scholarly journals Comparison of Swine and Human Computational Hemodynamics Models for the Study of Coronary Atherosclerosis

2021 ◽  
Vol 9 ◽  
Author(s):  
Giuseppe De Nisco ◽  
Claudio Chiastra ◽  
Eline M. J. Hartman ◽  
Ayla Hoogendoorn ◽  
Joost Daemen ◽  
...  
Keyword(s):  
Coronary Arteries ◽  
Coronary Atherosclerosis ◽  
Computational Models ◽  
Fluid Dynamic ◽  
Western World ◽  
Dynamic Simulations ◽  
Anatomical Features ◽  
Coronary Syndrome ◽  
Flow Features ◽  
Long Time

Coronary atherosclerosis is a leading cause of illness and death in Western World and its mechanisms are still non completely understood. Several animal models have been used to 1) study coronary atherosclerosis natural history and 2) propose predictive tools for this disease, that is asymptomatic for a long time, aiming for a direct translation of their findings to human coronary arteries. Among them, swine models are largely used due to the observed anatomical and pathophysiological similarities to humans. However, a direct comparison between swine and human models in terms of coronary hemodynamics, known to influence atherosclerotic onset/development, is still lacking. In this context, we performed a detailed comparative analysis between swine- and human-specific computational hemodynamic models of coronary arteries. The analysis involved several near-wall and intravascular flow descriptors, previously emerged as markers of coronary atherosclerosis initiation/progression, as well as anatomical features. To do that, non-culprit coronary arteries (18 right–RCA, 18 left anterior descending–LAD, 13 left circumflex–LCX coronary artery) from patients presenting with acute coronary syndrome were imaged by intravascular ultrasound and coronary computed tomography angiography. Similarly, the three main coronary arteries of ten adult mini-pigs were also imaged (10 RCA, 10 LAD, 10 LCX). The geometries of the imaged coronary arteries were reconstructed (49 human, 30 swine), and computational fluid dynamic simulations were performed by imposing individualized boundary conditions. Overall, no relevant differences in 1) wall shear stress-based quantities, 2) intravascular hemodynamics (in terms of helical flow features), and 3) anatomical features emerged between human- and swine-specific models. The findings of this study strongly support the use of swine-specific computational models to study and characterize the hemodynamic features linked to coronary atherosclerosis, sustaining the reliability of their translation to human vascular disease.

scholarly journals An Accelerated Thrombosis Model for Computational Fluid Dynamics Simulations in Rotary Blood Pumps

2022 ◽  
Author(s):  
Christopher Blum ◽  
Sascha Groß-Hardt ◽  
Ulrich Steinseifer ◽  
Michael Neidlin
Keyword(s):  
Clinical Data ◽  
Computational Models ◽  
Thrombus Formation ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Model Parameters ◽  
Dynamic Simulations ◽  
Heartmate Ii ◽  
Blood Pumps ◽  
Rotary Blood Pumps

Abstract Purpose Thrombosis ranks among the major complications in blood-carrying medical devices and a better understanding to influence the design related contribution to thrombosis is desirable. Over the past years many computational models of thrombosis have been developed. However, numerically cheap models able to predict localized thrombus risk in complex geometries are still lacking. The aim of the study was to develop and test a computationally efficient model for thrombus risk prediction in rotary blood pumps. Methods We used a two-stage approach to calculate thrombus risk. The first stage involves the computation of velocity and pressure fields by computational fluid dynamic simulations. At the second stage, platelet activation by mechanical and chemical stimuli was determined through species transport with an Eulerian approach. The model was compared with existing clinical data on thrombus deposition within the HeartMate II. Furthermore, an operating point and model parameter sensitivity analysis was performed. Results Our model shows good correlation (R2 > 0.93) with clinical data and identifies the bearing and outlet stator region of the HeartMate II as the location most prone to thrombus formation. The calculation of thrombus risk requires an additional 10–20 core hours of computation time. Conclusion The concentration of activated platelets can be used as a surrogate and computationally low-cost marker to determine potential risk regions of thrombus deposition in a blood pump. Relative comparisons of thrombus risk are possible even considering the intrinsic uncertainty in model parameters and operating conditions.

scholarly journals Computational fluid dynamic simulations of image-based stented coronary bifurcation models

2013 ◽  
Vol 10 (84) ◽  
pp. 20130193 ◽  
Author(s):  
Claudio Chiastra ◽  
Stefano Morlacchi ◽  
Diego Gallo ◽  
Umberto Morbiducci ◽  
Rubén Cárdenes ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Coronary Arteries ◽  
Fluid Dynamic ◽  
Patient Specific ◽  
Conventional Coronary Angiography ◽  
Coronary Bifurcation ◽  
Dynamic Simulations ◽  
Stent Restenosis ◽  
Relative Residence Time ◽  
In Stent Restenosis

