Currently-used mechanical and biological heart valve prostheses have several disadvantages. Mechanical prostheses, based on carbon, metallic and polymeric components, require permanent anticoagulation treatment, and their usage often leads to adverse reactions, e.g. thromboembolic complications and endocarditis. Xenogenous and allogenous biological prostheses are associated with immune reaction, thrombosis and degeneration, and thus they have a high rate of reoperation. Biological prostheses of autologous origin, such as pulm onary autografts, often burden the patient with a complicated surgery and the risk of reoperation. Therefore, efforts are being made to prepare bioartificial heart valves with an autologous biological component by methods of tissue engineering. They should be biocompatible, durable, endowed with appropriate mechanical properties and able to grow with a child. For this purpose, scaffolds composed of synthetic materials, such as poly(lactic acid), poly(caprolactone), poly(4-hydroxybutyrate), hydrogels or natural polymers, e.g. collagen, elastin, fibrin or hyaluronic acid, have been seeded with autologous differentiated, progenitor or stem cells. Promising results have been obtained with nanostructured scaffolds, and also with cultivation in special dynamic bioreactors prior to implantation of the bioartificial grafts into an animal organism., E. Filová ... [et al.]., and Obsahuje seznam literatury
An assemblage of Al-low titanite and ilmenite is present in Ti-rich microgranodiorites intruded in the Moldanubian Zone of the Bohemian Massif. Titanite is characterized by coupled substitution (Al, Fe3+) + (F, OH) ⇔ Ti +O, with a slight excess of (Al, Fe3+)-OH component over of (Al, Fe3+)-F component. Ilmenites have FeTiO3 amount between 86 and 95 mol. % and are partly enriched in the MnTiO3 (pyrophanite) component (4-10 mol. %). The relatively low content of MnTiO3 component in ilmenite, together with absence of magnetite suggests that first crystallization phase of microgranodiorites connected with origin of ilmenite started in conditions of low fO2. However, titanite together with ferroactinolite originated in late-magmatic stage most likely due to hydration reaction such as clinopyroxene + ilmenite + quartz + H2O = titanite + amphibole during some increasing of fO2 and fH2O., Miloš René., and Obsahuje bibliografii
Titanium-rich biotite from granodiorite belonging to redwitzite suite of the Slavkovský les Mts. alters to mixture of low-Al titanite, Mn-enriched ilmenite, REE-fluorocarbonate (parisite) and very fine-grained mixture of chlorite and clay minerals. Titanite consists from 1.1 to 2.3 wt. % Al2O3 and from 0.4 to 1.0 wt. % Fe2O3. Titanite shows some Al+Fe3+ excess over F with significant amount of (Al+Fe3+)-OH titanite component (4-9 mol. %). Ilmenite contains considerable amount of pyrophanite component (5-8 mol. %). The retrograde assemblage of titanite with considerable amount of (Al+Fe3+)-OH titanite component and presence of ilmenite, together with chlorite, argued for low-temperature breakdown of biotite in reducing conditions., Miloš René., and Obsahuje bibliografii
An assemblage of Al-bearing titanite, ilmenite and magnetite is present in polymetamorphic metabasite environment of the Varied group of the Moldanubian Zone. Titanite is characterized by coupled substitution (Al, Fe3+)+ (F, OH) - Ti + O, with a slight excess of (Al, Fe3+)-F component. Complex reaction rims of titanite around ilmenite occur in some cases. Ilmenites have FeTiO3 amounts usually above 96 mol.%, with some enrichment by MnTiO3 component (max. 8 mol.%). Magnetite has a negligible ulvöspinel component (max. 1 mol.%)., Miloš René., and Obsahuje bibliografii