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Introduction: Non-carious tooth substances loss pose a major health problem of a modern man. The literature often collectively describes all non-carious lesions and is therefore difficult to compare results obtained by different authors. Chemical factors are one of the predisposing factors responsible for the formation of wedge-shaped erosions. Aim: Examination of chemical risk factors as one of the predisposing causes responsible for the formation of wedge-shaped lesions. Method: We examined 62 patients with wedge-shaped erosions (mean age 45.52 ± 12.03 years, 58.1% of men) and 60 patients without erosions in the control group (mean age 34.40 ± 9.28 years, 60% men) . The entire examination was completed by using a questionnaire at the Dental Clinic of the University of Pristina - Kosovska Mitrovica. salivary pH was measured by the pH meter. Results: The results show that the wedge-shaped lesions often occur equally in both men and women. Considerably often it might appear in older people but can also occur in teenagers. Patients with wedge-shaped erosion have increased acidity of saliva, a heightened sense of acid in the mouth and consume a lot more carbonated drinks compared to patients without erosions. Conclusion: Wedge-shaped lesions are more common in people older than 40 years. Taking into account the results obtained in this study it can be concluded that the chemical risk factors truly fall within the predisposing factors that may be responsible for the creation of wedge-shaped erosions.

The most tooth whitening is a procedure that removes stains and various discolorations of tooth surface. Discoloration of teeth may be endogenous and exogenous nature. The aim of this study was to investigate the impact of bleaching combined with daily use of drinks that cause tooth discoloration. Evaluated the changes in surface structure of enamel, and changes in hardness after bleaching. Were 20 extracted teeth. The teeth are marked with longitudinal lines halves (medial vestibular and distal surfaces). Tretitana mesial half of the 16% carbamide peroxide, a distal was left as control. NDT device HL-400DL, duroskopskom method of enamel hardness was measured before treatment, after treatment and after remineralization. Olympus inverted microscope GX41 enamel structures were observed in the treated and control half of the tooth. After bleaching there is a difference compared to the untreated surface, that surface is bleached a few shades lighter, but after the use of coffee and soft drinks teeth back to the original dark color. Enamel microhardness after the treatment is somewhat small but not significant. With a magnification of 2000x and see the structural changes in enamel. Tooth whitening, but that the remineralization and the abstinence from prebojenih beverages and tobacco.

High energy ball milling was used in order to improve dispersion of metal oxide in Ag-SnO2 electrical contact materials. The processed Ag-SnO2 (92:8) and Ag-SnO2In2O3 (87.8:9.30:2.9) powder mixtures were subsequently consolidated to bulk solid pieces by conventional powder metallurgy method. The characterization of the prepared samples included microstructural analysis by XRD and SEM, as well as measurements of physical properties such as density, hardness and electrical conductivity. The results of X-Ray analysis point to reduction of crystallite size after milling of about ten times. Microstructures of sintered Ag-SnO2 and Ag-SnO2 In2O3 materials display very fine dispersion of the oxide components in silver matrix. Somewhat higher uniformity was obtained for Ag-SnO2 In2O3 material which was illustrated by results of SEM analysis and more consistent microhardness values. The obtained values of studied physical properties were found to be in accordance with observed higher dispersion of metal oxide particles and comparable to properties of commercial electrical contact materials of this type. [Projekat Ministarstva nauke Republike Srbije, br. OI 172037, br. OI 172035 i br. TR 34023]

In order to measure the very low oxygen potential by use of stabilized zirconia solid electrolyte emf method, a new cell construction was devised. The idea was based on Janke but a zirconia rod was used instead of the zirconia crucible which contacts liquid alloy electrode. The cell was used for determination of the oxygen potentials in liquid dilute Cu-Cr and Cu-Zr alloys. The reference electrode was Cr,Cr2O3. Emf measurements were performed in the temperature range of 1400-1580K and composition range of 0.198-3.10at%Cr-Cu alloys, and 1380-1465K, 0.085-0.761at%Zr-Cu alloys. The composition of liquid alloys were determined by picking up from the liquid alloys and ICP analysis. By use of the newly devised cell construction in this study, stable emf values were obtained at each temperature and alloy composition. Emf values were corrected by using the parameter for electronic contribution of the YSZ. Activity of Cr obeys Henry’s law and activity coefficient at infinitely dilute alloys of Cr in Cu-Cr alloys are: lng0 Cr =(3.80 at 1423K), (3.57 at 1473K), (3.38 at 1523K) and (3.20 at 1573K). At 1423 K activity coefficient of Zr at infinitely diluted alloy is lnγo Zr = -4.0.

