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The influence of the treatment of experimental acute liver failure by FPSA/Prometheus on intracranial pressure
Pražák, Josef ; Cvachovec, Karel (advisor) ; Červinková, Zuzana (referee) ; Kieslichová, Eva (referee)
Background: Cerebral edema is a well-known and fatal complication of acute liver failure (ALF). The influence of the treatment by artificial liver devices on the cerebral damage caused by ALF is usually monitored by only measuring the intracranial pressure (ICP). The aim of this work was to determine the influence of Fractionated Plasma Separation and Adsorption (FPSA), nonbiological artificial liver device, on the intracranial pressure. The second goal of this work was to determine the potential role of cerebral microdialysis in monitoring of the efficiency of fractionated plasma separation and adsorption (FPSA) treatment of ALF. Methods: Two types of surgical resection model of ALF were used in two separate experiments in pigs. In the first study data from monitoring of the intracranial pressure of ALF group (animals with ALF only) and FPSA group (animals with ALF treated by FPSA) were compared. In the second study data from monitoring by cerebral microdialysis and ICP of the ALF group (animals with ALF only), FPSA group (animals with ALF treated by FPSA) and SHAM group (animals with only laparotomy) were compared using statistical analyses. Results: In both experiments, the ICP was significantly higher in the ALF group than in the FPSA group from the 9th hour of the experiment. In the second...
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The influence of the treatment of experimental acute liver failure by FPSA/Prometheus on intracranial pressure
Pražák, Josef ; Cvachovec, Karel (advisor) ; Červinková, Zuzana (referee) ; Kieslichová, Eva (referee)
Background: Cerebral edema is a well-known and fatal complication of acute liver failure (ALF). The influence of the treatment by artificial liver devices on the cerebral damage caused by ALF is usually monitored by only measuring the intracranial pressure (ICP). The aim of this work was to determine the influence of Fractionated Plasma Separation and Adsorption (FPSA), nonbiological artificial liver device, on the intracranial pressure. The second goal of this work was to determine the potential role of cerebral microdialysis in monitoring of the efficiency of fractionated plasma separation and adsorption (FPSA) treatment of ALF. Methods: Two types of surgical resection model of ALF were used in two separate experiments in pigs. In the first study data from monitoring of the intracranial pressure of ALF group (animals with ALF only) and FPSA group (animals with ALF treated by FPSA) were compared. In the second study data from monitoring by cerebral microdialysis and ICP of the ALF group (animals with ALF only), FPSA group (animals with ALF treated by FPSA) and SHAM group (animals with only laparotomy) were compared using statistical analyses. Results: In both experiments, the ICP was significantly higher in the ALF group than in the FPSA group from the 9th hour of the experiment. In the second...
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3D Micromodels of Porous Structures
Pražák, Josef
Speaking about modeling in technical sciences, we have in mind an analysis of mathematical (computational) or physical analogies of objects to be studied. Physical modeling means a systematic building of physical objects heaving some analogy with the studied physical reality. For the models of porous structures, the notion micromodels has been introduced. The micro- means that the model represents only a small fraction of real porous structure and that some essential schematization of reality is included. The difference between a micromodel and a simple probe of a natural porous material (a small volume of soil, sand, etc.) consist in the fact that some exact geometrical information is ahead. Very often, the real porous space is schematized into a regular graph network. The Lenormand´s micromodels are 2D objects where a random square network has been cut in a sophisticated way into a layer of resin between two layers of plexiglass.
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3D Micromodels of porous structures
Pražák, Josef
The 2D micromodels of porous structures have been used already 30 years. They have brought much interesting information, but an actual application of them on the 3D reality has natural limitation. That is why 3D micromodels have been developed. A multi-layer structure seems to be optimal for the construction of them. It allows not only a wide variety of modeled porous structures but a rich statistics of experiment as well.
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New suspect in the investigation into the cause of flash floods
Bíl, M. ; Fürst, T. ; Vodák, R. ; Pražák, Josef ; Šír, Miloslav ; Tesař, Miroslav
The aim of this contribution is to introduce a new possibility of the description of unsaturated porous media flow. The approach presented here is entirely different from the traditional ways (e.g. the Richards‘ Equation). It will be explained why the traditional models often fail to describe various observed phenomena. The new approach provides certain interesting forecasts, among others a possible mechanism for flash-flood formation. The authors explain why they think that, under specific conditions, porous medium discharge may substantially exceed the infiltration due to rainfall.
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Experimental study concerning stimulated outflow from porous structures
Pražák, Josef ; Biskup, B. ; Šír, Miloslav
It is generally supposed that the water flow in massive spates occurring in small catchments areas have two components. The first one is the direct surface flow of the water from a preceding rain (new water) the second one is caused by the water “pending” in the soil already before the rain (old water) stimulated by the rain to flow out. The stimulated outflow has been studied in a series of experiments. It was found that in laboratory test, a situation where the stimulated outflow exceeds the stimulating inflow can be simulated in an easy way.
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Fyzikální modelování srdečně cévní soustavy na ÚT AVČR
Pražák, Josef
The physical modeling remains an important tool for theoretical and practical studies of CVS. Nowadays, the most important applications of physical modeling of CVS are the testing and developing of artificial substitutions of CVS elements and the application of it as a counterpart for mathematical models. On the IT, the physical modeling of the CVS flow phenomena is developed since the last century (more then six years) in the Laboratory of biomechanics. In its contemporary state, the IT physical model of CVS represents a universal system (construction kit) suitable for a large class of applications.
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Simulation and Evaluation of the UHMWPE Surface Wear
Franta, L. ; Jeníková, Z. ; Sieber, D. ; Synková, Hana ; Pražák, Josef ; Suchánek, J.
The goal of this research project is to increase the lifetime of total knee joint replacement. Therefore the “In vitro“ simulation of realistic physiological conditions is important. For the knee joint replacement experiments, a KKK ELO 98001 simulator is used. The simulator enables the combination of rolling and sliding motion of replacement components with sinusoidal loading. During the experiment, a considerable amount of wear particles of the UHMWPE component is produced and the friction surfaces are irreversibly changed. Initially, the irregularities of tibia component are smoothed. Consequently, large amounts of UHMWPE wear are released. The surface changes of specimens were evaluated.
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