National Repository of Grey Literature 47 records found  beginprevious22 - 31nextend  jump to record: Search took 0.00 seconds. 
Use of Raman mapping for investigation of carbonaceous matter of rocks
Řáhová, Jaroslava ; Jehlička, Jan (advisor) ; Culka, Adam (referee)
Raman spectroscopy is an irreplaceable method for chemical and structural characterization of many substances. This is especially true for carbonaceous matter. It is non-destructive and capable of determining the crystallinity of the studied carbonaceous phase, and subsequently, with the aid of empirical relations, also the temperature of formation of the rock under study. Until very recently, the most of the Raman spectroscopy measurements was conducted only single point-wise on grains chosen on purpose, e.g., in an optical microscope. Alongside with the evolution and affordability of the Raman spectroscopic technique it is now very appealing to utilize the possibility of Raman mapping coupled to the automated analysis of large quantities of acquired spectra. The aim of this study was to critically evaluate the pros and cons of such an approach on selected rocks with varying carbon content and crystallinity of the carbonaceous phase. The samples range from graphite, Karelian shungite, elemental carbon-rich carbonates, alpine schist to eclogite. In general, we can rate the large area mapping as suitable in many cases, however, there are certain issues associated with the method, especially concerning the sample preparation and automated analysis. Several actions are proposed to limit the pitfalls...
Estimation of structural state of carbonaceous matter of metasedimentary rocks using Raman spectroscopy
Kdýr, Šimon ; Jehlička, Jan (advisor) ; Machovič, Vladimír (referee)
Metamorphic processes can transform the organic matter in sedimentary rocks into structurally organized carbonaceous matter, in ideal conditions to graphite. In the centre of West Alpine arch, the metasedimentary rocks are rich in dispersed carbonaceous matter and were used in this thesis to specify the thermal range of metamorphism based on the structural state. Previous studies have used mainly the Raman spectrometers to determine the structural state of carbonaceous matter. Unfortunately this method doesn't allow in-situ analyses which, in addition to Earth studies, can be essential for studying other planetary bodies and moons of our solar system. As only the smallest and lightest instruments are required for analyses during potential planetary missions to Mars, it is important to verify that the small instruments are able to detect even the small concentrations of carbonaceous matter. Currently available miniature and portable Raman spectrometers have started to become more precise but are still not as precise as laboratory Raman microspectrometers. This thesis is divided into two parts. First part aims to duplicate the results from previous studies by Raman microspectrometers in the West Alpine arch. Furthermore, the excitation laser wave length dependence of spectral signs in carbonaceous...
Identification of precious stones using portable Raman spectrometers: advantages and limits during in situ applications
Minaříková, Laura ; Jehlička, Jan (advisor) ; Machovič, Vladimír (referee)
This thesis investigates the potential and limits of portable Raman spectrometers for their application in situ in the environment of museum collections. The data sets were obtained at the two locations. The first measurement took place in the Jewish Museum in Prague. Here we have studied stones from a silver Torah shield from the first half of the nineteen century. This shield is decorated with a set of precious and semi-precious stones and glass imitations. The shield originates from Poland and has been studied using two portable Raman spectrometers (785 nm and 532 and excitations). The second measurement took place in the premises of the Prague Loreto where we had available, at that time still unshown, objects of art for the forthcoming new exhibition. It was about jewelry like earrings, rings, bracelets and brooches, also about ordinary objects of daily use like mirrors, bowls and perfume bottles, or about the objects with religious themes, mostly crowns for the Virgin Mary and baby jesus. The obtained Raman bands correspond well with the reference values of the minerals, the deviation ranged in the order of +/- 3 cm-1 , which in general permits unambiguous identification of phases. Portable handheld Raman spectrometers working with a laser wavelength of 785 nm and 532 nm were able to quickly...
Raman spectrometry of pigments of cyanobacteria, algae and lichens in the astrobiology context
Kovács, Michal ; Jehlička, Jan (advisor) ; Osterrothová, Kateřina (referee)
This work deals with the possibility of Raman spectroscopical identification of selected biomarkers of extremophile species. It focuses mainly on selected cyanobacteria, algae and lichens with an emphasis on the ability to detect carotenoids. These pigments exhibit three characteristic bands of Raman spectra which represent stretching vibrations C=C; C-C and bending vibration C-CH3 in molecules of carotenoids. Raman spectra were measured not only by laboratory microspectrometers (λ - 514 nm and 532 nm), but also by portable and handheld spectrometers (λ - 532 nm, 785 nm and 700 - 1100 nm). In the case of cyanobacteria, the spectroscopical analysis was performed also on the fractions obtained by high performance liquid chromatography (HPLC). This work critically evaluates the possibilities of Raman spectroscopy to identify the carotenoids of cyanobacteria, algae and lichens. Besides the signal of carotenoids, interpretation of other bands in the Raman spectra corresponding to the presence of other biomarkers is given here for selected samples. The obtained Raman spectra of carotenoids should be interpreted with great caution, because of the ifluence of several factors, which potentially cause unsystematic shifts in the positions of Raman bands (carotenoids bond in biological tissue, interactions with...
