Showing papers in "Journal of Biomechanical Engineering-transactions of The Asme in 1981"
TL;DR: In this article, the authors present a sketch of the history and scope of the field of bio-physiology and discuss the meaning of the Constitutive Equation and the flow properties of blood.
Abstract: Prefaces. 1. Introduction: A sketch of the History and Scope of the Field. 2. The Meaning of the Constitutive Equation. 3. The Flow Properties of Blood. 4. Mechanics of Erythrocytes, Leukocytes, and Other Cells. 5. Interaction of Red Blood Cells with Vessel Wall, and Wall Shear with Endothelium. 6 Bioviscoelastic Fluids. Bioviscoelastic Solids. 8. Mechanical Properties and Active Remodeling of Blood Vessels. 9. Skeletal Muscle. 10. Heart Muscle. 11. Smooth Muscles. 12. Bone and Cartilage. Indices
3,670 citations
TL;DR: Preliminary studies indicate that certain endothelial cell functions, including fluid endocytosis, cytoskeletal assembly and nonthrombogenic surface properties, also are sensitive to shear stress, which suggests that fluid mechanical forces can directly influence endothelialcell structure and function.
Abstract: We have developed an in-vitro system for studying the dynamic response of vascular endothelial cells to controlled levels of fluid shear stress. Cultured monolayers of bovine aortic endothelial cells are placed in a cone-plate apparatus that produces a uniform fluid shear stress on replicate samples. Subconfluent endothelial cultures continuously exposed to 1-5 dynes/cm2 shear proliferate at a rate comparable to that of static cultures and reach the same saturation density (congruent to 1.0-1.5 X 10(5) cells/cm2). When exposed to a laminar shear stress of 5-10 dynes/cm2, confluent monolayers undergo a time-dependent change in cell shape from polygonal to ellipsoidal and become uniformly oriented with flow. Regeneration of linear "wounds" in confluent monolayer appears to be influenced by the direction of the applied force. Preliminary studies indicate that certain endothelial cell functions, including fluid endocytosis, cytoskeletal assembly and nonthrombogenic surface properties, also are sensitive to shear stress. These observations suggest that fluid mechanical forces can directly influence endothelial cell structure and function. Modulation of endothelial behavior by fluid shear stresses may be relevant to normal vessel wall physiology, as well as the pathogenesis of vascular diseases, such as atherosclerosis.
1,140 citations
TL;DR: The results obtained to date suggest that endothelial cell morphology and orientation around a branch vessel may be a natural marker or indicator of the detailed features of blood flow.
Abstract: A quantitative study of the en face size and shape of endothelial cells from aortic intercostal ostia has been carried out in rabbits. Photomicrographs were taken from vascular casts of the rabbit aorta and the endothelial cell outlines were analyzed quantitatively using a digitizer and digital computer. The morphology of the endothelial cells was described using 8 calculated parameters (area, perimeter, length, width, angle of orientation, width: length ratio, axis-intersection ratio and shape index). Marked changes in cell morphology were found in the regions proximal and distal to ostia as well as around flow dividers. Cells on the aorta are aligned with the flow direction, and the endothelial cells within the ostia have an angle of orientation of approximately 45 deg to the axis of the vessel. The results obtained to date suggest that endothelial cell morphology and orientation around a branch vessel may be a natural marker or indicator of the detailed features of blood flow.
329 citations
TL;DR: It was found that the quasi-linear viscoelastic theory can adequately describe the time and history-dependent rheological properties of the canine medial collateral ligament.
Abstract: The viscoelastic properties of the canine medial collateral ligament (MCL) were investigated. Stress-strain relationships at different strain rates, long-term stress relaxation and cyclic stress-strain curves of the MCL were obtained experimentally using a bone-MCL-bone preparation. The experimental data were used in conjunction with the quasi-linear viscoelastic theory as proposed by Fung [15] to characterize the reduced relaxation function, G(t) and elastic response sigma e (epsilon) of this tissue. It was found that the quasi-linear viscoelastic theory can adequately describe the time and history-dependent rheological properties of the canine medial collateral ligament.
272 citations
TL;DR: The digital flexor tendons of the miniature swine were studied and it was found that training augments the strength of the tendon insertion site, but has minimal effect on the tendon substance.
