Heavy metals concentration in soils from parks and green areas in Belgrade

The current study included the investigation of several metals and their distribution in urban soils from parks and green areas in the city of Belgrade. The soils were sampled in January and February 2008. The concentrations of Cd, Co, Cu, Pb, Mn and Zn were measured, as well as the pH values and organic matter contents. The obtained results showed that there was a significant level of contamination in some samples, especially with lead, and that it was most probably caused by anthropogenic activities, mostly from traffic. The results were compared with the National legislation and Netherlands standards. Also, the recent results were compared with the data from previous work and it was concluded that there has been a certain increase of the Pb concentration in the past three years. The level of pollution in playground soil was very high and each analyzed sample exceeded the Dutch target value for Cd, Co and Pb

Forming of titanium titnate

Lately a great attention is spared development of materials, possessing high stable dielectric properties. Among such materials a considerable place is occupied by titanates of metal series, including titanate of magnesium. In the present work titanates of magnesium got by co-operation at the high temperatures of magnesium oxides (MgO) and titanium oxides (TiO2) , taken in correlation 2:1. To improve the interaction of components it was investigated influence of time of foregrinding of initial components – magnesium and titanium oxides on composition of sintering material. After grinding during 5 and 10 minutes phase composition does not change practically. After 20 minutes of grinding along with the phases described higher the washed out weak lines appear reflections which behave to the phase of TiO2 with an orthorhombic structure. At the increase of grinding lime intensity of X-ray reflection lines from the orthorhombic oxide of titan is grown. Pays attention on itself a fact that from data [1 ] orthorhombic phase ofTiO2 with the structure of type ?- PbO2 is formed in the conditions of high pressures. Format10n of it at grinding testifies to deformation influence on the particles of the process. On the same points to the fact that after grinding of powders already during 10 minutes the x-ray reflection lines from all phases begin to broaden and with the increase of grinding time broadening of lines is grown. Weak and washed out reflection lines of phase MgTiO) is appeared after 80 and 120 minutes of grinding. It is possible to suppose that forming of high pressure orthorhombic phase TiO2 is necessary precondition to begin formation of triple rhombohedral phase of magnesium titanate MgTiO) .\ud At the same time the start of magnesium titanate forming at grinding of oxides powders mixtures is accompanied with weakening of reflection lines intensity from the anatase TiO2, At all annealing temperatures (900, 1000, \100 °c) was noticed that d-spaced distances and the crystalline grate periods of magnesium titanate MgTiO, change accordingly, increased with the increase of foregrinding time. It points out the connection possesses the area of homogeneity, what the state diagram of the system MgO - Ti02 also testifies [2] . Possibility to make changes of magnesium titanate composition MgTi03 by a change time of mechanochemical rough-down of initial oxides mixtures can create pre-conditions and also for varying of properties, necessary for different application and devices domains this connection is used. A preliminary grade promotes also to forming of sppinel phase for magnesium titanate Mg,TiO4' as brings in imperfectness in oxides, facilitating interaction betwcen them

