SHEARING EFFECTS ON THE ELECTRORHEOLOGICAL RESPONSE

2001 ◽  
Vol 15 (06n07) ◽  
pp. 930-937 ◽  
Author(s):  
K. TANAKA ◽  
S. HASHIMOTO ◽  
T. TAKENOUCHI ◽  
I. SUGIMOTO ◽  
A. KUBONO ◽  
...  
Keyword(s):  
Shear Rate ◽  
Electric Field ◽  
Transient Response ◽  
Stress Responses ◽  
Experimental Conditions ◽  
Transient Stress ◽  
Shear Rates ◽  
Lower Shear ◽  
Mason Number ◽  
The Individual

The steady and transient stress responses were investigated from lower shear rates to higher shear rates at a given strength of the electric field, and the individual experimental conditions were reduced to Mason number ( M n). The electro-rheological response was found in the region with higher M n of the order of 10, and the transient response became faster as the shear rate increased. These results show that the effect of chance of collision among the polarized particles would play an important role even in the region.

Formation and Destruction of Platelet Aggregates in Viscometric Flow

1975 ◽  
Author(s):  
H. Rieger ◽  
H. Schmid-Schönbein
Keyword(s):  
Initial Rate ◽  
Aggregate Stability ◽  
Creeping Flow ◽  
Experimental Conditions ◽  
Shear Rates ◽  
Independent Variables ◽  
Lower Shear ◽  
Platelet Aggregates ◽  
Blood Elements ◽  
Shape Changes

Even after pseudopodia formation platelets - unlike all other known formed blood elements - remain dispersed in stasis and creeping flow and become aggregated only in the presence of a minimum amount of shearing. The “rheoaggregometer” (Rieger et al., Pflüger’s Archiv, 343, R 33, 1973) allows to measure the minimum shear rates necessary for platelet aggregation (PA), as well as the initial rate and the maximum extent of PA in citrated PRP.PA is quantified photometrically as a function of variable shear rates. The initial rate of PA steadily increases with increasing shear rates up to 460 sec-1. However, the maximal extent of PA (indicating the mechanical integrity of formed aggregates) saturates at about 35 sec-1 and then decreases because of a destruction of formed aggregates and of prevention of further PA. The aggregability of the platelets, as reflected by various degrees of shape changes, is enhanced by a drop of temperature and a rise in pH as well as by the so called aggregating agents (e.g. epinephrine 10-6 up to 10-9 M/l) : consecutively lower shear rates (lower effects of collision) are necessary to induce PA. In citrated PRP stable platelet aggregates are produced only within a defined range of shear rates. Platelet aggregability and aggregate stability are independent variables influenced by different experimental conditions.

scholarly journals Effects of posture on shear rates in human brachial and superficial femoral arteries

2008 ◽  
Vol 294 (4) ◽  
pp. H1833-H1839 ◽  
Author(s):  
S. C. Newcomer ◽  
C. L. Sauder ◽  
N. T. Kuipers ◽  
M. H. Laughlin ◽  
C. A. Ray
Keyword(s):  
Shear Rate ◽  
Femoral Artery ◽  
Brachial Artery ◽  
Superficial Femoral Artery ◽  
Upright Posture ◽  
Brachial Artery Diameter ◽  
Shear Rates ◽  
Femoral Arteries ◽  
Lower Shear ◽  
Relative Shear

Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 ± 5, 91 ± 11, and 97 ± 13 s−1) compared with the superficial femoral (53 ± 4, 39 ± 77, and 44 ± 5 s−1) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.

Observations of rapidly flowing granular-fluid materials

1985 ◽  
Vol 150 ◽  
pp. 357-380 ◽  
Author(s):  
Daniel M. Hanes ◽  
Douglas L. Inman
Keyword(s):  
Shear Rate ◽  
Granular Material ◽  
Volume Concentration ◽  
Yield Criterion ◽  
Internal Boundary ◽  
Similar Data ◽  
Shear Rates ◽  
Lower Shear ◽  
High Shear Rates ◽  
Entire Flow

The rapid shearing of a mixture of cohesionless glass spheres and air or water was studied in an annular, parallel-plate shear cell designed after Savage (1978). Two types of flow were observed. In the first type of flow the entire mass of the granular material was mobilized. At high shear rates the shear and normal stresses were found to be quadratically dependent upon the mean shear rate (at constant volume concentration), in general agreement with the observations of Bagnold (1954) and Savage & Sayed (1984), and the ‘kinetic’ theory of Jenkins & Savage (1983). The stresses were found to be weakly dependent on the volume concentration up to approximately 0.5, and strongly dependent above this concentration. For flows in which water was the interstitial fluid, the ratio of the shear stress to the normal stress was slightly higher (than in air), and the stresses at lower shear rates were found to be more nearly linearly related to the shear rate. It is suggested that these effects are contributed to by the viscous dampening of grain motions by the water. The second type of flow was distinguished by the existence of an internal boundary above which the granular material deformed rapidly, but below which the granular material remained rigidly locked in place. The thickness of the shearing layer was measured to be between 5 and 15 grain diameters. The stress ratio at the bottom of the shearing layer was found to be nearly constant, suggesting the internal boundary is a consequence of the immersed weight of the shearing grains, and may be described by a Coulomb yield criterion. A scaled concentration is proposed to compare similar data obtained using different-sized materials or different apparatus. An intercomparison of the two types of flow studied, along with a comparison between the present experiments and those of Bagnold (1954) and Savage & Sayed (1984), suggests that the nature of the boundaries can have a significant effect upon the dynamics of the entire flow.

Kinetics of rouleaux formation using TV image analyzer. I. Human erythrocytes

1983 ◽  
Vol 245 (2) ◽  
pp. H252-H258 ◽  
Author(s):  
T. Shiga ◽  
K. Imaizumi ◽  
N. Harada ◽  
M. Sekiya
Keyword(s):  
Ph Effect ◽  
Three Dimensional ◽  
Image Analyzer ◽  
Autologous Plasma ◽  
Human Fibrinogen ◽  
Shear Rates ◽  
Lower Shear ◽  
Time Courses ◽  
The Individual ◽  
Rouleaux Formation

An apparatus for determining the velocity of erythrocyte rouleaux formation was constructed, combining an inverted microscope, a transparent cone-plate viscometer, a TV image analyzer, and a computer. At lower shear rates, the overall process is the sedimentation and the rouleaux formation followed by the development of three-dimensional aggregates. The individual erythrocyte could be observed and the process was expressed by the time courses of the changes in the count and area of particles; taking the computed increment in the area/count, the rate of rouleaux formation could be estimated. The effects of shear rates, hematocrits, plasma proteins, and pH were quantified. The rate of rouleaux formation in autologous plasma increased by (1) lowering the shear rates (1.9 less than or equal to gamma less than or equal to 15 s-1),2) increasing the hematocrit (up to 0.6%), 3) adding human fibrinogen (up to 600 mg/dl) or gamma-globulin, and 4) increasing pH. The transformation to echinocytes or to stomatocytes decreased the rate of rouleaux formation. The pH effect was explained by the increase in mean corpuscular volume at lower pH rather than by the changes in the electrostatic repulsion or in the protein binding.

scholarly journals Altered microvascular hemodynamics during the induction and perpetuation of chronic gut inflammation

2009 ◽  
Vol 296 (4) ◽  
pp. G750-G754 ◽  
Author(s):  
Norman R. Harris ◽  
Joseph R. Whatley ◽  
Patsy R. Carter ◽  
Georgia A. Morgan ◽  
Matthew B. Grisham
Keyword(s):  
T Cells ◽  
Shear Rate ◽  
Large Bowel ◽  
Proximal Colon ◽  
Hemodynamic Changes ◽  
Gut Inflammation ◽  
Shear Rates ◽  
Inflammatory Bowel ◽  
The Individual ◽  
Hemodynamic Measurements