One of the relevant phenomenon associated with in-stent restenosis in coronary arteries is an altered haemodynamics in the stented region. Computational fluid dynamics (CFD) offers the possibility to investigate the haemodynamics at a level of detail not always accessible within experimental techniques. CFD can quantify and correlate the local haemodynamics structures which might lead to in-stent restenosis. The aim of this work is to study the fluid dynamics of realistic stented coronary artery models which replicate the complete clinical procedure of stent implantation. Two cases of pathologic left anterior descending coronary arteries with their bifurcations are reconstructed from computed tomography angiography and conventional coronary angiography images. Results of wall shear stress and relative residence time show that the wall regions more prone to the risk of restenosis are located next to stent struts, to the bifurcations and to the stent overlapping zone for both investigated cases. Considering a bulk flow analysis, helical flow structures are generated by the curvature of the zone upstream from the stent and by the bifurcation regions. Helical recirculating microstructures are also visible downstream from the stent struts. This study demonstrates the feasibility to virtually investigate the haemodynamics of patient-specific coronary bifurcation geometries.

scholarly journals A Fluid Dynamics Approach for Assessing the Intelligent Geomorphic Design of the Japanese Pufferfish Nest

Geosciences ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 22
Author(s):  
Abdulla Jailam Shameem ◽  
Manousos Valyrakis ◽  
Hossein Zare-Behtash
Keyword(s):  
Shear Stress ◽  
Flow Velocity ◽  
Fluid Dynamic ◽  
Central Zone ◽  
Nest Structure ◽  
Dynamic Simulations ◽  
Site Analysis ◽  
Nesting Site ◽  
Flow Features

Research into the geometric nests built by white-spotted pufferfish indicated the nest’s potential for flow control and reduction in flow velocity. However, studies to date have only focused on the construction process and behaviour of the male pufferfish. Hence, the form and functions of the unique features of the nest remain unclear. The present study aims to explore the flow features most useful in understanding the habitat conditions of the nest through a combination of photogrammetric reconstructions of the nest features and two-dimensional (2D) computational fluid dynamic simulations. The findings show the role of the nest structure in reducing the flow velocity and shear stress within the nesting site. Analysis of shear stress indicates that male pufferfish build the outer zones of the nest with coarser material that improves the overall shear strength of these areas. The study identified the function of the nest structure in the protection of the eggs through reduction in flow variations and improved aeration. The addition of shell fragments to the nest peaks by the male pufferfish contributes to the resiliency of the nest structure and ensures a stable bed surface at the central zone.

Computational Predictions of Aero-Thermal Performance of a Turbine Filleted Blade Cascade With Endwall Film Cooling

2012 ◽  
Author(s):  
G. Barigozzi ◽  
S. Ravelli ◽  
M. Maritano ◽  
R. Abram
Keyword(s):  
Thermal Performance ◽  
Film Cooling ◽  
Fluid Dynamic ◽  
Secondary Flows ◽  
Dynamic Simulations ◽  
Film Cooling Effectiveness ◽  
Numerical Predictions ◽  
Cascade Arrangement ◽  
Flow Features ◽  
Endwall Film Cooling

In this study computational fluid dynamic simulations of a turbine blade with endwall film cooling were compared to measurements of both aerodynamic and thermal performance. The experimental data were collected at low Mach number (Ma2is = 0.3) in a linear cascade arrangement with 7 blades which geometry is typical of first stage high pressure turbine. A junction between the blade hub and the platform is provided by a 3D fillet. Coolant is injected through ten cylindrical holes distributed along the blade pressure side. Coolant to mainstream mass flow ratio was set to assure an inlet blowing ratio of M1 = 2.4 and M1 = 3.2. The simulations were carried out using the Shear Stress Transport (SST) k-ω turbulence model. Numerical predictions were compared against experimentally measured secondary flows and endwall film cooling effectiveness, at different injection conditions. Simulation results agreed with the experiments for what concerns the general shape and the location of secondary flows. However, some limitations in the modeling were highlighted when going into the details of loss computation and vortex structure. Predictions overestimated both secondary and midspan blade wake losses. Moreover, the effect of the fillet on the aerodynamic flow features was not fully captured. Predicted film cooling results showed the sweeping of coolant across the passage in agreement with experiments even though jets persistency was higher than that measured. Levels of adiabatic effectiveness were generally well simulated.

Abstract 15117: The Catheter Uncertainty Principle: Does the Presence of a Catheter Alter Hemodynamics?

