In the present paper the influence of both time and low pressure on the surface potential decay of porous composite films of poly(D-lactic acid) and poly(ε-caprolactone) was investigated. The samples were charged in a corona discharge by means of a corona triode system under room conditions. Positive or negative voltage was applied to the corona electrode and voltage of the same polarity as that of the corona electrode was applied to the grid. After charging, the initial surface potential was measured using the method of the vibrating electrode with compensation. Two groups of tests were performed. In the first group, after charging, the electrets were placed into a vacuum chamber where the pressure was reduced step by step in the range from 1000 mbar to 0.1 mbar. At each step the samples were stored for 1 minute. After that the electrets were removed from the vacuum chamber, their surface potential was measured again and the normalized surface potential was calculated. The influence of low pressure was analyzed by the equation that describes processes of desorption from the electret’s surface. In the second group, after charging, the electret surface potential was measured by the time of storage. The possible surface potential decay mechanisms responsible for the electret’s behavior were discussed. It was established that the surface potential decay depends on both corona polarity and type of films. It was shown that the samples charged in a positive corona are more stable than those charged in a negative corona.

The manuscript considers the effects of the sharp temperature increase on the exchangeable forms of 137Cs, from one to three months after its entrance in the soil. The impact of the sharp increase of the environmental temperature on the migration ability of 137Cs and bioaccumulation in orchard grass was investigated in soils taken from five different regions in Bulgaria. The soil samples were contaminated with an aqueous solution of 137Cs and stored at different temperature regimes, simulating temperate and hot summer conditions for a period from one to three months. The exchangeable forms of the radionuclide were determined by single extractions with 1 M NH4NO3, followed by gamma-spectrometric determination. Vegetation experiments with the conditioned soil samples were carried out and the transfer factors (TFs) of orchard grass (Dactylis glomerata L.) were determined. The results showed that the conditioning for one month at increased temperature, two months after contamination caused a decrease in the exchangeable 137Cs and the transfer factors. A reduction of the exchangeable forms of radiocesium with the increase of the content of muscovite in the soils was observed. It was found that the change in TFs provoked by the temperature raise two months after contamination increased with increasing potassium concentration in the soils.

Non-alcoholic fatty liver disease has emerged as one of the main causes of chronic liver damage, which occurs as a result of a wide range of complications such as obesity, T2DM, inflammation, fibrosis, and the development of nonalcoholic steatohepatitis, and cirrhosis. Elevated serum-free fatty acid concentrations, hepatic triglyceride accumulation, cytotoxic reactive oxygen species, and increased levels of oxidative stress are believed to be major contributors to the development and progression of the disease. The present study highlights the application of the stable nitroxide radical TEMPOL as an effective redox sensor for redox changes monitoring in T2DM and NAFLD patients. The oxidative stress levels and antioxidant status were investigated in T2DM and NAFLD patients (group 2) and healthy volunteers (group 1) by conventional EPR spectroscopy. The obtained data show a statistically significant increase in ROS levels and EPR signal intensity of nitroxide and hydroxylamine in patients with NAFLD and T2DM compared to the control group - healthy volunteers without metabolic disorders (post hoc test; (*) p < 0.05 vs. control). The spectroscopic analysis allows the prediction of diabetic complications and will guide the scientific community and clinicians to conduct effective antioxidant therapy.

In recent years the development of eco-friendly remediation technologies with economical advantage is based on the incorporation of microorganisms or their enzyme systems in the degradation processes. In the present study purified laccase with specific activity 105.8 U/mg, obtained after submerged cultivation of the basidiomycete Trametes versicolor, was used in free and immobilized form for pyrene degradation. The alginate gel entrapment method and the encapsulation in amphiphilic dendritic-linear-dendritic block copolymers were applied as immobilization techniques. The free form of the enzyme was able to reduce the concentration of pyrene by 15 ppm to a final concentration of 185 ppm at the 20th day. The application of the enzyme, encapsulated in amphiphilic dendritic-linear-dendritic block copolymers, resulted in a decrease of the concentration of pyrene ranging from 4 ppm to 28 ppm for the different preparations. The degradation of pyrene with laccase immobilized in Ca-alginate gel led to a decrease in the concentration of the compound by 26 ppm for 20 days.