Magnetic NiFe2O4 structure formation was studied through structural, compositional and magnetic characterization of obtained reaction products of a simple, high yielding and low-cost solid-state reaction. Initial annealing of the starting oxides mixture at 700ºC did not allow us to observe formation of the desired magnetic phase. In contrast, subsequent thermomagnetic measurements up to 800ºC indicated the considerable increase of the magnetic moment, which can be reasonably assigned to the changes in phase composition and formation of magnetic NiFe2O4 structure during the heating cycle of measurements. Nanosized NiFe2O4 phase formation has been confirmed by the following XRD and MS phase analyses and its nanocrystalline structure by XRD and SEM/TEM techniques. The obtained hysteresis loop taken after TM measurements suggest the increased volume of magnetically active material and thus additionally support the previous findings.

The results of phase relations investigation in bismuth-rich part of ternary Bi-Ga-Ni system are presented in this paper. Two sections with constant bismuth content equal to 80 and 90 at% were investigated experimentally using DSC and SEM-EDS methods and predicted thermodynamically by CALPHAD method. Calculated phase diagrams showed reasonable agreement with experimental data. [Projekat Ministarstva nauke Republike Srbije, br. OI172037]

Changes in physical properties such as density, porosity, hardness and electrical conductivity of the Ag-SnO2 and Ag-SnO2In2O3 electrical contact materials induced by introduction of metal oxide nanoparticles were investigated. Properties of the obtained silver-metal oxide nanoparticle composites are discussed and presented in comparison to their counterparts with the micro metal oxide particles as well as comparable Ag-SnO2WO3 and Ag-ZnO contact materials. Studied silvermetal oxide composites were produced by powder metallurgy method from very fine pure silver and micro- and nanoparticle metal oxide powders. Very uniform microstructures were obtained for all investigated composites and they exhibited physical properties that are comparable with relevant properties of equivalent commercial silver based electrical contact materials. Both Ag-SnO2 and Ag- SnO2In2O3 composites with metal oxide nanoparticles were found to have lower porosity, higher density and hardness than their respective counterparts which can be attributed to better dispersion hardening i.e. higher degree of dispersion of metal oxide in silver matrix.

Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism.

The article surveys current state of the art and challenges in the development of the electrical contact materials in the light of the EU Directive on Restriction of Hazardous Substances (RoHS). The focus was placed on widely used silver-cadmium alloys. According to this directive, as of July 1, 2006, use of six hazardous materials, including cadmium, are restricted for applicable electrical and electronic products intended for the EU market. In contrast, traditionally preferred material for production of electrical contacts is Ag-CdO, due to its outstanding functional properties. These conflicting interests result in present state where RoHS directive has not yet been implemented in its original form and has undergone numerous amendments and exceptions regarding the use of cadmium. Main reason for this seems to be the unrealistic time frame imposed by legislation. Although, significant effort has been put into research and development of alternative materials, there are still cases where adequate replacement materials had not been found. Therefore, importance of synchronicity between legislation and technological progress i.e. communication between legislative administration and industry and academia is brought to light as well as some common issues that may arise with an introduction of new replacement materials or product modification. [Projekat Ministarstva nauke Republike SRbije, br. OI 172037 and TR 34023]

Ternary Pb-Zn-Ag system is typical for some physicochemical processes going on in refining phase in the extractive metallurgy of lead. Therefore, investigation of mentioned system is important from both theoretical and practical research of the phenomena occurring during the lead desilverizing process. The results of experimental investigation using differential thermal analysis (DTA) and thermodynamic calculation of phase equilibria in Pb-Zn-Ag system according to CALPHAD method, in the sections with Zn:Ag mass ratio equal to 90:10, 70:30 and 50:50, are presented in this paper.

