This paper presents the results of application of Scanning Electron Microscopy (SEM) to examinations of the samples of natural gypsum and phosphogypsum. Phosphogypsum has a well developed crystalline structure, and appear in two polymorphous forms, of rombic and hexagonal shape crystals. Natural gypsum has a poorly crystalline structure. The differences in crystalline structure influence the chemical behavior of these row materials

Selenium is a trace mineral chemically related to sulfur and tellurium. In the body selenium combines with protein molecules to form selenoproteins and it is distributed in low concentrations and unequally in air, soil and water all over the world. Edible mushrooms are known to be selenium accumulators. Since mushrooms contain relatively high protein levels, and they can accumulate large amounts of selenium, it is reasonable to expect that selenium could be incorporated into proteins. The growth of mycelia and fruit body formation of different medicinal mushroom strains of Pleurotus ostreatus (Hk-35 and P70) over the wide range of concentrations of inorganic form of selenium were examined. Mushrooms were cultivated on agar base media and on substrates based on sawdust. Vegetative growths of mycelium were measured as colony diameter in pure cultures supplemented with inorganic form of Se supplements, prepared as Na2SeO4 and Na2SeO3 in concentrations of: 1, 10, 25, 50, 75, 100 and 150 mg/l. Inorganic form of Se supplements, showed stimulation effects (in concentration of 1-50 mg/l) and toxic effects in higher concentration. On the standard industrial sawdust based substrate, supplemented with 100 mg/kg Na2SeO4 and Na2SeO3, accumulation of Se in fruit bodies was determined by the method of flameless atomic absorption spectrophotometer. The readings were performed on Varian SpectrAA-10 spectrophotometer equipped with VGA-76. Se as Na2SeO4 and Na2SeO3 was effectively taken up from substrates and accumulated in fruit bodies. Mushrooms accumulated selenium between 120 and 250 mg/kg dry weight. In mushrooms cultivated without Se supplement, Se contents were only about 1 mg/kg and in substrate about 0.1 mg/kg

The analysis of scale originated from drinking water on the house water heater, showed that scale is basically calcium carbonate that crystallizes hexagonally in the form of calcite. Scale taken as a sample from different spots in Belgrade – upper town of Zemun (sample 1) and Pančevo (sample 2) showed different configuration although it came from the same waterworks. That indicates either that the water flowing through waterworks pipes in different parts of the city is not the same or the waterworks net is not the same (age, maintaining, etc). All the elements which are dominant in drinking water (Ca, Mg, K, and Na), and which could be found in water by natural processes, are by their content far below the values regulated by law. The analysis also showed the presence of many metals: Ti, Pb, Zn, Cu Li, Sr, Cd, and Cr in the first sample, which are not found in the scale taken near Pančevo. The results obtained by calculating the mass concentration in drinking water on the basis of scale content, showed that both waters belonged to the category of low mineral waters. Contents of inorganic substances in these waters (117.85 mg/dm3 for sample 1 or 80.83 mg/dm3 for sample 2) are twice lower than the values predicted by the legislation. Gammaspectrometric analysis indicates the presence of radioactive elements – uranium and strontium which can influence human health

It is estimated that all over the world there are more than 550 million road vehicles in everyday use. Annually, 1.3 billion used tyres are dismantled from these vehicles due to safety reasons. A small number of these tyres end up reused as second-hand tyres or, after being retreated, as new ones. The rest are end of life tyres which are recycled or used as tire derived fuels under controlled combustion conditions. Modern vehicle tyres are a high-technological product containing, on the average, 85% hydrocarbon, 10-15% steel, as well as some other chemical materials. Tyres belong to high caloric materials, with calorific value of a passenger car tyre of approx. 30.2 MJ/kg being more than of hard coal and comparable to calorific value of petrol-coke. Having this in mind many countries use end of life tyres as safe alternative fuel in cement works or power plants. Undeveloped countries dump end of life tyres on legal and illegal scrap stockpiles. End of life tyres, if deposed correctly, don’t endanger the environment because they are chemically inert. However, since they can easily be burnt there is a real possibility of tyre dump fires, which in effect can lead to harmful products emission that extremely pollute the environment. End of life tyres represent a very important secondary material, which when recycled is transformed into a number of raw materials used in rubber industry, for road construction, sports facilities, residential and business buildings, artificial fish habitats in shallow seas, sea walls, steel production, etc. By the industrial procedures of controlled degradation, which have been uneconomical up till now, gaseous and liquid fuel can be obtained by natural rubber, steel and soot recycling. The countries of the EU, together with Norway and Switzerland, were the world leaders in the field of effective end of life tyre management in the year 2009. Out of 2.62 million tonnes of end of life tyres, 95% were restored or used as energents, and 5% settled on dumps. About 26.000 t of used tyres are collected in Serbia each year. In accordance with adopted legal legislations, up to 30% can be used as tire derived fuels while 70% are being recycled. Serbia belongs to the group of countries which have solved the problem of used tyres in a modern way, and in accordance with EU Legislation practice

Trust in information originating from a company is becoming essential, as consumer preferences are increasingly versatile and oriented towards credence attributes. Social media, which emerged as a dominant means of online communication, might help increase consumers’ trust in companies. The paper empirically investigates a conceptual trust-building mechanism that could occur on companies’ social media pages. A survey was conducted among social media users in Belgrade (Serbia). The collected data were analyzed using covariance-based structural equation modeling. It confirmed that in an interactive environment of companies’ social media pages, trust can be built towards two objects. The first one is trust among consumers, and the second one is trust towards a company. The results also confirm a connection between trust and an intention to purchase, both being also related to a consumer’s willingness to obtain information. Therefore, the result can serve as a basis for creating more effective marketing campaigns where a company is the source of information regarding credence (added-value) attributes of its products.