The quality of human life is mainly determined by the quality and safety of consumed food. The purpose of the present study was physicochemical characterization of Bulgarian monofloral bee honeys. A total of 40 honey samples (rape n=14 and lime n=26) were analysed. Botanical origin of the honey samples was determined by mellisopalynological analysis. Color (mm Pfund), water content (%), electrical conductivity (mS.cm-1), specific rotation ([α]20D), pH, diastase (Gothe units), invertase (U.kg-1), proline (mg.kg-1), hydroxymethylfurfural (HMF, mg.kg-1) were assessed in order to provide physicochemical characterization. In the present study monofloral rape and lime honeys meet the quality standards of European legislation for the parameters studied. The results confirmed that physicochemical properties of honeys were closely related to their floral sources. The honeys produced in Bulgaria are of good quality in relation to the studied parameters, confirming the general image of products with high quality. Significant linear correlations were confirmed between diastase and invertase in rape honey and also between color and electrical conductivity in lime honey.

The Republic of Bulgaria regulates the quality of surface waters for drinking and domestic purposes, monitoring anions like F-, Cl-, Br-, I-, BrO3-, NO2-, NO3-, SO42-, PO43-, and SCN-. The presence of NO3- and NO2- in water is undesirable, as they have a harmful effect on human health. It is also well known that CN- as opposed to SCN- has acute toxic and lethal effects on living organisms including humans. In the present study, an instrumental method was developed and optimized for the separation and quantification of inorganic anions in surface and drinking water using ion chromatography. The analytical characteristics of the proposed instrumental method were determined. The oxidation of CN- to OCN- was investigated, and the optimal experimental conditions for the oxidation were established. The achieved low LOD and LOQ of the analyzed inorganic anions allows their detection and quantification in surface and drinking waters. The applicability of the proposed chromatographic method was determined in the analysis of surface and bottled waters. The analyzed anions in bottled waters were close to the label's values, only one spring water showed significant deviations.

Oregano and its extracts are rich in a variety of biologically active substances, which makes them suitable for use in food industry, pharmacy, etc. The influence of the technological parameters – solvent concentration, temperature and duration of ultrasound-assisted extraction on the yield and tannin content of extracts of white oregano (Origanum heracleoticum L.) was studied. The data were compared with those obtained with conventional extraction methods. The resulting ethanol extracts are highly viscous liquids with a dark brown color, characteristic of the plant spice smell and a specific burning taste. The highest yield and highest tannin content in ultrasound-assisted extraction of cultured white oregano was obtained with 70% ethanol at a temperature of 60°C during the process, hydromodule 1:10 and duration 60 min. The use of ultrasound-assisted impact to extract tannins from cultured white oregano allows to achieve higher yields and reduce the duration of the process, compared to conventional extraction methods.

Cu2ZnSnS4 (CZTS) materials were obtained using two synthesis protocols. Ascorbic acid (ASC sample) and polyvinylpyrrolidone (PVP sample) were used as surfactants. X-ray diffraction data reveal a single phase CZTS (kesterite) material for the PVP sample, while the ASC sample is a mixture of Cu2ZnSnS4, ZnS, ascorbic acid and possibly Cu2SnS3. UV-vis spectroscopy was used in complementary manner in order to determine the presence of ascorbic acid in ASC final product. The morphology shows particles of 2-5 nm “fused” in larger agglomerates. The delivered initial capacities are 1148 mAh g-1 (ASC) and 1141 mAh g-1 (PVP). The capacity loss is more than 90% for ~12 cycles for both samples. The conversion of Cu2ZnSnS4 to Li2S and alloys seems to be partially reversible, most likely due to Li2S dissolution in the electrolyte.

Three new bis 1,3,5-trisubstituted hydantoins were synthesized by combining an Ugi four-component condensation reaction with a base induced cyclization. In the two-step sequence, first three new bis Ugi compounds were synthesized by the Ugi four-component condensation reaction, and then bis 1,3,5-trisubstituted hydantoins were obtained by intramolecular cyclization reaction.