The first outbreak of brucellosis in the region of Šabac

Background/Aim. In Serbia brucellosis is a primary disease of the animals in the southern parts of the country. The aim of this study was to describe the first outbreak of human and animal brucellosis in the region of Šabac, Serbia. Methods. An epidemiological investigation was conducted to identify a source of outbreak and the ways of transmission of brucellosis infection in human population. A descriptive and analytical epidemiological methods (cohort study) were used. Additional data included monthly reports of the infectious diseases from the Institutes of Public Health and data from the Veterinary Specialistic Institute in Šabac. The serological tests for human brucellosis cases were performed in the Laboratory of the Military Medical Academy; laboratory confirmation of animal brucellosis cases was obtained from the reference laboratory of the Faculty of Veterinary Medicine, Belgrade. Results. Twelve cases of brucellosis were recorded from February 9 to September 1, 2004. Total attack rate was 8.1% (7.5% of males, 14.2% of females). Relative risk (RR) of milk consumption was 8.9 (95% confidence interval: 1.63-13.38), and RR for direct contact with animals was 14 (95% confidence interval: 3.5-55.6). The prevalence of seropositive animals in 33 villages of the Mačva region accounted for 0.8%. Regarding animal species, sheep were predominant - 264 (95.7%). Out of a total number of seropositive animals, ELISA results were positive in 228 (88.7%) of them. Conclusion. As contact epidemics generally last longer, it is probable that the implemented measures of outbreak control did reduce the length of their duration

Dry-fermented sausage as probiotic carrier food

The aim of this research is to explore the potential use of Lactobacillus curvatus and Enterococcus faecium isolated from traditional fermented sausage from Southeast Serbia as probiotics. Analytic criteria for determining the probiotic potential included haemolysis, autoagreggation and coaggregation tests as well as the test for hydrophobicity of natural isolates. The best autoaggregation ability was observed in Lb. curvatus, sk217 and sk65 (73%) while the lowest level of grouping was shown by the isolate sk110 (68%), as the coaggregation ability ranged from 34% to 58%. The value of autoaggregation of examined strains of enterococci ranged from 47% to 55.2%, while coaggregation ranged from 31.9% to 45.2%. Haemolytic reaction was not observed in researched isolates. Hydrophobicity was determined by bacterial adherence to hydrocarbons, nhexadecane, xylene and chloroform. All isolates possessed a high level of hydrophobicity. The results of this study of probiotic characteristics of Lactobacillus curvatus and Enterococcus faecium indicate that the tested strains can be recommended as good candidates for use in the food industry.Publishe

Ab Initio Study of Graphene Interaction with O-2, O, and O-

A systematic ab initio (DFT-GGA) study of adsorption of various oxygen species on graphene has been performed in order to find out general trends and provide a good starting point to analyze the oxidation of more complex carbon materials. Particular attention was paid to finding an appropriate supercell model. According to our findings, atomic O is characterized by stable adsorption on graphene and very strong adsorption on defective graphene. On the other hand, O-2 does not adsorb on graphene and is allowed to diffuse freely to the defect, where it is expected to dissociate into two strongly adsorbed O atoms. The obtained results were compared with available theoretical data in the literature and good agreement was achieved

Semi-interpenetrirajuće polimerne mreže na bazi POLI(N-izopropilakrilamida) i POLI(N-vinilpirolidona)

Three series of semi-interpenetrating polymer networks based on cross-linked poly(N-isopropylacrylamide), PNIPA, and 1, 2 and 3 wt% of linear poly(N-vinylpyrrolidone), PVP, were synthesized in order to improve the mechanical properties of PNIPA gels. The effect of the incorporation of the linear PVP polymer into the temperature responsive networks on the phase transition temperature, swelling behavior and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with various molar ratios (25/1 to 100/1) of the monomer (N-isopropylacrylamide) to the cross linker (N,N'-methylene-bisacrylamide). The hydrogels were characterized by determination of the equilibrium degree of swelling at 25 °C, the dynamic shear modulus and the effective crosslinking density, as well as the ultimate hydrogel properties, such as the tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was also studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling, the highest values of which were obtained for samples with 2 and 3 wt% of PVP and the NIPA/MBA molar ratio of 75/1 and 100/1. The highest reinforcement effect, evaluated from the ratio of G'red(semi-IPN) to G'red(PNIPA), was obtained by incorporation of 2 wt% PVP. The tensile strength of the semi-IPNs reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these semi-IPNs varied between 22 and 55%, which are 22-41% larger than those for single PNIPA networks. The tensile measurements confirmed that the presence of 2 wt% of the linear polymer significantly reinforced the PNIPA network.Tri serije semi-interpenetrirajućih polimemih mreža, semi-IPN, na bazi umreženogpoli(N-izopropilakrilamida), PNIPA, i 1, 2 i 3 mas. % linearnog poli(N-vinilpirolidona), PVP, sintetisane su sa ciljem da se poboljšaju mehanička svojstva PNIPA gelova. Ispitivan je uticaj prisustva različite količine linearnog hidrofilnogpolimera na temperaturom indukovani pseudo-fazni prelaz, proces bubrenja, kao i na mehanička svojstva hidrogelova. Polimerne mreže sa četiri različite gustine umreženosti dobijene su variranjem molskog odnosa monomera (N-izopropilakrilamid) i umreživača (N,N'-metilenbisakrilamid, MBA) od 2511 do 100/1. Hidrogelovi su karakterisani određivanjem ravnotežnog stepena bubrenja, dinamičkog modula na smicanje, efikasnosti umreženja, zatezne čvrstoće i izduženja do kidanja. Uvođenjem linearnog hidrofilnog PVP-a u PNIPA mrežu ravnotežni stepen bubrenja raste i kreće se u opsegu od 7 do 16,5. Najveće vrednosti ravnotežnog stepena bubrenja pokazuju semi-IPN sa 2 i 3 mas. % PVP i molskim odnosom NIPA/MBA od 75/1 i 100/1. U odnosu na PNIPA hidrogelove ravnotežni stepen bubrenja kod ovih uzoraka veći je za 25-38%. Najveći efekat ojačanja, izračunat iz odnosa G'red(semi-IPN)/G'red'(PNIPA), postignut je uvođenjem 2 mas. % PVP-a. Vrednosti zatezne čvrstoće semi-interpenetrirajućih mreža ojačanih linearnim PVP-om veće su od vrednosti za PNIPA mreže i kreću se u intervalu od 5-12 kPa. Izduženje do kidanja za ove semi IPN je između 22 i 55%, što je za 22-41 % veće od vrednosti za PNIPA mreže. Ispitivanja mehaničkih svojstava na istezanje pokazala su (i potvrdila) da prisustvo 2 mas. % linearnog PVP polimera, značajno ojačava PNIPA mrežu

High strength thermoresponsive semi-IPN hydrogels reinforced with nanoclays

Two series of nanoclay reinforced, thermoresponsive hydrogels were prepared, one based on poly(N-isopropylacrylamide) (PNIPA) and the other on semi-interpenetrating networks containing PNIPA and poly(N-vinyl pyrrolidone) (PVP), designated as SIPNs. The gels were crosslinked with 1, 3, and 5 wt % inorganic clay (hectorite) and SIPN gels additionally contained 1 wt % of PVP. The hydrogels were tested in the "as-prepared state," i.e., at 10 wt % PNIPA concentration in water and at equilibrium (maximum) swelling. Increasing the concentration of nanoclays increases crosslink density, modulus, tensile strength, elongation (except in equilibrium swollen gels), hysteresis and with decreases in the degree of swelling, broadening of the phase transition region, and a decrease in elastic recovery at high deformations. The presence of linear PVP in the networks increases porosity and the pore size, increases swelling, deswelling rates, and hysteresis, but decreases slightly lower critical solution temperature (LCST), tensile strength, elongation, and elastic recovery. The strongest hydrogels were ones with 10 wt % PNIPA and 5 wt % of nanoclays, displaying tensile strengths of 85 kPa and elongation of 955%. All properties of hydrogels at the equilibrium swollen state are lower than in the as-prepared state, due to the lower concentration of chains per unit volume, but the trends are preserved

Semi-Interpenetrating Networks Based on Poly(N-isopropyl acrylamide) and Poly(N-vinylpyrrolidone)

Three series of novel semi-interpenetrating polymer networks, based on crosslinked poly(N-isopropylacrylamide), PNIPA, and different amounts of the linear poly(N-vinylpyrrolidone), PVP, were synthesized to improve the mechanical properties and thermal response of PNIPA gels. The effect of the incorporation of the linear PVP into the temperature responsive networks on the temperature-induced transition, swelling/deswelling behavior, and mechanical properties Was Studied. Polymer networks with four different crosslinking densities were prepared with varying molar ratios (25/1 to 100/1) of the monomer (N-isopropylacrylamide) to the crosslinker (N,N'-methylenebisacrylamide). The hydrogels were characterized by determination of the equilibrium degree of swelling, the dynamic shear modulus and the effective crosslinking density, as well as tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling. The tensile strength of the semi-interpenetrating networks (SIPNs) reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these SIPNs varied between 22%, and 55%, which are 22 - 41% larger than those for pure PNIPA networks

A kinetic study of D-glucose oxidation by bromine in aqueous solutions

The kinetics of the oxidation Of D-glucose to D-gluconic acid by bromine in aqueous solution were studied using potentiometric techniques and theoretical considerations of complex bromine-bromide-pH equilibria. The pH has a strong influence on reaction rate. At pH lt 8 the reaction is very slow, while in the pH range pH 8-9.5 the reaction is sufficiently fast and seems optimal for the reaction. The proposed active species at that pH region is hypobromous acid. At pH gt 9.5, the reaction is further accelerated due to the formation of hypobromite. The proposed kinetics expression for gluconic acid formation, based on the determined kinetic parameters at pH 9.24, is of the form dc(GA)/dt = 160c(2)(G)c(0)(HOBr)c(0)(H+)c(0)(Br

Improving thin film flexible supercapacitor electrode properties using ion-track technology

A novel self-supporting carbon thin film flexible supercapacitor electrode with high volumetric and areal capacitance was developed. The increase in capacitance performance is achieved by introducing channels across the carbon thin film using ion-track technology. In the first step of the electrode synthesis, latent tracks are inscribed in the starting polyimide (Kapton) foil by irradiation with 253 MeV Kr ions. Next, macropores in the form of cylindrical channels are formed by selective chemical etching with NaOCl along the ion tracks, creating ion-track polymer. With subsequent carbonization and activation of the ion-track polymer, activated ion-track carbon is produced. A range of samples are obtained by varying the chemical etching time of the irradiated polymer. In addition to channel formation the chemical etching time influences the composition of surface functional groups. The best results are obtained by chemical etching for 40 min, the thickness of the sample is 21 A mu m with channel density 2.4 x 10(6) cm(-2) and average channel diameter 430 nm. Beside cylindrical macro channels this material is mainly microporous with 0.62 nm pore diameter and shows the highest areal (494 mF/cm(2)), volumetric (224 F/cm(3)) and gravimetric (178 F/g) capacitance. As a consequence of channel formation, the rate capability of the supercapacitor was also increased

Performance comparison of modified poly(vinyl alcohol) based membranes in alkaline fuel cells

There are several problems which are holding back the use of fuel cells. The utilization of fuel cells depends on the start-up costs which are very high due to the use of expensive materials for their construction. In that respect, we describe a cost-effective alkaline fuel cell (AFC) that uses solid, polymer based, membrane instead of conventionaly used, highly concentrated, corrosive, liquid alkaline electrolyte. This approach to AFC is potentially the basis of a simple, low-cost system, that can solve one of the problems of the highly-efficient and environment-friendly AFC. The focus of this paper are low cost composite alkaline membranes, based on poly(vinyl alcohol) (PVA). The PVA matrix is made by solution cast method and gamma irradiation crosslinking. Three different types of membranes are obtained in this manner plain PVA membrane, PVA membrane cross-linked using gamma irradiation (gamma-PVA) and composite PVA membrane doped with Mo (PVA-Mo). These membranes are immersed in the alkaline solution and investigated as anion exchange membranes. The performance of the solid alkaline fuel cells (SAFCs) containing these PVA membranes has been studied under hydrogen and oxygen gas flow on the Pt/C catalyst. Both, gamma-PVA and PVA-Mo membranes are modified to absorb larger amounts of alkaline solution than the PVA membrane, thus greatly improving the performance of the SAFC, in terms of output power. This is clearly indicated in the polarisation curves. The electrochemical impedance spectroscopy measurements during the SAFC operation were also performed to give better insight in the effect observed. Investigation presented in this paper clearly indicates that solid alkaline PVA membranes can be used for the construction of the SAFCs. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

Energy consumption and stability of the Ni-Mo electrodes for the alkaline hydrogen production at industrial conditions

Hydrogen production via electrolysis of water from alkaline aqueous electrolytes is a well-established conventional technology. However, the cost of hydrogen produced in such a way is high. To improve this process we have investigated in situ activation with Ni-Mo electrocatalytic material for electrodes. This two d-metal combination possesses one of the highest known activities for the HER. Ni-Mo based catalyst was not applied at industrial applications yet, because under industrial conditions (high temperature and concentrated alkaline solution), permanent destruction of the Ni-Mo alloy coating occurs. The most important result of this study is that the Ni-Mo deposit obtained by in situ activation, under industrial conditions, exhibit long term stability and the electrodes retain their high catalytic performance. The process of adding Ni-Mo activating compounds in situ exhibits savings of the energy consumption that can go beyond 20% in some cases. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved