Biorheology - Volume 10, issue 3

Authors: Copley, A.L. | Scott Blair, G.W.

Article Type: Editorial

DOI: 10.3233/BIR-1973-10301

Citation: Biorheology, vol. 10, no. 3, pp. 293-293, 1973

Authors: Charman, Janet | Reid, Lynne

Article Type: Research Article

Abstract: Various combinations of temperature have been used for freezing, storage and thawing in order to assess their effect on sputum viscosity estimated with the Ferranti–Shirley viscometer. The temperature of thawing was found not to be critical and so rapid thawing at 25°C was preferred. Degradation was prevented by (i) rapid freezing in liquid nitrogen and storage at −13°C or below, (ii) both freezing and storage at −70°C. This was found for mucoid, mucopurulent and purulent sputum specimens from patients with chronic bronchitis, bronchiectasis, asthma and cystic fibrosis.

DOI: 10.3233/BIR-1973-10302

Citation: Biorheology, vol. 10, no. 3, pp. 295-301, 1973

Authors: Williams, A.R.

Article Type: Research Article

Abstract: Human erythrocytes in isotonic buffered (pH 7.4) saline/60 mM glucose containing 10% w/v Dextran 500 (a non-penetrating thickener) are reproducibly disrupted and/or fragmented when subjected to hydrodynamic shear stresses above a critical threshold. The haemoglobin-filled cell fragments (microspheres) resulting from cell break up closely resemble microdroplets formed from the break up of emulsion droplets, suggesting the possible application of elementary emulsion droplet theory. This theory provides an estimate of the tangential tension (Tm ) within the cell membrane at the point of rupture (Tm = 0.5–0.8 dyn/cm for the average cell, and 0.2–0.3 dyn/cm for the weakest cells after …5 min shear at 25°C). Erythrocyte fragmentation is due to the application of shear stress and not some other concomitant of the shearing process. Show more

DOI: 10.3233/BIR-1973-10303

Citation: Biorheology, vol. 10, no. 3, pp. 303-311, 1973

Authors: Williams, A.R.

Article Type: Research Article

Abstract: Tangential tensions are developed within the cell membranes of intact erythrocytes in viscous isotonic media, when they are subjected to large hydrodynamic shear stress. The magnitude of these tensions can be estimated by the application of elementary emulsion drop theory. The time taken for each cell membrane to rupture in response to a given tension enables an estimate to be made of the equivalent mechanical properties of the membrane. The values obtained are in excellent agreement with published estimates despite the fact that each author has used a different technique to apply the tension and a different theory to estimate …it. Show more

DOI: 10.3233/BIR-1973-10304

Citation: Biorheology, vol. 10, no. 3, pp. 313-319, 1973

Authors: Barbee, James

Article Type: Research Article

Abstract: The complete study of the rheological properties of human blood requires the use of a capillary viscometer. In a capillary viscometer, the blood in the feed reservoir must be continuously stirred in order to prevent sedimentation. The density difference between the plasma and the red cell that causes the red cells to settle in stationary blood may cause a radial concentration gradient when the blood is stirred with a rotating stirring bar. The radial concentration distribution of red cells in a healthy human blood sample contained in a capillary viscometer feed reservoir and stirred by a magnetic stirring bar …rotating on the bottom of the reservoir was investigated. The results indicate that centrifugal stirring can be used to agitate blood (and attain complete mixing and rouleaux breakup) in the feed reservoir of a capillary viscometer. This is accomplished at a fairly low rotational speed; plasma denaturation due to continuous production of fresh blood–air interface is negligible. Show more

DOI: 10.3233/BIR-1973-10305

Citation: Biorheology, vol. 10, no. 3, pp. 321-323, 1973

Authors: Dellimore, J.W. | Gosling, R.G.

Article Type: Research Article

Abstract: The mechanism of the decrease in erythrocyte volume on packing in a haematocrit centrifuge is considered. It is shown that experimental observations are inconsistent with the view that the change is caused, primarily, by a loss of intracellular medium. A possible mechanism is suggested.