Raman spectrometry of carotenoids of selected microorganisms
Novotná, Julie ; Jehlička, Jan (advisor) ; Machovič, Vladimír (referee)
In this thesis Raman spectroscopy is evaluated as a tool of identification and discrimination of carotenoids from microbial biomass. Microorganisms, halophilic or nonhalophilic, belong to Cyanobacteria, Proteobacteria, Chlorophyta, Rhodophyta and to others. Biomass was cultiveted under laboratory conditions and yielded varied colours. Raman spectra were recorded succesfully from lyophilized biomass by excitation wavelenth 514.5 nm (dispersive Raman microspectrometr) and 1064 nm (FT Raman spectrometer). Results were compared with Raman spectroscopic data from pigment extracts. Spectra of carotenoids are characterized by the main Raman bands υ1, υ2 a υ3 due to C=C stretching, C-C stretching and C-CH3 deformation. HPLC/UV-VIS allows effective pigment separation from extracts and detection of separated pigments by UV-VIS analyzator. Assessment of Raman analysis and its potential to detect microbial carotenoids are discused. Sarcinaxantin is an unusual carotenoid identified together with more common β - carotene. Raman spectroscopic results obtained on carotenoids recorded from colonies which accumulated more than one carotenoid need to be interpreted carefully. Powered by TCPDF (www.tcpdf.org)
Use of portable Raman spectrometers for detection of sulfates: potential application in exobiology
Košek, Filip ; Jehlička, Jan (advisor) ; Němec, Ivan (referee)
The detection of mineral phases under in situ conditions has become a primary but sometimes also challenging task in many fields of geoscience. Raman spectroscopy has been used as a powerful tool for the identification of various minerals and organic compounds. The advantages and the relative simplicity made this method a promising choice in the future planetary exploration missions to Mars. The deposits of aqueous minerals including sulfates have been found on the Martian surface. With the development of miniaturized handheld spectrometers there is a need for evaluation of Raman spectroscopy as a method of identification of sulfate phases in their natural conditions. In the first part of this work a handheld spectrometer equipped with 532 nm excitation laser was tested under laboratory conditions during which the ability to distinguish mineral samples representing sulfates of different chemical composition and different degree of hydration was investigated. In the second part, two handheld Raman spectrometers equipped with 532 and 785 nm excitation lasers were used for the characterization of sulfate phases on sites of their natural occurrence located in the Czech Republic. The quality of the Raman spectra acquired under outdoor conditions by both spectrometers was rather average but sufficient to...
Europa and its importance for exobiology - life in ice
Suchánek, Vladimír ; Jehlička, Jan (advisor) ; Culka, Adam (referee)
Generally we can say, that for life similar to the life on the Earth it is necessary to meet three basic prerequisites. On the surface or below the surface of the planet or the moon there must be liquid water, basic biogenic elements and no less important source of energy. If these requirements are at least partially met, the given place in the universe can be described as a potential source of life. This scientific work is dealing with the possible origins of life on one of Jupiter's moons, named Europa. The thesis is divided into four chapters, where the first three chapters deal with Europa as a place suitable for life. The fourth chapter is focused on the future research of the moon. This work is based on the data obtained from satellites Pioneer 10, Pioneer 11, Voyager 1, Voyager 2 and Galileo. Powered by TCPDF (www.tcpdf.org)
Use of handheld Raman spectrometers for identification of secondary minerals in situ
Kdýr, Šimon ; Jehlička, Jan (advisor) ; Culka, Adam (referee)
Summary: The sulfates are secondary minerals, that are occurring in the different terrestrial conditions. Their study is useful for understanding of the processes, that are leading to occurence the acid mine drainage. Next sphere of research is out of our globe (it means Mars). The Raman spectroscopy is nondestructive analytical method, that it is advantage of this method. It has occured great development on the field of miniaturisation in a few last years. It is opportunity for aplication out of laboratory and it is possible to make a study in field conditions. At the introduction, this work is occupied with instrumentations, advantages and disadvantages of the use mobile Raman spectrometers. You find there summarises publications, that are occupied with mineralogy, origin of sulfates and opportunities of application mobile Raman spectrometers for their study. At the end of the recherche, it shows some particular localities, where it could be applicable for study sulfates by Raman spectroscopy and where mobile Raman spectrometers were used for identification of sulfate minerals.
Use of Raman spectrometry in the environmental areas
Šotkovský, Jakub ; Jehlička, Jan (advisor) ; Machovič, Vladimír (referee)
This work deals with the use of Raman spectroscopy in environmental analysis focused on aerosols and slags from pyrometallurgical processes. This is a practical analysis of the publications in which the authors deal with chemical conditions and the structure of these waste products resulting from metallurgical processes in the context of their risks and the impact on the environment. Raman spectroscopy is a suitable method for identification of substances for the qualitative and quantitative structural analysis. This method can detect even very small particles and speciation or oxidation states. The advantage of this method is its nondestructivity. Also there is no chemical changes and no thermal damage of the sample while using this method. Another indisputable advantages of the mobile Raman spectrometer is the speed at which the system can detect the desired properties of materials in-situ and even in extreme conditions.

National Repository of Grey Literature : 47 records found   beginprevious22 - 31nextend  jump to record:
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