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Methodology of conservation-restoration of glazed ceramics
Kloužková, A. ; Svobodová, Ljuba ; Dvořáková, P. ; Kolářová, M. ; Kohoutková, M. ; Randáková, S. ; Šefců, R. ; Kloužek, J. ; Vokáč, M. ; Kubásek, J.
The methodology is focused on the conservation-restoration of glazed ceramics with regard to the stability and porosity of the ceramic shard. It provides a comprehensive overview of suitable procedures for processing this type of material. It contains an overview of suitable methods for assessing the degree of damage (both ceramic body and glaze), sampling procedures and methods for identifying chemical and mineralogical composition of ceramics and glazes and the stability of the system. It also describes cleaning options, procedures for consolidation, bonding and filling of missing fragments, and possible retouching of the ceramic body and glaze. It also contains principles for the appropriate storage of these objects and annotated examples are given to understand the individual results.
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Metodika konzervování-restaurování glazované keramiky
Kloužková, Alexandra ; Svobodová, Ljuba ; Dvořáková, Pavla ; Kolářová, Mária ; Kohoutková, Martina ; Randáková, Simona ; Šefců, Radka ; Kloužek, Jaroslav ; Vokáč, Miroslav ; Kubásek, Jiří
Metodika je zaměřena na konzervování-restaurování glazované keramiky s ohledem na stabilitu a pórovitost keramického střepu. Podává ucelený přehled o vhodných postupech pro zpracování materiálu tohoto typu. Obsahuje přehled vhodných metod pro hodnocení stupně poškození (jak střepu, tak glazury), postupy odběru vzorku a metody pro identifikaci chemického a mineralogického složení keramiky i glazury a stability jejich celkového systému. Dále popisuje možnosti čištění, postupy konsolidace, lepení a doplňování chybějících fragmentů a případné retuše střepu i glazury. Obsahuje rovněž zásady pro vhodné uložení těchto předmětů a pro pochopení jednotlivých výsledků jsou uvedeny komentované příklady.
Fulltext:  PDF; PDF
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High-temperature oxidation of selected complex concentrated alloys
Jača, Eliška ; Minárik, Peter (advisor) ; Kubásek, Jiří (referee)
The increasing industry demands give rise to a continuous call for materials with an improved combination of mechanical and oxidation properties. Recently developed Complex concentrated alloys - alloys consisting of multiple elements in near-equiatomic ratios - may fulfill these criteria. One of the promising group of these alloys comprises base FeAlCr and other alloying elements such as vanadium, nickel or cobalt. In this study, we focused on the detailed characterization of the microstructure and high-temperature oxidation of FeAlCr-Ni-V alloys with vari- ous content of nickel and vanadium. We have found out that investigated alloys FeAlCrNiV and FeAlCrNi exhibit promising BCC/B2 microstructure, possibly providing a preferable combination of ductility and strength. However, our fin- dings have shown that vanadium, even in a reduced amount, deteriorates oxi- dation resistance of the materials and leads to the formation of complex mul- tilayered oxide scale. Presumably, the formation of V2O5 impairs alumina and chromia scale and limits the formation of more protective scales. Generally, this study also reveals limitations in the characterization of complex oxide scales and presents the complexity of the oxidation process of Complex concentrated alloys.
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ZnMg0.8Ca/Sr0.2 ternary alloys - the influence of the third element on material properties
Čapek, Jaroslav ; Pinc, Jan ; Kubásek, J. ; Molnárová, Orsolya ; Maňák, Jan ; Drahokoupil, Jan
Zinc-based materials alloyed with the elements of the 2nd group of the periodic table have been studied as potential materials for the fabrication of various biodegradable implants. In this study, we prepared two ternary alloys: ZnMg0.8Ca0.2 (wt.%) and ZnMg0.8Sr0.2. The microstructure of both ternary alloys was similar, the main difference was in the size and morphology of the Ca/SrZn13 phase. The SrZn13 phase formed fine particles with a submicron size and had more significant hardening effect in the as-cast state compared to the CaZn13 phase. The annealing led to a transformation of the eutectic structure into the “massive” Mg2Zn11 phase which caused a significant increase of both hardness and compressive yield stress. In the annealed states, comparable hardness was observed for both alloys and higher compressive yield strength for the Ca-containing alloy.
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Microstructure and mechanical properties of the potentially biodegradable ternary system Zn-Mg0. 8-Ca0.2
Pinc, Jan ; Čapek, Jaroslav ; Kubásek, J. ; Veřtát, Petr ; Hosová, K.
Zinc and zinc alloys exhibit suitable corrosion properties for biodegradable implants. Insufficient mechanical properties (for some applications) or low biocompatible Zn2+ concentrations can be modified by the alloying by essential elements like magnesium, calcium or strontium. The alloying elements also enhance the biocompatibility of zinc due to a decrease of Zn2+ release which could be toxic in a concentration exceeding 100 µM. In this study, the microstructure and hardness of a potentially biodegradable alloy ZnMg0.8Ca0.2 were observed in relation to different cooling rates. It was found that zinc dendrites, Mg2Zn11 (MgZn2) and CaZn13 phases occur in the material structure. The micro-hardness measurements revealed constant hardness of the particular phases, however, the macro-harness slightly decreased with the decreasing cooling rate due to changes in phase sizes and distribution.
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Changes in the photosynthetic apparatus of european beech and Norway spruce under long-term exposure to elevated CO2
Holišová, Petra ; Šprtová, Miroslava ; Kubásek, Jiří ; Lhotáková, Z. ; Mašková, P. ; Lipavská, H. ; Kočová, M. ; Holá, D. ; Radochová, Barbora ; Albrechtová, J. ; Urban, Otmar
The changes of photosynthetic performance caused by increasing CO2 concentration are refl ected at diff erent hierarchical levels of photosynthetic apparatus from the effi ciency of individual photosynthetic processes to changes in leaf structure. Th e aim of this study was to elucidate the relationships between the ultrastructure and function of photosynthetic apparatus under elevated CO2 concentration. We studied two common tree species – the European beech and the Norway spruce – grown under ambient (AC) and elevated CO2 concentrations (EC). Photosynthetic parameters were obtained using the gas-exchange system LI-6400 (LI-COR, USA). Th e characteristics of chlorophyll a fl uorescence were obtained in vivo with FluorPen FP100max (PSI, CZE) and in vitro polarographically in a suspension of isolated chloroplasts. Non-structural soluble saccharides and starch accumulation was quantifi ed using HPLC. Th e chloroplast ultrastructure was quantifi ed by stereological methods (Ellipse 2.08, SK) on the images acquired on a JEOL JEM-1011 (JEOL, JPN). Th e light-saturated CO2 assimilation rate was stimulated by EC in both species. Th e assimilation capacity of EC plants slightly decreased and was accompanied by a slight decrease in the rate of electron transport and the rate of Rubisco carboxylation. Th e growth in EC induced higher energy dissipation by light-harvesting antennae, diminished PSII activity, resulted in greater PSI capacity and in higher accumulation of starch and soluble sugars in the leaves of both species.
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Effects of UV radiation and drouhgt on the accumulation of UV-screening compounds and photosynthetic parameters in selected herbs and grasses of the mountain grassland ecosystem
Klem, Karel ; Holub, Petr ; Urban, Otmar ; Rajsnerová, Petra ; Kubásek, Jiří
The main objective of the experiment conducted on a mountain grassland ecosystem was to investigate the interactive eff ects of UV treatment and drought on the changes in accumulation of UV-screening compounds and photosynthetic parameters in selected herb (Hypericum maculatum) and grass (Agrostis tenuis) species. Th e experimental plots were manipulated using roof constructions enabling exclusion or transmission of incident precipitation and UV radiation, respectively. Generally, UV and drought treatments had a similar eff ect on the accumulation of fl avonols. UV exclusion resulted in a slight reduction of UV-screening compounds, particularly under the conditions of ambient precipitation. Likewise, drought treatment caused an increase in the accumulation of fl avonols per area unit. Under UV exclusion, drought slightly reduced the light-saturated CO2 assimilation rate (Amax) in both the species studied. Th e presence of UV radiation, however, led to less of a diff erence in Amax between [wet] and [dry] treatments. In addition to the increased induction of fl avonols, UV radiation increased water use effi ciency and alleviated thus the negative impact of drought on photosynthesis.
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