The effect of Womersley number and particle radius on the accumulation of lipoproteins in the human aorta

The Molecular Dynamics technique is used to investigate size segregation by shaking in cohesionless granular materials. Temporal evolution of the height h of the tagged particle with different size and mass is measured for various values of the particle radius and specific gravity. It becomes evident that h approaches the steady state value h∞ independent of initial positions. There exists a threshold of the specific gravity of the particle. Below the threshold, h∞ is an increasing function of the particle size, whereas above it, h∞ decreases with increasing the particle radius. The relaxation time τ towards the steady state is calculated and its dependence on the particle radius and specific gravity is clarified. The pressure gradient of pure systems is also measured and turned out to be almost constant. This suggests that the buoyancy force due to the pressure gradient is not responsible to h∞.

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Mimicking the Mechanical Properties of Aortic Tissue with Pattern-Embedded 3D Printing for a Realistic Phantom

Materials ◽

10.3390/ma13215042 ◽

2020 ◽

Vol 13 (21) ◽

pp. 5042

Author(s):

Jaeyoung Kwon ◽

Junhyeok Ock ◽

Namkug Kim

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

3D Printing ◽

Mechanical Characteristics ◽

Aortic Wall ◽

Tensile Tests ◽

Human Aorta ◽

Aortic Tissue ◽

Medical Field ◽

Base Materials

3D printing technology has been extensively applied in the medical field, but the ability to replicate tissues that experience significant loads and undergo substantial deformation, such as the aorta, remains elusive. Therefore, this study proposed a method to imitate the mechanical characteristics of the aortic wall by 3D printing embedded patterns and combining two materials with different physical properties. First, we determined the mechanical properties of the selected base materials (Agilus and Dragonskin 30) and pattern materials (VeroCyan and TPU 95A) and performed tensile testing. Three patterns were designed and embedded in printed Agilus–VeroCyan and Dragonskin 30–TPU 95A specimens. Tensile tests were then performed on the printed specimens, and the stress-strain curves were evaluated. The samples with one of the two tested orthotropic patterns exceeded the tensile strength and strain properties of a human aorta. Specifically, a tensile strength of 2.15 ± 0.15 MPa and strain at breaking of 3.18 ± 0.05 mm/mm were measured in the study; the human aorta is considered to have tensile strength and strain at breaking of 2.0–3.0 MPa and 2.0–2.3 mm/mm, respectively. These findings indicate the potential for developing more representative aortic phantoms based on the approach in this study.

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Oxidative Activity of Aortic Tissue of Man, the Rabbit and the Dog, With Special Reference to Succinic Dehydrogenase and Cytochrome Oxidase

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1958.195.2.476 ◽

1958 ◽

Vol 195 (2) ◽

pp. 476-480 ◽

Cited By ~ 16

Author(s):

Nelicia Maier ◽

Henry Haimovici

Keyword(s):

Special Reference ◽

Cytochrome Oxidase ◽

Abdominal Aorta ◽

Abdominal Segment ◽

Species Difference ◽

Succinic Dehydrogenase ◽

Hepatic Tissue ◽

Human Aorta ◽

Aortic Tissue ◽

Enzymatic Systems

Succinic dehydrogenase and cytochrome oxidase activities were determined in homogenates of three aortic segments (ascending and arch, descending thoracic, abdominal) and liver of man, the rabbit and the dog. Both enzymes exhibited the lowest activity in human aorta. Succinic dehydrogenase exhibited the highest activity in the thoracic aorta of the dog and intermediate activity in the latter's abdominal segment and the rabbit's aorta. Cytochrome oxidase, in contrast, exhibited the highest activity in the rabbit's aorta. A slight gradient of decreasing activity from thoracic to abdominal aorta was noted for cytochrome oxidase in both the rabbit and dog and for succinic dehydrogenase in the rabbit, whereas a significant decrease in the latter enzyme was noted in the abdominal segment of the dog. No gradient of activity was apparent in man. Liver exhibited the lowest activity for both enzymes in man, highest in the dog and intermediate in the rabbit. The above findings suggest a biologic species difference between the aorta of man, the rabbit and the dog, which may be partly ascribed to a difference in the components of the above two enzymatic systems. The same species difference holds true for hepatic tissue.

