scholarly journals Nanoparticle diffusion in sheared cellular blood flow

2019 ◽  
Vol 871 ◽  
pp. 636-667 ◽  
Author(s):  
Zixiang Liu ◽  
Jonathan R. Clausen ◽  
Rekha R. Rao ◽  
Cyrus K. Aidun
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Large Scale ◽  
Diffusion Tensor ◽  
High Shear ◽  
Critical Shear Rate ◽  
Flow Solver ◽  
Wide Range ◽  
Time Regime ◽  
Long Time

Using a multiscale blood flow solver, the complete diffusion tensor of nanoparticles (NPs) in sheared cellular blood flow is calculated over a wide range of shear rate and haematocrit. In the short-time regime, NPs exhibit anomalous dispersive behaviors under high shear and high haematocrit due to the transient elongation and alignment of the red blood cells (RBCs). In the long-time regime, the NP diffusion tensor features high anisotropy. Particularly, there exists a critical shear rate (${\sim}100~\text{s}^{-1}$) around which the shear-rate dependence of the diffusivity tensor changes from linear to nonlinear scale. Above the critical shear rate, the cross-stream diffusivity terms vary sublinearly with shear rate, while the longitudinal term varies superlinearly. The dependence on haematocrit is linear in general except at high shear rates, where a sublinear scale is found for the vorticity term and a quadratic scale for the longitudinal term. Through analysis of the suspension microstructure and numerical experiments, the nonlinear haemorheological dependence of the NP diffusion tensor is attributed to the streamwise elongation and cross-stream contraction of RBCs under high shear, quantified by a capillary number. The RBC size is shown to be the characteristic length scale affecting the RBC-enhanced shear-induced diffusion (RESID), while the NP submicrometre size exhibits negligible influence on the RESID. Based on the observed scaling behaviours, empirical correlations are proposed to bridge the NP diffusion tensor to specific shear rate and haematocrit. The characterized NP diffusion tensor provides a constitutive relation that can lead to more effective continuum models to tackle large-scale NP biotransport applications.

The Simulation of Aggregated Colloids Under Flow

1992 ◽  
Vol 289 ◽  
Author(s):  
John R. Melrose
Keyword(s):  
Shear Rate ◽  
Large Scale ◽  
Shear Thinning ◽  
High Shear ◽  
Shear Rates ◽  
Rouse Model ◽  
High Shear Rates ◽  
Structural Breakdown ◽  
Large Scale Simulations ◽  
Low Shear

AbstractAn overview is given of theories of aggregates under flow. These generally assume some sort of structural breakdown as the shear rate is increased. Models vary with both the rigidity of the bonding and the level of treatment of hydrodynamics. Results are presented for simulations of a Rouse model of non-rigid, (i.e. central force) weakly bonded aggregates. In large scale simulations different structures are observed at low and high shear rates. The change from one structure to another is associated with a change in the rate of shear thinning. The model captures low shear rate features of real systems absent in previous models: this feature is ascribed to agglomerate deformations. Quantitatively, the model is two orders of magnitude out from experiment but some scaling is possible.

Nonnewtonian Flow of Poly(Dimethyl Siloxane)

1967 ◽  
Vol 40 (5) ◽  
pp. 1483-1491
Author(s):  
Yoshio Ito
Keyword(s):  
Shear Rate ◽  
Polymer Solutions ◽  
Flow Behavior ◽  
Degree Of Polymerization ◽  
High Shear ◽  
Newtonian Viscosity ◽  
Shear Rates ◽  
Molecular Weights ◽  
Dimethyl Siloxane ◽  
Wide Range

Abstract Nonnewtonian flow of poly(dimethyl siloxanes) of various molecular weights has been studied with a short capillary viscosimeter. The experiment covered a wide range of shear rate, from 10−1 to 3×106sec−1. Results were as follows: (1) Flow behavior of the sample changes with the degree of polymerization. For siloxanes with degrees of polymerization less than 1.55×102, flow of the fluid is newtonian throughout the whole range of shear rates; for siloxanes with degrees of polymerization from 3.22×102 to 2.63×103, flow is nonnewtonian at moderate shear rates; it again becomes newtonian at high shear rates. With degrees of polymerization more than 3.31×103, the spiral flow rises to a high shear rate. (2) Plow behavior of the samples is expressed by modifying Shishido's equation proposed for nonnewtonian polymer solutions. (3) When the observed flow curve contains its inflection point, the upper newtonian viscosity can be estimated by a new method proposed here. (4) The relations among the end correction of capillary, the pressure loss, and the shear stress proposed by Shishido for polymer solutions are applicable to poly(dimethy! siloxane) also.

