Low Shear Rate Values Research Articles

Relationship between blood viscosity and thrombus burden in ST-segment elevation myocardial infarction.

İncreased whole blood viscosity (WBV) is associated with increased infarct area, impaired microvascular circulation and mortality in patients with ST-elevation myocardial infarction (STEMI). We aimed to analyze the association between the WBV and thrombus burden (TB) in STEMI patients. This cross-sectional study included 167 STEMI patients who received primary percutaneous coronary intervention. WBV values were assessed using hematocrit and total protein values, and low shear rate(LSR) and high shear rate(HSR) were calculated. Angiographic TB was assessed according to the definition of the Thrombolysis in Myocardial Infarction (TIMI) study group. The cases were dichotomized into low TB (grade 1-3) (n = 87) and high TB (grade 4-5) (n = 80) groups. The mean HSR and LSR values of the high TB group were significantly increased compared to the low TB group (p < 0.001, for each). In ROC analysis,for prediction of TB, a cut-off value of 3.83 WBV for HSR had a 71% sensitivity and a 60.7% specificity, and a cut-off value of 21 WBV for LSR had a 70% sensitivity and 59.9% specificity (p < 0.001,for each). Multivariate regression analysis showed that both HSR (OR = 2.408;p=0.020) and LSR (OR = 1.055;p=0.021) were independent predictors for high TB. İncreased WBV was an independent predictor for the presence of high TB in patients with STEMI.

Relationship Between Blood Viscosity and No-Reflow Phenomenon in St-Segment Elevation Myocardial Infarction Performed in Primary Percutaneous Coronary Interventions

Background: This study aimed to analyze the associations between no-reflow (NR) phenomenon development and whole-blood viscosity in patients with ST-elevated myocardial infarction. Methods: A total of 217 patients with ST-elevated myocardial infarction were included. whole-blood viscosity values were assessed using hematocrit and total protein values, and low shear rate (LSR) and high shear rate (HSR) were calculated. Results: The average LSR and HSR values of the study group were significantly higher than the control group (p<0.001). Multivariate logistic regression analysis showed that both HSR (odds ratio: 4.957; p<0.001) and LSR (odds ratio: 1.114; p<0.001) were independent predictors for NR development. Conclusion: This study found that increased blood viscosity was an independent predictor for NR development.

Determining the effect of the composition of an aluminosilicate binder on the rheotechnological properties of adhesives for wood

Main rheotechnological properties of aluminosilicate adhesives for gluing wood arrays have been investigated. It was established that for adhesives based on the alkaline aluminosilicate binding agent with a composition of Na 2 O×Al 2 O 3 ×4.5SiO 2 ×17.5H 2 O dynamic viscosity in the range of speeds from 0 to 200 RPM varies from 6.933 sP to 368.4 Sp, and the mean plastic viscosity takes the magnitude of 86.27 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.7973) and the largest coefficients of wetting ( s =0.8986) and spreadability ( f =–6.5 mN/m), as well as the work of adhesion forces ( Wa =58.23 mN/m), wetting ( Wa =58.23 mN/m), are demonstrated by beech backing, followed by alder, ash, pine, birch, and oak. For adhesives based on the alkaline aluminosilicate binding agent with a composition of Na 2 O×Al 2 O 3 ×6SiO 2 ×20H 2 O dynamic viscosity in the speed range from 0 to 200 RPM varies from 5.340 sP to 374.4 sP, and the mean plastic viscosity takes the magnitude of 85.72 sP. At the same value of surface tension and cohesive work, the smallest angle of wetting (cosQ=0.5876) and the largest coefficients of wetting ( s =0.7938) and spreadability ( f =–19.34 mN/m), as well as the work of adhesion forces ( Wa =74.46 mN/m), wetting ( Ww =27.56 mN/m), are demonstrated by alder backing, followed by pine, oak, birch, beech, and ash. For the adhesive with a composition of Na 2 O×Al 2 O 3 ×4.5SiO 2 ×17.5H 2 O, at low values of shear rate, from 0.0378 to 1.05 1/sec, the shear force increases from 26.21 dyne/cm 2 to 48.64 dyne/cm 2 . The data obtained significantly exceed the same indicators for a liquid glass at high shear rates, from 14 to 39 1/sec. For the adhesive with a composition of Na 2 O×Al 2 O 3 ×6SiO 2 ×20H 2 O, at low shear speeds there is a sharp increase in the shear effort, from 40 to 110 dyne cm 2 . This is due to the dispersion processes in the silica component. At an increase in the shear speed values from 5 to 42 1/sec, the shear effort increases from 110 to 158 dyne/cm 2 . This relates to the stabilization of viscosity values with the formation of a homogeneous adhesive structure

Different Blood Flow Models in Coronary Artery Diseases: Effects on hemodynamic parameters.

