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Biorheology is an international interdisciplinary journal that publishes research on the deformation and flow properties of biological systems or materials. It is the aim of the editors and publishers of
Biorheology to bring together contributions from those working in various fields of biorheological research from all over the world. A diverse editorial board with broad international representation provides guidance and expertise in wide-ranging applications of rheological methods to biological systems and materials.
The aim of biorheological research is to determine and characterize the dynamics of physiological processes at all levels of organization. Manuscripts should report original theoretical and/or experimental research promoting the scientific and technological advances in a broad field that ranges from the rheology of macromolecules and macromolecular arrays to cell, tissue and organ rheology. In all these areas, the interrelationships of rheological properties of the systems or materials investigated and their structural and functional aspects are stressed.
The scope of papers solicited by
Biorheology extends to systems at different levels of organization that have never been studied before, or, if studied previously, have either never been analyzed in terms of their rheological properties or have not been studied from the point of view of the rheological matching between their structural and functional properties. This biorheological approach applies in particular to molecular studies where changes of physical properties and conformation are investigated without reference to how the process actually takes place, how the forces generated are matched to the properties of the structures and environment concerned, proper time scales, or what structures or strength of structures are required.
Biorheology invites papers in which such 'molecular biorheological' aspects, whether in animal or plant systems, are examined and discussed. While we emphasize the biorheology of physiological function in organs and systems, the biorheology of disease is of equal interest. Biorheological analyses of pathological processes and their clinical implications are encouraged, including basic clinical research on hemodynamics and hemorheology.
In keeping with the rapidly developing fields of mechanobiology and regenerative medicine,
Biorheology aims to include studies of the rheological aspects of these fields by focusing on the dynamics of mechanical stress formation and the response of biological materials at the molecular and cellular level resulting from fluid-solid interactions. With increasing focus on new applications of nanotechnology to biological systems, rheological studies of the behavior of biological materials in therapeutic or diagnostic medical devices operating at the micro and nano scales are most welcome.
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.
Keywords: Poiseuille equation, extra stress in tissue, tissue pressure, separation flow, friction coefficients, reflection coefficient, permeability, diffusion coefficient
vol. 19, no. 1-2, pp. 111-127, 1982
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.
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.
Keywords: Red blood cells, erythrocytes, micropipette aspiration, red cell membrane, microcirculation
vol. 19, no. 1-2, pp. 137-141, 1982
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.
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.
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.
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.
Keywords: Viscosity, haematocrit, shear
vol. 19, no. 1-2, pp. 175-184, 1982