Biorheology - Volume 24, issue 2

Authors: Lanir, Y.

Article Type: Research Article

Abstract: A theory for the rheological behavior and fluid flux in swelling tissues under small deformations is presented. Tissues are considered as bicomponent solid-fluid mixtures. Concentration effects are included. The driving forces (body, surface and interactive), are discussed and their constitutive relationships to the tissue’s deformation are specified. Mass and momentum balance equations are developed for each component and for the tissue as a whole. The concept of swelling stress emerges from the theory as an anisotropic generalization of the commonly used swelling pressure. It is shown to be a measure of the total chemical potential combining both mechanical and concentration …effects. The theory shows that concentration effects modify the tissue’s bulk stiffness in a manner consistent with experimental observations. Show more

Keywords: swelling tissues, bicomponent mixture theory, concentration effects, swelling stress

DOI: 10.3233/BIR-1987-24210

Citation: Biorheology, vol. 24, no. 2, pp. 173-187, 1987

Authors: Lanir, Y.

Article Type: Research Article

Abstract: The response of a cartilage disc to unconfined compressive loading under small deformations is analyzed. The cartilage is considered as a transversely isotropic bicomponent (solid-fluid) tissue. Concentration effects (commonly termed osmotic pressure) are accounted for. The tissue’s permeability is taken to be isotropic. Its concentration force is assumed to vary linearly with volume. The analysis shows that if the tissue’s fibrous structure is taken into consideration, then the instantaneous response to a step loading depends on the tissue’s elasticity and on its concentration force. The subsequent creep response, under commonly used experimental conditions, has a time constant which depends …on the concentration force and permeability, but independent of its elastic response. The equilibrium volume is predicted to depend only on the concentration force. Where data is available it confirms the model’s predictions. It is concluded from the present analysis that inclusion of concentration effects and the tissue’s fibrous structure has significant consequences in terms of the relative roles of the collagen fibers (solid) vs. the ground substance (fluid) in the response of the cartilage to compressive loading. Show more

Keywords: cartilage disc, unconfined compression, bicomponent mixture theory, concentration effects, small deformations

DOI: 10.3233/BIR-1987-24211

Citation: Biorheology, vol. 24, no. 2, pp. 189-205, 1987

Authors: Djordjevich, Ljubomir | Kashani, Abdollah | Miller, Irving F. | Ivankovich, Anthony D.

Article Type: Research Article

Abstract: Measurements were made of the viscosity of suspensions of synthetic erythrocytes composed of hemoglobin solutions encapsulated in liposomes, as a function of shear rate, temperature, suspension concentration, lipid membrane composition, and the viscosity of the suspending medium. It was found that the viscous behavior of the synthetic erythrocyte suspensions was non-Newtonian and nearly the same as that of suspensions of natural erythrocytes prepared similarly, with the major difference being that synthetic erythrocyte suspensions are somewhat more viscous. Suspensions of Fluosol FC-43 prepared similarly were found to be essentially Newtonian fluids, and substantially different and more viscous than either erythrocyte suspension. …The higher viscosity of synthetic erythrocyte suspensions probably accounts for the ability of these suspensions to maintain normal systemic vascular resistance in transfusion experiments, in spite of the fact that synthetic erythrocytes are smaller than natural erythrocytes. Show more

Keywords: synthetic erythrocytes, artificial blood, artificial RBC, viscosity of artificial RBC

DOI: 10.3233/BIR-1987-24212

Citation: Biorheology, vol. 24, no. 2, pp. 207-217, 1987

Authors: Takano, Y. | Sakanishi, A.

Article Type: Research Article

Abstract: The bulk modulus of a dilutely dispersed system of spherical shell structures is obtained taking into account interfacial tensions at both the interfaces of the shell as follows: κ ∗ = κ Q + 4 3 c μ Q ′ Q − c Q ′ where Q = K ′ K m − Δ K ′ Δ MA 3 , Q …′ = K ′ Δ K − Δ K ′ KA 3 , K m = 3 κ m + 4 μ − 2 γ / a , Δ K = 3 κ m − 3 κ − 2 γ / a , Δ M = 4 μ m − 4 μ + 2 γ / a , K = 4 μ m + 3 κ + 2 γ / a , K ′ = 3 κ ′ + 4 μ m − 2 γ ′ / a ′ , Δ K ′ = 3 κ m − 3 κ ′ + 2 γ ′ / a ′ , A = a′/a, a and a′ are the outer and the inner radii of the shell, γ and γ ′ the interfacial tensions at r = a and r = a′, in which r is the radial distance from the origin at the center of the shell structure, κ and μ the bulk modulus and the rigidity of the medium, in which the prime and the subscripts m denote the quantities for the inside (r<a′) and the shell (a′<r<a) regions, respectively, and c the volume concentration of shell structures. Show more

Keywords: bulk modulus, dispersed system, spherical shell, interfacial tension

DOI: 10.3233/BIR-1987-24213

Citation: Biorheology, vol. 24, no. 2, pp. 219-226, 1987

Authors: Mackie, Linda Haile | Frank, Robert S. | Hochmuth, Robert M.

Article Type: Short Communication

Keywords: Erythrocytes, Erythrocyte Membrane, Density Gradient

DOI: 10.3233/BIR-1987-24214

Citation: Biorheology, vol. 24, no. 2, pp. 227-230, 1987

Authors: Shake, Michael P. | Dresdner, Robert | Gruenauer, Lois M. | Yeates, Donovan B. | Miller, Irving F.

Article Type: Short Communication

Keywords: rheology, viscosity, elasticity, mucus

DOI: 10.3233/BIR-1987-24215

Citation: Biorheology, vol. 24, no. 2, pp. 231-235, 1987

Authors: Andre, J.C. | Bouchy, M. | Donner, M.

Article Type: Review Article

Abstract: The following paper is a brief presentation of problems related to the concepts of diffusion coefficient D and so-called viscosity η used to characterize the cohesion of biological membranes. The first approach to this problem is a recall of the definition of D and η in liquids. It appears that the models developed with exogenous probes to account for the diffusion-viscosity relationship are not verified in membranes. The existence of complex diffusional mechanisms, the influence of the size of the probe are presented. The results of a model calculation suggest that there is no direct correlation other than …great simplifications, between the diffusion coefficient and viscosity. The calculations are then extended to actual biological assemblies and the influence of proteins on the motion of the probe considered. The limitations of the methods involving exogeneous probes for determining the cohesion of biological membranes are discussed. Show more

Keywords: Biological membranes, viscosity, diffusion coefficient

DOI: 10.3233/BIR-1987-24216

Citation: Biorheology, vol. 24, no. 2, pp. 237-272, 1987

Article Type: News

DOI: 10.3233/BIR-1987-24217

Citation: Biorheology, vol. 24, no. 2, pp. 273-276, 1987

Article Type: Addendum

DOI: 10.3233/BIR-1987-24218

Citation: Biorheology, vol. 24, no. 2, pp. 277-277, 1987

Article Type: Announcement

DOI: 10.3233/BIR-1987-24219

Citation: Biorheology, vol. 24, no. 2, pp. 279-281, 1987