Search Results
You are looking at 1 - 3 of 3 items for
- Author or Editor: M. Kovaľ x
- Refine by Access: All Content x
Abstract
Presence of pathogenic strains of Escherichia coli in foodstuffs may pose a health risk for a consumer. Therefore, knowledge on the effect of environmental factors on the growth ability of E. coli is of great importance. In this work, the effect of incubation temperature (6–46 °C) and the combined effect of temperature and water activity (0.991–0.930) on the growth dynamic of E. coli PSII were analysed. Based on the growth curves obtained, growth parameters were calculated by using the Baranyi D-model. Growth parameters were further analysed in secondary phase of predictive modelling. Using the CM model that describes the effect of combined factors, cardinal values (T min = 4.8 ± 0.4 °C, T opt = 41.1 ± 0.8 °C, T max = 48.3 ± 0.9 °C, a wmin = 0.932 ± 0.001, and a wopt = 0.997 ± 0.003) for the isolate were calculated. Under optimal conditions, the specific growth rate is µ opt = 2.84 ± 0.08 h−1. The results obtained may contribute to the assessment of the risk associated with the possible E. coli presence in raw materials and to the search for preventive measures with defined degree of accuracy and reliability.
Abstract
An on-column radiometric detector for capillary isotachophoresis is described. Design of the detector follows its intended use, i.e., mainly the detection of14C labelled ionogenic compounds separable by this electromigration method. A key part of the detector is a small volume (70 or 200 nl) cell with the sensing part made of plastic scintillator with counting efficiencies of 13–15%. An equation correlating the precision of radioactivity measurements with physical and geometrical characteristics of the cell and isotachophoretic conditions has been derived providing a guide in optimizing both the geometrical dimensions of the cell and the isotachophoretic working conditions. A minimum detectability calculated for14C radionuclide (21 Bq for a 3 mm thickness of the sensing part of the cell) was in a good agreement with the value determined experimentally (16 Bq). Other parameters evaluated experimentally include resolving power, short- and long-term reproducibilities of the response. It was also shown that optimized driving current during the detection enables to improve the precision of the radioactivity measurement.
Silicon nanocomposites (nc-Si) with rare earth metals (REM) were synthesized by electron-beam evaporation. The structure of nanocomposites was studied by atomic-force microscopy. The size of nanocrystallites was about 10–40 nm. Also chemical composition of obtained material was examined. The distribution of rare earth elements (REE) was uniform in film thickness, but it was characterized by a presence of maximum peak at the interface film-substrate. In the work the electrical and optical properties of nanocomposites Si:REE were investigated. Silicon nanocomposites with Eu or Y were characterized by high sensitivity to visible radiation. The ratio of dark to light resistance was achieved to 2 orders of magnitude, making this material very promising to use in thin-film photosensors. After deposition of nanocomposites Si:REE on silicon substrate, the heterojunction was formed at the interface film-substrate, for which the sensitivity to visible radiation was observed too (1–2 mA/lmV). Also, the presence of photovoltaic effect in such structures was shown, so they can be the basis of cheap thin-film solar cells, using the relevant design solutions.