National Repository of Grey Literature 24 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Crystal and molecular structure study of garnets from selected localities of the České středohoří Mts.
Píšová, Barbora ; Skála, Roman (advisor) ; Laufek, František (referee)
Major and minor element contents of garnets from mantle peridotites and eclogites brought to the surface by volcanic rocks of the České středohoří Mts. were determined by an electron probe microanalyzer. Garnets are homogenous and their chemical composition corresponds to solid solution containing 65-71 % pyrope, other end members significantly present are almandine, uvarovite and grosulare. This method also help to discover polyphase inclusions chemically corresponding to amphiboles (pargasite, cummingtonite, magnesio-hornblende and katophorite). Next to amphiboles following minerals were found in inclusions: omphacite, carbonates, phlogopite, clinochlore, olivine, apatite, spinel group minerals, and sulfidic phases potentially close to pentlandite. Samples were also analyzed by powder X-ray diffraction. Qualitative phase analysis confirmed pyrope homogeneity. The refinement of crystal structure parameters was performed by the Rietveld method. Raman microspectroscopy showed shifts of individual bands in the Raman spectra compared to those of pure pyrope. Position of bands in spectra differs due to the substitution of Ca for Mg at the dodecahedral sites of the structure. Mutual positive correlations among elements Cr, Ca, Mg, Al, Si, Mn, Ti and Na were observed. Correlations were found also between...
Structural and Chemical Aspects of Calcium Phosphate Formation in Tooth Enamel
Kallistová, Anna ; Skála, Roman (advisor) ; Frýda, Jiří (referee) ; Oldak, Janet (referee)
Tooth enamel is the hardest and most resistant highly mineralized inorganic component in mammalian bodies that significantly affects both the life quality and expectancy of an indi- vidual. Its specific qualitative properties are given by the biomineralization process responsible for its formation. In this process the mineralization of hydroxyapatite (HAp), the only inor- ganic phase composing the mammalian hard tissues, is controlled by activity of enamel-forming cells ameloblasts and their products. Over the past years, the studies of enamel matrix pro- teins, their structure, composition and function has become the prevalent field of experimental investigation. However, unique enamel qualities, which enable the teeth to withstand high pressure and stress demands, cannot be accurately assessed without the thorough systematical study of its mineral compound. In this thesis, I focus on the crystallographic and compositional characteristics of enamel hydroxyapatite and their influence on the mechanical properties of teeth. Obtained results are discussed in context of developmental and adaptation dynamics of mammalian species. The main aspect of the work is to extend our knowledge about the protein-mediated mineraliza- tion process from the perspective of inorganic compound and its contribution to the...
Variability of chemical composition of apatites from alkaline rocks of the Bohemian Massif
Mészárosová, Noemi ; Skála, Roman (advisor) ; Filippi, Michal (referee)
III Summary This thesis is focused on crystal chemistry and crystal structure of apatites from alkaline rock of the Bohemian Massif. Fifteen samples of volcanic rocks, mostly of the Cenozoic age was selected for the study. Sample No. 5 is of the Silurian age. Sample No. 15 originates from volcanic rock of the Cenozoic age from the Slovak Western Carpathians. This sample was chosen for this study due to its substantially different chemical composition. The contents of major and minor elements in apatites were measured on an electron microprobe, the contents of some minor and trace elements were determined by laser ablation inductively coupled plasma mass spectrometry. Selected samples were investigated by cathodoluminescence (CL) spectrometry. Crystal structure of studied apatites was characterized by X-ray diffraction and Raman spectroscopy. It was found that dominant anion at position X is fluorine. The OH content calculated on the basis of the fully occupied position X is significant in some samples. The amount of Cl is generally low. The exception is the sample No. 15 where Cl reached up to 0.6 apfu (Z = 2). Studied apatites contain many substitutions but they are generally of minor extent. Strontium, iron and REE at position M belong to the most common and most important substituents for calcium in...
Thermobarometry of ultramafic rocks in ophiolites of the Vardar Zone in FYR Macedonia
Fikar, Lukáš ; Skála, Roman (advisor) ; Kallistová, Anna (referee)
This thesis is divided into review section followed by an experimental part. The first part focuses on geothermobarometry, illustrates its history and provides its detailed principles. Furthermore, it discusses various possibilities of the use of different mineral assemblages for purposes of thermometry and barometry. This part puts an emphasis on exchange reactions, the role of solvus in themometry, reactions based on weight transfers, and reactions involving gas phases. A chapter on Macedonian geography and regional geology provides a detailed description of the Vardar ophiolite belt, which was the source of the samples used in experimental part of the thesis, and its relationship toand other geological units in Macedonia, namely the Eastern Vardar Ophiolite zones, the Kopaonik unit, and the western part of the Vardar Ophiolite zone. Finally, a process of exsolution in subsolidus, which is impostant for the group of pyroxenes, is discussed. The area of interest is the use of the process of exsolution in thermometry. The thermodynamic conditions for exsolution are important features of the exsolution. The experimental part of the thesis includes a description of the samples and results of chemical analyses carried out with an electron probe microanalyzer. Chemical data were processed with two...
Determination of geological provenance by cathodoluminescence spectroscopy of apatites and carbonates
Pánik, Róbert ; Matějka, Dobroslav (advisor) ; Ježek, Josef (referee) ; Skála, Roman (referee)
This work presents new method for determination of geological provenance based on the statistical analysis of cathodoluminescence spectra of marbles and carbonate rocks from various localities in the Bohemian Massif. Analysis is based on the combination of data from seven different measures of spectral similarity and provides results that are more robust than those obtained by approach based only on a single measure of similarity. These results may be further improved by employing meta-analysis that evaluates behaviour of spectra during the individual steps of analysis. Analysis was performed on the original cathodoluminescence spectra, as well as on the residual spectra in which relative variability was amplified by the subtraction of Gaussian trend present in all spectra of carbonates. By combining results from analysis and meta-analysis of both original and residual spectra it was possible to almost unambiguously determine provenance of samples from all studied localities. Agglomerative hierarchical clustering was employed as a supplementary method for classification of spectra. Out of 72 different methods for clustering, one was selected for both original and residual data based on the number of correctly classified spectra. Second part of this work presents analysis of cathodoluminescence...

National Repository of Grey Literature : 24 records found   1 - 10nextend  jump to record:
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1 Skala, Richard
8 Skala, Roman
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