the mean shear-rate varies, at constant wall shear-stress. The present paper attempts to show how, in principle, a complete family of “constant-rate” (rotational) curves can be computer-plotted from two suitably-spaced capillary-tube measurements. The reverse process, involving the correction of “playback” errors, is touched upon. A variable “Einstein coefficient” is derived from the …principal parameters in the computer solution; and the basic problems of compatibility in “rates of shear” are discussed. Show more

Keywords: Viscosity, haematocrit, shear

DOI: 10.3233/BIR-1982-191-220

Citation: Biorheology, vol. 19, no. 1-2, pp. 175-184, 1982