scholarly journals Shear‐Rate‐Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels

2018 ◽  
Vol 45 (2) ◽  
pp. 766-777 ◽  
Author(s):  
Gianvito Scaringi ◽  
Wei Hu ◽  
Qiang Xu ◽  
Runqiu Huang
Keyword(s):  
Shear Rate ◽  
Rate Dependent ◽  
Dependent Behavior ◽  
Bimaterial Interfaces ◽  
Stress Levels

Dynamic evolution of shear rate-dependent behavior of rock discontinuity under shearing condition

2021 ◽  
Vol 28 (6) ◽  
pp. 1875-1887
Author(s):  
Lin-lin Gu ◽  
Zhen Wang ◽  
Feng Zhang ◽  
Fei Gao ◽  
Xiao Wang
Keyword(s):  
Shear Rate ◽  
Dynamic Evolution ◽  
Rock Discontinuity ◽  
Rate Dependent ◽  
Dependent Behavior

Adenosine Diphosphate-Induced Aggregation of Human Platelets in Flow Through Tubes: III. Shear and Extrinsic Fibrinogen-Dependent Effects

1994 ◽  
Vol 71 (01) ◽  
pp. 078-090 ◽  
Author(s):  
H L Goldsmith ◽  
M M Frojmovic ◽  
Susan Braovac ◽  
Fiona McIntosh ◽  
T Wong
Keyword(s):  
Shear Rate ◽  
Single Cells ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
Size Analysis ◽  
Fibrinogen Concentration ◽  
Human Fibrinogen ◽  
Shear Rates ◽  
Rate Dependent ◽  
Induced Aggregation

SummaryThe effect of shear rate and fibrinogen concentration on adenosine diphosphate-induced aggregation of suspensions of washed human platelets in Poiseuille flow at 23°C was studied using a previously described double infusion technique and resistive particle counter size analysis (1). Using suspensions of multiple-centrifuged and -washed cells in Tyrodes-albumin [3 × 105 μl−1; (17)] with [fibrinogen] from 0 to 1.2μM, the, rate and extent of aggregation with 0.7 μM ADP in Tyrodes-albumin were measured over a range of mean transit times from 0.2 to 43 s, and at mean tube shear rates, Ḡ, = 41.9, 335 and 1,335 s−1. As measured by the decrease in singlet concentration, aggregation at 1.2 μM fibrinogen increased with increasing Ḡ up to 1,335 s1, in contrast to that previously reported in citratcd plasma, in which aggregation reached a maximum at Ḡ = 335 s−1. Without added fibrinogen, there was no aggregation at Ḡ = 41.9 s1; at Ḡ = 335 s1, there was significant aggregation but with an initial lag time, aggregation increasing further at Ḡ = 1,335 s−1. Without added fibrinogen, aggregation was abolished at all Ḡ upon incubation with the hexapeptide GRGDSP, but was almost unaffected by addition of an F(ab’)2 fragment of an antibody to human fibrinogen. Aggregation in the absence of added fibrinogen was also observed at 37°C. The activation of the multiple-washed platelets was tested using flow cytometry with the fluorescently labelled monoclonal antibodies FITC-PAC1 and FITC-9F9. It was shown that 57% of single cells in unactivated PRT expressed maximal GPIIb-IIIa fibrinogen receptors (MoAb PAC1) and 54% expressed pre-bound fibrinogen (MoAb 9F9), with further increases on ADP activation. However, incubation with GRGDSP and the F(ab’)2 fragment did not inhibit the prebound fibrinogen. Moreover, relatively unactivated cells (8% expressing receptor, 14% prebound fibrinogen), prepared from acidified cPRP by single centrifugation with 50 nM of the stable prostacyclin derivative, ZK 36 374, and resuspension in Tyrodes-albumin at 5 × 104 μl−1, aggregated with 2 and 5 μM ADP at Ḡ = 335 and 1,335 s−1 in the absence of added fibrinogen. We therefore postulate that a protein such as von Willebrand factor, secreted during platelet isolation or in flow at sufficiently high shear rates, may yield the observed shear-rate dependent aggregation without fibrinogen.

