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Porous composites based on siloxane resin for hard tissue replacements
Suchý, T. ; Balík, Karel ; Sochor, M. ; Černý, Martin ; Hulejová, H. ; Pešáková, V.
A composite material based on polysiloxane and first on glass fabrics was prepared. The composite samples were prepared with controlled open porosity, the sizes of which were in the range: i) 0,2-0,4 mm, ii) 0,4-0,6 mm, and iii) >0,6 mm. For further improvement of osseointegration, a powder hydroxyapatite, particle size of 0,005 mm in the amount of 10 wgt %. The effects of surface treatment and hydroxyapatite matrix additives on osseointegration were studied by methods in vitro and in vivo.
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Simulace a vyhodnocování otěrových procesů pro UHMPE elementů náhrady kolenního kloubu
Franta, L. ; Jeníková, Z. ; Sieber, D. ; Synková, Hana ; Pražák, Josef ; Suchánek, J.
The demands on artificial knee joint replacement are steadily increasing. Major motivation of this research project, is to increase the lifetime of present prosthesis designs .The main problem of the commonly used UHMWPE / Steel–Implants is the appearance of polyethylene wear which leads to aseptic loosening and therefore to long-term prosthesis failing. In vitro simulations can be an important instrument to predict the wear behavior of new prosthesis designs and materials. ISO 14243 has been developed to obtain comparable results testing on different in vitro simulators. The aim of this study is to verify, how the simplifications made by the in-vitro simulations influence the simulation results and how today’s prosthesis testing can be made more realistic.
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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.
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Tribologické metody testování materiálů umělých kloubních náhrad
Pražák, Josef ; Chlup, Hynek ; Franta, L.
In order to achieve a high functional quality of the total artificial joints (TAJ), a special attention must be paid to the selection of suitable materials for the construction (Dumbleton; 1981, O´Kelly; 1979). Nowadays, it seems that the metal parts of the assembly (femoral part for the knee joint) do not pose any problem, but problems of the “soft” parts (tibial part) persist. A careful tribologic testing of considered materials is necessary, consequently. On the other hand, a relevant tribologic testing in a conventional way is extremely time-consuming (a simulation of a 5 km/day for 10 years activity represents a 150 day test approx.). The application of an accelerated testing method is desirable, therefore. Such a method consisting of an application of a special experimental set-up and of an optical evaluation was developed. It was used for a study concerning the lubrication of artificial joints (Pražák; 2000).
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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.
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Samobuzené oscilace elastické trubice
Chlup, Hynek ; Macková, H. ; Maršík, František ; Konvičková, S.
Our paper studies experimentally the self-excited oscillations of thin-walled elastic tubes with respect to the Korotkoff sounds. The self-excited oscillation is a phenomenon, when an elastic tube looses stability of its shape and starts to oscillate, loaded only by continual flow, therefore without any external excitation. An experimental set-up was designed for the experiments. The mean flow rates, pressures at the ends of the tube and external pressures were recorded under various modes of oscillation. The effective cross-section and elastic modulus of the tube were calculated by simplified formulas. The data analysis showed an increase of the oscillation frequency with a decrease of the tube wall compliance. It means the frequency of the oscillation is dependent on ratio of the wall thickness and the tube diameter. The mode of the oscillation is also influenced by the transmural pressure.
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Hydrodynamika mozkomíšní tekutiny v páteřním kanálu
Kaczmarská, A. ; Vaněk, P. ; Maršík, František ; Převorovská, Světlana ; Otáhal, S. ; Otáhal, J.
In previous modelling study of the cerebrospinal fluid transportation we have shown that main source of the hydrodynamical resistance and compliance of the craniospinal system is cervical part of the spinal canal. The aim of our present study is the investigation of the influence of the cervical spine degenerative changes on the hydrodynamical parameters of the craniospinal system. The results obtained by using of the numerical model of the cerebrospinal fluid flow show the significant influence of the cervical spine degenerative changes on the hydrodynamics of this system.
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Numerická simulace účinků léčiv na srdeční akční potenciál
Převorovská, Světlana ; Maršík, František
The aim of the paper is a numerical simulation of the antiarrhythmic drugs effects on the cardiac action potential realized by the numerical model of the human cardiovascular system. The pulsating blood flow of the cardiovascular system is generated by the electrochemical and mechanical activity of heart muscle. This system is being modelled by four segments of the pulsating heart and by twenty three vascular segments of pulmonary and systemic circuits connected with the heart segments in series. The behaviour of the cardiovascular system is described by the heart rate and by its hemodynamical variables, i.e. the blood pressure, volume, flow, by the cardiovascular parameters such as the blood inertia, compliances and resistances in corresponding segments and by the physicochemical variables such as the cardiac action potential, the calcium, sodium and potassium ionts concentration.
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