Rheologic Behavior of Bovine Calf Serum

Recent studies have illuminated the rheological behavior of synovial fluid and the role of protein and hyaluronan (HA). However, with respect to artificial joint replacement in standardized wear simulations, bovine serum is used as fluid test medium. Little is known about the rheological characteristics of bovine serum, which are needed for precise tribological investigations. The steady shear viscosity η of bovine calf serum is determined for protein concentrations used in standardized wear simulations depending on shear rate γ˙ and temperature T. Additionally, the density of the serum is determined for both protein concentrations. The results show shear thinning behavior of bovine calf serum with a nearly Newtonian behavior in the range of high shear rates. Within the range of high shear rates, mean viscosities of η = 0.82–0.88 mPa·s were found for protein concentrations of 20 g/L and mean viscosities of η = 0.88–0.94 mPa·s for 30 g/L, decreasing with temperature. Densities of 1.004–1.005 g/cm3 and 1.007–1.008 g/cm3 were found for 20 and 30 g/L protein concentrations, respectively.

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Platelet von Willebrand factor: evidence for its involvement in platelet adhesion to collagen

Blood ◽

10.1182/blood.v70.4.1214.bloodjournal7041214 ◽

1987 ◽

Vol 70 (4) ◽

pp. 1214-1217

Author(s):

E Fressinaud ◽

D Baruch ◽

C Rothschild ◽

HR Baumgartner ◽

D Meyer

Keyword(s):

Shear Rate ◽

Von Willebrand Factor ◽

Platelet Adhesion ◽

Von Willebrand Disease ◽

High Shear ◽

Shear Rates ◽

High Shear Rates ◽

Von Willebrand ◽

Willebrand Factor

Although it is well established that plasma von Willebrand Factor (vWF) is essential to platelet adhesion to subendothelium at high shear rates, the role of platelet vWF is less clear. We studied the respective role of both plasma and platelet vWF in mediating platelet adhesion to fibrillar collagen in a parallel-plate perfusion chamber. Reconstituted blood containing RBCs, various mixtures of labeled washed platelets and plasma from controls or five patients with severe von Willebrand disease (vWD), was perfused through the chamber for five minutes at a shear rate of 1,600 s-1. Platelet-collagen interactions were estimated by counting the radioactivity in deposited platelets and by quantitative morphometry. When the perfusate consisted of normal platelets suspended in normal plasma, platelet deposition on the collagen was 24.7 +/- 3.6 X 10(6)/cm2 (mean +/- SEM, n = 6). Significantly less deposition (16 +/- 2.3) was observed when vWD platelets were substituted for normal platelets. In mixtures containing vWD plasma, significantly greater deposition (9 +/- 2.2) was obtained with normal than with vWD platelets (1 +/- 0.4) demonstrating a role for platelet vWF in mediating the deposition of platelets on collagen. Morphometric analysis confirmed these data. Our findings indicate that platelet, as well as plasma, vWF mediates platelet-collagen interactions at a high shear rate.

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Rheological and Wetting Properties of Environmentally Acceptable Lubricants (EALs) for Application in Stern Tube Seals

Lubricants ◽

10.3390/lubricants6040100 ◽

2018 ◽

Vol 6 (4) ◽

pp. 100 ◽

Cited By ~ 2

Author(s):

F. Borras ◽

Matthijn de Rooij ◽

Dik Schipper

Keyword(s):

Surface Tension ◽

Shear Thinning ◽

Mineral Oil ◽

Experimental Techniques ◽

High Shear ◽

Shear Rates ◽

Wetting Properties ◽

High Shear Rates ◽

Significant Difference ◽

Newtonian Behavior

The use of Environmentally Acceptable Lubricants (EALs) for stern tube lubrication is increasing. Although the machine components of a sailing vessel are designed to operate together with mineral oil-based lubricants, these are being replaced by the less environmentally harmful EALs. Little is known about the rheological performance of EALs in particular at the high shear rates that occur in stern tube seals. In this study, the viscosity and wetting properties of a set of different EALs is analysed and compared to traditional mineral oil-based lubricants using a set of experimental techniques. Some of the EALs present Newtonian behavior whereas other show shear thinning. No significant difference in surface tension was observed between the different lubricants.

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Correction of the platelet adhesion defect in delta-storage pool deficiency at elevated hematocrit--possible role of adenosine diphosphate

Blood ◽

10.1182/blood.v87.10.4214.bloodjournal87104214 ◽

1996 ◽

Vol 87 (10) ◽

pp. 4214-4222 ◽

Cited By ~ 18

Author(s):

HJ Weiss ◽

B Lages ◽

T Hoffmann ◽

VT Turitto

Keyword(s):

Platelet Adhesion ◽

Thrombus Formation ◽

Adenosine Diphosphate ◽

Dense Granule ◽

High Shear ◽

Shear Rates ◽

Storage Pool ◽

Corrective Effect ◽

High Shear Rates

Previous studies on patients with storage pool deficiency (SPD) who are specifically deficient in platelet dense granules (delta-SPD) have suggested a role for dense granule substances, in all likelihood adenosine diphosphate (ADP), in mediating thrombus formation on subendothelium at high shear rates. The role of dense granule substances in mediating platelet adhesion appears to be more complicated Previous studies in delta-SPD suggested an adhesion defect that was strongly influenced by the patient's hematocrit (Hct) value. To explore further the possibility that red blood cells (RBCs) may influence the role that platelet storage granules play in mediating adhesion at high shear rates, we have measured adhesion (and thrombus formation) throughout a preselected range of Hct values (30% to 60%) in normal subjects and in patients with delta-SPD. The present studies confirm the defect in platelet adhesion in patients with delta-SPD, most significantly at Hct values of 30% to 40%. This defect (but not that of thrombus formation) can be completely corrected by the addition of RBCs. The correction of the platelet adhesion defect by RBCs was specific for delta-SPD; it was not observed in either von Willebrand's disease or thrombasthenia. Studies performed on normal blood under conditions that could be expected to block any effect of ADP on adhesion and an analysis of the type of adhesion defect in delta-SPD suggest that ADP may be involved in the process required for platelet spreading on the subendothelium. The corrective effect of RBCs on platelet adhesion in delta-SPD appears to be chemical rather than physical in nature, possibly due to shear-induced release of RBC ADP or to other recently described properties of RBCs that enhance collagen- induced platelet interactions.