Platelet and Shear Rate Promote Tumor Cell Adhesion to Human Endothelial Extracellular Matrix - Absence of a Role for Platelet Cyclooxygenase

1989 ◽  
Vol 61 (03) ◽  
pp. 485-489 ◽  
Author(s):  
Eva Bastida ◽  
Lourdes Almirall ◽  
Antonio Ordinas
Keyword(s):  
Cell Adhesion ◽  
Shear Rate ◽  
Tumor Cell ◽  
Umbilical Vein ◽  
Blood Platelets ◽  
Flow Conditions ◽  
Tumor Cell Adhesion ◽  
Rate Dependent ◽  
Static Conditions

SummaryBlood platelets are thought to be involved in certain aspects of malignant dissemination. To study the role of platelets in tumor cell adherence to vascular endothelium we performed studies under static and flow conditions, measuring tumor cell adhesion in the absence or presence of platelets. We used highly metastatic human adenocarcinoma cells of the lung, cultured human umbilical vein endothelial cells (ECs) and extracellular matrices (ECM) prepared from confluent EC monolayers. Our results indicated that under static conditions platelets do not significantly increase tumor cell adhesion to either intact ECs or to exposed ECM. Conversely, the studies performed under flow conditions using the flat chamber perfusion system indicated that the presence of 2 × 105 pl/μl in the perfusate significantly increased the number of tumor cells adhered to ECM, and that this effect was shear rate dependent. The maximal values of tumor cell adhesion were obtained, in presence of platelets, at a shear rate of 1,300 sec-1. Furthermore, our results with ASA-treated platelets suggest that the role of platelets in enhancing tumor cell adhesion to ECM is independent of the activation of the platelet cyclooxygenase pathway.

scholarly journals Hydrodynamic Shear Effects on Grafted and Non-Grafted Collapsed Polymers

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 926 ◽  
Author(s):  
Richard Schwarzl ◽  
Roland Netz
Keyword(s):  
Shear Rate ◽  
Brownian Dynamics ◽  
Tensile Force ◽  
Grafted Polymers ◽  
Critical Shear Rate ◽  
Rate Dependent ◽  
Coil Transition ◽  
Hydrodynamic Shear ◽  
Linear Shear ◽  
Dynamics Simulations

We study collapsed homo-polymeric molecules under linear shear flow conditions using hydrodynamic Brownian dynamics simulations. Tensile force profiles and the shear-rate-dependent globular-coil transition for grafted and non-grafted chains are investigated to shine light on the different unfolding mechanisms. The scaling of the critical shear rate, at which the globular-coil transition takes place, with the monomer number is inverse for the grafted and non-grafted scenarios. This implicates that for the grafted scenario, larger chains have a decreased critical shear rate, while for the non-grafted scenario higher shear rates are needed in order to unfold larger chains. Protrusions govern the unfolding transition of non-grafted polymers, while for grafted polymers, the maximal tension appears at the grafted end.

Model Development for PZT Bimorph Actuation Employed for Micro-Air Vehicles

2016 ◽  
Author(s):  
John Crews ◽  
Nikolas Bravo ◽  
Ralph Smith
Keyword(s):  
Model Development ◽  
Micro Air Vehicles ◽  
Energy Model ◽  
Comprehensive Model ◽  
Actuator Dynamics ◽  
Rate Dependent ◽  
Dependent Behavior ◽  
Bimorph Actuators ◽  
Homogenized Energy Model ◽  
Air Vehicles

In the paper, we discuss the development of a model for PZT bimorph actuators used to power micro-air vehicles including Robobee. Due to highly dynamic drive regimes required for the actuators, models must quantify the nonlinear, hysteretic, and rate-dependent behavior inherent to PZT in these regimes. We employ the homogenized energy model (HEM) framework to model the actuator dynamics and numerically we illustrate the capability of the model to characterize the inherent hysteresis. This provides a comprehensive model, which can be inverted and implemented for certain control regimes.

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