Publications by authors named "Yordanka Karakirova"

Article Synopsis
  • * Results showed these strains have strong antibacterial and antifungal properties, with unique abilities to inhibit various harmful fungi and significant antioxidant capacity.
  • * The research also indicates that one of the strains has potential effects on leukemia cell growth, paving the way for future development of targeted probiotics, while further safety studies are needed for validation.
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Dried figs were studied by Electron Paramagnetic Resonance (EPR) spectroscopy for identification of radiation treatment and dosage assessment. Gamma-irradiated samples show a multicomponent "sugar-like" EPR spectrum with line width of 6-8 mT, centered at g = 2.004.

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  • New research explores how titanium dioxide (TiO) impacts palladium (Pd) catalysts in the oxidation of methane, focusing on their behavior in the presence of water (HO) and sulfur oxides (SO).
  • Various characterization techniques (like XRD and SEM) reveal changes in the catalyst with aging, including Pd-cluster growth and alterations in TiO phases, affecting their performance.
  • The modified catalyst shows improved resistance to sulfur compounds and operates under the Mars-van Krevelen mechanism; practical applications were tested using a two-dimensional model simulating industrial methane oxidation.
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A comparative investigation of amino acids (proline, cysteine, and alanine) as dosimetric materials using electron paramagnetic resonance (EPR) spectroscopy in the absorbed dosage range of 1-25 kGy is presented. There were no signals in the EPR spectra of the samples before irradiation. After irradiation, the complex spectra were recorded.

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Gamma irradiation has been applied as an efficient and inexpensive method for the sterilization of nuts for years. However, along with the benefits of such treatment, negative effects are possible because of the formation of reactive oxygen species with a toxic effect on important biologically active substances. Because of the scarce and contradictory information in the literature about gamma-irradiated almonds, the aim of our work was the examination of the lipid changes, antioxidant activity, and oxidative stability of almonds treated by 10 and 25 kGy gamma rays, as well as changes in intensity of the EPR spectra as an indicator for the stability of radiation-induced free radicals.

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CuFeS/TiO nanocomposite has been prepared by a simple, low-cost mechanochemical route to assess its visible-light-driven photocatalytic efficiency in Methyl Orange azo dye decolorization. The structural and microstructural characterization was studied using X-ray diffraction and high-resolution transmission electron microscopy. The presence of both components in the composite and a partial anatase-to-rutile phase transformation was proven by X-ray diffraction.

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Yttrium-doped barium cerate (BCY15) was used as an anode ceramic matrix for synthesis of the Ni-based cermet anode with application in proton-conducting solid oxide fuel cells (pSOFC). The hydrazine wet-chemical synthesis was developed as an alternative low-cost energy-efficient route that promotes 'in situ' introduction of metallic Ni particles in the BCY15 matrix. The focus of this study is a detailed comparative characterization of the nickel state in the Ni/BCY15 cermets obtained in two types of medium, aqueous and anhydrous ethylene glycol environment, performed by a combination of XRD, N physisorption, SEM, EPR, XPS, and electrochemical impedance spectroscopy.

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Introduction: Antibacterial photodynamic therapy is a promising treatment modality in the anti-infective therapy of numerous oral diseases. It involves photo activation of a reactive substance (dye), thus releasing reactive oxygen species (ROS-radicals) which are highly destructive to the bacterial cell. However, thorough investigation of radical production properties of different dyes is not common in literature.

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The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased.

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Several types of laboratory glasses such as: "Jena", "Rasotherm", "Thüring" as well as window and windscreen glasses were studied by the method of EPR spectroscopy as possible emergency radiation dosimeters for gamma-ray irradiation. The most appropriate values of modulation amplitude and microwave power were found to obtain best sensitivity for the measured signals. Dose measurements have shown a linear dependence between the EPR signal intensity of radiation created defects in glasses and applied dose in the dose range 50-500 Gy.

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