Abstract: The digital flexor tendons of the miniature swine were studied after 12 mo of running exercise. Using a newly developed methodology whereby the properties of tendon substance and tendon-bone composite are measured simultaneously, it was found that training augments the strength of the tendon insertion site, but has minimal effect on the tendon substance. Biochemical analyses also showed that the collagen concentration in the tendon substance remains unchanged following exercise. There was also moderate, but not significant, tendon hypertrophy. The present results on flexor tendon differ from those previously obtained for the swine digital extensors [6]. Such difference in response to functional stress may be attributed to the biochemical composition and mechanical properties of these tissues.
242 citations
TL;DR: This investigation studied the influence of M and Ro = koHA/Uh (where HA is the elastic equilibrium modulus of the solid matrix, h is the tissue's thickness and U is the rate of compression applied onto the surface via a rigid, porous, free-draining filter) on the stress history of circular plugs of cartilage specimens attached to the bone.
Abstract: The compressive viscoelastic behavior of articular cartilage, a fiber-reinforced, porous, permeable solid matrix filled with water, is predominately governed by the flow of the interstitial water within the tissue and its exudation across the articular surface. The fluid flow is in turn governed by the permeability of the tissue and the loading imposed upon its surface. But for articular cartilage, the permeability depends nonlinearly on the strain; k = ko exp (Me). Here, M is the nonlinear flow-limiting parameter and e is the dilatation. In this investigation, we studied the influence of M and Ro = koHA/Uh (where HA is the elastic equilibrium modulus of the solid matrix, h is the tissue's thickness and U is the rate of compression applied onto the surface via a rigid, porous, free-draining filter) on the stress history of circular plugs of cartilage specimens attached to the bone. It was found that these two parameters have profound effects on the predicted compressive stress history. For very large Ro, the fluid flow effects become negligible. For small Ro and large M, large instantaneous compressive stresses several times larger than those observed at equilibrium are predicted. This amplification of compressive stress is due to the increase of importance of the relative fluid flow effect, i.e., Ro leads to 0, and nonlinear flow-limit effect, i.e., M greater than 0. Also, the theoretical curves predict that the rate of increase of stress initially decreases (convex) and finally becomes a constant. The results of our 5 percent offset compression experiments are in good agreement with the theoretical predictions.
233 citations
TL;DR: Using a pulse transmission ultrasound method, the elastic properties of bone samples taken from along the length and around the periphery of a bovine femur are determined using nine of the orthotropic elastic constants.
Abstract: Using a pulse transmission ultrasound method, we have determined the elastic properties of bone samples taken from along the length and around the periphery of a bovine femur. Twenty specimens, in the form of 5-mm cubes, were tested. All nine of the orthotropic elastic constants were determined for each specimen. Analysis of our data indicate that there are statistically significant variations from the usual assumption of transverse isotropy.
178 citations
TL;DR: The use of simultaneous streaming potential and stiffness data with an appropriate theory appears to be an important tool for assessing the relative contribution of fluid flow, intrinsic matrix viscoelasticity, or other molecular mechanisms to energy dissipation in cartilage.
Abstract: The compressive stiffness of articular cartilage was examined in oscillatory confined compression over a wide frequency range including high frequencies relevant to impact loading. Nonlinear behavior was found when the imposed sinusoidal compression amplitude exceeded a threshold value that depended on frequency. Linear behavior was attained only by suitable control of the compression amplitude. This was enabled by real time Fourier analysis of data which provided an accurate assessment of the extent of nonlinearity. For linear viscoelastic behavior, a stiffness could be defined in the usual sense. The dependence of the stiffness on ionic strength and proteoglycan content showed that electrostatic forces between matrix charge groups contribute significantly to cartilage's compressive stiffness over the 0.001 to 20 Hz frequency range. Sinusoidal streaming potentials were also generated by oscillatory compression. A theory relating the streaming potential field to the fluid velocity field is derived and used to interpret the data. The observed magnitude of the streaming potential suggests that interstitial fluid flow is significant to cartilage behavior over the entire frequency range. The use of simultaneous streaming potential and stiffness data with an appropriate theory appears to be an important tool for assessing the relative contribution of fluid flow, intrinsic matrix viscoelasticity, or other molecular mechanisms to energy dissipation in cartilage. This method is applicable in general to hydrated, charged polymers.
168 citations
TL;DR: Comparison shows that healthy subjects definitely possess a more efficient shock-absorbing capacity than do those subjects with joint disorders, and that degenerative changes in joints reduce their shock absorbing capacity, which leads to overloading of the next shock absorber in the locomotor system.