Coronary arteries are medium-small caliber vessels, in which low shear rate values are encountered, where non-Newtonian blood effects cannot be neglected. This work aims to study a comparison between Newtonian and non-Newtonian blood behaviors in a cohort offorty-eight 3D patient-specific stenotic vessels (right (RCA), left (LAD) and circumflex (LCX) coronary artery) at different grades of stenosis. Numerical simulation was carried out by means of Computational Fluid Dynamics (CFD) Analysis to investigate the blood velocity and distribution of the shear stress indices at different times of the cardiac cycle. A statistical analysis was performed to have a prediction ofincrement or decrement ofthe various hemodynamic parameters. The results show that the non-Newtonian effects are mostly important in shear stress indices distributions.

Investigating the rheological behavior of Algerian crude oil stemming from station of separation (quagmire)

ABSTRACTAn experimental study was conducted to investigate the rheological behavior of Algerian crude oil stemming from station of separation (quagmire) of the Tin Fouye Tabankort sector (southern Algeria). The rheological measurements at different temperatures (20°C, 30°C and 50°C) were performed employing AR 2000 rheometer of TA-Instruments. Several parameters such as shear rate, the temperature and the presence of crude oil from another quagmire on the rheological properties have been studied. The experimental results show that the studied crude oil displays non-Newtonian shear thinning behavior at low values of shear rate and a Newtonian behavior at high values of shear rate, which can be best presented by the Casson model. The rheological examination tests (flow and dynamic mode (oscillation)) have shown that the rheological properties of the crude oil were significantly influenced by the temperature and the crude oil addition.

The Influence of Processing Conditions on the Polypropylene Apparent Viscosity Measured Directly in the Mold Cavity

Measurements of rheological properties of polymeric materials play an increasingly important role in the polymer plastics industry. Knowledge about the plasticized material flow behavior is essential at the injection molds design stage. The polymeric viscosity curves usually are determined by a capillary rheometer tests. Nevertheless, the rheological properties determined this way differ from those observed during actual processing conditions. This paper presents a comparison of apparent viscosity measurements of polypropylene conducted by three methods. The first one was plastometer measurements made at different masses of test load. The second method evaluated the viscosity in the injection mold cavity equipped with pressure and temperature sensors. Capillary rheometer was used as the third method. It was observed that polypropylene viscosity curves, determined by different methods have a similar pattern. Comparing changes in apparent viscosity values obtained with the capillary rheometer and directly in the mold cavity, the largest differences were found for the shear rate below 1000 s −1. This proves the non‐isothermal measurement in the injection mold cavity. In the range of shear rate above 1000 s−1, the apparent viscosity determined directly in the injection mold was about 40 Pa · s greater than that measured by the rheometer, regardless of the test temperature. The results recorded by the plastometer reflect the real polypropylene viscosity curve at low shear rate values in a better way.

Application of artificial neural networks and support vector regression modeling in prediction of magnetorheological fluid rheometery

In this study, rheological properties of Magnetorheological Fluid (MRF) have been investigated by Artificial Neural Network (ANN) and Support Vector Regression (SVR) methods The effects of temperature and magnetic field strength on rheological properties have been modeled. The experimental results (about 600 data) have been estimated about 3 percent average error in interpolations and about 5 percent average error in extrapolation of models. Low accuracy of data at low shear stresses and inability to determine the reliable values of dynamic yield stress are challenging problems in using analytical models for MRF rheological properties prediction. The shear stress has been predicted by using ANN and SVR models at low range of shear rates (to 10−5s−1) and the results showed that SVR is the most reliable model in predicting shear stress as well as dynamic yield stress (at low shear rate values). Therefore, the dynamic yield stress has been obtained with log extrapolation prediction of experimental data, Herschel-Bulkley model, ANN and SVR models. It was revealed that Herschel-Bulkley model was unable to predict the dynamic yield stress in a wide range of temperature and magnetic field strength. The SVR model showed the most reliable predicting results both in interpolations as well as extrapolations when trying to predict the dynamic yield stress. The SVR model had an appropriate estimation of shear stress at low shear rates, also a good coincidence with existing experimental data.

Flow behaviour of inulin‐enriched dairy desserts: influence of inulin average chain length

SummaryThe effect of the addition of different types of inulin (long‐chain, native and short‐chain inulin) at four concentrations (0, 2.5, 5 and 7.5% w/w) on flow properties of semisolid dairy desserts formulated with either skimmed or whole milk and three modified tapioca starch concentrations (2.5, 3.25 and 4% w/w) was studied. All samples displayed shear‐thinning flow behaviour. The addition of the three types of inulin to whole milk samples with low starch concentrations (2.5 and 3.25% w/w) led to combined hysteresis loops: samples showed antithixotropy at low shear rate values, but thixotropy at high shear rate values. The remaining samples showed thixotropic behaviour. The effect of the different types of inulin on the flow properties was not only highly dependent on the inulin concentration but also on milk type and starch concentration. On adding 7.5% of long‐chain inulin, which significantly increased consistency index values and significantly decreased flow index values in both types of milk and for all starch concentrations.