The results of thermodynamic analysis and characterization of some alloys in Bi-Cu-Sb lead-free solder system are presented in this paper. Thermodynamic analysis was done using general solution model, while optic microscopy, hardness and electroconductivity measurements were used in order to determine structural, mechanic and electric characteristics of selected samples in section from bismuth corner with molar ratio Cu:Sb=3:7.

In this paper the practice of mine Majdanpek during sixties and seventies of the XVI century has been investigated with an accent on copper production. The attention has been also given to various subjects from considering copper treatment and use to forbidden activities connected to copper illegal production and trade with Persia.

The kinetics of oxidation process of realgar and orpiment natural mineral mixture was studied under non-isothermal conditions. The proposed reaction mechanism and chemical transformation investigated by SEM-EDX, XRD and thermal analysis, are discussed. Using mathematical modeling on results obtained during analysis in non-isothermal conditions, activation energy of this process was determined.

Remains of metallurgical activities have been discovered recently at the locality Felix Romuliana near Zaječar (Eastern Serbia), with a lot of slag occurrences and metal findings. Samples, taken from this locality, have been investigated using different characterization methods - chemical analysis, XRD and SEM-EDX, in order to clarify the Early Byzantine metallurgical activities at Felix Romuliana.

Thermodynamic calculations of three binary Ti-based alloys: Ti-Al, Ti-Fe, and Al-Fe, as well as ternary alloy Ti-Al-Fe, is shown in this paper. Thermodynamic calculations involved thermodynamic determination of activities, coefficient of activities, partial and integral values for enthalpies and Gibbs energies of mixing and excess energies at different temperatures: 1873K, 2000K and 2073K, as well as calculated phase diagrams for the investigated binary and ternary systems. The FactSage is used for all thermodynamic calculations.

Thermodynamic predicting analysis of Si-based binary systems - Ti-Si, and Al-Si, are shown in this paper. Thermodynamic analysis involved thermodynamic determination of activities, coefficient of activities, partial and integral values for enthalpies and Gibbs energies of mixing and excess energies at different temperatures: 2000K, 2400K and 2473K, as well as calculation of phase diagrams for the investigated binaries. The FactSage was used for all thermodynamic calculations. .

Thermodynamic study of Ti-V and Al-V binary systems is presented in this paper. Investigations included thermodynamic determination of activities, coefficient of activities, partial and integral values Gibbs energies of mixing and excess energies at four different temperatures: 2000K, 2073K, 2200K and 2273K, as well as calculated phase diagrams for the investigated systems. The FactSage program was used for all thermodynamic calculations.

The results of investigation of kinetics and mechanism for synthetic a-CoS oxidation process are presented in this paper. Based on experimental data obtained using DTA and XRD analysis and constructed PSD diagrams for Co-S-O system, mechanism of synthetic a-CoS oxidation process is suggested. Characteristic kinetic parameters were obtained for experimental isothermal investigations of desulfurization degree using Sharp method.

Water binding ability (WBA), held water (HW) and gel-forming properties of silver carp (Hypophthalmichthys molitrix Val) and carp (Cyprinus carpio Lin) meat were examined in this paper. Two variants of fish meat gels: A with 50% of meat and B with 60% of meat were examined at temperatures: 70 75, 80, 85 and 90 oC. The variant A of silver carp meat gels has shown the maximum of WBA and HW at 80 oC, and the variant B at 75 oC. In both variants of carp meat gels slow increase of WBA and HW with rise of temperature to 80oC was established. Silver carp meat gels have had better WBA than control gels (beef and poultry meat), and carp meat gels have better HW, but somewhat worse WBA than control gels. In gels of variant A of silver carp meat the highest module of elasticity (6.862 N/cm2) was found at thermal treatment at 85 oC, but statistically significant differences in relation to other temperatures were not established. In variant B, with the rise of temperature, the module of elasticity increases; statistically significant differences were established among gels treated at 70 oC and others. Differences between variants A and B were statistically significant at all examined temperatures. Meat gels of silver carp have significantly lower module of elasticity compared to control gels. Under conditions of our experiment the module of elasticity of carp meat was below measuring limit.