Abstract: A method to measure the capability of the human shock absorber system to attenuate input dynamic loading during the gait is presented. The experiments were carried out with two groups: healthy subjects and subjects with various pathological conditions. The results of the experiments show a considerable difference in the capability of each group's shock absorbers to attenuate force transmitted through the locomotor system. Comparison shows that healthy subjects definitely possess a more efficient shock-absorbing capacity than do those subjects with joint disorders. Presented results show that degenerative changes in joints reduce their shock absorbing capacity, which leads to overloading of the next shock absorber in the locomotor system. So, the development of osteoarthritis may be expected to result from overloading of a shock absorber's functional capacity.
130 citations
TL;DR: Changes in the tensile force induced by changing the bath neutral salt concentration surrounding the specimen appear to be rate-limited by the diffusion of salt into the specimen, which indicates that Ca++ and H+ ions are binding to the cartilage matrix macromolecules.
Abstract: Studies were conducted of some of the nonequilibrium, electrolyte-activated, electromechanical and osmotic processes that can affect the tensile properties of articular cartilage. We measured changes in tensile force that were induced by altering the ionic environment of strips of cartilage held at fixed length. We compared the kinetics of changes in these macroscopically measured isometric tensile forces to theoretical estimates of the time constants that characterize the underlying physical and chemical mechanisms occurring within the cartilage specimens during the experiment. Changes in the tensile force induced by changing the bath neutral salt concentration surrounding the specimen appear to be rate-limited by the diffusion of the salt into the specimen. That is, the mechanical stress relaxation process resulting from changes in salt concentration seems to be occurring at least as rapidly as the diffusion of salt into the matrix. When the bath concentration of CaCl2 or HCl is varied, the rate of change in the resulting isometric stresses indicates that Ca++ and H+ ions are binding to the cartilage matrix macromolecules.
121 citations
TL;DR: The present communication presents a single microprobe technique for measuring tissue thermal properties based on the dissipation of a measured amount of energy and the observation of the resulting temperature rise a given time later, which results were independent of the probe shape, size and properties.
Abstract: The present communication presents a single microprobe technique for measuring tissue thermal properties based on the dissipation of a measured amount of energy and the observation of the resulting temperature rise a given time later. An advantage of this method is that the effective sampling volume can be varied by varying the measurement time. Using a measurement time of a few seconds, the sampling volume was estimated to be several orders of magnitude greater than the probe volume. Hence artifacts due to probe-induced trauma or stress would be insignificant. Additional advantages of the technique are: the results were independent of the probe shape, size and properties, and hence represents absolute measurements without the need for calibration; the required electronics and computations are simple; the determination of thermal conductivity requires only a single measurement; and comparison of data at different measurement times yields a clear and unequivocal indication of nonconductive contributions of heat transfer, if present.
TL;DR: From measurements, the characteristic length for bone in couple stress theory is obtained and the existence of couple stress is demonstrated by measuring the effect of size on apparent stiffness of compact bone in quasi-static torsion.
Abstract: Couple stress theory, which admits an internal moment per unit area as well as the usual force per unit area, is a generalization of classical elasticity. Experimentally we have demonstrated the existence of couple stress by measuring the effect of size on apparent stiffness of compact bone in quasi-static torsion. From these measurements, we obtain the characteristic length for bone in couple stress theory.
TL;DR: In this article, a working model consisting of an elastic membrane filled with viscous fluid was proposed for understanding the viscous and viscoelastic behavior of blood flow at junctions, through stenoses, in bends and in capillary blood vessels.
Abstract: The historical development of the mechanics of blood flow can be traced from ancient times, to Leonardo da Vinci and Leonhard Euler and up to the present times with increasing biological knowledge and mathematical analysis. In the last two decades, quantitative and numerical methods have steadily given more complete and precise understanding. In the arterial system wave propagation computations based on nonlinear one-dimensional modeling have given the best representation of pulse wave propagation. In the veins, the theory of unsteady flow in collapsible tubes has recently been extensively developed. In the last decade, progress has been made in describing the blood flow at junctions, through stenoses, in bends and in capillary blood vessels. The rheological behavior of individual red blood cells has been explored. A working model consists of an elastic membrane filled with viscous fluid. This model forms a basis for understanding the viscous and viscoelastic behavior of blood.
TL;DR: Structural properties of growing canine long bones were determined from three and four-point bending tests and found to follow a biphasic growth process, with a rapid increase in bending strength and moment of inertia from l to 24 wk of age and a substantially decreased rate thereafter to maturity.
