National Repository of Grey Literature 10 records found  Search took 0.01 seconds. 
Mechanical and structural properties of collagen nanofribrous layers under simulated body conditions
Říhová, J. ; Suchý, Tomáš ; Vištejnová, L. ; Horný, L. ; Šupová, Monika
The theme of this paper is the analysis of mechanical and structural properties of nanofibrous COL under simulated body conditions and in the presence of osteoblasts and dermal fibroblasts. COL were prepared by electrostatic spinning of 8 wt% collagen type I dispersion with 8 wt% (to COL) of PEG in phosphate buffer/ethanol solution (1/1 vol). The stability of COL was enhanced by means of cross-linking with EDC and NHS at a molar ratio of 4:1. COL were exposed in culture medium for 21 days and human SAOS-2 human dermal fibroblasts and osteoblasts were cultured therein for 21 days as well.
Microscopic structura and mechanical properties of aorta and pulmonary artery
Kubíková, Tereza ; Tonar, Zbyněk (advisor) ; Kučera, Tomáš (referee) ; Horný, Lukáš (referee)
Introduction: This dissertation thesis consists of seven studies, the common aim of which was to describe the functional histology of the aorta and some of its branches, as well as the pulmonary artery. The thesis focuses on analysis of the microscopic composition of various segments of the porcine aorta during ontogenesis as an experimental model, as well as cryopreserved samples of human aorta, pulmonary artery and their valves. Further it assesses damage to the renal artery during its denervation, and evaluates cell colonization of synthetic vascular substitutes after their implantation into the abdominal aortas of mice. The introduction gives an overview of the structure of the aorta and pulmonary artery and their valves, selected diseases affecting large vessels, and histological and biomechanical methods used for their characterization. Methods: We used the paraffin section method with basic and advanced stains, immunohistochemical detection of antigens (α-smooth muscular actin, desmin, vimentin, chondroitin sulfate, von Willebrand factor, neurofilament protein, tyrosine hydroxylase) and biomechanical tests (uniaxial tensile tests) for determination of ultimate strain, ultimate stress and Young's modulus of elasticity. We used stereological methods based on the interaction of test grids of...
Analysis of spontaneous collapse in elastic tubes
Netušil, Marek ; Maršík, František (advisor) ; Horný, Lukáš (referee)
Interaction of fluid with elastic tube is complicated issue studied by many scientific departments around the world. Object of this thesis is to analyze simplified one-dimensional model. At the beginning, used balance equations and basics of hyper-elasticity are presented. Then we review three most common materials used for the description of blood vessels and other soft tissues. For these materials we introduce a method which we use to derive a relation between tube deformation and transmural pressure (i.e. difference between inner and outer pressure). In mathematical section we give brief review of theory of nonlinear hyperbolic equations and some relatively new results in the field of existence and uniqueness of a solution of one-dimensional hyperbolic system. The "building stone" of these results is a solution of the so-called Riemann problem. We use a method for finding exact solutions to the Riemann problem to analyze studied model of fluid-tube interaction and study dependence of the qualitative behavior of the solution on the material properties of the tube wall.
Stress-Strain Analysis of Aortic Aneurysms
Polzer, Stanislav ; Holeček, Miroslav (referee) ; Horný, Lukáš (referee) ; Burša, Jiří (advisor)
Tato práce se zabývá problematikou aneurysmat břišní aorty a možností využít konečnoprvkovou deformačně-napěťovou analýzu těchto aneurysmat ke stanovení rizika ruptury. První část práce je věnována úvodu do problematiky, popisu kardiovaskulární soustavy člověka s důrazem na abdominální aortu, anatomii, fyziologii a patologii stěny tepny s důrazem na procesy vedoucí ke vzniku aneurysmatu. Dále se práce věnuje rizikovým faktorům přispívajících ke vzniku aneurysmat spolu s analýzou současných klinických postupů ke stanovení rizika ruptury spolu se srovnáním navrhovaného kritéria maximálního napětí. Dominantní část této disertace je věnována identifikaci faktorů ovlivňujících napjatost a deformaci stěny aneurysmatu spolu s návrhem nových postupů, prezentací vlastních poznatků vedoucích ke zpřesnění určení rizika ruptury pomocí deformačně- napěťové analýzy a metody konečných prvků. Nejprve je analyzován vliv geometrie, vedoucí k závěru, že je nezbytné používání individuálních geometrií pacienta. Dále je pozornost zaměřena na odbočující tepny, které ve stěně působí jako koncentrátor napětí a mohou tedy ovlivňovat napjatost v ní. Jako další podstatný faktor byl identifikován vliv nezatížené geometrie a bylo napsáno makro pro její nalezení, které bylo opět zahrnuto jako standardní součást do výpočtového modelu. Mechanické vlastnosti jak stěny aneurysmatu, tak intraluminálního trombu jsou experimentálně testovány pomocí dvouosých zkoušek. Také je zde analyzován vliv modelu materiálu, kde je ukázáno, že srovnávání maximálních napětí u jednotlivých modelů materiálu není vhodné díky zcela rozdílným gradientům napětí ve stěně aneurysmatu. Dále je zdůrazněna potřeba znalosti distribuce kolagenních vláken ve stěně a navržen program k jejímu získání. Intraluminální trombus je analyzován ve dvou souvislostech. Jednak je ukázán vliv jeho ruptury na napětí ve stěně a jednak je analyzován vliv jeho poroelastické struktury na totéž. Posledním identifikovaným podstatným faktorem je zbytková napjatost ve stěně. Její významnost je demonstrována na několika aneurysmatech a i tato je zahrnuta jako integrální součást do našeho výpočtového modelu.Na závěr jsou pak navrženy další možné směry výzkumu.