Phase Formation at the Sintering of Sa, Zn, Ti Oxides

Complex compounds with oxide phases of Ba, 2n, and 11 are widely used in instrument engineering. It is also important to find such production routes for ceramics, which provide their stable structure and properties. Phase formation was investigated for titan, zirconium and barium oxides mixtures during their sintering, after pretreatment by milling of oxides mixtures with high power planetary-type mill. It was shown that active interaction of transferred oxides is observed after milling in the planetary mill. In addition to the presence of initial oxides, formation of complex compounds (barium and zinc titanates – Ba4Ti12O27 BaTiO3, ZnTiO3) was visible after 10 and 20 minutes of milling. The phase composition did not practically change after milling for 40 and 80 minutes. Furthermore, all reflection lines were strongly broadened and overlapped. Sintering of these mixtures after milling was conducted at temperatures 900, 1000 and 1100 °C for 2 hours on air with heating rate of 10 C/min. The complex oxide phase, close to BaZn2Ti4O11 composition, was found as a result of sintering of powders mixture at 900 °C, powder mixture was pretreated for 5 minutes at planetary mill. In addition, phases of ZnTiO3 and BaTiO3 were present. These phases were preserved for long-continued milling, but main components' ratio changed. The formation of BaZn2Ti4O11 phase with changes of interplanar spacings was investigated with variation of time of milling and sintering at temperatures of 1000 and 1100 °C. The Zn2TiO4 cubic phase was also present, its amount decreases only after 80 minutes of high power milling and sintering at 1100 °C. Results of our work showed, that for the system of three oxides active interaction was observed already on the high power milling stage. Sintering at the temperatures of 1000 and 1100 °C resulted in formation ofBaZn1Ti40 l1 oxide phase with composition variation in its homogeneity region

Formation of microstructures and oxides on steel surface by laser irradiation in air and liquids

Features of submicron structures and oxides formation on steel in air and liquids under laser irradiation are investigated experimentally.Proceedings of the XI Belarusian-Serbian Symposium "Physics and Diagnostics of Laboratory and Astrophysical Plasmas" (РDР-11), December 15-19, Minsk, Belaru

Testing Reactive Probabilistic Processes

We define a testing equivalence in the spirit of De Nicola and Hennessy for reactive probabilistic processes, i.e. for processes where the internal nondeterminism is due to random behaviour. We characterize the testing equivalence in terms of ready-traces. From the characterization it follows that the equivalence is insensitive to the exact moment in time in which an internal probabilistic choice occurs, which is inherent from the original testing equivalence of De Nicola and Hennessy. We also show decidability of the testing equivalence for finite systems for which the complete model may not be known

Swelling, Mechanical and Antimicrobial Studies of Ag/P(HEMA/IA)/PVP Semi-IPN Hybrid Hydrogels

A simple and fast approach to the design and production of new hybrid polymeric biomaterials with silver particles is presented in this work. Silver/semi-interpenetrating network hybrid hydrogels (Ag/semi-IPNHHs) were prepared through an optimized solution crosslinking copolymerization of 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA), in the presence of PVP, a silver salt and a reducing green agent (Ag/P(HEMA/IA)/PVP). PVP was chosen due to its protective, reduction, and nucleation properties in the production of metal particles. The structure of the Ag/semi-IPNHH was characterized by Fourier transform infrared spectroscopy (FTIR). The presence of silver and PVP in the network was confirmed by FTIR spectra. The results obtained by dynamic mechanical analysis (DMA) showed good mechanical properties for all samples. The swelling studies of Ag/P(HEMA/IA)/PVP were conducted in the temperature range of 25-55 degrees C, in the buffer of pH 7.40. The Ag/semi-IPNHH showed temperature-sensitive swelling properties, with the lower critical solution temperature (LCST) values in the physiologically interesting interval. The antimicrobial activity of the samples was tested using E. coli, S. aureus and C. albicans pathogens. It was concluded that the antimicrobial potential depends on the hydrogels composition and the type of microbes12th Annual YUCOMAT Conference, Sep 06-10, 2010, Herceg Novi, Montenegr

Antibacterial activity of copper nanoparticles

Copper nanoparticles (CuNPs), with an average particle size of about 5 nm, was prepared by the simple chemical reduction procedure. TEM and UV– Vis spectroscopy contributed to the analysis of size and optical properties of CuNPs, and their antibacterial activity was evaluated toward human pathogenic bacteria Escherichia coli and Staphylococcus aureus, in a concentration dependent manner. The changes in the cell membrane morphology of tested strains were investigated by atomic force microscope (AFM), after 2 h of their contact with CuNPs. It was found that CuNPs cause different types of cell membrane disruptions, as well as that S. aureus bacteria were slightly resistant to the cell membrane damage than E. coli