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Creating a Low Volume Model of Occlusive Thrombosis

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53624 ◽

2011 ◽

Author(s):

Andrea N. Para ◽

David Ku

Keyword(s):

Plaque Rupture ◽

High Shear ◽

Industrialized Countries ◽

Heart Attacks ◽

Shear Rates ◽

Coronary Syndrome ◽

High Shear Rates ◽

Model Independent ◽

Delayed Phase

Heart disease is the leading cause of death in industrialized countries. Heart attacks and strokes can cause mortality within an hour following plaque rupture. Unfortunately, as it is impossible to study heart attacks in real time, little is known about the mechanism which contributes to mortality. The mechanism of thrombosis under high shear is currently in dispute. Some investigators have shown that GPIIb/IIIa is important in stabilizing a thrombus under high shear conditions.[1] We have independently shown occlusive thrombosis in a gravity-fed tubular stenosis is predicated on a delayed phase of Rapid Platelet Accumulation (RPA) that occurs only at pathologically high shear rates with fast occlusion times consistent with Acute Coronary Syndrome.[2] However, Ruggeri has recently shown that platelet deposition and aggregation can occur at high shear model independent of GPIIb/IIIa which must be activated for binding.[3] Thus, the role of GPIIb/IIIa on high shear thrombosis to occlusion is not known.

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Platelet von Willebrand factor: evidence for its involvement in platelet adhesion to collagen

Blood ◽

10.1182/blood.v70.4.1214.1214 ◽

1987 ◽

Vol 70 (4) ◽

pp. 1214-1217 ◽

Cited By ~ 36

Author(s):

E Fressinaud ◽

D Baruch ◽

C Rothschild ◽

HR Baumgartner ◽

D Meyer

Keyword(s):

Shear Rate ◽

Von Willebrand Factor ◽

Platelet Adhesion ◽

Von Willebrand Disease ◽

High Shear ◽

Shear Rates ◽

High Shear Rates ◽

Von Willebrand ◽

Willebrand Factor

Abstract Although it is well established that plasma von Willebrand Factor (vWF) is essential to platelet adhesion to subendothelium at high shear rates, the role of platelet vWF is less clear. We studied the respective role of both plasma and platelet vWF in mediating platelet adhesion to fibrillar collagen in a parallel-plate perfusion chamber. Reconstituted blood containing RBCs, various mixtures of labeled washed platelets and plasma from controls or five patients with severe von Willebrand disease (vWD), was perfused through the chamber for five minutes at a shear rate of 1,600 s-1. Platelet-collagen interactions were estimated by counting the radioactivity in deposited platelets and by quantitative morphometry. When the perfusate consisted of normal platelets suspended in normal plasma, platelet deposition on the collagen was 24.7 +/- 3.6 X 10(6)/cm2 (mean +/- SEM, n = 6). Significantly less deposition (16 +/- 2.3) was observed when vWD platelets were substituted for normal platelets. In mixtures containing vWD plasma, significantly greater deposition (9 +/- 2.2) was obtained with normal than with vWD platelets (1 +/- 0.4) demonstrating a role for platelet vWF in mediating the deposition of platelets on collagen. Morphometric analysis confirmed these data. Our findings indicate that platelet, as well as plasma, vWF mediates platelet-collagen interactions at a high shear rate.

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The Viscous Behavior of Polymer Modified Lubricating Oils Over a Broad Range of Temperature and Shear Rate

Journal of Tribology ◽

10.1115/1.2920276 ◽

1990 ◽

Vol 112 (3) ◽

pp. 417-425 ◽

Cited By ~ 11

Author(s):

C. S. Peter Wu ◽

T. Melodick ◽

S. C. Lin ◽

J. L. Duda ◽

E. E. Klaus

Keyword(s):

Shear Rate ◽

Polymer Concentration ◽

Mineral Oil ◽

Capillary Viscometer ◽

Viscous Heating ◽

Shear Stresses ◽

High Shear ◽

Shear Rates ◽

High Shear Rates ◽

Newtonian Behavior

A high-shear capillary viscometer was used to determine the viscosity of mineral oil lubricants containing an olefin copolymer up to shear rates of a million reciprocal seconds. Comprehensive measurements were conducted for a range of polymer concentrations from 1–3 wt percent polymer and a temperature range of 38–120° C. The experimental technique utilizes a theoretical analysis procedure to handle the complications associated with viscous heating, the influence of pressure on the viscosity, and the excess pressure drop which occur at the entrance and exit of the capillary. The viscosity of the polymer solutions is determined over the complete range of shear rate starting from the lower Newtonian limit, through the shear-thinning region, and finally, the Newtonian behavior at high shear rates. It is shown that the standard ASTM plot for viscosity-temperature behavior can be used to correlate the viscous behavior for a given polymer concentration over this broad range of shear rates and shear stresses.

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