National Repository of Grey Literature 31 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Application of Raman spectroscopy for detection of sulfates of self-ignited coal heaps
Košek, Filip ; Jehlička, Jan (advisor) ; Němec, Ivan (referee) ; Vandenabeele, Peter (referee)
This Ph.D. thesis was focused on the application of Raman spectroscopy as the main analytical method for the characterization of neo-formed minerals, notably sulfates, from burning coal waste dumps. This environment associated with subsurface fires gives rise to a variety of uncommon and rare minerals. The specific features of these minerals (metastability, hygroscopy, mixed aggregates) causes that the mineralogical investigation is a challenging task using traditional laboratory-based techniques. Advantages such as the non-destructive nature, the sensitivity to the changes in the hydration degree of sulfates, little or none pretreatment, and the option of measurements directly in the field were the main reasons for applying this spectroscopy method. The scarce availability of spectroscopic data of most gas-vent minerals can be considered as the disadvantage. Therefore, artificial prepared samples of six anhydrous sulfates, which are rarely found in nature, were analyzed by Raman laboratory spectroscopy and a miniature a Raman spectrometer, and specific Raman features as well the differences with hydrated counterparts are shown. Laboratory investigation of two natural hydrated aluminum sulfates, alunogen and khademite, were carried out using Raman spectroscopy and other methods in order to obtain...
Carotenoids of snow algae as biomarkers for exobiology: Raman spectroscopic perspective
Němečková, Kateřina ; Jehlička, Jan (advisor) ; Němec, Ivan (referee)
The major aim of this thesis is critical evaluation of Raman spectroscopy in the detection of carotenoids of extremophiles, namely snow algae. Extremophilic microorganisms play an important role in exobiology since they set hypothetical boundaries for the presence of life on Earth. Raman spectroscopy will be a part of two mission to Mars. Here, a laboratory Raman microspectrometer was used for the analysis of 11 samples of snow algae from different locations over the years 2002-2017. The acquired spectra were compared with HPLC/UV-VIS analysis. The results showed that the ability of Raman spectroscopy to discriminate between structurally slightly differing carotenoid pigments or several carotenoids in an admixture is limited. Contrary, HPLC/UV-VIS permitted to detect various structurally similar carotenoids (and chlorophylls). However, HPLC/UV-VIS worked with overall pigment extracts during which some structural information can be lost. Raman microspectrometer allowed analysis of cells in different life-cycle stages and thus several various spectra could be studied. Raman microspectrometer was therefore more suitable for carotenoid detection in mixtures of various life-stages than HPLC/UV-VIS. Key words carotenoids, snow algae, exobiology, habitability, biomarker, Raman spectroscopy, HPLC/UV-VIS
Application of Raman spectroscopy for the identification of organic inclusions in minerals for the field of exobiology
Osterrothová, Kateřina ; Jehlička, Jan (advisor) ; Němec, Ivan (referee) ; Vandenabeele, Peter (referee)
The multidisciplinary field of astrobiology has grown rapidly in recent years. The major goals of research in the field have been the search for habitable environments both within and outside our solar system, the search for evidence of prebiotic chemistry and life on Mars and other bodies in our solar system, laboratory and field research into the origins and early evolution of life on Earth, and studies of the potential for life to adapt to challenges on Earth and in space. NASA and ESA are heavily focused on a number of upcoming exploratory missions (e.g., the Mars Science Laboratory, with its planned launch in the fall 2011; ExoMars 2018; and the follow-up Mars Sample Return missions beyond 2020). A Raman spectrometer is now being miniaturized for the ExoMars Rover Instrument Suite. This Raman instrument is expected to be used to identify organic compounds and mineral products that could be related to signatures of life, as well as provide a general mineralogical overview, especially those minerals produced by water- related processes. This thesis describes the results of laboratory investigation into the feasibility of Raman spectroscopy to detect different types of biomarkers (pigments, carboxylic acids, and aminoacids) first mixed in the mineral matrices and...
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...

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2 Jehlička, Jakub
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