Optimalizace měření rychlosti pulzní vlny v tepnách

Measurements of the pulse wave velocity (PWV) in human arteries are important for two different reasons: an early diagnostics of atherosclerosis and identification of material properties of the vessel wall for numerical simulations. The PWV in blood vessels is not constant and classical methods of pressure wave shift between two points are not sufficient. We consider three methods: optical measurements of vessel wall displacement in several points by high speed camera, continual optical measurements of vessel wall displacement by correlator Q-450 and measurements of flow rate and displacements by ultrasonic device. The first method can determine the PWV only between several points. The second method can show 3D reconstruction of displacements with very good resolution. The ultrasound measurements need combination of Doppler ultrasound velocimetry and B-scan imagining. However, the common devices used in medicine do not have any data output. It causes bad resolution

Numerické modelování ustáleného a pulzačního proudění v elastické trubici

Numerical model of an elastic tube loaded by pulsatile flow for valiadation of experimentally determined constitutive laws of arterial walls. Hyperbolic system of PDE is solved using finite volu method and calculated pulse wave velocity is compared with experimental results for a latex tube

Neinvazivní potické měření deformací elastických trubic

Noninvasive optical measurement and evaluation of the pulse wave velocity of a self-oscillating elastic tube was done. A latex tube was loaded by self-excited internal pulsatile flow as a simple model of human big arteries. The method is based on evaluation of high speed camera recordings and edges detection algorithm. Displacements of the tube edge were evaluated by a given scale factor from a standard gauge inserted to the recorded scene. Our goal is to recognize the pulse wave and measure its velocity along the tube

Magnetism in GaN layers implanted by La, Gd, Dy and Lu

We present a complex study of rare earth elements implanted GaN layers grown by low pressure metalorganic vapor phase epitaxy on c-plane sapphire substrates. Gd, Dy, La and Lu ions were implanted with energies of 200 key and doses ranging from 5 x 10(13) to 4 x 10(17) atoms.cm(-2). The chemical composition and concentration profiles of ion-implanted layers were studied by secondary ion mass spectrometry and Rutherford back scattering. The structural properties of the layers were characterized by Rutherford back scattering/channeling and X-ray diffraction reciprocal space mapping. Gd implanted layers exhibit ferromagnetic behavior persisting up to similar to 720 K. Since the ferromagnetic behavior was not observed in the case of La and Lu implanted layers, it cannot be attributed to the structural damage of the layer. Based on the fact that the samples are electrically conducting we conclude that the ferromagnetism can be associated with doped electrons mediating the ferromagnetic interaction between local moments on Gd and Dy. (C) 2011 Elsevier B.V. All rights reserved