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EPR Study of Radical Intermediates of H-transfer from Oxygeneous, Carboneous and Nitrogeneous Donors
Marešová, Renata ; Mazúr, Milan (referee) ; Stopka, Pavel (referee) ; Omelka, Ladislav (advisor)
Within the PhD. thesis the problems of H-transfer from selected types of phenols, aromatic secondary amines and compounds with acidic CH bond were investigated. This process was initiated by the action of redox agents, mostly PbO2, in nonpolar solvents. The abstraction of hydrogen atom results in the formation of radical intermediates, which were detected by EPR spectroscopy. Because in most cases, highly unstable radicals were produced, it was neccessary to apply the technique of indirect detection, so called spin trapping. This method enables to interpret the character of generated radicals on the basis of EPR parameters of radical adducts, which are formed by their reaction with suitably chosen compounds, spin traps, which are added to the reaction system. As spin traps, the aromatic nitrosocompounds were preferentially used. Due to the fact that EPR spectra of radical adducts were in most cases very complex, their interpretation was possible only using the computer simulation. Based on this approach, new information about the character of addition of phenoxyl tradicals to aromatic nitrosocompounds, stability of alkyl substituents in methyl substituted phenols and character of C-radicals, generated from substituted coumarines and beta-diketones, was obtained. Simultaneously, the small ability of nitrogen radicals, primary products of the splitting of NH bond, to enter the reaction with spin traps was proved by aromatic secondary amines.
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Metody individuální identifikace u vybraných druhů ptáků
Stopka, Pavel
Studie obsahuje návrh spolupráce Ministerstva životního prostředí s referenční laboratoří a souhrnnou studii zaměřenou na zmapování konkrétních metod prokazování původu zvláště chráněných druhů sov a dravců včetně zvážení výhod a nevýhod jednotlivých metod. Součástí studie je seznam pracovišť vybavených technickým zázemím umožňujícím analýzu DNA výše zmíněnými metodami.
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Lithium Phosphate Glasses stabilized with Tungsten Oxide
Míka, M. ; Mladonický, P. ; Vondrák, Jiří ; Stopka, Pavel ; Klápště, Břetislav
Glass exhibiting an increased ionic conductivity could be an attractive material for the construction of electrochemical solid-state devices such as ion-selective sensors, batteries, fuel cells, and electrochromic devices. In these devices the glass can function as a membrane, solid electrolyte or electrode if shows mixed electric conductivity. Amorphous nature gives glass considerable advantages comparing to polycrystalline materials.If we use chemical composition systems with a good glass-forming ability, we can add many different cations and this way "tune" glass properties. Because a large portion of glass volume is occupied by oxygen atoms, many glass properties are strongly influenced by the state of oxygen atoms, especially by the the electron density. God glass-forming ability is exhibited for example by alkali-phosphate glass.
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EPR study of beer samples and brewing materials
Stopka, Pavel
Hydroxyl (OH.), nitroxide (NO.)and stable organic free radicals were identified and determined in samples of beer. The maximum of their concentration is 5-10 min. after the opening of bottle. The influence of UV irradiation and hydrogen peroxide is de
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