Ageing of low-firing prehistoric ceramics in hydrothermal conditions

Remains of a prehistoric ceramic object, a moon-shaped idol from the Bronze Age found in archaeological site Zdiby near Prague in the Czech Republic, were studied especially in terms of the firing temperature. Archaeological ceramics was usually fired at temperatures below 1000 °C. It contained unstable non-crystalline products, residua after calcination of clay components of a ceramic material. These products as metakaolinite can undergo a reverse rehydration to a structure close to kaolinite. The aim of this work was to prove whether the identified kaolinite in archaeological ceramics is a product of rehydration. The model compound containing high amount of kaolinite was prepared in order to follow its changes during calcination and hydrothermal treatment. Archaeological ceramics and the model compound were treated by hydrothermal ageing and studied by XRF, XRD and IR analyses. It was proved that the presence of kaolinite in the border-parts of the archaeological object was not a product of rehydration, but that it originated from the raw materials

The preparation of dental glass-ceramic composites with controlled fraction of leucite crystals

This work is dealing with synthesis of leucite powder, which can be used for the preparation of dental glassceramic composites by subsequent thermal treatment. Newly developed procedure is based on preparation of dental raw material as a mixture of two separate compounds: the crystalline leucite powder prepared at relatively low temperature and a commercial matrix powder.Hydrothermal synthesis of tetragonal leucite particles (KAlSi2O6) with the average size of about 3 μm was developed in our laboratory. The leucite dental raw material was prepared by mixing of 20 wt.% of synthetic tetragonal leucite with commercial matrix. Dental composites were prepared from the dental raw material by uniaxial pressing and firing up to 960°C. Dilatometric measurements confirmed that the coefficient of thermal expansion increased by 32% when 20 wt.% of the tetragonal leucite was added into the basic matrix. In addition, it was showed that the synthesized leucite powder was suitable for the preparation of leucite composites with controlled coefficient of thermal expansion. High value of the thermal expansion coefficient enables application of prepared composite in metal-ceramics restorations

Hepcidin and ferritin levels as markers of immune cell activation during septic shock, severe COVID-19 and sterile inflammation

IntroductionMajor clinically relevant inflammatory events such as septic shock and severe COVID-19 trigger dynamic changes in the host immune system, presenting promising candidates for new biomarkers to improve precision diagnostics and patient stratification. Hepcidin, a master regulator of iron metabolism, has been intensively studied in many pathologies associated with immune system activation, however these data have never been compared to other clinical settings. Thus, we aimed to reveal the dynamics of iron regulation in various clinical settings and to determine the suitability of hepcidin and/or ferritin levels as biomarkers of inflammatory disease severity.CohortsTo investigate the overall predictive ability of hepcidin and ferritin, we enrolled the patients suffering with three different diagnoses – in detail 40 patients with COVID-19, 29 patients in septic shock and eight orthopedic patients who were compared to nine healthy donors and all cohorts to each other.ResultsWe showed that increased hepcidin levels reflect overall immune cell activation driven by intrinsic stimuli, without requiring direct involvement of infection vectors. Contrary to hepcidin, ferritin levels were more strongly boosted by pathogen-induced inflammation – in septic shock more than four-fold and in COVID-19 six-fold in comparison to sterile inflammation. We also defined the predictive capacity of hepcidin-to-ferritin ratio with AUC=0.79 and P = 0.03.DiscussionOur findings confirm that hepcidin is a potent marker of septic shock and other acute inflammation-associated pathologies and demonstrate the utility of the hepcidin-to-ferritin ratio as a predictor of mortality in septic shock, but not in COVID-19

Business Plan

The diploma thesis deals with the creation of a realistic and applicable business plan for a new business – a forest nursery. The diploma work is divided into four main parts. Part one describes the objective and methodology of work. Followed by the second part, a theoretical one, in which the theoretical knowledge and the starting point needed to create the business plan are described and explained. In the third part, I analysed, with help of the theoretical knowledge, the current market situation and the internal and external business environment. The last part includes suggestions for the business plan and is closed with a final summary and recommendations, which should contribute to the establishment and to the further development of the firm in the future

Degradation Processes of Medieval and Renaissance Glazed Ceramics

Corrosion effects in deposit environments (soil, waste pit, etc.), together with the glaze adherence and fit, could cause severe deterioration accompanied by different types of defects or growth of corrosion products. The aim of this work was to identify the source of surface degradation of the lead-glazed ceramics sets from the Prague area from the Romanesque to the Renaissance period. A combination of X-ray fluorescence (XRF), X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and simultaneous thermal analysis (STA) techniques along with stress state calculations was used to study the defects. Based on the interpretation of the possible sources of the observed defects, four types of degradation effects were schematically expressed for the archaeological samples. It was shown that the glazes were already appropriately chosen during the production of the Romanesque tiles and that their degradation occurred only due to long-term exposure to unsuitable environmental conditions

Metodika konzervování-restaurování nízkopálené nestabilní keramiky

Metodika je zaměřena na konzervování-restaurování nízkopálené nestabilní keramiky. Podává ucelený přehled o vhodných postupech pro zpracování materiálu tohoto typu. Obsahuje souhrn vhodných metod pro hodnocení stupně poškození, postupy odběru vzorku a doporučené analýzy pro identifikaci chemického a mineralogického složení keramiky. Dále popisuje možnosti čištění, postupy konsolidace, lepení a doplňování chybějících fragmentů a případné retuše. Obsahuje rovněž zásady pro vhodné uložení těchto předmětů a pro pochopení jednotlivých metod jsou uvedeny komentované příklady

Metodika konzervování-restaurování glazované keramiky

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

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

International audienceAbstract Although the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency