Biorheology - Volume 8, issue 3-4

Authors: Coulter Jr., N.A. | Singh, Megha

Article Type: Research Article

Abstract: Womersley’s theory of oscillatory flow is used to derive a parameter, the equivalent viscosity, which characterizes the rheological state of a non-Newtonian fluid under oscillatory conditions. The equivalent viscosity so obtained is analogous to the apparent viscosity determined from Poiseuille’s Law in steady flow, and reduces to apparent viscosity at zero frequency. Experimental studies of the oscillatory flow of blood at different frequencies but the same flow amplitudes show that the equivalent viscosity is frequency dependent. The effect is demonstrated in tubes of radii ranging from 0.0304 to 0.162 cm. This frequency dependence is associated with a marked deviation in …hydraulic resistance from that of a Newtonian fluid, but with a negligible effect on inertial reactance. Show more

DOI: 10.3233/BIR-1971-83-401

Citation: Biorheology, vol. 8, no. 3-4, pp. 115-124, 1971

Authors: Evans, Robert L. | Kirkwood, R. Bruce | Opsahl, David G.

Article Type: Research Article

Abstract: Measurements were made of the stress-strain behavior of human blood during two transition sequences (from rest to eventually a 25 sec−1 strain rate, and from 64 sec−1 to an eventual 127 sec−1 strain rate) in a modified Brookfield cone-and-plate viscometer. The data were obtained laboriously from movies of the viscometer and a stop watch at 24 and 64 frames/sec, respectively, and are shown in Figs. 1 and 2. These show major changes of stress (in both experiments) prior to any appreciable changes of the strain rates of the blood. The first experiment shows a yield stress of …about 0.5 dyne/cm2 , jerky starting of the blood, and an eventual fluidity of 10.5 cm sec/g. The second experiment shows first a prompt fluidity fall from 14 to 9 cm sec/g with rising stress and almost constant strain rate, then most of 2 sec at about fluidity 9, a sudden jump to about fluidity 15 (accompanied by a sharp drop in actual stress to near its eventual value), and subsequent marked oscillations of strain rate and fluidity. In this interval the fluidity passed through a maximum above 20 and then settled down to an eventual value of 16 cm sec/g. Show more

DOI: 10.3233/BIR-1971-83-402

Citation: Biorheology, vol. 8, no. 3-4, pp. 125-128, 1971

Authors: Bettelheim, F.A. | Epstein, S. | Gorvoy, J.D.

Article Type: Research Article

Abstract: A new rheological parameter, β , was designed to measure the tackiness or superfluidity of submaxillary secretions. The β parameter represents the increase in surface area of the saliva per unit force when a strand of saliva is extended. It is measured in terms of viscosity coefficients, surface tensions, and densities of the submaxillary secretions. It was found that while the viscosity coefficient, surface tension, or the extendibility of the saliva alone could not differentiate between healthy and afflicted donors, the β parameter separates the C.P. patients into two distinct groups—one of which have β values which …are higher than those of normal donors. Show more

DOI: 10.3233/BIR-1971-83-403

Citation: Biorheology, vol. 8, no. 3-4, pp. 129-138, 1971

Authors: Kaibara, M. | Fukada, E.

Article Type: Research Article

Abstract: Measurements of dynamic elastic modulus E ′ and loss modulus E ″ of clotting blood and fibrinogen solutions were carried out. When the blood is collected into a siliconized polyethylene test tube, the saturated value of E ′ is smaller and that of E ″ is larger, and the clotting time is longer than those when the blood is collected into a non-siliconized glass tube. In the aqueous solution of fibrinogen added with thrombin, the lower …concentration of thrombin yielded the smaller E ′ and the larger E ″ for the clotted gel and the longer clotting time. As the concentration of thrombin is low, the polymerization of fibrin would be impeded by the presence of partly formed gel and the formation of fibrin network would become incomplete. It is supposed that the siliconization of the surface of tube may influence the rate of production and the concentration of thrombin in the blood. Show more

DOI: 10.3233/BIR-1971-83-404

Citation: Biorheology, vol. 8, no. 3-4, pp. 139-147, 1971

Authors: Fukada, E. | Dintenfass, L.

Article Type: Research Article

Abstract: Clotting curves for human blood, plasma and fibrinogen-thrombin solutions were determined by means of the variable-frequency-thromboviscometer (VFTV) and viscoelastorecorder (VER). A maximum stress was observed in curves obtained with VFTV, whereas no maximum was observed with VER. This might be related to the mean shear strain which is 40 times larger in VFTV than in VER and might be responsible for disruption of the polymerization pathway of fibrinogen and/or the gel structure of the clot. The clotting times of fibrinogen-thrombin systems in VFTV are affected only by thrombin concentration and not shear rate or shear strain; the apparent viscosity …of these systems is greatly affected by the shear rate, decreasing rapidly with increasing VFTV frequency of oscillation. Show more

DOI: 10.3233/BIR-1971-83-405

Citation: Biorheology, vol. 8, no. 3-4, pp. 149-155, 1971

Authors: Huang, Ching-Rong | Whelan, J.A. | Wang, Huei-Hsiung | Copley, A.L.

Article Type: Research Article

DOI: 10.3233/BIR-1971-83-406

Citation: Biorheology, vol. 8, no. 3-4, pp. 157-163, 1971

Authors: Stoltz, J.F. | Lefort, M. | Wackenheim, E. | Larcan, A.

Article Type: Research Article

Abstract: Après un rappel des principaux travaux hydrodynamiques concernant le problème des embranchements dans le lit vasculaire et après avoir rappélé la notion de “zone d’influence”, les auteurs rapportent leurs résultats concernant l’étude d’un modèle bidimensionnel. Ils montrent en particulier l’existence de la ligne de courant limitant la zone d’influence ainsi que l’existence de deux zones mortes en aval de la bifurcation. L’extension à un modèle tridimensionnel est envisagée.

DOI: 10.3233/BIR-1971-83-407

Citation: Biorheology, vol. 8, no. 3-4, pp. 165-169, 1971

Authors: Harkness, John

Article Type: Review Article

DOI: 10.3233/BIR-1971-83-408

Citation: Biorheology, vol. 8, no. 3-4, pp. 171-193, 1971