The paper describes the mechanical properties and the corrosion behaviour of three Al?Si alloys in 0.5 M NaCl solution. The alloys have exhibited similar values of hardness, but the highest tensile strength and the lowest elongation have shown the specimens of alloy with 11.38 % of silicon. Higher content of both copper and magnesium has contributed to better tensile strength and lower elongation of as-cast hypoeutectic alloys. The harmful effects of iron on mechanical properties of all alloys have been reduced to some extent by nickel and cobalt addition. The differences in the values of the open circuit potential of the examined alloys were insignificant. The thickness of the protective oxide layer has increased over time, and the layer has become very compact. Slight differences in the values of the corrosion potential of the alloys were determined, whereas the lowest value of the corrosion current was indicated for the hypereutectic alloy. The presence of intermetallic phases in the alloys has shown that the oxide film was not consistent. The severe pits have not been found at the surface of the corroded samples. Based on the obtained results, the examined alloys may be used for the manufacturing of the internal combustion engine parts.

The incidence of thyroid dysfunction in the area of central Bosnia with special reference to hyperthyroidism was being monitored. Considering that there were disagreements among earlier authors and even their contradictory results, the goal was to determine the percentage ratio between the thyroid hyperfunction and other dysfunctions and to identify the degree of correlation between thyroid hormones and the age structure of women. The study included 76 women aged 20 to 82 years with increased values of thyroid hormones and 49 women with reduced values of thyroid hormones. Thirty female patients with baseline thyroid hormone levels comprised a control group. Hyperthyroidism was observed in 60.8 % of women, with the highest percentage of getting ill in their fourth and fifth decade of life (64 %). The monitoring of TSH, FT4 and FT3 hormone values in thyroid dysfunction compared to women with thyroid gland hormone reference values by age groups showed that there was a statistically significant difference in the age group between 40 and 59 years (p < 0.05). For the age group of 60 years and older, there was no significant difference (p > 0.05). The TSH hormone value and the age of women are positively correlated and mutually dependent (p < 0.05). The observed reduction in the thyroid hormone values with an increase in women’s age can be considered an adaptation of the organism to the reduced need for energy and represents an important metabolic parameter of the biological process of aging.

It is known that oxidoreductase is responsible for the regulation of oxidative stress in organisms, and pathological changes occur within the cell in the form of accumulation or lack of superoxide and peroxide radicals if the oxidoreductase activity is disturbed. Currently, the development of drugs that target the affected cells while leaving healthy cells unaffected is of great interest. The action of potential drugs is based on the inhibition / activation of oxidoreductase. In this work, we studied the electrochemical parameters of superoxide dismutase as well as the action of the potential drug of boroxine - dipotassium trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]) as a target therapeutic for enzyme activity. Electrochemical tests were carried out in a classical three-electrode system using cyclic voltammetry and chronoamperometry techniques, and the obtained results were presented in the form of the kinetic parameters with the maximum value of the current obtained when the solution was saturated with the substrate (Imax) and the Michaelis-Menten constant (Km). K2[B3O3F4OH] was proven to be a reversible inhibitor, and the obtained Imax without inhibitor value of 0.014 mM and Km = 12.09 mM. The results from the Lineweaver - Burk diagram show that the inhibition is a partial noncompetitive inhibition type.

In this study, boroxine derivative (K2[B3O3F4OH]) was tested as an inhibitor of horseradish peroxidase (HRP) by spectrophotometric and electrochemical methods. The activity of horseradish peroxidase was first studied under steady-state kinetic conditions by a spectrophotometric method which required the use of guaiacol as a second substrate to measure guaiacol peroxidation. The results of this method have shown that, by changing the concentration of guaiacol as the literature suggests, a different type of inhibition is observed than when changing the concentration of hydrogen peroxide as the substrate. This suggests that guaiacol interferes with the reaction in some way. The electrochemical method involves direct electron transfer of HRP immobilized in Nafion nanocomposite films on a glassy carbon (GC) electrode, creating a sensor with an electro-catalytic response to the reduction of hydrogen peroxide. The electrochemical method simplifies kinetic assays by removing the requirement of reducing substrates.

Recently research shows that horseradish peroxidase, HRP, when combined with other compounds, is highly reactive toward different human tumour cells and that better understanding of catalytic mechanism and inhibition HPR could lead to a new targeted cancer therapy. Thus, the inhibition of HRP activity by dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was investigated for possible explanation of previously observed antitumour activities of this promising drug. HRP activity was studied under steady-state kinetic conditions by a spectrophotometric method. In the absence of the inhibitor values of = 0.47 mM and = 0.34 mM min−1, respectively, were determined. The hydrogen peroxide H2O2 kinetic measurements show a competitive inhibition with the inhibition constant = 2.56 mM. The activation energy values were found to be very similar for both reactions; in the absence of inhibitor activation energy was 17.7 kJ mol−1 and in the presence of inhibitor activation energy was 16.3 kJ mol−1. The values of Arrhenius constants were found to be different; = 4.635 s−1 was measured in the absence of inhibitor while in the presence of inhibitor Arrhenius constant was 1.745 s−1 showing that K2[B3O3F4OH] initiates conformational change in the structure of the HRP and subsequently reduces its activity.

Underground waters have very important role as sources for settlements' water supply. Pollution of underground waters from one side depends on the environment's burden with pollutants substances of anthropogenic origin, and from the other side, on physical-geographic conditions, of which geologic factors have the greatest role. Geological field structure, besides, affects determining of conditions on underground water's forming, as well as its chemical composition. In this work, the influence of geological structure was presented on the quality of underground waters in the area of Ljubija, the specific large deposits of iron ore. During researches for this paper's needs, analyses were carried out of the general physical-chemical parameters of underground waters' quality.