Biorheology - Volume 13, issue 6

Authors: Azelvandre, F. | Oiknine, C.

Article Type: Research Article

Abstract: Nous avons étudié expérimentalement les effets Fahraeus et Fahraeus-Lindqvist en faisant écouler dans des tubes de verre dont le diamètre varie entre 30 μ m et 1 mm des suspensions d’hématies lavées ou rigidifiées. A l’aide des résultats expérimentaux nous avons testé les différentes hypothèses avancées pour expliquer ces deux phénomènes.

DOI: 10.3233/BIR-1976-13601

Citation: Biorheology, vol. 13, no. 6, pp. 325-335, 1976

Authors: Azuma, Takehiko | Fukushima, Takayoshi

Article Type: Research Article

Abstract: A model study was undertaken to investigate disturbances of blood flow through stenotic blood vessels. Both axisymmetric and nonsymmetric models, having different diameter ratios of constriction, were used in the experiments. (1) Experiments with steady flow . A sudden decrease in the critical Reynolds number took place as the degree of axisymmetric constriction increased. Even at Reynolds numbers far below the critical value, a region of flow separation was clearly seen just behind the constriction. An eddying wake inside the separated region spread downstream as the Reynolds number increased. At the critical Reynolds number vortices were formed at the distal …end of the wake and shed downstream in succession. Two symmetrical standing eddies were noticed within the separated region behind a hemispherical bulge projecting into the boundary layer. Further increase in Reynolds number resulted in the formation of secondary flow. The horse-shoe vortex, which passed round the front of the bulge in both directions and led to a vortex pair trailing downstream, is a secondary flow ensued from a radial pressure gradient generated by a bluff obstacle within the boundary layer. (2) Experiments with nonsteady flow . A striking feature of a pulsatile laminar flow through a circular cylinder was the appearance of reverse flow near the wall at the end of the decelerating phase. The presence of an axisymmetric constriction caused pulsatile disturbances. With the progress of acceleration, large vortices were formed near the constriction, shed downstream and broken down into turbulence. The turbulent flow thus formed did not diminish during the decelerating phase but spread upstream against the flow direction until the start of next accelerating phase. Pulsation seemed to facilitate not only the production of vortices but also the backward spread of turbulence formed downstream. Show more

DOI: 10.3233/BIR-1976-13602

Citation: Biorheology, vol. 13, no. 6, pp. 337-355, 1976

Authors: Blake, Thomas R. | Gross, Joseph F.

Article Type: Research Article

Abstract: A mathematical analysis is presented of transcapillary fluid exchange during microocclusion of a single capillary, wherein both the capillary filtration coefficient and the tissue hydrostatic and osmotic pressures are dependent upon the axial distance along the capillary. In this model, the plasma is assumed to comprise an incompressible viscous fluid with the protein being a dilute solute in the fluid; we neglect the presence of erythrocytes. A system of one dimensional, time dependent equations describes the motion of this fluid including the influences of both fluid filtration and solute transport. Within the context of this model, we interpret in vivo …data from microvascular experiments on occluded capillaries and infer the relative merits of experimental methods to diagnose axial variations in capillary filtration parameters. Show more

DOI: 10.3233/BIR-1976-13603

Citation: Biorheology, vol. 13, no. 6, pp. 357-366, 1976

Authors: An, Kai-Nan | Salathe, Eric P.

Article Type: Research Article

Abstract: A previous analysis of fluid movement across capillary walls is extended to the physiologically more realistic case of variable capillary radius and filtration coefficient. Although the mathematical problem is considerably more complex, a method of solution is suggested by the results of the earlier study. An asymptotic solution is obtained which provides accurate results for most conditions of physiological interest.

DOI: 10.3233/BIR-1976-13604

Citation: Biorheology, vol. 13, no. 6, pp. 367-378, 1976

Authors: Dunn, Patrick F. | Picologlou, Basil F.

Article Type: Research Article

Abstract: An experimental technique suitable for the determination of the rheological properties of minute, biological viscoelastic solid specimens is presented. This technique is employed to ascertain the viscoelastic properties of the rabbit cumulus oöphorus. The experimental results when analyzed using the finite theory of elasticity reveal that the cumulus oöphorus can be adequately characterized as an incompressible elastic solid (retardation time less than 0.5 sec) with a strain energy function of the Mooney type. For small deformations, the elastic modulus was determined to be 1500 dynes/cm2 . It is concluded that for the physiological case of oviductal transport the cumulus should …be considered to behave essentially as a perfectly elastic body. Show more

DOI: 10.3233/BIR-1976-13605

Citation: Biorheology, vol. 13, no. 6, pp. 379-384, 1976

Authors: Biswas, Anuradha

Article Type: Research Article

Abstract: The present study is concerned with some physical changes of blood caused by cold exposure in toads (Bufo.m.). Specific viscosity of whole blood in terms of plasma viscosity was 0.563 ± 0.090 in control group and 1.656 ± 0.220 in exposed group. Mean total number of corpuscles was 332.6 ± 47.6 and 467.6± 102.7 × 103 /ml in control and exposed groups respectively, i.e. the specific viscosity increases by more than 300% over the control with 140% increase in the number of corpuscles in the exposed group. Mean lengths of major and minor axes of cells were 16.02 ± …2.14 and 10.76 ± 1.34 μ m in control and 18.31 ± 2.21 and 13.31 ± 1.64 μ m in exposed group. Mean ratio of major and minor axes where 1.59 and 1.33 in control and exposed group respectively. This indicates that the cells of the exposed group are less ellipsoidal compared with those of the control group. It is suggested that due to cold exposure, the number of the blood corpuscles increases and the shape of cells also undergo significant change. These factors contribute towards the increase in the blood viscosity. Show more

DOI: 10.3233/BIR-1976-13606

Citation: Biorheology, vol. 13, no. 6, pp. 385-387, 1976