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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: The history of capillary flow is presented from the earliest observations to the most recent experiments. Parallel theoretical developments are traced from early work on continuous fluids to modern work in which the discrete nature of each blood cell is taken into account. A comparison of theory and experiments shows that most features of capillary flow are well understood qualitatively, e.g. the variations of cell concentration and apparent viscosity with microvessel diameter. Quantitative comparisons between theory and experiments, however, are not yet possible. There is a need for the development of theoretical solution for non-axisymmetric flow of flexible particles…in a capillary, as well as flow at junctions.
Abstract: This paper describes the behavior of isolated neutrally buoyant particles and particle groupings flowing through a thin rectangular channel of high aspect ratio (Hele-Shaw flow). The most significant finding is the tendency of two or more particles travelling within a critical distance from each other to interact, moving toward each other and acquiring characteristic equilibrium configurations. This phenomenon helps explain previous observations of the behavior of low concentration suspensions of neutrally buoyant spherical particles flowing in the laminar inertial range through the same type of channel.
Abstract: The apparent viscosity of blood measured with a capillary viscometer is influenced not only by the size of the capillary tube (sigma effect), but also by its wall surface condition. Copley, Scott Blair et al. reported that the apparent viscosities always showed a decrease when blood, plasma or serum were in contact with fibrin as compared with glass and other surfaces such as silicone (Copley-Scott Blair phenomenon). In order to offer a reasonable explanation of the Copley-Scott Blair phenomenon, the role of the electric double layer existing at the interface between the fibrin-coated glass surface and blood, plasma or serum…has been emphasized. The influence of an electric double layer upon the Poiseuille flow of an electrolyte solution has been treated theoretically. The effect of an electric double layer is expressed through a nondimensional parameter α = ε σ ζ / ( 2 π K η R ) where σ and ζ are respectively the surface charge density and zeta potential of the electric double layer, ε , K and η are respectively the dielectric constant, specific conductivity and viscosity of the Newtonian liquid, and R is the radius of the tube. The parameter α becomes significant when the product σ ζ is large, as is expected for fibrin surfaces, while it will take small values for glass, silicone and polyethylene surfaces. Moreover, the parameter α becomes significant for small values of R, showing that the effect of an electric double layer becomes especially significant in capillaries and microvessels. Experimental confirmation of our theory and the extension of our theory to blood are desirable.
Keywords: Capillary blood flow, Electric double layer, Wall surface effect and Zeta potential
vol. 18, no. 3-6, pp. 347-353, 1981
Abstract: Phase separation between red cells and plasma were studied using blood perfused model systems which consisted of glass capillaries (I.D. between 3.3 and 11.0 μ m) branching from a large bore (I.D. 1.5 mm) feed channel. The orifice of the capillaries was either positioned in the centerline of the feed channel (model A) or flush with its wall (model B). Capillary discharge hematocrit (HD ) was measured at different flow conditions and related to the hematocrit in the feed channel (HF ). The ratio HD /HF was found to be correlated to the ratio between wall shear stress in…the capillary and in the feed channel (τ T / τ F ). While at low τ T / τ F almost no cells entered the capillary, HD increased with increasing τ T / τ F and approached HF in model A. In model B, HD did not reach HF within the experimental range of τ T / τ F ’ The flow fractionation in model B can be explained by “plasma skimming”. In model A cell entry into the capillary is determined by the relationship between forces acting on the red cell either in the direction of the feed channel or of the capillary. For this mechanism the term “screening effect” is proposed. This effect decreases with increasing HF and increasing capillary diameter and vanishes when capillary diameter approaches 12 μ m.
Abstract: The need for accurate determination of the geometry of red blood cells is discussed. To overcome the difficulty of wave diffraction which casts a fuzzy border around any object in light microscopy and thus causing an uncertainty in measurements, the method of interference holography was used. Samples of human red blood cells were taken from 14 healthy subjects and the cell geometry was measured from photographs taken in a Leitz interference microscope of the Mach-Zender type. The images were analyzed as holographs. The method has a resolution of 0.02 μ m. Statistical results on cell diameter, minimum and maximum thickness,…surface area, volume and sphericity index, as well as the correlations between these parameters are reported. For the total samples collected, the average human red cell diameter was found to be 7.65 ± 0.05 μ m (SEM), with a standard deviation of 0.67 μ m. The mean values of the surface area and volume computed from holograms were 129.95 ± 1.03 μ m2 (SEM) and 97.91 ± 1.06 μ m3 (SEM) respectively. The standard deviations of the area and volume were 15.86 μ m2 and 16.16 μ m3 respectively. The correlation between diameter vs volume and diameter vs surface area are discussed. Applications of these data are illustrated. In the appendix the geometric parameters of the red cells of the rabbit are presented.
