10.1063/5.0131552.2

Segmental blood flow and rheological determinants in diabetic patients with peripheral occlusive arterial disease

Enhancement of flocculant-aided filtration performance of coal tailings under alternating low and high shear rates

Whole blood viscosity in microvascular angina and coronary artery disease: Significance and utility

The current investigations are related to presenting the characteristics of flow at very high and low shear rates along with the melting process over the geometry of Riga plate. Carreau nanofluid is most appropriate mathematical viscosity model that can deal with low and high shear rates. Transportation of energy is discussed through melting conditions, thermal radiation and viscous dissipation. In this study, electromagnetic hydrodynamic aspect of nanofluid is discussed by using electromagnetic surface (Riga plate) and this system generates Lorentz force parallel to wall that keeps its effect on velocity of nanofluid. Partial differential equations (PDEs) are moved in ordinary differential equations and numerical approach named Keller Box and Shooting scheme are exercised to fetch the numerical solution of the system. An augmentation in Q leads to an enrichment in an external magnetic field. The velocity as well as momentum boundary layer booms by the virtue of an improvement in an external magnetic field. The viscosity of the nanofluid increases by the virtue of a magnification in β. Nanofluid becomes more radiated and absorbs more heat as a result of magnification in Nr, which escalates the heat transfer rate.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Edward J. Stancik, Anne L. Hawkinson, Jan Vermant, Gerald G. Fuller; Dynamic transitions and oscillatory melting of a two-dimensional crystal subjected to shear flow. Journal of Rheology 1 January 2004; 48 (1): 159–173. https://doi.org/10.1122/1.1631425 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Society of RheologyJournal of Rheology Search Advanced Search |Citation Search

The spatial organization of particles in a colloidal gel controls the macroscopic properties, such as the rheological ones or the macroscopic gel stability. However, the suspension microstructure depends in a non-trivial manner on the colloidal interactions, the concentration and the flow history. Especially the effect of the latter is so far ill-understood and difficult to study in bulk suspensions. In the present work, well-characterized two dimensional suspensions are used to study the flow-induced structure in colloidal gels. Both a parallel band apparatus and a four roll mill are used to generate surface flows and the resulting steady state structures are analyzed using video microscopy. Because of the 2D nature of the suspensions, a high temporal and spatial resolution can be obtained, rendering the visualization for a wide range of surface coverages and flow rates possible. In this wide parameter space, two different regimes can be distinguished. At low surface coverages or high shear rates, only isolated flocs exist, whereas at high surface coverages or low shear rates, a transient network structure is encountered. In the two micro structural regimes the evolution of the characteristic length scales, the dominant orientation and anisotropy and the local aggregate or cluster densities is investigated. For individual aggregates, a simple analysis of hydrodynamic forces on the aggregates is used to evaluate the shear rate dependence of the aggregate size and aggregate density.

Melt rheological properties of the blend of isotactic polypropylene (PP) and ethylene propylene diene rubber (EPDM) at varying ratios and of the glass fiber (GF) filled PP and PP/EPDM blend by varying both GF loading and blending ratio of the polyblend matrix are studied. Rheological measurements at 220°C in shear rate range 101−104s−1 were made on a capillary rheometer. Scanning electron micrographs of the extrudates are presented to show the morphology and the alignment of the glass fibers with respect to the flow direction. Variations of pseudoplasticity index, melt viscosity, and melt elasticity with EPDM content in PP/EPDM blend, and with varying GF content at any given composition of the matrix in PP/EPDM/GF ternary system, in the studied range are presented and discussed. Resultes on melt viscosity and melt elasticity show (i) reduced effect of GF at high shear rates on these properties and (ii) upward deviation of melt viscosity versus shear rate curve at low shear rates. A change in flow behavior in presence of GF is observed around a critical shear rate 2 × 103 s−1 and is attributed to the difference of interaction of GF and the dispersed rubber droplets at high and low shear rates. Elastic recovery showed nonequilibrium behavior at low shear rates.