Adoptive transfer of naïve CD4+T cells into lymphopenic mice induces chronic small and large bowel inflammation similar to Crohn's disease. Although much is now known regarding the immunopathology in this model of inflammatory bowel disease, virtually nothing is known about the microvascular hemodynamic changes during the induction and perpetuation of chronic gut inflammation. In this study, CD4+CD45RBhighT cells obtained from healthy C57BL/6 donor mice were transferred into lymphopenic recombinase-activating gene-1-deficient (RAG knockout) mice, which induced small and large bowel inflammation. At various time points following reconstitution (3 days-9 wk), intravital microscopy was used to examine the microvessels in the submucosa of the ileum and proximal colon following infusion of fluorescently labeled platelets and injection of rhodamine 6G (to label leukocytes). Hemodynamic measurements and the extent of blood cell adhesion to the venular wall were compared with measurements in unreconstituted RAG knockout controls. In <1 wk following reconstitution, velocity and wall shear rate of the arterioles decreased by >50% compared with controls, with this decrease also observed at 4–5 and 7–9 wk postreconstitution. At 7–9 wk, arteriolar diameters were found to be ∼15% larger than in controls, but, despite this dilation, flow rates in the individual vessels were decreased by ∼30%. Venular platelet and leukocyte adherence were not significantly elevated above controls; however, an association was found between platelet adherence and venular shear rate. In summary, significant decreases in arteriolar velocity and shear rates are observed in this model of chronic gut inflammation.

Variable Shear Rate Viscosity of SBR-Filler-Plasticizer Systems

1974 ◽  
Vol 47 (4) ◽  
pp. 825-836 ◽  
Author(s):  
G. C. Derringer
Keyword(s):  
Shear Rate ◽  
Experimental Design ◽  
Individual Contribution ◽  
Model Application ◽  
Shear Rates ◽  
Variable Shear ◽  
Wide Range ◽  
Mooney Viscosity ◽  
The Individual ◽  
Low Shear

Abstract Variable shear rate viscosity studies of compositions with variable filler and plasticizer levels have led to the development of a unifying viscosity model. Application of the model indicated that the fillers studied are less effective as stiffeners at shear rates typical of factory processing operations than at the low shear rates characteristic of the Mooney viscosity test. Thus, for proper comparative evaluations of pigment effect on processing, Mooney measurements are inadequate. The effect of shear rate on plasticizer efficiency will require more work to make definitive statements. Plasticizer evaluations appear to be a fruitful avenue for further exploration. The model developed has proved useful in understanding the individual contribution to the viscosity of the compound by the raw elastomer, the filler, and the plasticizer over a wide range of shear rates. The availability of this model will also result in an economy of experimentation as each shear rate of interest need not be studied separately. Having a valid model makes it possible to optimize the experimental design with regard to cost and information.

HYSTERESIS PHENOMENON IN FLOW-CURVES OF ER FLUIDS CONTAINING SULFONATED POLYMER PARTICLES

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1070-1077 ◽  
Author(s):  
RYUJI AIZAWA ◽  
SHEILA L. VIEIRA ◽  
MASAMI NAKANO ◽  
YOSHINOBU ASAKO
Keyword(s):  
Shear Rate ◽  
Electric Field ◽  
Volume Fraction ◽  
Hysteresis Phenomenon ◽  
Polymer Particles ◽  
Concentric Cylinder ◽  
Flow Curves ◽  
Shear Rates ◽  
Dispersed Particles ◽  
Er Fluids

The ER fluids containing sulfonated polymer particles were continuously sheared at increasing and decreasing shear rates using a rotary concentric cylinder rheometer and the hysteresis in the up- and down-flow-curves were analyzed. The ER fluids show hysteresis of shear stress and current density. The up-curve (when shear rate increased) was located below the down-curve (when shear rate decreased). As the electric field increased, the area in the hysteresis curves increased. The hysteresis depended on the electric field strength, the time of the applied electric field, the volume fraction of particles and the water content of the particles. Hysteresis phenomenon was explained, based on the formation of agglomerations of dispersed particles in the ER fluid and on changes of the lamellar formations