Prisutnost Candida sp. u svježem voćnom soku

Fruit juices are popular soft drinks with an important role in human nutrition. Fruit juices are often infested by yeast species that can survive different storage conditions. The aim of this study was to determine the degree of yeast contamination of freshly squeezed juices in three large supermarkets in Zagreb, Croatia. The analysis included 84 juice samples obtained from freshly squeezed orange, lemon, grapefruit, and apples. Their acidity varied between pH 2.1 and pH 4.9. Juice samples were plated directly on Sabouraud 4 % glucose Agar (Merck, 1.05438) and processed according to standardised methods (HRN ISO 7954:2002). Yeasts were isolated in all 84 samples and ranged between 0.005x103 and 23x103 colony forming units per mL (CFU mL-1). The most common yeasts identifi ed using the API 20C AUX yeast kit included Candida guillermondii, C. krusei, C. famata, C. spherica, C. colliculosa, C. albicans, Trichosporon mucoides, Kloeckera spp. and yeast-like fungus Cryptococcus neoformans. C. guillermondii prevailed in 55.95 % of all samples.Voćni su sokovi tekući ekstrakti voća dobiveni cijeđenjem zrelog voća te su vrlo važan čimbenik u svakodnevnoj prehrani ljudi. Najčešće zastupljeni mikroorganizmi u svježem voćnom soku su kvasci koji preživljavaju niske temperature skladištenja. Svrha ovog istraživanja bila je odrediti prisutnost i brojnost kvasaca u svježim voćnim sokovima uzorkovanim u supermarketima na području Republike Hrvatske, odnosno glavnom gradu Zagrebu. Ukupno su uzorkovana i pregledana 84 uzorka svježe iscijeđenih naranči, limuna, grejpfruta i jabuka. pH-vrijednost se kretala od 2.1 do 4.9. Uzorci su nacijepljivani direktno na Sabouraudov agar s 4 % glukoze (Merck, Njemačka) u skladu s propisanom normom HRN ISO 7954:2002. U sva 84 uzorka utvrđena je prisutnost kvasaca u broju od 0.005x103 do 23x103 CFU mL-1. Identifi kacija je provedena testom API 20 C AUX (bioMérieux, 20 210). Najčešće su izolirani sljedeći kvasci: Candida guillermondii, C. krusei, C. famata, C. spherica, C. colliculosa, C. albicans, Trichosporon mucoides, Kloeckera spp. i kvascu slična gljivica Cryptococcus neoformans. U svim uzorcima C. guillermondii bila je najčešće izolirani kvasac (55.95 %)

A fluorescent nanoprobe for single bacterium tracking: functionalization of silver nanoparticles with tryptophan to probe the nanoparticle accumulation with single cell resolution

The investigation of the interaction of silver nanoparticles and live bacteria cells is of particular importance for understanding and controlling their bactericidal properties. In this study, the process of internalization of silver nanoparticles in Escherichia coli cells was followed by means of synchrotron excitation deep ultraviolet (DUV) fluorescence imaging. Antimicrobial nanostructures that can absorb and emit light in the UV region were prepared by functionalization of silver nanoparticles with tryptophan amino acid and used as environmentally sensitive fluorescent probes. The nanostructures were characterized by morphological (TEM) and spectroscopic methods (UV-vis, FTIR, XPS, and photoluminescence). The TEM images and the analyses of the UV-vis spectra suggested that the addition of tryptophan led to the formation of hybrid nanostructures with pronounced eccentricity and larger sizes with respect to that of the initial silver nanoparticles. The DUV imaging showed that it was possible to distinguish the fluorescent signal pertaining to silver-tryptophan nanostructures from the autofluorescence of the bacteria. The spatial resolution of the fluorescence images was 154 nm which was sufficient to perform analyses of the accumulation of the nanostructures within a single bacterium. The DUV imaging results imply that the tryptophan-functionalized silver nanoparticles interact with cell membranes via insertion of the amino acid into the phospholipid bilayer and enter the cells