bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Characteristics in Symmetrically Branched Tubes Simulating the Human Aortic Bifurcation
Authors: Walburn F. , Stein P.
Published: June 2009

The purpose of this study was to investigate the characteristics of flow in a symmetrically branched tube that had an area ratio (0.8) and angle of branching (70 deg) that were comparable to the human descending aorta. Velocity profiles were measured in steady and pulsatile flow with a laser Doppler anemometer. A region of transient flow reversal was found along the outer wall during minimal flow in the pulsatile cycle. Flow separation did not occur. For both steady and pulsatile flow, the shear rates were higher along the inner wall and lower along the outer wall in the region of the vertex of the bifurcation.
A Note on the Leakage of the New Omniscience/tm Pivoting Disk Prosthetic Heart Valve
Authors: Reif T. H. , Cocolin G. , Huffstutler M. C.
Published: June 2009

Measurements of the steady-state leakage of the new Medical Incorporated Omniscience/tm cardiac valve prosthesis are presented. These results are compared to those obtained from the SJM bi-leaflet cardiac valve/tm. The new Omniscience/tm valve shows significantly less leakage than the bi-leaflet valve. Consideration is given to problems in similitude as well as to the general nature of the flow field.
Spatial Kinematic Analysis of the Upper Extremity Using a Biplanar Videotaping Method
Authors: Langrana N. A.
Published: June 2009

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.
Effect of Protective Helmet Mass on Head/Neck Dynamics
Authors: Huston R. L. , Sears J.
Published: June 2009

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 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 simulation 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.
An Experimental Study of the Flow-Induced Mass Transfer Distribution in the Vicinity of Prosthetic Heart Valves
Authors: Galanga F. L. , Lloyd J. R.
Published: June 2009

An experimental study of the flow-induced mass transfer distribution in the vicinity of a model disk valve and a ball valve was conducted using electrochemical techniques. Reynolds numbers ranged from 1000 to 6000, which are characteristic of physiologic conditions. Local instantaneous and time average data are presented. It was found that the flow-induced mass transfer distribution was high in regions of both low and high shear. It was also demonstrated that the fluctuations in the mass transfer to the wall of the test section around the valve are significantly affected by valve design. The regions of high mass transfer measured in this study were found to correlate very closely to regions where thrombus formations have been documented in in-vivo studies.
Blood Freezing to Nearly Absolute Zero Temperature: −272.29°C
Authors: Cravalho E. G. , Huggins C. E. , Diller K. R. , Watson W. W.
Published: June 2009

Human erythrocytes were collected in ACD anticoagulant, glycerolized with an equal volume of 8.6 M glycerol, 8 percent glucose, 1 percent fructose, and 0.3 percent Na2 EDTA solution, sealed in glass ampules, and frozen to −272.29°C (0.86°K) in liquid helium under high vacuum. Biological assays performed after thawing and three-stage dialysis to remove the glycerol showed less than 1 percent hemolysis. Intracellular potassium, 2,3 DPG, and ATP were within the normal range.
Wave Speed in Noncircular Collapsible Ducts
Authors: Bonis M. , Ribreau C.
Published: June 2009

The wave speed in initially elliptical collapsible tubes was studied. The celerity c of pressure waves of small amplitude was calculated from the numerically defined area-pressure law of the buckled cross section. In addition to the fact that the wave speed variation with transmural pressure was strongly dependent upon the initial eccentricity of the cross section, the wave speed value was found to be discontinuous at the contact pressure pc and reached a minimum on the right-hand side of the discontinuity. These results were compared with experimental data obtained in an annular duct.
Elasticity of Small Pulmonary Veins in the Cat
Authors: Yen R. T. , Foppiano L.
Published: June 2009

The distensibility of pulmonary veins of cats, in the diametric range of 100–1200 μm, was studied as a function of the venous pressure pv and pleural pressure pPL, while the alveolar air pressure was maintained at zero (atmospheric). The resulting percentage changes in diameter normalized with respect to the diameter at ΔP of 10 cm H2O (D10) are expressed as function of ΔP = pv − pPL. It was found that in most cases the diameter varies linearly with ΔP: D/D10=1+α(pv−pPL) where α 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 α for vessels in the ranges of diameters of 100–200 μm, 200–400 μm, 400–800 μm and 800–1200 μm 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 μm and 800–1200 μm the compliance constant α is not affected by inflation of the lungs (changes in pleural pressure to more negative values). For smaller veins in the size ranges 100–200 μm and 200–400 μm our results show an increase in compliance from 2.05 to 2.79 and from 1.44 to 2.01 percent per cm H2O or Pa−1, respectively, when pleural pressure is changed from −10 to −15 cm H2O. When the pleural pressure is more negative than −15 cm H2O, however, the compliance of the vessels in the foregoing two size ranges is observed to decrease.
Biomechanical and Neurological Response of the Spinal Cord of a Puppy to Uniaxial Tension
Authors: Hung Tin-Kan , Chang Guan-Liang
Published: June 2009

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 for finite strain. Both the sensory response and motor function of the puppies were fully recovered within 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.
Force Wave Transmission Through the Human Locomotor System
Authors: Voloshin A. , Wosk J. , Brull M.
Published: June 2009

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.
ASME Centennial Historical Perspective Paper: Mechanics of Blood Flow
Authors: Skalak R. , Keller S. R. , Secomb T. W.
Published: June 2009

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.
Effect of Vessel Tapering on the Transition to Turbulent Flow: Implications in the Cardiovascular System
Authors: Walburn F. J. , Stein P. D.
Published: June 2009

The purpose of this study is to explore the effect of tapering upon the tendency of flow to become turbulent in straight symmetric tubes. Velocity was measured with a laser Doppler anemometer in plexiglass tubes which tapered 0.5 deg, 1.5 deg, and 2.5 deg measured from the centerline to the wall. These angles were comparable to the angles of tapering observed in the abdominal aorta of normal subjects, 1.5 deg ± 0.2 deg (mean ± SEM) (range 0 deg to 3 deg). The transition Reynolds number (based on the diameter of the tube at the piont of measurement) increased as the angle of tapering increased. When the angle of tapering was constant, the transition Reynolds number increased with increasing distance into the tapered section. These observations suggest that tapering of the abdominal aorta tends to promote laminar flow.
Effects of Nonlinear Strain-Dependent Permeability and Rate of Compression on the Stress Behavior of Articular Cartilage
Authors: Lai W. M. , Mow Van C. , Roth V.
Published: June 2009

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 / U˙h (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 → 0, and nonlinear flow-limit effect, i.e., M > 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.
Ultrasonic Measurement of Orthotropic Elastic Constants of Bovine Femoral Bone
Authors: Van Buskirk W. C. , Cowin S. C. , Ward R. N.
Published: June 2009

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.
Application of Hydroelastic Waves to the Removal of Small Gallstones
Authors: Wu Y. P. , Wong G. R. , Tau T. L.
Published: June 2009

We have used hydroelastic waves to remove small gallstones in hepatic and common bile ducts. These stones were shaken off by the action of progressive and reflected traveling waves. The mechanical properties of the bile ducts were measured and an analysis of the propagation of hydroelastic waves in the liver-bile ducts was made. A practical system was designed, constructed, and clinically tested to remove the gallstones that remained in the hepatic or common bile ducts after surgical operations. The system was found to be effective.
On the Hemolytic and Thrombogenic Potential of Occluder Prosthetic Heart Valves From In-Vitro Measurements
Authors: Figliola R. S. , Mueller T. J.
Published: June 2009

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 perfomed 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.
The Role of Secondary Variables in the Measurement of the Mechanical Properties of the Lumbar Intervertebral Joint
Authors: Tencer A. F. , Ahmed A. M.
Published: June 2009

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.
Flow Visualization in a Mold of an Atherosclerotic Human Abdominal Aorta
Authors: Walburn F. J. , Sabbah H. N. , Stein P. D.
Published: June 2009

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.
The Dynamic Response of Vascular Endothelial Cells to Fluid Shear Stress
Authors: Dewey C. F. , Bussolari S. R. , Gimbrone M. A. , Davies P. F.
Published: June 2009

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 (≃ 1.0–1.5 × 105 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.
Vesicle Transport in Arterial Endothelium and the Influence of Mechanical Factors on Macromolecular Permeability
Authors: Chien S. , Weinbaum S.
Published: June 2009

The time-dependent transport of labeled vesicles in arterial endothelium has been modeled, taking into account the space-varying electrodynamic and hydrodynamic forces and the steric hindrance of vesicle attachment by the already attached vesicles. With the aid of laboratory model experiments to assess the steric hindrance effect, theoretical computation has been made on time-dependent labeled vesicle concentration profiles, and the results agree reasonably well with the published experimental data. Oscillatory length variations (5–10 Hz for 15 min) and elevation of transmural pressure (from 0–100 and 200 mmHg) caused increases in 125I-albumin uptake by the canine common carotid artery. Theoretical computations based on ultrastructural determination of free vesicle density indicate that there was negligible enhancement of vesicle diffusion by these mechanical disturbances. The increases in albumin uptake following length oscillation and pressure elevation to 100 mmHg were accompanied by increases in luminal surface area, and the albumin permeability remained unchanged. The albumin permeability was elevated following pressure elevation to 200 mmHg, and this was attributable to (a) a decrease in transendothelial diffusion distance, and (b) facilitation of vesicle loading into the vesicles.
Correlation of Human Arterial Morphology With Hemodynamic Measurements in Arterial Casts
Authors: Friedman M. H. , Hutchins G. M. , Bargeron C. B. , Deters O. J. , Mark F. F.
Published: June 2009

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<0.005) was between IT and “pulse shear rate” (PSR), defined by analogy with pulse pressure. Sudanophilia also correlated negatively with PSR (p<0.01). Medial thickness correlated positively with shear rate, and most strongly with the mean (i.e., time-average) rate (p<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 inter facial shear.
Location of Early Atheroma in the Human Coronary Arteries
Authors: Fox B. , Seed W. A.
Published: June 2009

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.
The Significance of Electromechanical and Osmotic Forces in the Nonequilibrium Swelling Behavior of Articular Cartilage in Tension
Authors: Grodzinsky A. J. , Roth V. , Myers E. , Grossman W. D. , Mow V. C.
Published: June 2009

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.