Whats is the definition of shear rate?5 answersShear rate is a crucial parameter in various fields such as fluid dynamics and soil mechanics. In the context of fluid dynamics, shear rate refers to the rate at which adjacent layers of fluid move with respect to each other. It plays a significant role in determining the heat transfer coefficient of non-Newtonian fluids at different shear rates. Additionally, in the study of soil mechanics, shear rate is essential for understanding the rate dependency of residual strength in clay soils. Moreover, shear rate has been linked to endothelial and smooth muscle cell function, neointimal hyperplasia, and atherosclerotic plaque progression in the context of vascular studies. Understanding shear rate is crucial for various scientific and engineering applications, influencing phenomena ranging from fluid behavior to soil stability and vascular health.
Why shear stress is higher on arteriovenous malformations?5 answersShear stress is higher on arteriovenous malformations (AVMs) due to the hyper-sensitivity of vascular cells to mechanical stimuli, leading to increased angiogenesis. Studies have shown that both vascular smooth muscle cells (VSMCs)and endothelial cells (ECs)in AVMs exhibit elevated expression levels of pro-angiogenic factors under shear stress conditions compared to normal tissues. Additionally, disturbed blood flow in AVMs activates Notch receptors, promoting endothelial mesenchymal plasticity. Loss of Smad4 in endothelial cells increases sensitivity to flow, resulting in AVMs characterized by excessive elongation and polarity against the flow, along with increased proliferation and loss of arterial identity. Furthermore, wall shear stress measurements in feeding arteries of facial superficial AVMs can serve as a prognostic indicator, distinguishing stable from progressive AVMs.
How do different types of insulin pumps handle shear stress, and what are the implications for patient safety?5 answersDifferent types of insulin pumps handle shear stress differently, and this has implications for patient safety. One study evaluated the number of steps required to operate different insulin pump systems and found that the level of guidance provided by the systems varied depending on the specific task. Another study assessed the safety features of insulin pump therapy and recommended adjustments to enhance overall safety. Potential safety problems identified included software, wireless communication, hardware, alarms, human factors, and bolus-dose calculation. Additionally, a feasibility evaluation of a steel catheter in a patch pump found good tolerability and wear comfort of both the steel needle and the adhesive in patients with diabetes for up to 5 days. These findings suggest that the design and handling of insulin pumps play a significant role in ensuring patient safety and minimizing potential risks associated with shear stress.
What is the shear rate of blood?5 answersThe shear rate of blood varies depending on the specific conditions and situations being studied. In the context of investigating rheological properties of blood, shear rates ranging from 14 to 440 s−1 were used. In another study using a falling needle rheometer, shear rates in the range of 0 to 400 s−1 were observed. A computational fluid dynamics model of an end-to-side femoral anastomosis considered shear rates ranging from 1 to 1200 s−1. A clinical blood viscometer measured blood flow characteristics in the shear rate range of 100 to 10,000 s−1. Shear-induced aggregation in whole blood was studied using a cone-and-plate viscometer, with shear rates below 500 sec-1 leading to the development of aggregates. Overall, the shear rate of blood can vary depending on the experimental setup and conditions being investigated.
What is the relation between wall shear stress and plaque in carotid artery?5 answersWall shear stress (WSS) has been found to be related to plaque composition in the carotid artery. High time-averaged WSS (TAWSS) values have been correlated with larger macrophage areas and necrotic core sizes in advanced carotid plaques. Additionally, areas exposed to high TAWSS or low oscillatory shear index (OSI) have been found to have larger necrotic core sizes and macrophage areas. Furthermore, a combination of low TAWSS and low OSI has been associated with larger cap thickness in carotid plaques. These findings suggest that WSS plays a role in plaque vulnerability and composition in the carotid artery.
In fluid dynamics stoke flow is necessary to study avm hemodynamics?5 answersSteady flow simulations can be used to study the hemodynamics of cerebral aneurysms and evaluate the wall shear stress (WSS) field. Computational fluid dynamics (CFD) simulations can provide a better understanding of hemodynamics in aneurysms and improve diagnosis and treatment. In the study conducted by Geers et al., steady flow simulations accurately approximated the time-averaged (TA) WSS field of an aneurysm, but not the peak systole (PS) and end diastole (ED) WSS fields. The fast computation time of 6 minutes per simulation could help facilitate the introduction of CFD into clinical practice. However, it is important to note that this study specifically focused on cerebral aneurysms and may not directly address the question of whether stoke flow is necessary to study arteriovenous malformation (AVM) hemodynamics.