Publications by authors named "Rostislav Váňa"

4 Publications

  • Page 1 of 1

The Effect of a Taper Angle on Micro-Compression Testing of Mo-B-C Coatings.

Materials (Basel) 2020 Jul 8;13(14). Epub 2020 Jul 8.

Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.

This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4-14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young's modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young's modulus if the taper angle was <10°.
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http://dx.doi.org/10.3390/ma13143054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7411628PMC
July 2020

Synthesis and Characterization of Erbium Oxide Nanocrystallites.

J Nanosci Nanotechnol 2019 05;19(5):2934-2937

Nanotechnology Centre, VŠB - Technical University of Ostrava, 17. listopadu 15, 708 33 Ostrava - Poruba, Czech Republic.

The present article describes a method of the preparation of erbium oxide nanocrystallites (nano Er₂O₃) via thermal decomposition of a transient complex formed from Er(NO₃)₃·5H₂O and glycine. Decomposition of the complex occurred at about of (250±10) °C. Ultra-fine light pink powder of erbium oxide nanocrystallites was obtained via this method. The resulting nanocrystallites were characterized using X-ray powder diffraction analysis, which showed the nanocrystallites having the crystallite size equal to 10 nm. Morphology of the nanocrystallites was examined by scanning and transmission electron microscopy. Electron diffraction observed in transmission electron microscopy corresponds to the results obtained from X-ray diffraction analysis. The elemental composition of the product was confirmed by EDS analysis.
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http://dx.doi.org/10.1166/jnn.2019.15857DOI Listing
May 2019

and the Pink Discoloration Defect in Cheese.

mSystems 2016 May-Jun;1(3). Epub 2016 Jun 14.

Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; APC Microbiome Institute, Cork, Ireland.

A DNA sequencing-based strategy was applied to study the microbiology of Continental-type cheeses with a pink discoloration defect. The basis for this phenomenon has remained elusive, despite decades of research. The bacterial composition of cheese containing the defect was compared to that of control cheese using 16S rRNA gene and shotgun metagenomic sequencing as well as quantitative PCR (qPCR). Throughout, it was apparent that , a carotenoid-producing genus, was present at higher levels in defect-associated cheeses than in control cheeses. Prompted by this finding and data confirming the pink discoloration to be associated with the presence of a carotenoid, a culture-based approach was employed, and was successfully cultured from defect-containing cheeses. The link between and the pinking phenomenon was then established through the cheese defect equivalent of Koch's postulates when the defect was recreated by the reintroduction of a isolate to a test cheese during the manufacturing process. Pink discoloration in cheese is a defect affecting many cheeses throughout the world, leading to significant financial loss for the dairy industry. Despite decades of research, the cause of this defect has remained elusive. The advent of high-throughput, next-generation sequencing has revolutionized the field of food microbiology and, with respect to this study, provided a means of testing a possible microbial basis for this defect. In this study, a combined 16S rRNA, whole-genome sequencing, and quantitative PCR approach was taken. This resulted in the identification of , a carotenoid-producing thermophile, in defect-associated cheeses and the recreation of the problem in cheeses to which was added. This finding has the potential to lead to new strategies to eliminate this defect, and our method represents an approach that can be employed to investigate the role of microbes in other food defects of unknown origin.
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http://dx.doi.org/10.1128/mSystems.00023-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5069761PMC
June 2016

ZnO/graphite composites and its antibacterial activity at different conditions.

J Photochem Photobiol B 2015 Oct 22;151:256-63. Epub 2015 Aug 22.

Nanotechnology Centre, VŠB-Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic; Regional Materials Science and Technology Centre, VŠB-Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic.

The paper reports laboratory preparation, characterization and in vitro evaluation of antibacterial activity of ZnO/graphite nanocomposites. Zinc chloride and sodium carbonate served as precursors for synthesis of zinc oxide, while micromilled and natural graphite were used as the matrix for ZnO nanoparticles anchoring. During the reaction of ZnCl2 with saturated aqueous solution of Na2CO3a new compound is created. During the calcination at the temperature of 500 °C this new precursors decomposes and ZnO nanoparticles are formed. Composites ZnO/graphite with 50 wt.% of ZnO particles were prepared. X-ray powder diffraction and Raman microspectroscopy served as phase-analytical methods. Scanning electron microscopy technique was used for morphology characterization of the prepared samples and EDS mapping for visualization of elemental distribution. A developed modification of the standard microdilution test was used for in vitro evaluation of daylight induced antibacterial activity and antibacterial activity at dark conditions. Common human pathogens served as microorganism for antibacterial assay. Antibacterial activity of ZnO/graphite composites could be based on photocatalytic reaction; however there is a role of Zn(2+) ions on the resulting antibacterial activity which proved the experiments in dark condition. There is synergistic effect between Zn(2+) caused and reactive oxygen species caused antibacterial activity.
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http://dx.doi.org/10.1016/j.jphotobiol.2015.08.017DOI Listing
October 2015