Nonlinear, time-dependent shear flow behaviour, and shear-induced effects in wheat flour dough rheology

Retardation test, step-shear rate experiments, low-amplitude and large-amplitude dynamic measurements have been combined to study the nonlinear and time-dependent viscosity of dough and shear-induced effects of flow on dough structure. Despite large quantitative differences in linear viscoelastic constants, doughs from different flours or with different water contents display the same type of flow behaviour. Shear-induced structural changes cause flow to shift from a high viscosity steady-state regime to a low viscosity one. The process, irreversible, is responsible for the time-dependent character of dough viscosity and seems to be controlled by the mechanical energy absorbed. Nevertheless, the two steady-state viscosities follow the same shear-thinning flow curve, fitted by a Cross equation with an exponent close to 1; the Newtonian plateau is approached at very low shear rate values. Viscosity data obtained on different doughs yield a unique flow master curve in reduced coordinates. Shear-induced structural changes cause also the linear viscoelastic plateau modulus of dough to decrease; this progressive weakening of the network structure is irreversible and seems governed by the accumulated strain. These characteristics of dough rheology are discussed with reference to the behaviour of concentrated suspensions.

Rheological behaviour of Galician honeys

In the present paper, rheological behaviour of different Galician honeys (north-west of Spain) with the specific designation “miel de Galicia” (Galician honey) has been analysed to classify this food such as a Newtonian or non-Newtonian fluid. To carry out this study, a rotational viscosimeter has been used to analyse the effect of time and shear rates upon the apparent viscosity. Measurements have been carried out at 25 °C. The work developed in the present paper indicates that Galician honeys have a pseudoplastic behaviour in all cases when low values of shear rate are applied. For this reason, Ostwald model (power law) to correlate pseudoplastic behaviour has been used to fit experimental data with acceptable results.

Rheological properties of lyotropic liquid crystals

Rheological studies of liquid crystalline systems based on sodium decylsulphate are reported. It was verified that for low shear rates, disk-like (N d ) micellar nematic mesophases show typical pseudo-plastic rheopectic behaviour, associated with a favourable orientation of anisometric micelles in the flow field. The existence of a recovery time was observed, probably due to an orientational competition between flow effects and intermicellar interactions. The same sample observed at higher shear rates exhibited Newtonian behaviour, acting as a “dilute” system in which the interactions between the components are not sufficiently strong to prevent free diffusion. For rod-like (N c ) micellar nematic mesophases at low shear rates, rheopectic behaviour was observed. Additionally, a typical structural viscosity was detected, attributable to a superstructure break down arising from the shearing flow. For N c systems, the existence of a recovery time was observed only for low shear rate values, indicating that for higher values the flow completely orients the sample.

A terminally anchored polymer chain in shear flow: Self-consistent velocity and segment density profiles

The behavior of a terminally anchored freely-jointed bead-rod chain, subjected to solvent shear flow, was investigated via Brownian dynamics simulations. Previous calculations have been improved by computing the segment density and fluid velocity profiles self-consistently. The segment density distributions, components of the radius of gyration, and chain attachment shear and normal stresses were found to be sensitive to low values of shear rate. Additionally, it was found that the thickness of a model polymer layer was a strong function of the shear rate, and that the functional dependence on shear rate changed dramatically as the chain length increased. For the longest chains studied, the thickness of the model polymer layer first increased as the shear rate increased, passed through a maximum, and then decreased at high shear rates, in accordance with experimental results in theta solvents. These results suggest that a dilute or semi-dilute layer model may explain hydrodynamic behavior previously thought to be due to the entanglements that occur in dense surface bound polymer layers.

Rheological characterization of dextran‐enzymatic synthesis media

AbstractThe bacteria Leuconostoc mesenteroides (strain NRRL‐B512) has been used for the fermentative production of the polysaccharide dextran from sucrose. The polysaccharide production was carried out via a four‐step process involving (1) production of the enzyme dextransucrase (DS), (2) bacteria removal from the culture broth, (3) enzyme purification by gel permeation chromatography, and (4) enzymatic synthesis of dextran in a cell‐free reaction medium.The enzymatic reaction was followed measuring the change in rheological properties of the reaction medium with time at different initial substrate concentrations. The influence of other parameters, such as temperature, addition of acceptor molecules (maltose), and enzyme purity, were also considered.The microbial extracellular polysaccharide is responsible for the non‐newtonian character of the reaction media. At low shear rate values the flow behavior was newtonian, whereas at higher shear rates the reaction media exhibited a marked shear‐thinning behavior. The Carreau equation appears to fit fairly well the experimental data over several decades of shear rate. The reaction media showed elastic behavior as well.