Experimental Investigations on the Formation of Rosettes during Shear

2016 ◽  
Vol 256 ◽  
pp. 199-204
Author(s):  
Siri Harboe ◽  
Vijenthan Sothyratnam ◽  
Michael Modigell ◽  
Annalisa Pola
Keyword(s):  
Shear Rate ◽  
Experimental Investigations ◽  
Coalescence Process ◽  
Shear Rates ◽  
Lower Shear ◽  
System A

In this work, the effect of stirring conditions on agglomeration and coalescence-coarsening in isothermal, globulitic, semisolid AlCu10%wt was investigated. It is shown that for the investigated system, a shear rate regime exists which promotes crystallographic alignment of the agglomerated grains, leading to a rapid coalescence process, thereby the formation of rosettes. It is also experimentally validated that for lower shear rates, the size and porosity of aggregates are increased compared to that at higher level of shear.

scholarly journals Reductions in physiologic shear rates lead to CD11/CD18-dependent, selectin-independent leukocyte rolling in vivo

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 345-350 ◽  
Author(s):  
JP Gaboury ◽  
P Kubes
Keyword(s):  
Shear Rate ◽  
Platelet Activating Factor ◽  
Leukocyte Rolling ◽  
Shear Rates ◽  
Inflammatory Conditions ◽  
Rate Dependent ◽  
Lower Shear ◽  
Independent Mechanism ◽  
Rolling Leukocytes

Abstract In this study, we tested the hypothesis that reducing shear rates in postcapillary venules causes CD18-dependent, selectin-independent leukocyte rolling. Intravital microscopy was used to assess shear rate- dependent leukocyte rolling in 25- to 40-microns rat mesenteric venules. Pretreatment of animals with 25 mg/kg fucoidin, a carbohydrate moiety that binds to and inhibits selectin function, essentially abolished the number of spontaneously rolling leukocytes. When shear rates were reduced by 50% (from 438 +/- 36 s-1 to 222 +/- 19 s-1) in the presence of fucoidin, leukocyte rolling increased fourfold, suggesting a selectin-independent mechanism of leukocyte rolling. Administration of CL26, an anti-CD18 antibody, prevented the leukocyte rolling associated with reduced shear rates. A second objective was to determine if the integrin-mediated leukocyte rolling at reduced shear rates would lead to firm adhesion of leukocytes in the presence of a chemotactic stimulus. Animals were pretreated with fucoidin and 100 nmol/L platelet-activating factor (PAF) was superfused over the mesentery. Fucoidin prevented leukocyte rolling and subsequent PAF- induced adhesion at normal shear rates; however, when shear rates were reduced by 50%, a significant CD18-dependent increase in leukocyte rolling (10-fold) and adhesion (5-fold) was noted within 15 minutes. These data raise the possibility that, at lower shear rates, as is the case in various inflammatory conditions, selectin-independent, CD18- dependent leukocyte rolling and subsequent adhesion can occur in postcapillary venules.

Effects of Chance of Collision Among Particles on Electro-Rheological Response

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1814-1821 ◽  
Author(s):  
K. Tanaka ◽  
K. Nakamura ◽  
K. Takada ◽  
F. Iwaki ◽  
A. Kubono ◽  
...  
Keyword(s):  
Shear Rate ◽  
Electric Field ◽  
Cation Exchange ◽  
Applied Electric Field ◽  
Exchange Resin ◽  
Volume Fraction ◽  
Cation Exchange Resin ◽  
Continuous Phase ◽  
Hydrodynamic Interactions ◽  
Experimental Conditions

The electro-rheological (ER) responses of suspensions with cation exchange resin particles and polyaniline particles were measured under different experimental conditions such as the strength of applied electric field, the viscosity of continuous phase, the shear rate, and the volume fraction of particles. The ER response became faster as the strength of applied electric field, the shear rate, and the volume fraction of particles increased while it became slower as the viscosity of continuous phase increased. These results were discussed in terms of the electrical and hydrodynamic interactions, as well as the chance of collision among particles.

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