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Determination of Zero Dimensional, Apparent Devolatilization Kinetics for Biomass Particles at Suspension Firing Conditions

Energies ◽

10.3390/en14041018 ◽

2021 ◽

Vol 14 (4) ◽

pp. 1018

Author(s):

Anna Espekvist ◽

Tian Li ◽

Peter Glarborg ◽

Terese Løvås ◽

Peter Arendt Jensen

Keyword(s):

Aspect Ratio ◽

Particle Density ◽

Fluid Dynamic ◽

Particle Radius ◽

Biomass Combustion ◽

Least Squares Regression ◽

Gas Temperature ◽

Density Maximum ◽

Parameter Ranges ◽

The Impact

As part of the strive for a carbon neutral energy production, biomass combustion has been widely implemented in retrofitted coal burners. Modeling aids substantially in prediction of biomass flame behavior and thus in boiler chamber conditions. In this work, a simple model for devolatilization of biomass at conditions relevant for suspension firing is presented. It employs Arrhenius parameters in a single first order (SFOR) devolatilization reaction, where the effects of kinetics and heat transfer limitations are lumped together. In this way, a biomass particle can be modeled as a zero dimensional, isothermal particle, facilitating computational fluid dynamic calculations of boiler chambers. The zero dimensional model includes the effects of particle aspect ratio, particle density, maximum gas temperature, and particle radius. It is developed using the multivariate data analysis method, partial least squares regression, and is validated against a more rigorous semi-2D devolatilization model. The model has the capability to predict devolatilization time for conditions in the parameter ranges; radius (39–1569 μμm), density (700–1300 kg/m3), gas temperature (1300–1900 K), aspect ratio (1.01–8). Results show that the particle radius and gas phase temperature have a large influence on the devolatilization rate, and the aspect ratio has a comparatively smaller effect, which, however, cannot be neglected. The impact of aspect ratio levels off as it increases. The model is suitable for use as stand alone or as a submodel for biomass particle devolatilization in CFD models.

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Nanonet force microscopy for measuring forces in single smooth muscle cells of the human aorta

Molecular Biology of the Cell ◽

10.1091/mbc.e17-01-0053 ◽

2017 ◽

Vol 28 (14) ◽

pp. 1894-1900 ◽

Cited By ~ 9

Author(s):

Alexander Hall ◽

Patrick Chan ◽

Kevin Sheets ◽

Matthew Apperson ◽

Christopher Delaughter ◽

...

Keyword(s):

Smooth Muscle ◽

External Perturbation ◽

Human Aorta ◽

Cycle Times ◽

Force Microscopy ◽

Cell Matrix ◽

Innovative Methods ◽

A Cell ◽

Inside Out

A number of innovative methods exist to measure cell–matrix adhesive forces, but they have yet to accurately describe and quantify the intricate interplay of a cell and its fibrous extracellular matrix (ECM). In cardiovascular pathologies, such as aortic aneurysm, new knowledge on the involvement of cell–matrix forces could lead to elucidation of disease mechanisms. To better understand this dynamics, we measured primary human aortic single smooth muscle cell (SMC) forces using nanonet force microscopy in both inside-out (I-O intrinsic contractility) and outside-in (O-I external perturbation) modes. For SMC populations, we measured the I-O and O-I forces to be 12.9 ± 1.0 and 57.9 ± 2.5 nN, respectively. Exposure of cells to oxidative stress conditions caused a force decrease of 57 and 48% in I-O and O-I modes, respectively, and an increase in migration rate by 2.5-fold. Finally, in O-I mode, we cyclically perturbed cells at constant strain of varying duration to simulate in vivo conditions of the cardiac cycle and found that I-O forces decrease with increasing duration and O-I forces decreased by half at shorter cycle times. Thus our findings highlight the need to study forces exerted and felt by cells simultaneously to comprehensively understand force modulation in cardiovascular disease.

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