Water hammer experiment in artificial blood vessel
Hromádka, D. ; Horný, L. ; Žitný, R. ; Chlup, Hynek
This paper presents a water hammer experiment performed on an artificial blood vessel and the latex tube. Artificial blood vessel was manufactured from latex tubes and textile rubber bands. These bands were wound on outer surface of latex tube and they imitated reinforcing effect of collagen fibres. Mathematical model describes pulsation of pressure after instantaneous closing of valve at outlet of pipeline a part of which is a short elastic tested tube. It is shown that the observed pressure responses can be approximated by a simplified mathematical model assuming linear relationship between internal pressure and inflated volume.
Residual Strains of Arteries as Forensic Index
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Žitný, R.
It has been known for long time that arteries are pre-strained in situ. These residual strains play crucial role in arterial load-bearing capacity. However, to the best of authors’ knowledge they have never been considered from forensics point of view. This paper concerns a possibility of employing the longitudinal pre-strain of human aortas as an indicator of human subject age. Lengths of abdominal aorta were measured within autopsies before and after segment resection. Longitudinal stretch ratio was calculated for 45 male and 12 female cadavers. It was found that both male and female data samples give approximately the same mean of the stretch ratio = 1.2. The correlation coefficients between the pre-strain and age were R=-0.7926, R=-0.8684 in male and female samples, respectively. Linear regression equation with confidence intervals was employed. The correlation between pre-strain and age seems to be suitable statistics to be used in forensic sciences.
Konstitutivní modelování tepenné stěny
Horný, L. ; Chlup, Hynek ; Adámek, T. ; Zitny, R. ; Macková, H.
Inflation tests and uni–axial extension tests of arterial tissue were performed. Experimental data were used in nonlinear regression analysis to identify material model. Arterial tissue was assumed to be incompressible hyperelastic material. 5–parameter strain energy density function based on combination of isotropic Neo–Hookean expression and Fung–type orthotropic expression was used. Computational model for material parameters identification was based on thick–wall tube with axial pre–strains. Residual strains were included. Internal structure of arterial wall was not considered. Fitted material models correspond to experimental data very well.
Zbytková deformace v bifurkaci lidské aorty
Adámek, T. ; Horný, L. ; Chlup, Hynek ; Franta, L.
At the present paper we report values of opening angles in human aortic bifurcations. A standard method of opening angle measurement was used. Three aortas were measured. Ten samples were excised from each aorta. Three rings were obtained from abdominal aorta close to the bifurcation, arteria iliaca communis dextra and sinistra and one form the bifurcation. The last one was composed of two rings, left and rignt, which were measured together. The residual strains were occurred in human aortic bifurcations and had different values in the left and the right branch of the bifurcated artery. The results of at the bifurcation can be influenced by fact that the branches of iliac arteries are still intergrown here. Two kinds of the opening angle investigation at the bifurcation were tested, a bifurcation septum fixed method and a circular sector fixed method. But both revealed differences in the opening angle values at the bifurcation.
Určování mechanických vlastností věnčitých tepen
Beneš, J. ; Horný, L. ; Konvičková, S. ; Chlup, Hynek
Samples of human coronary arteries underwent inflation tests to obtain parameters which characterize its mechanical behavior. A pressure-diameter relationship was determined. Strain energy density function was used to model constitutive behavior. Its numerical characterization was found by regression analysis of experimental data.
Zkušenosti s tahovými zkouškami vrstev tepenné stěny
Horný, L. ; Chlup, Hynek ; Sedláček, R. ; Konvičková, S.
Uni-axial tensile tests were performed with layers of aortic wall. Specimens underwent loading in both longitudinal and circumferential directions. Experimental data were used in regression analysis which offered base for constitutive relationships. Uni-axial stress-strain relations for aortic media and adventitia were found.

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2 Horný, L.
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