Abstract: Structural properties of growing canine long bones were determined from three and four-point bending tests. Mechanical and geometric properties were found to follow a biphasic growth process, with a rapid increase in bending strength and moment of inertia from 1 to 24 wk of age and a substantially decreased rate thereafter to maturity. Predicted bone tissue material properties were also found to follow this biphasic developmental process.
TL;DR: It is argued and partially demonstrated that the features of Pauwels' qualitative theory of functional adaptation of bone tissue are expressed mathematically by the cubic approximation to the theory of internal remodeling presented by Cowin and Hegedus.
Abstract: In this paper it is argued and partially demonstrated that the features of Pauwels' qualitative theory of functional adaptation of bone tissue are expressed mathematically by the cubic approximation to the theory of internal remodeling presented by Cowin and Hegedus. Complete solutions for the steady stress and steady strain situations in the cubic approximation to the theory of internal remodeling are presented. The cubic remodeling rate equation is shown to correspond closely to the remodeling equation suggested by Kummer for the qualitative theory of Pauwels.
TL;DR: From an analysis of the fluid mechanical data, it appears possible to separate the effects of bifurcation geometry and the shape of the arterial cross section on interfacial shear.
Abstract: A realistic pulsatile flow was passed through a cast of the aortic bifurcation of a 63-yr-old male with mild atherosclerosis, and a laser Doppler anemometer was used to measure fluid velocities in the cast at 15 selected sites near the lateral and medial walls. Intimal, medial and adventitial thicknesses were measured and sudanophilia was scored at corresponding sites in the vessel from which the cast had been made. A negative correlation was found between intimal thickness (IT) and wall shear rate. The strongest negative correlation (p less than 0.005) was between IT and "pulse shear rate" (PSR), defined by analogy with pulse pressure. Sudanophilia also correlated negatively with PSR (p less than 0.01). Medial thickness correlated positively with shear rate, and most strongly with the mean (i.e., time-average) rate (p less than 0.005). From an analysis of the fluid mechanical data, it appears possible to separate the effects of bifurcation geometry and the shape of the arterial cross section on interfacial shear.
TL;DR: A two-dimensional, finite element model of a single-posted, metal, tibial prosthetic component implanted with PMMA in the proximal tibia is developed and the effects of post lengthening upon the maximum stress values around the post are highly dependent upon the assumed properties of the cancellous bone.
Abstract: A two-dimensional, finite element model of a single-posted, metal, tibial prosthetic component implanted with PMMA in the proximal tibia is developed. The effects upon the stresses at the PMMA-bone interface and in the cancellous bone around the component due to the inclusion in the model of the cortical shell and the heterogeneity and anisotropy of the cancellous bone, are demonstrated. Various lengths of the fixation post are considered. The cortical shell adds support and stiffness to the bone structure, and allows generation of significant stresses proximally. The heterogeneity of the cancellous bone, as assumed here, dictates the form of the stress distributions and the magnitudes and locations of the peak stress values around the post of the component. Peak stress values can occur at locations proximal to the post tip. The anisotrophy of the cancellous bone significantly alters the magnitudes of the stresses. Lower stresses along the post interface and higher stresses beneath the plate of the prosthesis are seen in the anisotropic models. Lengthening of the fixation post reduces stresses proximally, but the effects of post lengthening upon the maximum stress values around the post are highly dependent upon the assumed properties of the cancellous bone.
TL;DR: In this paper, an experimental investigation was conducted to determine the magnitude of shear stresses and areas of stasis of several types of prosthetic occluder heart valves in an axisymmetric aortic-shaped test chamber and an aqueous-glycerine solution.
Abstract: An experimental investigation was conducted to determine the magnitude of shear stresses and areas of stasis of several types of prosthetic occluder heart valves. These experiments were performed in a steady-flow test loop using an axisymmetric aortic-shaped test chamber and an aqueous-glycerine solution. The flow loop produced a low-turbulence intensity and uniform mean velocity profile upstream of the test chamber. Tests were performed on a Kay-Shiley disk, a Bjork-Shiley tilting disk and Starr-Edwards Models 1260 and 2320 ball prostheses at Reynolds numbers between 2000 and 6200. Momentum transfer and turbulence data were obtained both around and distal to the valve occluders using laser Doppler and hot-film anemometry. The region directly surrounding the valve occluders contained the largest stresses measured. Aortic wall shear measurements revealed magnitudes potentially damaging to the vessel lining. Regions of slowly moving separated flow found to exist in these occluder valve flow fields correlated with clinical findings of thrombus formation.
TL;DR: An in-vivo experimental method was developed to measure the stress-strain relationship of a spinal Cord segment of anesthetized puppies and both the sensory response and motor function of the puppies were fully recovered within the 5 days after the spinal cord segment in the first lumbar region was elongated once by 50 percent or less.
Abstract: An in-vivo experimental method was developed to measure the stress-strain relationship of a spinal cord segment of anesthetized puppies. A pseudo Young's modulus was defined for the linear region followed by a nonlinear rheological behavior of finite strain. Both the sensory response and motor function of the puppies were fully recovered within the 5 days after the spinal cord segment in the first lumbar region was elongated once by 50 percent or less. The usefulness of the in-vivo experiments was further elaborated by demonstrating the large artifacts that could be associated in an in-vitro experiment.
TL;DR: The location of early atheroma with vessel geometry in the major coronary arteries of subjects dying of noncardiovascular causes under 40 yr of age is correlated with vessel architecture in these vessels to determine patterns determined by local mechanical factors.
Abstract: We have correlated the location of early atheroma with vessel geometry in the major coronary arteries of subjects dying of noncardiovascular causes under 40 yr of age. We analyzed only those vessels affected minimally by very early (fatty) disease. In each of the three major branches, disease was concentrated close to the entrance and diminished with distance downstream. Circumferential distribution of disease was also not random. In the right coronary artery, lesions were concentrated on the inner wall of the major curvature. Immediately downstream of the entrances of both branches of the left coronary artery, the flow-dividing walls were spared. Further downstream in the left anterior, descending branch plaques followed a spiral distribution. We believe these patterns may be determined by local mechanical factors.
TL;DR: Four secondary independent variables, load axis position, nucleus pressure, the number of initial cycles and the load duration are shown to significantly affect the dependent variable, displacement.
Abstract: A general method is proposed for the testing of the structural properties of lumbar intervertebral joints. The apparatus designed includes a loading jig capable of applying any wrench resultant load while allowing unconstrained motion of the specimen and a three-dimensional displacement transducer for measurement of principal and coupled displacements. Four secondary independent variables, load axis position, nucleus pressure, the number of initial cycles and the load duration are shown to significantly affect the dependent variable, displacement. When performing this type of experiment, these secondary variables must be standardized and controlled.
TL;DR: A one-dimensional model of combined convective and diffusive mass transfer in a hemodialyser is presented and it is found that the overall clearance is always less than the sum of dialytic and UF clearances due to interaction between convectiveand diffusive transfers.
Abstract: A one-dimensional model of combined convective and diffusive mass transfer in a hemodialyser is presented. Solutions and results are given for two regimes of ultrafiltration (UF): at low transmembrane pressures when UF flow is proportional to transmembrane pressure and in the limit of large transmembrane pressures when UF is limited by protein concentration polarization. It is found that the overall clearance is always less than the sum of dialytic and UF clearances due to interaction between convective and diffusive transfers. For a given UF flow the clearance is not sensitive to UF flux distribution along the membrane. Model predictions of urea clearance are in good agreement with measurements obtained in vitro with saline on hemodialysers equipped with a polyacrylonitrile membrane.
TL;DR: In this paper, it was shown that the crash helmet can contribute to the hyperflexion/hyperextension injury hazard and that the proposed restraining devices can potentially provide protection against this hazard.
Abstract: The crash helmet which provides protection against injury due to direct head impact may actually contribute to injury in indirect head impact (e.g., hyperflexion or "whiplash") situations because of the added mass of the helmet on the head/neck system. It has been suggested that it may be possible to reduce this hyperflexion/hyperextension injury hazard while retaining the beneficial protection against direct impact through use of the helmet restraining collars, such as styrofoam or inflatable airbags. These claims are quantitatively and qualitatively examined and discussed in this paper. The UCIN HEAD/NECK computer stimulation model is used for the quantitative analysis. It is shown that the helmet can indeed contribute to the hyperflexion/hyperextension injury hazard and that the proposed restraining devices can potentially provide protection against this hazard.
TL;DR: Two different elastic models proposed for elastic soft tissues are studied, simple elongation of a cylindrical bar and the inflation of a spherical thick shell are studied and the material coefficients characterizing the elastic model are obtained via comparing theoretical results with existing experiments on tissues.
Abstract: Due to physiological structure of most of the soft biological tissues, measurable stresses develop after the specimen has been stretched to many hundreds of percent of its relaxed length. Therefore, the nonlinear stress-strain relations developed for vulcanized rubber cannot be applied to soft tissues, which are constitutionally much more nonlinear than other engineering materials. In this article, using two different elastic models proposed for elastic soft tissues, simple elongation of a cylindrical bar and the inflation of a spherical thick shell, which is deemed to be a model for a left ventricle, are studied and the material coefficients characterizing the elastic model are obtained via comparing theoretical results with existing experiments on tissues. Furthermore, the elastic stiffnesses which are very important for physiologists and cardiologists are discussed and the consistency of the result with experiments are indicated.
TL;DR: The results of the joint kinematics of the test subjects performing a diagonal reaching activity with and without an orthosis (or an assistive device) are presented.
Abstract: A biplanar videotaping system is used to generate spatial kinematic data of an upper extremity motion. The technique is based upon the characterization of each segment by four points in three-dimensional space using biplanar videotaping and subsequent analysis by computer-aided descriptive geometry. The tests were conducted to determine the system's accuracy and repeatability. The results of the joint kinematics of the test subjects performing a diagonal reaching activity with and without an orthosis (or an assistive device) are presented.
TL;DR: It was found that in most cases the diameter varies linearly with delta P: D/D10 = 1 + alpha (p upsilon - p PL) where alpha is the compliance coefficient, and that smaller veins of the cat are more compliant than larger veins.
Abstract: The distensibility of pulmonary veins of cats, in the diametric range of 100-1200 micrometer, was studied as a function of the venous pressure p upsilon and pleural pressure p PL, while the alveolar air pressure was maintained at zero (atmospheric). The resulting percentage changes in diameter normalized with respect to the diameter at delta P of 10 cm H20 (D10) are expressed as function of delta = p upsilon - p PL. It was found that in most cases the diameter varies linearly with delta P: D/D10 = 1 + alpha (p upsilon - p PL) where alpha is the compliance coefficient. The results show that smaller veins of the cat are more compliant than larger veins. For example, when pleural pressure is -10 cm H2O, the values of alpha for vessels in the ranges of diameters of 100-200 micrometer, 200-400 micrometer, 400-800 micrometer and 800-1200 micrometer are, respectively, 2.05, 1.44, 1.08 and 0.71 percent per cm H2O or Pa-1. The effects of lung inflation on the distensibility of pulmonary veins are also studied. Our results show that for vessel sizes in the range of 400-800 micrometer and 800-1200 micrometer the compliance constant alpha is not affected by the inflation of the lungs (changes in pleural pressure to more negative values). For smaller veins in the size ranges 100-200 micrometer and 200-400 micrometer our results show an increase in compliance from 2.05 to 2.79 and from 1.44 to 2.01 percent per cm H20 or Pa-1, respectively, when pleural pressure is changed from -10 to -15 cm H20. When the pleural pressure is more negative than -15 cm H20, however, the compliance of the vessels in the foregoing two size ranges is observed to decrease.
TL;DR: The theoretical predictions of the present model compare very favorably with experimental results for the enhanced uptake found in blue versus white areas reported in morphological studies of the endothelial surface.
Abstract: In this paper, the two-phase arterial wall model developed by Weinbaum and Caro [2] has been extended to obtain analytic solutions for the steady-state flux, uptake and concentration of macromolecules in the arterial wall due to the presence of periodically dispersed local sites of enhanced permeability. In the endothelial cell layer these sites are believed to be associated with the dying and regeneration of individual cells in the endothelial monolayer. Nir and Pfeffer [9] obtained similar solutions for a single dying cell in an otherwise undamaged endothelial cell layer. However this model requires that multiple cell turnover sites be spaced sufficiently far apart such that no interaction between neighboring sites takes place and hence cannot be applied to closely spaced endothelial injuries which have been observed experimentally in physiological studies. The theoretical predictions of the present model compare very favorably with experimental results for the enhanced uptake found in blue versus white areas reported in morphological studies of the endothelial surface (Bell, et al. [10, 11]).
TL;DR: Flow in a mold of an atherosclerotic human abdominal aorta and common iliac arteries was studied by flow visualization at a mean Reynolds number of 500 during both pulsatile and steady flow.
Abstract: Flow in a mold of an atherosclerotic human abdominal aorta and common iliac arteries was studied by flow visualization at a mean Reynolds number of 500 during both pulsatile and steady flow. Flow separation and transient flow reversals were found distal to atherosclerotic plaques during pulsatile flow; whereas flow separation resulting in regions of permanent eddies were observed distal to plaques only during steady flow.