DOI: 10.3233/BIR-1973-10306

Citation: Biorheology, vol. 10, no. 3, pp. 325-328, 1973

Authors: Mahalingam, R. | Poon, T.K.

Article Type: Research Article

Abstract: Based on rheological data for blood at various hematocrits and temperatures, a characterizing parameter to describe the behavior of formed elements can be derived by a quasi-thermodynamic approach. Further development on this parameter should enable one to establish a better basis for distinction between normal and abnormal erythrocytes and/or blood.

DOI: 10.3233/BIR-1973-10307

Citation: Biorheology, vol. 10, no. 3, pp. 329-341, 1973

Authors: Weihs, D.

Article Type: Research Article

Abstract: The mechanism of rapid acceleration from rest (lunging) in fishes is studied by means of a slender-body theory adapted to deal with unsteady, curvilinear large amplitude movements in water at high Reynolds numbers. The vortex wake is represented here by the circulation shed from the fins and body, calculated by means of indicial aerodynamic theory. The caudal fin is shown to play a dominant role in the production of the thrust force required for the tremendous accelerations measured in various species of fish (50 msec−2 for pike and 40 msec−2 for trout). The theoretical analysis also shows …that an optimal value of the ratio of thrust produced to energy expenditure is obtained when the caudal fin moves perpendicularly to the direction of movement of the fish’s centre of gravity, while being at a small angle of incidence. Filmed sequences of accelerating fish were examined. showing that for species with good lunging ability, the starting process is made up of three stages. First the fish, which was initially stretched straight curls up into an L-shaped curve. At the end of this, the tail swings around and moves in the manner predicted by the theory. This second stage is repeated in some cases and finally the fish straightens out moving at an angle to its original orientation, roughly proportional to the acceleration. The forces and moments on the fish calculated by the present method are in good agreement with these experimental observations. Show more

DOI: 10.3233/BIR-1973-10308

Citation: Biorheology, vol. 10, no. 3, pp. 343-350, 1973

Authors: Thurston, George B. | Wilkinson, Robert S.

Article Type: Research Article

Abstract: Through measurements of oscillatory flow birefringence of macromolecular solutions information on optical properties and relaxation effects are obtained for the molecules in a nearly unperturbed state. Small, oscillatory velocity gradients are used which are then directly proportional to the birefringence. Measurements are performed using an apparatus in which monochromatic light having circular polarization passes through a thin fluid layer which is confined between a fixed surface and an oscillating surface. The motion of the surface is monitored in amplitude and phase and from this the velocity gradient is determined. The light leaving the fluid now has an oscillating ellipticity which …is then monitored by passing it through a fixed plane analyzer and on to a photodetector. In the present apparatus the fluid is under precise temperature control and with its associated electronic instruments birefringence is measured in the frequency range from 0.02 to 1000 Hz. This apparatus is applied to the study of solutions of salmon sperm deoxyribonucleic acid, DNA. The relaxation times and magnitude of birefringence in solution are determined from measurements over a wide range of frequencies. This is done for several levels of shear degradation, the DNA being degraded by high speed chopping and by pressure cell induced flow. The ionic environment is considered as it influences the relaxation times. The method of oscillatory flow birefringence is also used to observe thermal denaturation of DNA. The birefringence undergoes a large change in magnitude and a reversal in sign as a consequence of the helix-coil transition. This method shows promise as a means for studying the kinetics of the process. Show more

DOI: 10.3233/BIR-1973-10309

Citation: Biorheology, vol. 10, no. 3, pp. 351-360, 1973

Authors: Meiselman, Herbert J. | Frasher, Wallace G. | Wayland, Harold

Article Type: Research Article

DOI: 10.3233/BIR-1973-10310

Citation: Biorheology, vol. 10, no. 3, pp. 361-373, 1973