scholarly journals Experimental determination and modeling of flow curves of xanthan gum solutions over a large range of shear rates

2021 ◽  
Vol 31 (1) ◽  
pp. 24-38
Author(s):  
Julian Sepulveda ◽  
Agnes Montillet ◽  
Dominique Della Valle ◽  
Thanina Amiar ◽  
Hubert Ranchon ◽  
...  
Keyword(s):  
Shear Rate ◽  
Xanthan Gum ◽  
Scaling Law ◽  
Polymer Concentration ◽  
High Shear ◽  
Shear Rates ◽  
Wide Range ◽  
Different Diameters ◽  
Plate Geometry

Abstract The viscosities of solutions formulated with xanthan gum and xanthan gum with whey protein isolates are experimentally characterized and modeled over a wide range of shear rates [10−3 to 105 s−1]. As shown by numerous studies [1, 2], the generation of vortices in the cone-plate geometry is making viscosity measurements beyond a certain shear rate unreliable. In the present work, an innovative technique, based on microfluidics and developed by the company Formulaction, has been employed to extend to high shear rates, the viscosity flow curve obtained with a rotational rheometer. The main highlights of this study are firstly, to propose a scaling law for the inertial transition in the cone-plate geometry for different diameters and angles through the determination of the maximum shear rate at which one can expect a true viscosity value. Secondly, the high shear rate measurements allow the determination of the second Newtonian plateau for these solutions thanks to the Williams-Carreau model. An attempt for the second plateau modeling is proposed following the concept of an intrinsic viscosity in the high shear equilibrium. In the same way, other fitted parameters from the Williams-Carreau law are modeled as a function of the polymer concentration. This procedure allows to provide a predictive model for the rheological behavior of xanthan gum-based solutions used in high shear processes like high pressure homogenization, emulsification, foaming, microfluidics, etc in food, pharmaceutical or cosmetics applications.

scholarly journals Non-hormonal options for the relief of menopausal disorders

2022 ◽  
pp. 190-196
Author(s):  
O. V. Yakushevskaya
Keyword(s):  
Large Scale ◽  
Estrogen Deficiency ◽  
Alternative Methods ◽  
Main Function ◽  
Hormonal Changes ◽  
Social Self ◽  
Number Of Patients ◽  
Wide Range ◽  
Long Time

Woman’s nature is unique. Taking into account some historical milestones, it can be noted that the role of women in society has undergone large-scale changes. The woman took a confident position in society. Its main function remains unchanged and it consists in procreation and procreation. A woman’s activity is consistent with the work of her reproductive system (RS). The gradual decrease, and then the cessation of the work of the ovaries, contributes to the life order and health of the fair sex. Menopause is a natural stage in a woman’s life, which corresponds to the peak of social self-realization. However, in some cases, hormonal changes characteristic of this period can serve as a favorable background for the formation of a number of pathological changes. The growing estrogen deficiency is becoming a pathogenetic impetus for the development of a wide range of climacteric disorders. Vasomotor symptoms and hyperhidrosis are the most frequent companions of women during the perimenopausal transition and early postmenopause. Maintaining optimal activity and the full quality of life of patients should be the goal of correcting the negative manifestations of estrogen deficiency and the complications associated with it. Compensating for estrogen deficiency with menopausal hormone therapy (HRT) is the benchmark for menopausal problems. However, there are a number of patients who have contraindications to prescribing HRT or who refuse to receive it for some reason. For this category of patients, alternative methods of diet correction. Combinations of plant extracts with vitamins and minerals have been successfully used in clinical practice for a long time. The article will provide information on the most studied phytoestrogens contained in soy.

scholarly journals Displacement of fluid droplets from solid surfaces in low-Reynolds-number shear flows

1997 ◽  
Vol 336 ◽  
pp. 351-378 ◽  
Author(s):  
P. DIMITRAKOPOULOS ◽  
J. J. L. HIGDON
Keyword(s):  
Reynolds Number ◽  
Shear Rate ◽  
Viscosity Ratio ◽  
Low Reynolds Number ◽  
Contact Angles ◽  
Solid Boundary ◽  
Critical Shear Rate ◽  
Wide Range ◽  
Low Reynolds ◽  
Yield Conditions

The yield conditions for the displacement of fluid droplets from solid boundaries are studied through a series of numerical computations. The study includes gravitational and interfacial forces, but is restricted to two-dimensional droplets and low-Reynolds-number flow. A comprehensive study is conducted, covering a wide range of viscosity ratio λ, Bond number Bd, capillary number Ca and contact angles θA and θR. The yield conditions for drop displacement are calculated and the critical shear rates are presented as functions Ca(λ, Bd, θA, Δθ) where Δθ=θA−θR is the contact angle hysteresis. The numerical solutions are based on the spectral boundary element method, incorporating a novel implementation of Newton's method for the determination of equilibrium free surface profiles. The numerical results are compared with asymptotic theories (Dussan 1987) based on the lubrication approximation. While excellent agreement is found in the joint asymptotic limits Δθ[Lt ]θA[Lt ]1, the useful range of the lubrication models proves to be extremely limited. The critical shear rate is found to be sensitive to viscosity ratio with qualitatively different results for viscous and inviscid droplets. Gravitational forces normal to the solid boundary have a significant effect on the displacement process, reducing the critical shear rate for viscous drops and increasing the rate for inviscid droplets. The low-viscosity limit λ→0 is shown to be a singular limit in the lubrication theory, and the proper scaling for Ca at small λ is identified.

Critical Role of Immobilized Factor VIII In Solid-Phase Blood Coagulation During Mural Thrombogenesis Under Whole Blood Flow Conditions

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2199-2199
Author(s):  
Masaaki Doi ◽  
Mitsuhiko Sugimoto ◽  
Hideto Matsui ◽  
Tomoko Matsumoto ◽  
Midori Shima
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Whole Blood ◽  
Solid Phase ◽  
Glass Plate ◽  
High Shear Rate ◽  
High Shear ◽  
Fibrin Deposition ◽  
Flow Conditions

Abstract Abstract 2199 Coagulation factor VIII (FVIII), lacking in hemophilic blood, plays an essential role in mechanisms of fibrin plug formation to arrest bleeding at sites of injured vessel walls. Physiologic activity of FVIII circulating in bloodstream (soluble FVIII; S-FVIII) could be extensively evaluated so far by classic plasma coagulation assays such as activated partial thromboplastin time. However, the in vivo functional relevance of FVIII bound to von Willebrand factor (VWF) which is immobilized in subendothelium (immobilized FVIII; I-FVIII) is more complex and remains to be addressed. Using an in vitro perfusion chamber system, we have therefore evaluated the function of I-FVIII in the process of mural thrombus generation under whole blood flow conditions. FVIII-free VWF was purified in the presence of 0.35 M CaCl2 from cryoprecipitate, and coated on a glass plate. Various concentrations (0 as a control, 0.1, 0.3, 1, or 3 U/ml) of recombinant FVIII (Kogenate FS provided by Bayer Pharmaceutical Co.) were reacted with the FVIII-free VWF-coated glass plate. After non-adherent proteins were washed out, the amount of FVIII immobilized to a glass surface via VWF (I-FVIII) was measured by ELISA-based assay using a peroxidase-conjugated anti-FVIII polyclonal antibody. Whole blood was then perfused over a glass plate described above in a parallel plate flow chamber with various shear rates, and the thrombus generation process on a glass surface was observed in real time by confocal laser scanning microscopy. The development of intra-thrombus fibrin deposition was assessed by immune-staining of thrombi with a fluorescence-labeled anti-fibrin specific monoclonal antibody (NYB-T2G1; Accurate Chem.), reflecting solid-phase blood coagulation reaction during mural thrombogenesis. In perfusion of control blood with a high shear rate (1500 s-1), the intra-thrombus fibrin deposition was found to increase as a function of I-FVIII, resulting in the 2.5-fold greater fibrin deposition at the plateau as compared to control thrombi generated in the absence of I-FVIII. This I-FVIII effect on intra-thrombus fibrin deposition was also confirmed in perfusion of synthetic hemophilic blood (S-FVIII activity < 1%) which was prepared by the incubation of control blood with an anti-FVIII human IgG (final inhibitor titer in synthetic blood; 5, 10, or 20 Bethesda U/ml). Indeed, I-FVIII normalized in a dose-dependent manner the reduced fibrin deposition (20-35% of normal control) within synthetic hemophilic thrombi generated in the absence of S-FVIII under a high shear rate condition. The improvement of impaired fibrin deposition by I-FVIII was unvarying regardless of the anti-FVIII inhibitor titer in synthetic hemophilic blood. In contrast, the direct addition of recombinant FVIII into synthetic hemophilic blood was poorly effective in this regard, due to the immediate neutralization of S-FVIII by an inhibitor involved in synthetic blood. Thus, these results clearly indicate that I-FVIII, independent of S-FVIII, does play a considerable role on the intra-thrombus fibrin-network formation in the process of mural thrombus generation under whole blood flow conditions with high shear rate, most relevant physiologically for the in vivo hemostasis and thrombosis. Our results might imply a possibility of novel strategic design targeting I-FVIII against hemophilic patients with a high titer anti-FVIII inhibitor. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Long-term Monitoring with Small and Medium-sized Telescopes on the Ground and in Space

