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The measurement of the heterogeneous particles in the steam
Bartoš, Ondřej ; Hrubý, Jan ; Ždímal, Vladimír ; Kolovratník, Michal ; Jiříček, I. ; Moravec, Pavel ; Zíková, Naděžda
The aim of this extended abstract is to reveal the work done as cooperation between several institutions which was presented and published in recent years (Kolovratník, 2014). The formation of droplets in low-pressure steam turbines has a significant impact on the efficiency of energy conversion due to the strongly nonequilibrium nature of this process . The condensed water also erodes the turbine blades. A very important question is to what extent heterogeneous nucleation contributes to the phase transition process . In the case of heterogeneous nucleation , the number of droplets depends only on the number of h eterogeneous particles in the system, whereas in the case of homogeneous nucleation, the number of created droplets is determined rather by the expansion rate - in a faster expansion, greater supersaturation and more droplets are formed until the released condensation enthalpy quenches the nucleation.\nThe specific number of droplets (number of droplets per unit mass of steam) formed in the turbine can be determined by optical probes, developed first by Walters and later in the Czech Republic improved by Petr and Kolovratník. Until recently, no information was available on the relative importance of heterogeneous nucleation in forming these droplets.
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Properties of point defects in CdTe at temperatures of 300 - 600 K
Korcsmáros, Gabriel ; Moravec, Pavel (advisor) ; Šikula, Josef (referee) ; Toušková, Jana (referee)
The thermal stability of p-type CdTe crystals by using conductivity and Hall-effect measurements have been studied at room and slightly increased temperatures. It was observed that thermal changes often implicate an anomalous behavior of the hole density characterized by reversible decrease/increase in a heating/cooling regime. This anomaly was explained by a transfer of fast diffusing donors between Te inclusions and the bulk of the sample. Sodium and potassium were determined by the Secondary Ion Mass Spectroscopy (SIMS) as the most probable diffusing species. To verify this behavior samples were also treated in saturated NaCl solution for different time intervals in order to examine the influence of the oxide layer and sodium on the surface of the sample. To determine the structure of the surface the sample was characterized by ellipsometric and X-ray photoelectron spectroscopy (XPS) and SIMS. Very low determined diffusion coefficient of Na was explained by trapping of Na in Cd sublattice
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MOCVD Iron Oxide Nanoparticle Generation not Only for Follow-Up Inalation Exposure Experiments.
Moravec, Pavel ; Schwarz, Jaroslav ; Vodička, Petr ; Kupčík, Jaroslav ; Švehla, Jaroslav
Iron oxide nanoparticles (NPs) are industrially produced and commercially available and they are also frequently emitted into the environment by iron making plants. In the human body, iron is maintained at homeostatic fairly low level. However, freshly generated iron oxide NPs cause febrile and inflammatory response known as metal fume fever, but the potential in vivo consequences of inhalation of iron oxide NPs from the atmosphere has not yet been investigated. An overview of recent studies evaluating iron oxide NPs cytotoxicity, genotoxicity, developmental toxicity and neurotoxicity was presented by Valdiglesias et al. (2015). Toxicity of iron oxide NPs has been studied both in vitro and in vivo. Exposure chamber for the whole body inhalation experiments with small laboratory animals was constructed at the Institute of Analytical Chemistry of the CAS (Večeřa et al., 2011) and some methods of NPs generation for these experiments were already tested in our laboratory (Moravec et al., 2015. Moravec et al., 2016). In this study we tested a method of long lasting generation of iron oxide NPs by pyrolysis and oxidation of ironIII acetylacetonate (FeAA3).
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Plný tet: SKMBT_C22018110212483 - PDF
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Effect of inhaled metal oxide nanoparticles on organs of exposed mice
Mikuška, Pavel ; Večeřa, Zbyněk ; Dočekal, Bohumil ; Čapka, Lukáš ; Křůmal, Kamil ; Coufalík, Pavel ; Moravec, Pavel ; Buchtová, Marcela ; Míšek, Ivan ; Vrlíková, Lucie ; Smutná, Tereza ; Dumková, J. ; Hampl, A. ; Fictum, P.
Adult mice were continuously exposed to metal oxide nanoparticles for different time intervals. At the end of experiment, mice organs (lung, brain, kidney, liver and spleen) were collected for chemical, biochemical, histological and electron microscopical analyses.
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Regional Air Pollution Transport and Its Influence to Pollution Hotspot in th Czech Republic.
Kozáková, Jana ; Vodička, Petr ; Pokorná, Petra ; Ondráčková, Lucie ; Ondráček, Jakub ; Hovorka, J. ; Křůmal, Kamil ; Mikuška, Pavel ; Moravec, Pavel ; Schwarz, Jaroslav
The aim of the study was to find out the local effect and the regional air pollution transport effect on the air quality of the Ostrava Radvanice district, the problematic air pollution hot spot.
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Plný tet: SKMBT_C22017103113061 - PDF
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Nanoparticle Generation for Follow-Up Exposure Studies by Oxidation of Copper Acetylacetonate.
Moravec, Pavel ; Schwarz, Jaroslav ; Vodička, Petr ; Švehla, Jaroslav ; Kupčík, Jaroslav
The exposure to nanoparticles (NPs) represents a severe problem to human health, because they are becoming more widely used and their number of applications continually increases. Particles containing copper are emitted from smelters, iron foundries, power stations and municipal incinerators (WHO, 1998), as well as from brake linings during braking, Kukutschova et al. (2011). Copper and copper oxide NPs are frequently used as catalysts, heat transfer fluids in machine tools (Kim et al., 2011), inks, anode material in lithium-ion batteries (Guo et al., 2002) and many others. Even though CuO NPs were found highly toxic, Karlsson et al. (2008) and it is likely that NPs enter human body via respiratory tract, the inhalation exposure experiments of CuO NPs with laboratory animals are still rather rare (Pettibone et al., 2008 and Lebedova et al., 2016). The exposure chamber for long lasting inhalation experiments was constructed at the Institute of Analytical Chemistry of the CAS (Večeřa et al., 2011) and some methods of NPs generation for these experiments were already tested in our laboratory (Moravec et al., 2015 and Moravec et al., 2016a). The generation of Cu/Cu2O NPs by thermal decomposition of copper acetylacetonate (CuAA) was reported by Moravec et al. (2016b) and here we present the results of long lasting generation of NPs by oxidation of CuAA.
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Plný tet: SKMBT_C22017103113062 - PDF
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Electrical and optical properties of ZnO single crystals
Zetek, Matyáš ; Belas, Eduard (advisor) ; Moravec, Pavel (referee)
In this thesis, we study electrical and optical properties of ZnO single crystals, by processing measurements of Hall effect to low temperatures. We also research how defects influence ZnO single crystal in terms of its electrical properties. We studied donors and acceptors levels in this material and their activation energies. We try to find what cause these donors and acceptors. We characterized material with its electrical conductivity, carrier concentration and carrier mobility. We carry an experiment of annealing ZnO in vapor of Zn, while we are looking for a change in mobility and a change in defect structure. As well we process photoluminescence measurement, the ZnO was excited with 355nm laser - light energy higher than the bandgap. We see green luminescence and its shift towards blue part of the spectra after annealing the crystals in ZnO vapor. Powered by TCPDF (www.tcpdf.org)
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