Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session F25: Biological FlowsLive
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Sponsoring Units: DFD Chair: Georgios Gounaris, University of Pennsylvania |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F25.00001: Effect of Valve Spacing on Pumping Performance of Lymphatic Vessels Ki Wolf, J. Brandon Dixon, Alexander Alexeev The lymphatic system is crucial for maintaining body’s homeostasis by transporting interstitial fluid (lymph), fatty acid, and immune cells. The lymph and various macromolecules are transported through networks of valves and contracting vessels, which allows unidirectional pumping without any centralized pump against adverse pressure gradient. For this work, we employ a fully coupled 3D fluid-structure interaction model to focus on the effect of lymphatic valve spacing and vessel contraction on pumping performance in terms of factors such as flowrate and pumping efficiency. Our results indicate that flowrate can be optimized by having valve spacing smaller than the vessel contraction wavelength, as such valve placement decreases the backflow caused during lymphatic pumping. On the other hand, smaller valve spacing increases viscous losses in the vessel. Thus, our results provide a greater understanding of the role that lymphatic valves play, specifically on how different valve positions alter lymphatic pumping performance. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F25.00002: Systematic in silico investigation of the blood hyperviscosity syndrome and its biophysical origins Elahe Javadi, Yixiang Deng, George Em Karniadakis, Safa Jamali Hyperviscosity syndrome (HVS) is a disease accompanied by an increase in the blood viscosity and is commonly classified with regards to its cause: (a) serum or plasma hyperviscosity due to an increase in immunoglobulins, and (b) whole-blood hyperviscosity associated with abnormalities in properties of red blood cell (RBC) or plasma protein fractions. The main causes of the whole-blood HVS are the aggregation of RBCs due to the increase of proteins especially fibrinogen, overproduction of RBCs called polycythemia, and changing the mechanical properties of RBCs such as loss of deformability. Blood viscosity measurement is an essential need in the process of diagnosis and treatment. The in vitro experimental rheometry techniques are challenging due to the lack of systematic control over all biophysical processes involved while numerical methods are accurate and powerful alternatives. In this work, we implement a Dissipative Particle Dynamic method to study the effects of some important factors like plasma viscosity, RBC volume fraction, aggregation, and RBC deformability on the overall viscosity of blood. Our results indicate that the increase in the fibrinogen concentration, leading to effective attraction to emerge between RBCs plays a major role in increasing blood viscosity. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F25.00003: The vasculature as a uniform perfusion network Georgios Gounaris, Miguel Ruiz Garcia, Eleni Katifori Life is water-based and as a result organisms have developed complex flow networks that optimize the transport of oxygen and nutrients. Given the rich hierarchical structure that characterizes animal and plant vasculature, a question arises: Is there an optimization principle that biological flow networks obey while they self-organize and remodel to efficiently perfuse the tissue? Considering dissipation alone is not enough since it leads to tree-like networks, far from the loopy architecture of animal micro-vasculature. We propose a novel local adaptation rule that stems from an approximation to the optimization process that accounts for homogeneous perfusion, energy dissipation and material cost. The competition between these terms produces rich network morphologies. We also show that our local rule gives promising results when it is applied to experimental data of the rat mesentery network. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F25.00004: Lingering dynamics of microvascular blood flow in vivo Alexander Kihm, Stephan Quint, Matthias Laschke, Michael Menger, Thomas John, Lars Kaestner, Christian Wagner The microcirculation in animals and humans is directly linked to their health state. Any alterations in this blood flow may lead to pathological states, e.g. ischemia. Since typical vessel dimensions in the capillary bed are in the range of individual red blood cells, the particulate nature of blood is well pronounced. While approaching a bifurcation apex, red blood cells can drastically reduce their velocity, and even rest at this apex. These so-called lingering events are well-known in the eld of hemodynamics, however, no systematic studies concerning the effects on the subsequent bloodstream exist. We present an experimental study on living hamsters investigating the lingering events and consequences thereof. Therefore, we perform a joint method of particle tracking and integrated signal evaluation of flowing red blood cells. We show evidence that lingering events lead to a shift of median durations of cell-free areas. Further, lingering events can be linked to the redistribution of consecutive red blood cells in the bifurcating geometry as well as a spatial distancing of red blood cells. |
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