2011 ◽  
Vol 7 (S285) ◽  
pp. 23-28
Author(s):  
P. A. Charles ◽  
M. M. Kotze ◽  
A. Rajoelimanana
Keyword(s):  
Large Scale ◽  
High Mass ◽  
Time Data ◽  
X Ray ◽  
Wide Range ◽  
Long Time ◽  
Sky Monitor ◽  
Real Time Data Processing ◽  
Large Telescopes

AbstractThe last 20 years have seen revolutionary developments of large-scale synoptic surveys of the sky, both from the ground (e.g., the MACHO and OGLE projects, which were targetted at micro-lensing studies) and in space (e.g., the X-ray All-Sky Monitor onboard RXTE). These utilised small and medium-sized telescopes to search for transient-like events, but they have now built up a huge database of long-term light-curves, thereby enabling archival research on a wide range of objects that has not been possible hitherto. This is illustrated with examples of long time-scale optical and X-ray variability studies from the field of X-ray binary research: the high-mass BeX binaries in the SMC (using MACHO and OGLE), and the bright galactic-bulge X-ray sources (mostly LMXBs, using RXTE/ASM). As such facilities develop greater capabilities in future and at other wavelengths (developments in South Africa will be described), real-time data processing will allow much more rapid follow-up studies with the new generation of queue-scheduled large telescopes such as SALT.

Smooth Robust Subspace Based Model Reduction

2013 ◽  
Author(s):  
David Chelidze
Keyword(s):  
Large Scale ◽  
Model Development ◽  
Reduced Order ◽  
Time Dynamics ◽  
Wide Range ◽  
Long Time ◽  
Numerical Instabilities ◽  
Dynamical Consistency ◽  
Computational Resources ◽  
New Framework

Long-time numerical simulations of large-scale mechanistic models of complex systems (e.g., molecular dynamics, computational fluid dynamics, structural finite element, or multi-body dynamics models) are still problematic, either due to numerical instabilities or the excessive necessary computational resources. Therefore, reduced models that can be simulated for long-time and provide truthful approximations to the actual long-time dynamics, are needed. A new framework — based on new concepts of dynamical consistency and subspace robustness — for identifying subspaces suitable for reduced-order model development is presented. Model reductions based on proper and smooth orthogonal decompositions (POD and SOD, respectively) are considered and tested using a nonlinear four-degree-of-freedom model. It is shown that the new framework identifies subspaces that provide accurate model reductions for a range of forcing parameters, and that only four and higher dimensional models could be dynamically consistent. In addition, for reduced-order models based on randomly driven data, a four-dimensional SOD-based model outperformed a five-dimensional POD-based model. Finally, randomly driven data-based models generally outperformed harmonically driven data-based models when tested for a wide range of forcing amplitudes.

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