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Soldatovic D.A.,Public Company Nuclear Facilities of Serbia | Vuksanovic J.M.,University of Belgrade | Radovic I.R.,University of Belgrade | Kijevcanin M.L.,University of Belgrade
Journal of Chemical Thermodynamics | Year: 2016

Density ρ, viscosity η and refractive index nD have been experimentally measured for four binary mixtures nicotine + 1-butanol, nicotine + 2-butanol, nicotine + 1,2-propanediol and nicotine + 1,3-propanediol over the temperature range T = (293.15–323.15) K with temperature step 5 K and at atmospheric pressure. Excess molar volumes VE, viscosity deviations Δη, deviations in refractive index ΔnD, excess Gibbs free energy of activation of viscous flow ΔG∗E, thermal expansion coefficients α, excess thermal expansion coefficients αE, partial molar volumes V‾i, excess partial molar volumes V‾i E and it's values at infinite dilutions V‾i E,∞ were calculated from experimental data and used to analyze non-ideal behavior of mixtures. Fourier-transform infrared analysis of binary mixtures and corresponding pure components was performed at 298.15 K in order to gain insight into the molecular structure of mixtures and possible intermolecular interactions. Performed infra-red analysis confirms the presence of hydrogen bonding between unlike compounds, except for the system nicotine + 1-butanol. Here, the non-ideal behavior of mixtures is contributed to strong intermolecular interaction or in the case of nicotine + 1-butanol due to geometrical packing or dispersion forces of different species. © 2016 Elsevier Ltd Source

Gizdavic-Nikolaidis M.R.,University of Auckland | Jevremovic M.,Public Company Nuclear Facilities of Serbia | Zujovic Z.D.,University of Auckland | Zujovic Z.D.,Serbian Institute of General and Physical Chemistry
Journal of Physical Chemistry C | Year: 2012

A series of energy- and time-efficient enhanced microwave syntheses (EMS) of polyaniline (PANI) have been performed and are discussed herein. The syntheses were performed at different microwave power levels while keeping the reaction system at a constant temperature of 24 ± 1 °C, with the samples extracted after 10 min of reaction. Molecular weights were determined with GPC (gel permeation chromatography) and showed that the molecular weight of the microwave-generated materials depends on applied power: the higher the power level, the greater the molecular weight. The chemical structure was investigated by FTIR and UV-vis spectroscopy, while the morphology was imaged using scanning electron microscopy (SEM). FTIR and UV-vis spectroscopy confirmed the formation of PANI, and SEM indicated the presence of a mixed morphology, with a prevalence of nanofibers with different aspect ratios. The conductivity of the samples (ca. 3-3.5 S cm -1) was found to be relatively independent of microwave power levels. Surface area measurements were carried out using Brunauer-Emmett-Teller (BET) method, with samples synthesized using EMS showing higher surface areas when compared with conventionally synthesized PANI. The fact that molecular weight depends on applied power implies that microwave-enhanced synthesis can be used to fine-tune PANI reaction conditions, directing it toward specific properties. © 2012 American Chemical Society. Source

Krstic D.,University of Kragujevac | Cuknic O.,Public Company Nuclear Facilities of Serbia | Nikezic D.,University of Kragujevac
Health Physics | Year: 2012

Efficiency of a whole body counter was calculated using MCNP5 code and measured experimentally. Measurements were performed using standard phantoms filled with water and a dissolved 137Cs isotope. The results obtained by calculation agree very well with the experimental ones for a set of different distances and axial shifts. The ORNL phantom of a human body was applied to investigate how representative the experimental calibration source is of the measured human subjects. Differences were found to be up to 20%, so corrections should be made if an accurate value of activity in the human body is desired. Experimental and theoretical work presented in this paper is related to a sodium iodide (NaI) detector, which has relatively low resolution. However, such systems are still in use in many laboratories. On the other hand, detection efficiency of a low-resolution system is larger than that for HpGe detectors, which might be important in an accidental situation when shorter measuring time is very important. Copyright © 2012 Health Physics Society. Source

Adnadjevic B.,University of Belgrade | Jovanovic J.,University of Belgrade | Lazarevic N.,Public Company Nuclear Facilities of Serbia
Journal of Applied Polymer Science | Year: 2011

The isothermal kinetic of the release of nicotine from a poly(acrylic acid) (PAA) hydrogel was investigated at temperature range from 26°C to 45°C. Specific shape parameters of the kinetic curves, the period of linearity and saturation time were determined. The change in the specific shape parameters of the kinetic curves with temperature and the kinetic parameters of release of nicotine Ea and ln A were determined. By applying the "model fitting" method it was established that the kinetic model of release of nicotine from the PAA hydrogel was [1-(1-α)1/3] = k Mt. The limiting stage of the kinetics release of nicotine was found to be the contracting volume of the interaction interface. The distribution function of the activation energy was determined and the most probable values of activation energies of 25.5 kJ mol-1 and 35 kJ mol-1 were obtained. Energetically heterogeneity of the interaction interface was explained by the existence of the two different modes of bonding the nicotine molecules onto the hydrogel network by hydrogen bond and electrostatic forces. © 2010 Wiley Periodicals, Inc. Source

Grujic S.,University of Novi Sad | Milosevic M.,Public Company Nuclear Facilities of Serbia | Kozmidis-Luburic U.,University of Novi Sad | Bikit I.,University of Novi Sad
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

This paper describes the modeling of the Passivated Implanted Planar Silicon (PIPS) detector for the beta particles response function simulations with the MCNP-5 code. The simulated and measured energy response functions were compared and a good agreement was found in the entire range of energies. The verified model of a PIPS detector was applied in a non-destructive method that determines the activity of beta emitters in the sample with a known geometry and atomic number densities. The procedure for the identification of beta emitters in the samples was also described. Finally, the application of the proposed method for the determination of 137Cs and 90Sr activity in water samples taken from the RA reactor spent fuel storage pools and from the paper filter taken from an air monitor operated during repackaging of spent fuel elements, was presented. © 2011 Elsevier B.V. All right reserved. Source

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