Spatial Variations in the Mechanical Properties of the Porcine Thoracic Aorta

2011 ◽  
Author(s):  
Jungsil Kim ◽  
Seungik Baek
Keyword(s):  
Mechanical Properties ◽  
Vascular Disease ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Vascular Tissue ◽  
Experimental Studies ◽  
Wall Stress ◽  
Clinical Decision ◽  
Arterial Tree

Characterization of the mechanical properties of a blood vessel is essential in understanding the progression of a vascular disease and for computational studies of vascular adaptation. For example, stiffness of vascular tissue is one of the major indicators to diagnose the vascular disease and make a clinical decision. Although previous studies reported the heterogeneity of the mechanical properties of arterial wall along the arterial tree [2], little was taken account for its circumferential variations. With the lack of experimental studies for investigating the circumferential variation, the aortic wall is typically assumed to have uniform deformation. Our previous study, however, has observed that there are circumferential variations in aortic wall stress and stiffness [1]. In addition to our previous study, we investigate further regional variations of the porcine thoracic aorta in both circumferential and longitudinal directions during the inflation test. Hence, we additionally test the distal thoracic aorta at each anterior and posterior side, respectively, and compare with the proximal thoracic aorta.

scholarly journals Properties of the high burnup structure in nuclear light water reactor fuel

2017 ◽  
Vol 105 (11) ◽  
Author(s):  
Thierry Wiss ◽  
Vincenzo V. Rondinella ◽  
Rudy J. M. Konings ◽  
Dragos Staicu ◽  
Dimitrios Papaioannou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Nuclear Fuel ◽  
Experimental Studies ◽  
Fuel Pellet ◽  
Extended Defects ◽  
Safety Margins ◽  
Fission Gas ◽  
High Burnup ◽  
Formed Structure

AbstractThe formation of the high burnup structure (HBS) is possibly the most significant example of the restructuring processes affecting commercial nuclear fuel in-pile. The HBS forms at the relatively cold outer rim of the fuel pellet, where the local burnup is 2–3 times higher than the average pellet burnup, under the combined effects of irradiation and thermo-mechanical conditions determined by the power regime and the fuel rod configuration. The main features of the transformation are the subdivision of the original fuel grains into new sub-micron grains, the relocation of the fission gas into newly formed intergranular pores, and the absence of large concentrations of extended defects in the fuel matrix inside the subdivided grains. The characterization of the newly formed structure and its impact on thermo-physical or mechanical properties is a key requirement to ensure that high burnup fuel operates within the safety margins. This paper presents a synthesis of the main findings from extensive studies performed at JRC-Karlsruhe during the last 25 years to determine properties and behaviour of the HBS. In particular, microstructural features, thermal transport, fission gas behaviour, and thermo-mechanical properties of the HBS will be discussed. The main conclusion of the experimental studies is that the HBS does not compromise the safety of nuclear fuel during normal operations.

scholarly journals Imaging-Based Biomarkers: Characterization of Post-Kawasaki Vasculitis in Infants and Hypertension Phenotype in Rat Model

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Roch Listz Maurice ◽  
Nagib Dahdah ◽  
Johanne Tremblay
Keyword(s):  
Mechanical Properties ◽  
Arterial Wall ◽  
Turning Point ◽  
Aortic Wall ◽  
Brown Norway ◽  
Carotid Stiffness ◽  
Old Rats ◽  
The Impact

Background. Investigating the mechanical properties of the arteries is essential in cardiovascular diseases. Recent imaging modalities allow mapping mechanical properties within the arterial wall.Aims. We report the potential ofimaging-based biomarker(ImBioMark) to investigate the effect of aging on the rat. We also present preliminary data with ImBioMark characterizing vascular sequelae of Kawasaki disease (KD) in young humans.Methods. We investigatedin vivothe effect of aging on male Brown Norway (BN) rats' (n=5) carotid stiffness. In a second experiment, the impact of KD on the ascending aorta (AA) was examined in KD children (n=2) aged 13 ± 1.41 years old compared to KD-free children (n=5) aged 13.13 ± 0.18 years old.Results. The stiffness of BN's carotid artery was three times stiffer in the old rats, with a turning point at 40 weeks old (P=0.001). KD had a very significant impact on the AA stiffness with strain estimates of 2.39 ± 0.51% versus 4.24 ± 0.65% in controls (P<0.001).Conclusion. ImBioMark phenotypes hypertension in rat models noninvasivelyin vivowithout resorting to euthanasia. Quantifying aortic wall remodeling is also feasible in humans. Future investigations target human cardiovascular disease.

scholarly journals Contribution of Collagen Fiber Undulation to Regional Biomechanical Properties Along Porcine Thoracic Aorta

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Shahrokh Zeinali-Davarani ◽  
Yunjie Wang ◽  
Ming-Jay Chow ◽  
Raphaël Turcotte ◽  
Yanhang Zhang
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Multiphoton Microscopy ◽  
Constitutive Models ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Model Parameters ◽  
Extracellular Matrix Components

As major extracellular matrix components, elastin, and collagen play crucial roles in regulating the mechanical properties of the aortic wall and, thus, the normal cardiovascular function. The mechanical properties of aorta, known to vary with age and multitude of diseases as well as the proximity to the heart, have been attributed to the variations in the content and architecture of wall constituents. This study is focused on the role of layer-specific collagen undulation in the variation of mechanical properties along the porcine descending thoracic aorta. Planar biaxial tensile tests are performed to characterize the hyperelastic anisotropic mechanical behavior of tissues dissected from four locations along the thoracic aorta. Multiphoton microscopy is used to image the associated regional microstructure. Exponential-based and recruitment-based constitutive models are used to account for the observed mechanical behavior while considering the aortic wall as a composite of two layers with independent properties. An elevated stiffness is observed in distal regions compared to proximal regions of thoracic aorta, consistent with sharper and earlier collagen recruitment estimated for medial and adventitial layers in the models. Multiphoton images further support our prediction that higher stiffness in distal regions is associated with less undulation in collagen fibers. Recruitment-based models further reveal that regardless of the location, collagen in the media is recruited from the onset of stretching, whereas adventitial collagen starts to engage with a delay. A parameter sensitivity analysis is performed to discriminate between the models in terms of the confidence in the estimated model parameters.

Changes in the biomechanical properties of skin and aorta induced by corticotrophin treatment

1980 ◽  
Vol 94 (1) ◽  
pp. 132-137 ◽  
Author(s):  
H. Oxlund
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Connective Tissue ◽  
Thoracic Aorta ◽  
Aortic Wall ◽  
Biomechanical Properties ◽  
Elastic Stiffness ◽  
Collagen Content ◽  
Dorsal Skin ◽  
Biophysical Properties

Abstract. The work presented here is an investigation of the effect of elevated levels of corticosteroids on the biophysical properties of skin, aorta and muscle tendon. Rats were given corticotrophin injections for 10, 30 and 60 days to elevate the level of plasma endogenous corticosteroids. The corticotrophin treatments did not change the water or collagen content of specimens from dorsal skin, thoracic aorta and peroneal muscle tendons, tested mechanically. Changes became evident after longer treatment times. For both skin and aorta, the tensile strength, elastic stiffness and failure energy were increased after 60 days of treatment. The corticotrophin treatment did not influence the mechanical properties of muscle tendons. Complete reversibility of changes in the mechanical properties induced by 30 days of corticotrophin treatment was found after an additional period of 30 days of saline injections. This study indicates that an increased level of plasma corticosteroids elicited by corticotrophin treatment may increase the stiffness of the connective tissue of the organism. In the aorta this results in loss of capacitive function with increased haemodynamic strain on the aortic wall.