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Michael Kaplan ◽  
Madhurima Vardhan ◽  
Amanda RANDLES
Keyword(s):  
Coronary Arteries ◽  
Lattice Boltzmann ◽  
Clinical Decision Making ◽  
Pressure Field ◽  
Fluid Dynamic ◽  
Diagnostic Procedures ◽  
Clinical Decision ◽  
Patient Specific ◽  
Dynamic Simulations ◽  
Catheter Size

Introduction: Catheters are an essential component of measuring invasive hemodynamic quantities. However, by the very nature of a catheter's presence, it acts to disturb the normal flow field, potentially altering measured pressures and derived quantities, such as FFR. Computational fluid dynamic simulations are performed to explore how vessel lumenal area and catheter size effect pressures. Methods: Patient-specific anatomical reconstructions are coupled with HARVEY, a massively parallel lattice-Boltzmann fluid solver, to calculate 3D blood flow around simulated catheters. We explore the effects of catheter size in vessels ranging from 5 mm in diameter, a right ventricle to pulmonary artery shunt (RVPAS) in a patient with HLHS, and smaller, in coronary arteries. Pressures sampled at the location corresponding to the distal end of the catheter are compared and FFR is calculated for the coronary models. Results: Figure 1A illustrates the calculated pressure waveforms for simulated catheter sizes in a RVPAS. In this case, the catheter does not significantly alter the pressure field unless unrealistically large catheters, such as a 13 Fr, are used. For adult coronary arteries (Figure 1B), reasonable catheter sizes result in appreciable decreases in sampled pressures and, consequently, in calculated FFR (Figure 1C). Conclusion: The presence of a sufficiently large catheter (>50% of the vessel lumenal area) causes a noticeable decrease in the pressures at the tip of the catheter. While unlikely to occur in larger vessels, this can occur during left heart catheterizations of diseased coronary arteries. This causes an artificial decrease in FFR, which can potentially alter clinical decision making. While catheters are the gold standard for pressure measurements, an improved understanding of the inherent sensitivity of their measurements to unobstructed vessel lumenal area is important for interpreting the results of catheter-based diagnostic procedures.

Psychology: Volume 5

2019 ◽  
Keyword(s):  
World View ◽  
Science Volume ◽  
Western World ◽  
Mental Life ◽  
Long Time ◽  
The Difference ◽  
New Perspective ◽  
Indian Setting ◽  
The Mind ◽  
The Relationship

This survey of research on psychology in five volumes is a part of a series undertaken by the ICSSR since 1969, which covers various disciplines under social science. Volume Five of this survey, Explorations into Psyche and Psychology: Some Emerging Perspectives, examines the future of psychology in India. For a very long time, intellectual investments in understanding mental life have led to varied formulations about mind and its functions across the word. However, a critical reflection of the state of the disciplinary affairs indicates the dominance of Euro-American theories and methods, which offer an understanding coloured by a Western world view, which fails to do justice with many non-Western cultural settings. The chapters in this volume expand the scope of psychology to encompass indigenous knowledge available in the Indian tradition and invite engaging with emancipatory concerns as well as broadening the disciplinary base. The contributors situate the difference between the Eastern and Western conceptions of the mind in the practice of psychology. They look at this discipline as shaped by and shaping between systems like yoga. They also analyse animal behaviour through the lens of psychology and bring out insights about evolution of individual and social behaviour. This volume offers critique the contemporary psychological practices in India and offers a new perspective called ‘public psychology’ to construe and analyse the relationship between psychologists and their objects of study. Finally, some paradigmatic, pedagogical, and substantive issues are highlighted to restructure the practice of psychology in the Indian setting.

scholarly journals Impact of Deuteration and Temperature on Furan Ring Dynamics

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2889
Author(s):  
Przemyslaw Dopieralski ◽  
Iryna V. Omelchenko ◽  
Zdzislaw Latajka
Keyword(s):  
Conformational Changes ◽  
Furan Ring ◽  
Computational Studies ◽  
Significant Progress ◽  
Dynamic Simulations ◽  
Cyclic Molecules ◽  
Ring Dynamics ◽  
Different Temperatures ◽  
Long Time ◽  
Shape And Size

Despite significant progress in conformational analysis of cyclic molecules, the number of computational studies is still limited while most of that available in the literature data have been obtained long time ago with outdated methods. In present research, we have studied temperature driven conformational changes of the furan ring at three different temperatures. Additionally, the effect of deuteration on the ring dynamics is discussed; in addition, the aromaticity indices following the Bird and HOMA schemes are computed along all trajectories. Our ab initio molecular dynamic simulations revealed that deuteration has changed the furan ring dynamics and the obvious consequences; in addition, the shape and size of molecule are expected to be different.

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