Multi-criteria analysis of soil pollution by heavy metals in the vicinity of the Copper Smelting Plant in Bor (Serbia)

This study highlights the consequences on soil pollution of one hund­red years of manufacturing in the Copper Mining and Smelting Complex RTB-Bor (Serbia). Soil sediments were taken via a probe from the surface layer of the soil at twelve different measuring points. The measuring points were all within 20 km of the smelting plant, which included both urban and rural zones. Soil sampling was performed using a soil core sampler in such way that a core of a soil of radius 5 cm and depth of 30 cm was removed. Subsequently, the samples were analyzed for pH and heavy metal concentrations (Cu, Pb, As, Cd, Mn, Ni and Hg) using different spectrometric methods. The obtained results for the heavy metal contents in the samples show high values: 2,540 mg kg-1 Cu; 230 mg kg-1 Pb; 6 mg kg-1 Cd; 530 mg kg-1 Ni; 1,300 mg kg-1 Mn; 260 mg kg-1 As and 0.3 mg kg-1 Hg. In this study, critical zones of polluted soil were iden­tified and ranked according to their metal contents by the multi-criteria deci­sion method Preference Organization Method for Enrichment Evaluation/Geo­metrical Analysis for Interactive Assistance – PROMETHEE/GAIA, which is the preferred multivariate method commonly used in chemometric studies. The ranking results clearly showed that the most polluted zones are at locations holding the vital functions of the town. Therefore, due to the high bioavail­abi­lity of heavy metals through com­plex reactions with organic species in the sediments, consequences for human health could drastically emerge if these metals enter the food chain

Sorption of Cu2+ and Co2+ from aqueous solutions onto sepiolite: an equilibrium, kinetic and thermodynamic study

The efficiency of natural sepiolite for the removal of Cu2+ and Co2+ from aqueous solution was determined using the batch method. The sorption experiments were performed as a function of the initial metal concentration, the equilibration time and temperature. Thermodynamic parameters, such as enthalpy, free energy and entropy, were calculated from the temperature dependent sorption isotherms and these values showed that the sorption of the investigated metals onto sepiolite was endothermic. The pseudo-second order kinetic model provides the best correlation of the experimental kinetic data

Mechatronics in architecture: design research methodology

Complex modeling presents new and contemporary subject in architecture. The loop between the idea, programming, digital modeling and physical models gives the possibility to come to new conclusions that help develop architectural projects. This paper aims to show the advantages of multidisciplinary architectural projects through a workshop held at the University of Belgrade - Faculty of Architecture. The participants of this workshop, from different backgrounds and faculties, have been doing a research about the use of mechatronics in architecture. The mechatronic system was analyzed on a physical model based on the project by the architectural studio 4of7 Architecture for Slavija square in Belgrade. One of the aims of this workshop was to show the user-object-environment relationship and to explore the advantages and disadvantages of this kind of architectural design. The final product of this workshop is an interactive physical model that can show the movement of architectural elements in real-time. This model can help in the education about the use of mechatronics as a new design method in architecture. The concluding argument would show the possibilities of mechatronics in architectural projects for urban space and it will aim to place it on the map of design methodologies in architecture

α-Tricalcium phosphate/fluorapatite-based cement – Promising dental root canal filling material

α-Tricalcium phosphate/fluorapatite (α-TCP/FAp) mixed powders were prepared in order to obtain dental root canal filling cements. Different liquids for cement pastes have been investigated and the most suitable one for obtaining rheologically optimal pastes was chosen for further analysis. Morphological changes in the cement materials as a consequence of the formation of hydroxyapatite (HAp) after the immersion in a simulated body fluid (SBF), an influence on the cell viability, and final success of the filling were investigated by field emission scanning electron microscopy. Treatment of the α-TCP/FAp mixtures in SBF at 37 °C resulted in a complete transformation of α-TCP into HAp after 10 days, while the exposure of MRC-5 human and L929 animal fibroblast cells to the cement showed complete absence of cytotoxicity. The root canal of an extracted tooth was filled with the α-TCP/FAp cement containing 5 wt.% of FAp and relatively strong adhesion between the cement and dentine was observed after 48 h. The same cement material was immersed during 10 days in SBF and after that both human and animal fibroblast cells during in vitro MTT tests showed higher cell viability compared to the control sample. These findings lead to a conclusion that the α-TCP/FAp based cement demonstrates potential for further development towards dental cement application

Doping of TiO2 nanotubes with nitrogen by annealing in ammonia for visible light activation: Influence of pre- and post-annealing in air

The ∼60 nm wide and ∼2 μm long TiO2 nanotubes were obtained by anodization of Ti films sputtered on F-doped tin oxide glass. For N-doping the samples were annealed in ammonia atmosphere. The effect of pre- and post-annealing in air on the nature and amount of incorporated N was studied by X-ray photoelectron spectroscopy. By measuring the absorption spectra of the obtained samples and interpreting the corresponding Tauc plots it was shown that the sample annealed just in ammonia showed the highest visible light absorption even after sputtering cleaning and a decrease of N amount from 3.8% to 1%. Pre and/or post annealing in air led to smaller amount of incorporated N, that caused less pronounced absorption enhancement and smaller band gap narrowing compared to the sample annealed only in ammonia. By fitting of N 1 s line, the contribution that was assigned to substitutional N was detected only in the samples that did not sustained post-annealing. The study showed that post-annealing in air might lead to partial conversion of N atoms in TiO2 to oxidized nitrogen species that are easily removed with sputtering. It is also possible that substitutional nitrogen was suppressed by oxygen from air to move to interstitial site. Weakly bonded NOx surface species, which are cleaned away by sputtering, can be removed by post-annealing in air. Those surface species could act as sensitizers and when their amounts are reduced, the core absorption properties, as a result of interstitial incorporation of N in TiO2 structure, were revealed. Much lower visible light sensitization was achieved in the case of pre-annealed sample in comparison to sample without pre-annealing, regardless the same quantity and type of incorporated nitrogen

Characterisation and antimicrobial activity of silver nanoparticles derived from Vascellum pratense polysaccharide extract and sodium citrate

Silver nanoparticles (AgNPs) were synthesized by “green”, cheap hydrothermal method in an autoclave using sodium citrate and Vascellum pratense polysaccharide extract as reducing and stabilizing agents. Presence of spherical AgNPs was confirmed by UV-VIS spectrophotometry and scanning electron microscopy; particle size was determined as ~ 40 nm. Even though colloidal solution had relatively low absolutevalue of zeta potential (-15 mV), short term stability studies suggested a stable system, with AgNPs being stabilized by both citrate and fungal polysaccharides, as FTIR spectra confirmed. The colloidal solution showed good antimicrobial activity against both G+/G- bacteria and Candida albicans, including methicilin resistant Staphylococcus aureus (MRSA). Products containing AgNPs and fungal polysaccharides, which possess various biological activities - most important being immunostimulation - may find use in treatment of skin conditions caused by pathogens. Keywords: Silver nanoparticles, mushroom polysaccharides, zeta potential, anitmicrobial activity, MR

The love affair with descriptive geometry: its history in Serbia

While Serbia was part of the federation of South-Slav countries for majority of the twentieth century, the history of its mathematics, and in particular the history of descriptive geometry in the country is sufficiently independent from that of the twentieth century Yugoslavia to merit a separate historical analysis. We do this here, although we offer some remarks which include an overview of the ‘Yugoslav’ years as the twentieth century was in many ways different to the tradition we investigate. We conclude with remarks about the love affair with descriptive geometry, and its longevity in the Serbian educational system