Deficiency of Platelet Membrane Glycoprotein Ia Associated With a Decreased Platelet Adhesion to Subendothelium: A Defect in Platelet Spreading

The viscosity of whole blood measured at low shear rates is determined partly by shear resistance of the red cell aggregates present, stronger aggregation increasing the viscosity in the absence of other changes. Effects of cell deformability can confound interpretation and comparison in terms of aggregation, however, particularly when the plasma viscosity is high. We illustrate the problem with a comparison of hematocrit‐adjusted blood from type 1 diabetes patients and controls in which it is found the apparent and relative viscosities at a true shear rate of 0.20 s $^{-1}$ are lower in the patient samples than age matched controls, in spite of reports that aggregation is increased in such populations. Because the plasma viscosities of the patients were higher on average than controls, we performed a series of experiments to examine the effect of plasma protein concentration and viscosity on normal blood viscosity. Dilution or concentration by ultrafiltration of autologous plasma and viscosity measurements at low shear on constant hematocrit red cell suspensions showed (a) suspension viscosity at 0.25 and 3 s $^{-1}$ increased monotonically with plasma protein concentration and viscosity but (b) the relative viscosity increased, in concert with the microscopic aggregation grade, up to a viscosity of approximately 1.25 mPa‐s but above this the value the relative viscosity no longer increased as the degree of aggregation increased in concentrated plasmas. It is suggested that in order to reduce cell deformation effects in hyperviscous pathological plasmas, patient and control plasmas should be systematically diluted before hematocrit is adjusted and rheological measurements are made. True shear rates should be calculated. Comparison of relative viscosities at low true shear rates appears to allow the effects of red cell aggregation to be distinguished by variable shear rate viscometry in clinical blood samples.

The electrorheology (ER) of suspensions based on polystyrene/polyaniline (PS/PANI) core/shell structured microspheres and those based on disk-like zeolite particles at different electric fields and particle volume fractions have been studied, respectively. Both types of ER fluids showed abrupt shear thickening under high electric fields and low shear rates, as well as shear thinning when the shear rate increased. A normalized method that considers the effects of electric field strength, shear rate and particle volume fraction was proposed to compare the rheological curves of the two ER fluids. The curves evaluated from the normalization method showed similar shear thinning at low shear rates and the hydrodynamic effect at high shear rates. Shear thinning represents the structure destroyed by shearing, and shear thickening at low shear regions indicates the dramatic structure change. The particle volume fraction and structure factor effects demonstrate that the mechanical contact between particles and the wall of the electrodes is crucial to the shear strength of ER fluids, indicating an electric/magnetic field modulated friction mechanism of the ER and magnetorheological (MR) effects.

Objective This article investigates the relationship of fractional flow reserve (FFR) with whole blood viscosity (WBV) in patients who were diagnosed with chronic coronary syndrome and significant stenosis in the major coronary arteries and underwent the measurement of FFR. Material and Method In the FFR measurements performed to evaluate the severity of coronary artery stenosis, 160 patients were included in the study and divided into two groups as follows: 80 with significant stenosis and 80 with nonsignificant stenosis. WBVs at low shear rate (LSR) and high shear rate (HSR) were compared between the patients in the significant and nonsignificant coronary artery stenosis groups. Results In the group with FFR < 0.80 and significant coronary artery stenosis, WBV was significantly higher compared with the group with nonsignificant coronary artery stenosis in terms of both HSR (19.33 ± 0.84) and LSR (81.19 ± 14.20) ( p < 0.001). In the multivariate logistic regression analysis, HSR and LSR were independent predictors of significant coronary artery stenosis (HSR: odds ratio: 1.67, 95% confidence interval: 1.17-2.64; LSR: odds ratio: 2.46, 95% confidence interval: 2.19-2.78). In the receiver operating characteristic (ROC) curve analysis, when the cutoff value of WBV at LSR was taken as 79.23, it had 58.42% sensitivity and 62.13% specificity for the prediction of significant coronary artery stenosis (area under the ROC curve: 0.628, p < 0.001). Conclusion WBV, an inexpensive biomarker that can be easily calculated prior to coronary angiography, was higher in patients with functionally severe coronary artery stenosis, and thus could be a useful marker in predicting the hemodynamic severity of coronary artery stenosis in patients with chronic coronary syndrome.

