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Three Years of Experience with Measurement of Cloud Condensation Nuclei Concentrations Using Cloud Condensation Nuclei Counter CCN-200
Moravec, Pavel ; Lhotka, Radek ; Ždímal, Vladimír
Aerosol particles in the atmosphere that allow water vapor to condense and form cloud droplets are called Cloud Condensation Nuclei (CCN). Elevated concentrations of \nCCN tend to increase the concentration and decrease the size of droplets. This can lead to suppression of precipitation in shallow and short-lived clouds and to greater convective \noverturning and more precipitation in deep convective clouds. The response of cloud properties and precipitation processes to increasing anthropogenic aerosol concentrations represents one of the largest uncertainties in the current understanding of climate change. One of the fundamental challenges is to determine the ability of aerosol particles to act as CCN under relevant atmospheric conditions. Knowledge of the spatial and temporal distribution in the atmosphere is essential to incorporate the effects of CCN into meteorological models of all scales, Huang et al. (2007). Long-term CCN measurements are performed at aerosol monitoring sites such as those forming ACTRIS (Aerosols, Clouds and Trace Gases Research Infrastructure) network. In this paper, we present the three-year experience of measuring CCN concentrations over the National Atmospheric Observatory Košetice (NAOK), a rural background site in the Czech Republic. The first results of these measurements were presented by Mishra et al. (2022)
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Electrooptic Pockels effect in X-ray radiation detectors
Rejhon, Martin ; Franc, Jan (advisor) ; Moravec, Pavel (referee)
In this work, we have added a temperature controller to an apparatus for measuring Pockels effect, which comprises of an integrated circuit and a Peltier element. Then the course of the electric field was measured in the sample of high resistance CdTe, a suitable detector on the high-energy radiation, depending on the voltage and temperature of the sample. Also the charge distribution in the sample was determined depending on time after the voltage and sample's temperature were reached. Finally, the activation energies of deep levels were determined, which are responsible for the polarization. Powered by TCPDF (www.tcpdf.org)
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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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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).
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22018110212483 - PDF
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