The complex distribution of arterial system mechanical properties, pulsatile hemodynamics, and vascular stresses emerges from three simple adaptive rules

2015 ◽  
Vol 308 (5) ◽  
pp. H407-H415 ◽  
Author(s):  
Phuc H. Nguyen ◽  
Sarah F. Coquis-Knezek ◽  
Mohammad W. Mohiuddin ◽  
Egemen Tuzun ◽  
Christopher M. Quick
Keyword(s):  
Mechanical Properties ◽  
A Priori ◽  
Experimental Studies ◽  
Wall Stress ◽  
Arterial System ◽  
Adaptive Responses ◽  
Hemodynamic Variables ◽  
Circumferential Wall Stress ◽  
Simultaneous Prediction ◽  
Parameter Values

Arterial mechanical properties, pulsatile hemodynamic variables, and mechanical vascular stresses vary significantly throughout the systemic arterial system. Although the fundamental principles governing pulsatile hemodynamics in elastic arteries are widely accepted, a set of rules governing stress-induced adaptation of mechanical properties can only be indirectly inferred from experimental studies. Previously reported mathematical models have assumed mechanical properties adapt to achieve an assumed target stress “set point.” Simultaneous prediction of the mechanical properties, hemodynamics, and stresses, however, requires that equilibrium stresses are not assumed a priori. Therefore, the purpose of this work was to use a “balance point” approach to identify the simplest set of universal adaptation rules that simultaneously predict observed mechanical properties, hemodynamics, and stresses throughout the human systemic arterial system. First, we employed a classical systemic arterial system model with 121 arterial segments and removed all parameter values except vessel lengths and peripheral resistances. We then assumed vessel radii increase with endothelial shear stress, wall thicknesses increase with circumferential wall stress, and material stiffnesses decrease with circumferential wall stress. Parameters characterizing adaptive responses were assumed to be identical in all arterial segments. Iteratively predicting local mechanical properties, hemodynamics, and stresses reproduced five trends observed when traversing away from the aortic root towards the periphery: decrease in lumen radii, wall thicknesses, and pulsatile flows and increase in wall stiffnesses and pulsatile pressures. The extraordinary complexity of the systemic arterial system can thus arise from independent adaptation of vessels to local stresses characterized by three simple adaptive rules.

Variation of mechanical properties and quantitative proteomics of VSMC along the arterial tree

2014 ◽  
Vol 306 (4) ◽  
pp. H505-H516 ◽  
Author(s):  
Carla Luana Dinardo ◽  
Gabriela Venturini ◽  
Enhua H. Zhou ◽  
Ii Sei Watanabe ◽  
Luciene Cristina Gastalho Campos ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Blood Flow ◽  
Thoracic Aorta ◽  
Regional Blood Flow ◽  
Circumferential Stress ◽  
Shotgun Proteomics ◽  
Arterial Tree ◽  
Static State ◽  
Cyclic Stretching ◽  
Anatomical Parameters

Vascular smooth muscle cells (VSMCs) are thought to assume a quiescent and homogeneous mechanical behavior after arterial tree development phase. However, VSMCs are known to be molecularly heterogeneous in other aspects and their mechanics may play a role in pathological situations. Our aim was to evaluate VSMCs from different arterial beds in terms of mechanics and proteomics, as well as investigate factors that may influence this phenotype. VSMCs obtained from seven arteries were studied using optical magnetic twisting cytometry (both in static state and after stretching) and shotgun proteomics. VSMC mechanical data were correlated with anatomical parameters and ultrastructural images of their vessels of origin. Femoral, renal, abdominal aorta, carotid, mammary, and thoracic aorta exhibited descending order of stiffness (G, P < 0.001). VSMC mechanical data correlated with the vessel percentage of elastin and amount of surrounding extracellular matrix (ECM), which decreased with the distance from the heart. After 48 h of stretching simulating regional blood flow of elastic arteries, VSMCs exhibited a reduction in basal rigidity. VSMCs from the thoracic aorta expressed a significantly higher amount of proteins related to cytoskeleton structure and organization vs. VSMCs from the femoral artery. VSMCs are heterogeneous in terms of mechanical properties and expression/organization of cytoskeleton proteins along the arterial tree. The mechanical phenotype correlates with the composition of ECM and can be modulated by cyclic stretching imposed on VSMCs by blood flow circumferential stress.

