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Wyświetlanie 1-4 z 4
Tytuł:
Effect of dissection on the mechanical properties of human ascending aorta and human ascending aorta aneurysm
Autorzy:
Kozuń, Marta
Płonek, Tomasz
Jasiński, Marek
Filipiak, Jarosław
Powiązania:
https://bibliotekanauki.pl/articles/306886.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
tętniak
rozwarstwienie
aorta
aneurysm
dissection
ascending aorta
blood vessel wall
Opis:
The aim of the presented work is to determine (i) mechanical properties of the ascending aorta wall (DAA) and the wall of the ascending aortic aneurysm (DAAA), in which spontaneous dissection resulting from the evolving disease occurred, and (ii) the strength of the interface between the layers in the above-mentioned vessels. Methods: The mechanical tests were divided into two steps. In the first step the mechanical properties of the of DAA and DAAA walls were examined on the basis of uniaxial stretching until rapture. In the next step the mechanical parameters of the interface between layers of DAA and DAAA walls were determined by the peeling test. Results: Higher values of tensile strength (max) and Young’s modulus (E) were obtained for the DAAA group, to which the dissecting wall of the ascending aortic aneurysm was classified. For circumferential samples, the difference between the DAAA and DAA groups was 39% in the case of tensile strength and 70% in the case of the Young’s modulus. Conclusions: Summarizing, the studies performed showed that the dissection process is different in the case of the ascending aortic aneurysm wall and the ascending aorta wall. The wall of the ascending aortic aneurysm is more susceptible to dissection, as evidenced by lower values of the mechanical parameters of the interface between the intima and the media-adventitia complex. The obtained results of mechanical properties tests confirm that dissection and aneurysm should be treated as separate disease entities that may coexist with each other.
Źródło:
Acta of Bioengineering and Biomechanics; 2019, 21, 2; 127-134
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical investigations of the unsteady blood flow in the end-to-side arteriovenous fistula for hemodialysis
Autorzy:
Jodko, D.
Obidowski, D.
Reorowicz, P.
Jóźwik, K.
Powiązania:
https://bibliotekanauki.pl/articles/306702.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
tętniak
anastomoza
choroba zatorowo-zakrzepowa
naprężenie styczne ścian
aneurysm
anastomosis
arteriovenous fistula
thrombosis
wall shear stress
intimal hyperplasia
Opis:
Purpose: The aim of this study was to investigate the blood flow in the end-to-side arteriovenous (a-v) fistula, taking into account its pulsating nature and the patient-specific geometry of blood vessels. Computational Fluid Dynamics (CFD) methods were used for this analysis. Methods: DICOM images of the fistula, obtained from the angio-computed tomography, were a source of the data applied to develop a 3D geometrical model of the fistula. The model was meshed, then the ANSYS CFX v. 15.0 code was used to perform simulations of the flow in the vessels under analysis. Mesh independence tests were conducted. The non-Newtonian rheological model of blood and the Shear Stress Transport model of turbulence were employed. Blood vessel walls were assumed to be rigid. Results: Flow patterns, velocity fields, the volume flow rate, the wall shear stress (WSS) propagation on particular blood vessel walls were shown versus time. The maximal value of the blood velocity was identified in the anastomosis – the place where the artery is connected to the vein. The flow rate was calculated for all veins receiving blood. Conclusions: The blood flow in the geometrically complicated a-v fistula was simulated. The values and oscillations of the WSS are the largest in the anastomosis, much lower in the artery and the lowest in the cephalic vein. A strong influence of the mesh on the results concerning the maximal and area-averaged WSS was shown. The relation between simulations of the pulsating and stationary flow under time-averaged flow conditions was presented.
Źródło:
Acta of Bioengineering and Biomechanics; 2016, 18, 4; 3-13
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Patient-specific hemodynamics and stress-strain state of cerebral aneurysms
Autorzy:
Ivanov, D.
Dol, A.
Polienko, A.
Powiązania:
https://bibliotekanauki.pl/articles/306900.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
materiał hipersprężysty
symulacja numeryczna
naprężenie efektywne
przepływ krwi
tętniak
hyperelastic material
numerical simulation
effective stress
blood flow
cerebral aneurysm
Opis:
Purpose: Approximately 5% of the adult population has one or more cerebral aneurysm. Aneurysms are one of the most dangerous cerebral vascular pathologies. Aneurysm rupture leads to a subarachnoid hemorrhage with a very high mortality rate of 45–50%. Despite the high importance of this disease there are no criteria for assessing the probability of aneurysm rupture. Moreover, mechanisms of aneurysm development and rupture are not fully understood until now. Methods: Biomechanical and numerical computer simulations allow us to estimate the behavior of vessels in normal state and under pathological conditions as well as to make a prediction of their postoperative state. Biomechanical studies may help clinicians to find and investigate mechanical factors which are responsible for the initiation, growth and rupture of the cerebral aneurysms. Results: In this work, biomechanical and numerical modeling of healthy and pathological cerebral arteries was conducted. Patient-specific models of the basilar and posterior cerebral arteries and patient-specific boundary conditions at the inlet were used in numerical simulations. A comparative analysis of the three vascular wall models (rigid, perfectly elastic, hyperelastic) was performed. Blood flow and stress-strain state of the two posterior cerebral artery aneurysm models was compared. Conclusions: Numerical simulations revealed that hyperelastic material most adequately and realistically describes the behavior of the cerebral vascular walls. The size and shape of the aneurysm have a significant impact on the blood flow through the affected vessel and on the effective stress distribution in the aneurysm dome. It was shown that large aneurysm is more likely to rupture than small aneurysm.
Źródło:
Acta of Bioengineering and Biomechanics; 2016, 18, 2; 9-17
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of collagen fibres and elastic lamellae content on the mechanical behaviour of abdominal aortic aneurysms
Autorzy:
Kobielarz, Magdalena
Powiązania:
https://bibliotekanauki.pl/articles/27324131.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
abdominal aortic aneurysm
mechanical properties
constitutive modelling
uniaxial tensile loading
collagen fibres
elastic lamellae
tętniak aorty brzusznej
właściwości mechaniczne
modelowanie konstytutywne
jednoosiowe obciążenie rozciągające
włókna kolagenowe
elastyczne lamele
Opis:
Purpose: The main purpose of this study was a detailed analysis of the mechanical and structural characteristics of human abdominal aneurysms in comparison with normal abdominal aortae and determination of the correlations between their mechanical behaviour and the microstructural content. Methods: Various mechanical properties, i.e., mechanical failure properties, elastic moduli, inflection point coordinates, index of anisotropy and incompressibility were determined under uniaxial loading conditions in the circumferential and axial directions. Constitutive parameters were derived from the commonly used constitutive model proposed by Holzapfel et al. [9]. The microstructural arrangement was examined by histological staining supported by scanning electron microscopy analysis. The content of collagen fibres and elastic lamellae was tested in relation to mechanical properties and constitutive parameters. Results: Significant differences were found in the microstructural arrangement and layer composition of the aneurysmal specimens, compared to the normal aorta group. The mechanical properties and constitutive parameters of the aneurysmal specimens were significantly altered, indicating a weakening of the load-bearing properties of the walls of the aneurysms. A comparative analysis discovered significant correlations between structural composition and mechanical parameters, in particular with respect to the number of collagen fibres and failure stress, which can be important for clinical evaluation of abdominal aortic aneurysm (AAA) rupture. Conclusions: Changes in the content of collagen fibres and elastic lamellae correlate with mechanical and constitutive parameters, indicating AAA severity
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 3; 9--21
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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