Natural monocrystalline pyrite and chalcopyrite were examined as new indicator electrodes for the potentiometric titration of weak acids in tert-butanol and iso-propanol. The electrodes investigated demonstrated a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 48 mV per decade for pyrite in tert-butanol. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be suitable titrating agents. The response time was less than 12 s and the lifetime of the electrodes was higher than 1 year. The advantages of the electrodes are long-term stability, rapid response, reproducibility, easy preparation and low cost.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.

This research presents a methodological framework for assessing the attractiveness of natural resources and landscapes and their importance for tourism development. The research is conducted in the area of Kopaonik Mountain in Serbia, which is partly, due to its natural values, declared a natural heritage of exceptional importance Protection Category I, i.e. the National Park. The goal of this paper is to identify and assess the tourist attractiveness of the natural resources (relief, hydrological and climatological characteristics, and vegetation) and landscapes in the National Park (NP) Kopaonik area. There are two independent methods used to assess the tourist attractiveness of natural resources and landscapes in this study. The first method is based on numerical and statistical analysis and quantitatively expresses the attractiveness of natural resources/elements (relief, climate, hydrology and vegetation) separately and all together, indicating the overall attractiveness of natural resources for tourism development. The second method envisages 8 criteria according to which natural landscapes are scored on a scale from 0 to 3. Based on a clearly defined model for assessing the attractiveness of natural resources and landscapes, we conclude that the area of Kopaonik National Park has a high level of tourist attractiveness.

A deuterium-palladium electrode was employed as a new indicator electrode for the titration of weak acids in acetonitrile and benzonitrile. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid in the concentration range from 0.001 M to 0.1 M with a Nernstian slope of 48 mV in acetonitrile. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide proved to be very suitable titrating agents for these titrations. The response time was less than 10-11 s and the lifetime of the electrode was limitless. Advantages of the electrode are: long-term stability, fast response, reproducibility, easy preparation and low cost.

The pygidial glands of carabids produce strong-smelling vapours. In this study, we examined the chemical composition of the gland secretions and the structure of the glands in five species of Carabini ground beetles (one species from the subtribe Calosomatina and four species from the subtribe Carabina): Calosoma (Calosoma) maderae (Fabricius, 1775), Carabus (Carabus) granulatus Linnaeus, 1758, C. (Limnocarabus) clathratus Linnaeus, 1760, C. (Carabus) ulrichii Germar, 1823, and C. (Procerus) gigas Creutzer, 1799. Additionally, we tested the antibacterial potential of the pygidial gland secretions of the two latter species against 11 bacterial strains. In order to detect the chemical content of the secretions, we used gas chromatography–mass spectrometry (GC–MS). The secretion extracts were applied against selected strains of medically important bacteria. We used bright-field microscopy to examine the morphology of the glands. We discovered a total of 11 chemical compounds in the pygidial gland extracts of the ground beetles we analysed. Ten of these compounds were identified as seven carboxylic acids, two hydrocarbons, and one aromatic aldehyde, while one chemical remained unidentified. Most of the components were isolated from the secretion of C. (L.) clathratus (nine), while the lowest number of compounds was found in C. (P.) gigas (two). Methacrylic acid was the most dominant compound by percentage in all five species, while angelic acid was also detected in all samples. As expected, salicylaldehyde was exclusively found in the species of the genus Calosoma Weber, 1801. The secretion of C. (P.) gigas was shown to achieve the highest level of antibacterial activity against Pseudomonas aeruginosa, Salmonella enterica, and S. typhimurium (even the same level as the positive control streptomycin), while the secretion of C. (C.) ulrichii achieved the highest antimicrobial potential against Staphylococcus epidermidis, S. aureus, Listeria monocytogenes, and Bacillus cereus. The most noticeable difference in the structure of the glands between the two genera is that the reservoir in Calosoma is more significantly narrowed as it leads into the efferent duct, compared to that of Carabus.

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