The ability to assess rheological properties of neat cement grout, such as those used in structural repair and for filling post-tension ducts, is of special interest for the evaluation of the ease of pumping, spreading into place, and filling of narrow spaces. There is an increasing need to identify dependable and simple test methods that can characterize the consistency of specialty cement grouts and reflect variations in rheological properties during handling and placement. Several tests can be used to evaluate the rheological characteristics of a cement grout suspension, including precise methods for the determination of rheological parameters and simple procedures to assess fluidity. Rheological properties can be accurately determined by using a coaxial cylinder viscometer. However, the use of such a viscometer is mainly limited to the laboratory, and simple methods including the mini-slump spread and the modified Marsh cone tests are usually employed in the field to verify the consistency for quality control. This paper attempts to establish relationships between rheological parameters and fluidity values obtained using simple test methods. Relationships are also determined between the wash-out resistance of structural cement grout and various fluidity and rheological parameters. The derived relationships are based on a wide variety of cement grouts covering up to 210 data points. The various grouts were prepared with W/C ranging between 0.30 and 0.50, Type I and III portland cements, as well as various silica fume replacement values (up to 8% by mass), blast-furnace slag contents of 20 to 60%, fly ash substitutions of 10 to 30%, and limestone filler replacements of up to 30%. The investigated grouts incorporated melamine- and naphthalene-based high-range water reducer, welan gum and cellulose-based viscosity-modifying admixtures, as well as set-retarding admixture. Test results highlight the difficulties of relying on a single empirical test to evaluate the fluidity of a given grout. Correlations between various simple measurements of fluidity and wash-out mass loss and apparent viscosities determined at different shear rates indicate that the mini-slump and wash-out mass loss measurements correspond well to viscosities determined at low-shear rates (5.1 s-1). In contrast, the modified Marsh cone measurement corresponds well to viscosity determined at high-shear rates ranging between 340 and 510 s-1. Because of the pseudo-plastic behavior of structural cement grouts, field quality control tests should include fluidity assessment at low and high shear rates to adequately evaluate the rheological behavior of the grouts.

Relative hydraulic resistance, shear rate, and pressure in a vascular network integrate the network's architecture via fluid flow, and determine vein dynamics, with a time delay, in the prototypical organism Physarum polycephalum.

Elevated blood viscosity in alloxan diabetic dogs and experimentally galactosemic dogs

A high content of magnesium hydroxide was filled into a polypropylene-type resin containing maleated polypropylene-type elastomer PER (MPER) and an ionically crosslinked compound was prepared. The rheological properties of the ionically crosslinked compound were measured and compared with those of a compound without MPER, MPER, PER, and a flexible polyvinyl chloride (PVC) resin. The temperature dependence of the viscosity of MPER is stronger than that of PER and the viscosity of MPER tends to rise at low shear rates, which suggests the existence of light crosslinking in MPER. The viscosity of the ionically crosslinked compound continues to increase linearly even at low shear rates. Therefore, it shows a very high value at the low shear rates encountered during drawdown of shaped molten articles. However, it scarcely differs from those of usual resins at the high shear rates of extrusion and injection molding. Although the change of viscosity with shear rate is large, the change with temperature is very small. The die swell ratio is nearly unity and the extrudate scarcely swells after leaving a die. The change of die swell ratio with temperature and shear rate is very small and the extrudate is stable at disturbances. The ionically crosslinked compound does not generate a melt fracture until high shear rates. The elongational viscosity is about one decade higher than those of other samples. The dynamic viscoelasticity shows a rubbery plateau modulus of 3×104Pa. These rheological properties come from the synergy between the ionic crosslinking and the filling effect of magnesium hydroxide. From these experimental results, it may be assumed that the ionically crosslinked compound is a kind of thermoplastic elastomer and is suitable for contour extrusion, vacuum/pressure molding, big blow molding and foam molding. Flexible PVC shows similar rheological behaviors to the ionically crosslinked compound and has good processability. However, it has a very high activation energy for flow (the temperature dependence of viscosity and other rheological properties) of 3-5 times that of the ionically crosslinked compound. It also shows a large die swell ratio of 1.1-1.3 in comparison with 1.0 for the ionically crosslinked compound. It shows a considerably lower viscosity at low shear rates than that of the ionically crosslinked compound at around 190°C which is a suitable Processing temperature for flexible PVC. It also has the drawback of easy generation of melt fracture. Accordingly it may be said that the ionically crosslinked compound in this study has better processability than flexible PVC.