Biorheology - Volume 10, issue 2

Authors: Scott Blair, George W. | Seaman, Geoffrey V.F.

Article Type: Introduction

DOI: 10.3233/BIR-1973-10201

Citation: Biorheology, vol. 10, no. 2, pp. 81-82, 1973

Authors: Copley, Alfred L.

Article Type: Other

DOI: 10.3233/BIR-1973-10202

Citation: Biorheology, vol. 10, no. 2, pp. 83-86, 1973

Authors: Copley, Alfred L.

Article Type: Other

DOI: 10.3233/BIR-1973-10203

Citation: Biorheology, vol. 10, no. 2, pp. 87-105, 1973

Authors: Copley, Alfred L.

Article Type: Other

DOI: 10.3233/BIR-1973-10204

Citation: Biorheology, vol. 10, no. 2, pp. 107-108, 1973

Authors: Silberberg, A.

Article Type: Other

DOI: 10.3233/BIR-1973-10205

Citation: Biorheology, vol. 10, no. 2, pp. 109-116, 1973

Authors: Bugliarello, George

Article Type: Research Article

Abstract: The connection between rheology on the one hand, and information theory and cybernetics on the other, can generate useful insights and new lines of inquiry for biorheology, as well as for the understanding of biological control mechanisms. Biological materials, and particularly biological fluids, serve to convey not only mass, heat or momentum, but also information. The nature, attenuation, modulation and bandwidth of the signal conveyed, and the information capacity of the channel, are related to rheological factors. Analyses show that the information capacity of the major arteries is likely to be moderate, but that of the capillaries is much higher. …Cybernetically, the rheological characteristics of biological materials, like those of any other materials, can be viewed as filters limiting the range of responses of the material. Since a filter is also a channel of communication, a connection is established between communication theory and rheology. Significant consequences include the propositions that any given rheological behavior can be produced by a number of possible microscopic arrangements, and that the memory of biological materials is not a wholly objective property of the fluid. Intrinsically, furthermore, rheological characteristics endow biological fluids with an ability to regulate and control flows. Show more

DOI: 10.3233/BIR-1973-10206

Citation: Biorheology, vol. 10, no. 2, pp. 117-127, 1973

Authors: Fukada, Eiichi | Kaibara, Makoto

Article Type: Research Article

Abstract: The dynamic rigidity and loss modulus of the solutions of fibrinogen with added thrombin have been determined by a viscoelastorecorder throughout the period of gelation. The rigidity of the fibrin gel is approximately proportional to the square of the concentration of fibrinogen. The dynamic rigidity of the fibrin gel depends upon the amplitude and frequency of oscillation applied during gelation. The logarithms of the rigidity and loss moduli decrease linearly with the square root of the dynamic shear rate, i.e. the angular frequency times amplitude. The mechanical agitation during gelation prevents the sufficient formation of the fibrin network. When the …gelation of fibrin is completed under a certain large amplitude of oscillation and the measuring amplitude is decreased from that given during gelation, the decrease of the rigidity modulus is observed, which suggests that the fibrin molecules between crosslinks of the network are fairly stretched by the applied strain during gelation. The kinetic analysis of the clotting curves also indicates that the gelation is caused by the crosslinks between fibrin polymers and by the stretching of the fibrin molecules between crosslinks. Show more

DOI: 10.3233/BIR-1973-10207

Citation: Biorheology, vol. 10, no. 2, pp. 129-138, 1973

Authors: Fung, Yuan-Cheng B.

Article Type: Research Article

Abstract: To understand the physiological function of vital organs we must know the mechanical properties of the tissues. Experimental determination of the mechanical properties of living tissues has many difficulties, such as the small size, large deformation, active contraction, damage due to dissection, inaccessibility or non-existence of a “natural” state, and the necessity of keeping the specimens alive. In this paper, major features of the rheology of soft tissues obtained in our laboratory are summarized, and a mathematical description is offered to serve as a starting point for the analysis of the function of the organs. Almost all published rheological …data on soft tissues were obtained in one-dimensional condition—simple elongation of a slender cylindrical body, strip-biaxial or homogeneous—biaxial tension of a membrane. Recently we have collected data on two-dimensional testing of the skin, and torsion of the mesentery. From these we propose the following stress (σ i j )-strain (e i j ) relation for such tissues as the skin, the mesentery, and the muscle in the passive state, when subjected to loading and unloading at a constant rate σ i j = C ijkl ′ e k l + C ijkl e k l exp { a m n ( e m n − e m n ( 0 ) ) + b ( J 2 − J 2 ( 0 ) ) δ i j } + p δ i where J 2 = 1 6 [ ( e 11 − e 22 ) 2 + ( e 22 − e 33 ) 2 + ( e 33 − e 11 ) 2 ] + e 12 2 + e 23 2 + e 31 2 is the second strain invarient; x 1 , x 2 , x 3 are axes of orthotropic symmetry, C ijkl , C ijkl ′ are orthotropic tensors of rank 4 familiar in the classical theory of elasticity, a m n and b are constants which differ in loading from unloading (defined by whether ∂ ( a m n e m n + b J 2 ) / ∂ t is positive or negative), but are only slightly dependent on the strain rate. This equation does not apply to highly structured tissues such as blood vessels or the lung. a m n e m n ( 0 ) and J 2 ( 0 ) are the largest values of these strain invariants for which the formulas are expected to be applicable. The indexes range over 1, 2, 3. For membranes in plane stress the indexes range over 1, 2 and the p term should be deleted. The summation convention over a repeated index is used. Show more

DOI: 10.3233/BIR-1973-10208

Citation: Biorheology, vol. 10, no. 2, pp. 139-155, 1973

Authors: Harkness, M.L.R. | Harkness, R.D.

Article Type: Research Article

DOI: 10.3233/BIR-1973-10209

Citation: Biorheology, vol. 10, no. 2, pp. 157-163, 1973

Authors: Joly, M. | Bourgoin, D. | Volf, E.

Article Type: Research Article

Abstract: La viscosité apparente et la dispersion diélectrique de solutions aqueuses de dextrane de poids moléculaire moyen 120.000 sont étudiées dans le domaine de concentration 10–60%. Les mesures de viscosité sont effectuées dans une gamme de vitesse de cisaillement allant de 1,8 × 10−2 à 1,8 × 102 sec−1 . Les mesures de dispersion diélectrique ont été faites dans les bandes de fréquence 7,5–10 GHz et 0,5–2,5 MHz. Les courbes représentant, en fonction de la concentration, les variations de la viscosité, de la constante diélectrique, du temps de relaxation moyen et du coefficient de distribution des temps de relaxation …présentent un brusque changement d’allure pour un titre des solutions de l’ordre de 0,4–0,43. Pour interpréter l’ensemble des résultats, on propose un modèle de structure des solutions concentrées dans lequel on fait jouer un rôle important à l’organisation des molécules d’eau entourant les molécules de dextrane. Le changement d’allure dans les comportements rhéologique et diélectrique se produisent pour une composition des solutions correspondant en moyenne à 1,5 couches de molécules d’eau autour de chaque molécule de dextrane. Show more

DOI: 10.3233/BIR-1973-10210

Citation: Biorheology, vol. 10, no. 2, pp. 165-177, 1973