Keywords: Red blood cells, human, rabbit, erythrocytes, diameter, surface area
vol. 18, no. 3-6, pp. 369-385, 1981
Abstract: Stereological parameters d(Heyn), Lamda, and S* /V* , have been applied (for the first time, we believe) to evaluation of kinetics and morphology of aggregation of human red cells obtained from healthy and ill donors. Anticoagulated blood was allowed to flow at shear rate of 230 sec−1 , flow was stopped am microphotographs taken at intervals till 12 minutes elapses. Aggregates increased in size for a period of 4 to 10 minutes, depending on blood sample. Sedimentation could be noticed after 10 minutes. Morphology of aggregates differed, rouleaux formation or clumping of red cells being quite clear under high…magnification. Colour slides were analyzed by the Zeiss Videomat 2 image analyzer using a Zeiss Monochromator. Aggregation of red cells can be described by plotting stereological parameters vs square root of time. Morphology of aggregates can be described by plotting d(Heyn) vs Lamda, or d(Heyn) vs S* /V* . Different samples can be compared by comparing slopes and elevations of linear regressions, or by comparing means and standard deviations of stereological parameters.
Abstract: The time variation of dynamic rigidity modulus G′ and loss modulus G″ of horse and human bloods was determined at 1 Hz after imposing the steady flow with different shear rates for a fixed period. At hematocrits below 45 %, the values of G′ and G′ increased and then decreased through a maximum, depending on the shear rate of the preceding steady flow. The rates of decrease of G′ and G″ after the maximum were greatest at the shear rate of about 10 sec−1 . The shortening of the duration of imposed steady flow reduced the shear rate dependence…of the time variation of G′ and G′. At high hematocrits the rate of decrease of G′ was independent of the shear rate. These observations indicate that the preceding steady flow gives a prolonged influence on the time change of the aggregation structure of red cells during viscoelastic measurement.
Keywords: Red cells, Rouleaux network, Shear rate, Viscoelasticity
vol. 18, no. 3-6, pp. 405-413, 1981
Abstract: Abnormally high shear stresses (Tw > 50–200 Pal are known to occur under exceptional conditions in vivo (e.g. during the formation of a hemostatic plug in a rapidly perfused artery after it has been cut). Likewise, blood flow over a stenosis and blood flow through many artificial organs produces shear stresses in the same order of magnitude. Shear stresses above 50 Pa are known to damage red cells and platelets. It is hypothesized that such “damage” of the blood cells provides a physiological stimulus which triggers key events of platelet activation (directly and indirectly via release of ADP…from ruptured red blood cells) and of the coagulation enzymes (via the demasking of procoagulatory phospholipids). Experiments are described in which the occurrence of the postulated biochemical events is documented under conditions of high shear tube flow. The concept of shear activation of platelets is incorporated in a combined biochemical-hemorheological theory of high shear thrombotic events such as they occur in arteries. In this theory, the process of thrombosis in high flow is considered to be initiated (on the afferent limb) by abnormally high shear stresses, but manifests itself subsequent to autokatalytic augmentation as the formation of white thrombi and deposits onto a wall (efferent limb).
Keywords: Hemorheology, Thrombosis, Blood flow, High flow, Forces, Erythrocytes, Platelets
vol. 18, no. 3-6, pp. 415-444, 1981
Abstract: We have studied the rheological behavior in transient flow of some pathological bloods (diabetic patients and patients with polycythemia). We have used a servo-controlled Couette microviscometer, which allowed us to plot the shear stress variations as a function of time for rectangular and triangular steps of shear rates. We have compared the rheological parameters so obtained with those of the controls, and thus deduced informations about the viscoelasticity, thixotropy and shear-thinning of the different pathological blood samples.