scholarly journals In vivo characterization of the aortic wall stress–strain relationship

Ultrasonics ◽  
2010 ◽  
Vol 50 (7) ◽  
pp. 654-665 ◽  
Author(s):  
Asawinee Danpinid ◽  
Jianwen Luo ◽  
Jonathan Vappou ◽  
Pradit Terdtoon ◽  
Elisa E. Konofagou
Keyword(s):  
Aortic Wall ◽  
Wall Stress ◽  
Stress Strain ◽  
Strain Relationship ◽  
In Vivo Characterization

Circumferential Variation of Mechanical Properties of Ascending Aorta (AA): A Comparative Study of Healthy and Dilated AA

2007 ◽  
Author(s):  
Dominique Tremblay ◽  
Raymond Cartier ◽  
Louis Leduc ◽  
Rosaire Mongrain ◽  
Richard Leask
Keyword(s):  
Mechanical Properties ◽  
Smooth Muscle ◽  
Aortic Valve ◽  
Aortic Wall ◽  
Vascular Tissue ◽  
Vascular System ◽  
Cardiovascular Complications ◽  
Ascending Aorta ◽  
Local Properties

The biomechanics within the ascending aorta (AA) characterizes the pressure and flow for the entire vascular system. In the aortic wall, it is the structured medial layer that is responsible for the mechanical properties of the AA. The mechanical properties are determined to a large extent by the composition of elastin, collagen and smooth muscle cells (SMCs). Changes in AA biomechanics that arise with age and/or disease can lead to cardiovascular complications and death. Most studies that have investigated the biomechanics of these diseases have assumed homogeneous and isotropic aortic wall properties. Very little work has been done in vitro to determine the local mechanical properties of human vascular tissue. In order to better understand the biomechanics of the human AA, the local properties of pathologic AA tissue from both tricuspid and bicuspid aortic valve patients have been studied and compared with the properties of healthy aortas.

Pressure-volume characteristics of aortas of harbor and Weddell seals

1986 ◽  
Vol 251 (1) ◽  
pp. R174-R180 ◽  
Author(s):  
E. A. Rhode ◽  
R. Elsner ◽  
T. M. Peterson ◽  
K. B. Campbell ◽  
W. Spangler
Keyword(s):  
Mechanical Properties ◽  
Stroke Volume ◽  
Thoracic Aorta ◽  
Marine Mammals ◽  
Wall Stress ◽  
Stroke Work ◽  
Descending Thoracic Aorta ◽  
Weddell Seals ◽  
Terrestrial Mammals ◽  
Total Potential

The mechanical properties of the radially enlarged proximal segment of the aorta of diving marine mammals was studied on 15 excised aortas of harbor seals and five aortas of Weddell seals. This was done by recording static pressure-volume relationships for the whole thoracic aorta, the aortic bulb, and the descending thoracic aorta and passive length-tension measurements of aortic strips. Aortic bulb volume distensibility was found to be much greater than that of the descending thoracic aorta or of an equivalent aortic segment of terrestrial mammals. The consequences were that the total potential energy and volume that may be stored within the aortic bulb is very large, with a capacity for storage of the stroke work of more than two normal heart beats and a volume of more than three times normal stroke volume. The aortic bulb has an average radius and wall thickness twice that of the descending aorta, but at any level of distension the wall stress (g/cm2) is the same throughout. The static mechanical properties of aortic strips from the bulb and descending thoracic aortas were not markedly different, so that the differences in the pressure-volume relationships are explained by differences in geometry of the two sections. The expanded aortic bulb functions through energy and volume storage actions and through uncoupling actions to maintain arterial pressures and stroke volume at near predive levels during a dive.

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