Biorheology - Volume 15, issue 3-4

Article Type: Correction

DOI: 10.3233/BIR-1978-153-422

Citation: Biorheology, vol. 15, no. 3-4, pp. I-XXXV, 1978

Article Type: Correction

DOI: 10.3233/BIR-1978-153-401

Citation: Biorheology, vol. 15, no. 3-4, pp. 143-143, 1978

Article Type: Announcement

DOI: 10.3233/BIR-1978-153-402

Citation: Biorheology, vol. 15, no. 3-4, pp. 145-145, 1978

Authors: Gaehtgens, P. | Albrecht, K.H. | Kreutz, F.

Article Type: Research Article

Abstract: Glass capillaries (I.D. 15–95 μ m) were perfused with red cell suspensions in buffered Ringer’s solution using driving pressures which corresponded to wall shear stresses between 5 and 400 dynes/cm2 . The hematocrit within the capillaries (HT ), in the discharge reservoir (HD ), and in the feed reservoir (HF ) as well as the volume flow rate through the capillaries were determined. It was observed that variation of flow rate resulted in significant changes of the screening effect (HD /HF < 1) and the Fahraeus effect (HT /HD < 1): cell screening increased and the Fahraeus effect …decreased upon reduction of volume flow rate (μ ¯ -values ranging from 10 to 103 sec−1 ). The combined effect of both mechanisms resulted in an increase of capillary hematocrit with decreasing flow rate. It is concluded that cellular overvelocity increases with shear stress due to shear-dependent axial concentration of flowing red cells. Show more

DOI: 10.3233/BIR-1978-153-403

Citation: Biorheology, vol. 15, no. 3-4, pp. 147-154, 1978

Authors: Gaehtgens, P. | Albrecht, K.H. | Kreutz, F.

Article Type: Research Article

Abstract: Suspensions of human red blood cells were drawn through glass capillaries (I.D. 15–95 μ m). The suspending medium contained high molecular weight dextran to induce extensive red cell aggregation. The effect of changes in flow rate on the Fahraeus effect and red cell screening was studied by determining capillary hematocrit (HT ), discharge hematocrit (HD ), feed hematocrit (HF ), and the volume flow rate through the capillaries. It was found that the flow dependence of cell screening was intensified compared to the results obtained in the absence of dextran. Furthermore the Fahraeus effect showed an inversed flow dependence: in …the range of low flow rates (u ¯ below 200 sec−1 ) reduction of flow rate resulted in a decrease of the ratio HT /HD indicating more pronounced dynamic hematocrit reduction within the capillary. Calculations of the cell-free layer of suspending medium near the tube wall showed values ranging between 10 and 30% of the tube radius (corresponding to a width between 1 and 7 μ m) depending on the diameter of the tube. The cell-free wall layer was found to increase both at low flow rates (due to increased cell aggregation) and at high flow rates (due to axial migration of disaggregated cells). Show more

DOI: 10.3233/BIR-1978-153-404

Citation: Biorheology, vol. 15, no. 3-4, pp. 155-161, 1978

Authors: Born, G.V.R. | Melling, A. | Whitelaw, J.H.

Article Type: Research Article

Abstract: Laser Doppler anemometry has been applied to the measurement of the local velocity of blood flowing in venules and in small-diameter glass tubes. As a consequence, the capabilities and limitations of the technique, for this purpose, are identified and quantified. It is shown that multiple scattering, absorption and wave front distortion preclude precise measurements at haematocrit values near those of whole blood. The location of measurement in round capillaries is impossible to identify with satisfactory resolution and it is suggested that the application of the technique, for local measurements, should be limited to plane channels with ghost cells or blood …of low haematocrit: in addition, approximate measurements of the integrated velocity can probably be obtained with whole blood in tubes of small diameter, say less than 50 μ m. Show more

DOI: 10.3233/BIR-1978-153-405

Citation: Biorheology, vol. 15, no. 3-4, pp. 163-172, 1978

Authors: Collins, R. | Kivity, Y.

Article Type: Research Article

Abstract: Shock-like waves are generated in fluid-filled silastic tubes, and their amplitudes recorded as a function of position and time. A simple theory is formulated for the steady-state “shock-structure”, based on a mathematical analogy with gas-dynamic shock waves. Comparison with the experimental results provides a general method for the evaluation of the dynamic rheology of viscoelastic biological vessels. The existence of shock-like propagation is seen to depend upon the form of the input pressure signal and most critically upon its maximum rate of rise dp/dt.

DOI: 10.3233/BIR-1978-153-406

Citation: Biorheology, vol. 15, no. 3-4, pp. 173-179, 1978

Authors: Vera, J.C. | Lefort, M.F. | L’Huillier, J.P. | Stoltz, J.F.

Article Type: Research Article

Abstract: Cette étude utilise une technique d’analyse spectrale basses fréquences, en temps réel, des signaux Doppler fournis par un débitmètre ultrasonore à émission continue. Les écoulements permanents réalisés sont engendrés, dans un tube viscoélastique, cylindrique circulaire, sur un banc de simulation hydrodynamique. La chaîne de mesures, comportant les différents capteurs et le système d’analyse, est brièvement. décrite. Les spectres d’amplitude des signaux Doppler servent de support aux informations concernant les paramètres caractéristiques des écoulements permanents (nombre de Reynolds ou vitesse moyenne débitante), quelqu’en soit la nature, laminaire ou turbulent.

DOI: 10.3233/BIR-1978-153-407

Citation: Biorheology, vol. 15, no. 3-4, pp. 181-191, 1978

Authors: Chaturani, P. | Upadhya, V.S.

Article Type: Research Article

Abstract: A method has been developed for the study of the pulsatile flow of a couple stress fluid (blood) through circular tubes. The first, second and third approximate solution for flow velocity, wall shear, flow rate and relative viscosity have been obtained in closed form in terms of couple stress parameter α ¯ and η ¯ , pulsatile Reynolds number α , phase ϕ and time factor nt. The velocity and flow rate variations with different parameter have been shown graphically which indicate that they are almost in phase with the …pressure gradient. Further, a method has been suggested to determine experimentally the value of pulsatile Reynolds number α for blood. The effects of the parameters α ¯ , η ¯ , α , ϕ and nt on relative viscosity have been discussed. It is found that the theoretical results, obtained by the present analysis, are in good agreement with the experimental and other theoretical results on blood flow. Show more

DOI: 10.3233/BIR-1978-153-408

Citation: Biorheology, vol. 15, no. 3-4, pp. 193-201, 1978

Authors: Urban, J.P.G. | Holm, S. | Maroudas, A.

Article Type: Research Article

Abstract: By comparing results obtained in vivo on penetration of (35 S) sulphate and (3 H) methyl glucose into the intervertebral disc of adult dogs, with those calculated using Fick’s law, and diffusion and partition coefficients obtained in vitro , diffusion was shown to be the main mechanism for transport of small solutes into the intervertebral disc. About 40 percent of the endplate area was found to be permeable to small solutes. However the amount of solute entering via the endplate was shown to be less for negatively charged solutes such as the sulphate ion, than for neutral solutes …such as glucose, because of charge exclusion in the region of the nucleus. The mean turnover time of 470 days found for sulphated glycosaminoglycans in the disc is similar to that reported for dog articular cartilage. Show more

DOI: 10.3233/BIR-1978-153-409

Citation: Biorheology, vol. 15, no. 3-4, pp. 203-223, 1978