Marija Todorović

Electrochemical Behavior and Antioxidant and Prooxidant Activity of Natural Phenolics

We have investigated the electrochemical oxidation of a number natural phenolics (salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, protocatechuic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, quercetin and rutin) using cyclic voltammetry. The antioxidant properties of these compounds were also studied. A structural analysis of the tested phenolics suggests that multiple OH substitution and conjugation are important determinants of the free radical scavenging activity and electrochemical behavior. Compounds with low oxidation potentials (Epa lower than 0.45) showed antioxidant activity, whereas compounds with high Epa values (>0.45) act as prooxidants.

Spectrophotometry Determination of Ciprofloxacin in Serum Using Iron(III) Ion as Chromogenic Agent

ABSTRACT An analytical procedure for the determination of ciprofloxacin in serum without previous extraction has been developed. The determination was carried out using iron(III) nitrate as chromogenic agent, with the addition of sodium dodecylsulfate, at pH = 3.0. Absorbance was measured at 430 nm. The range of linearity was between 0.5 – 20.0 μg/mL with a detection limit 0.2 μg/mL.

Renewable energy sources and energy efficiency for building's greening: From traditional village houses via high-rise residential building's BPS and RES powered co- and tri-generation towards net ZEBuildings and Cities

As an introduction to the current approaches to buildings greening and sustainability this paper outlines the intrinsic harmony of the traditional village houses encompassing efficiency and balanced use of renewable materials and energy sources. Further paper reviews technical advances in integrating energy efficiency, solar and other renewable energy sources in new and existing buildings, to approach sustainable net Zero Energy Buildings, villages and cities. Paper stresses importance of the BPS (Building Performance Simulation) and Co-simulation in developing reliable method/engineering procedures for RES co-utilization and interwoven “energy mix” scenarios optimization, including existing buildings RES integrated refurbishment. Finally, presented are study results on the technical feasibility of efficient/cost-effective use of relatively low temperature geothermal waters for co- and tri-generation of electricity and heat for heating and/or cooling by absorption refrigeration for building integration. As a result of global warming a need for air-conditioning is in extreme growth in Central and Southeastern Europe, as well as in many other regions in the world rich in low temperature geothermal waters <100°C (<212°F), and there is a growing interest to utilize these waters in an efficient and cost effective way. It is well known that Kalina thermodynamic cycle can convert relatively low temperature energy, at relatively low temperature difference towards environment, to mechanical power and further to electricity using as a working fluid mixture comprised of at least two different components (water and ammonia). However, its co-generation efficiency at the heat source temperatures below and about 100°C is too low. That was the reason to explore technical possibilities to expand the low-temperature Kalina cycles geo-water utilization for co- and tri-generation based on the co-utilization - hybridization of geothermal with solar or other renewable energy sources (RES).

EDXRF spectrometry determination of tungsten in tobacco plants after antiviral treatment with 12-tungstophosphoric acid and its compounds

In this study, we have developed a sensitive, rapid and simple procedure for the energy dispersive X-ray fluorescence (EDXRF) spectrometry measurement of tungsten in tobacco plant parts. Only 0.1g of dried plant material is needed instead of the usual 1g. EDXRF spectrometry is used for quantitative measurement, after the foliar application of solutions of tungstophosphoric acid (WPA), its magnesium salt and compounds with glycine (Gly) and alanine (Ala), in exact quantities. After that, the leaves, trunks and summits were collected and prepared separately. Tungsten is determined directly in raw dried material, and the overlap of the tungsten peak with zincs that is present is avoided by the spectral deconvolution to obtain quantitative results. The prepared dry tablets weighed 100mg, and measurement time was 2000s. The radioisotope excitation source used was (109)Cd and tungsten was identified and quantified at the L(alpha1) and L(alpha2) lines at the energies of 8397.6eV and 8335.2eV, respectively. EDXRF spectrometry was applied in a wide range of concentrations (up to 2000mg/kg), with an estimated detection concentration limit of 15mg/kg, calculated on dried material. Quantitative analysis of different parts of the treated plant plus the washings gave 94.47% recovery of the applied tungsten in different compound forms. After the foliar application of investigated WPA compounds, there were noticed both vertical and horizontal distributions of tungsten through out the tobacco plants, according to the EDXRF spectrometry results. This conclusion is also in agreement with the positive effects of WPA on Tobacco mosaic tobamovirus (TMV) infection of Nicotiana tabacum (Solanaceae).

Kinetic method for the determination of traces of thyroxine by its catalytic effect on the Mn(III) metaphosphate-As(III) reaction.

A new, highly sensitive and simple kinetic method for the determination of thyroxine was proposed. The method was based on the catalytic effect of thyroxine on the oxidation of As(III) by Mn(III) metaphosphate. The kinetics of the reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516 nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant was calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters were determined. Thyroxine was determined under the optimal experimental conditions in the range 7.0 x 10(-9) to 3.0 x 10(-8) mol L(-1) with a relative standard deviation up to 6.7% and a detection limit of 2.7 x 10(-9) molL(-1). In the presence of 0.08 mol L(-1) chloride, the detection limit decreased to 6.6 x 10(-10) mol L(-1). The proposed method was applied for the determination of thyroxine in tablets. The accuracy of the method was evaluated by comparison with the HPLC method.

Natural and Mixed Ventilation Design via CFD and Architectural Modelling

Abstract Numerical simulations and computational fluid dynamics can be usefully integrated with architectural modelling to provide designers with a powerful single CFD based architectural modelling and design framework. This framework can be interfaced with building thermal performance modelling thus further integrating the full thermal and flow domains within architectural modelling. CFD analysis is generally restricted to the building’s environment flows or indoor single rooms and flow in spaces. In addition the designer must supply boundary conditions in the form of the external and internal building envelope/wall surface conditions. In the case of natural and mixed ventilation, this presents a fundamental problem since the outdoor and indoor boundary conditions are dynamic, inter-related and interactive via the building’s architecture. Furthermore they are dependent on external weather conditions, the indoor environment, controls and related heat gains. Therefore, in this study the boundary conditions for both the inside and outside of the building are dynamically described in order to develop an integrated CFD, BPS and architectural modelling approach, as a unique new design framework. This leads to the energy efficiency optimisation of natural and mixed mode ventilation. This paper presents an implementation of such an approach in the design of a building complex in Belgrade in which predicted flow patterns are used to optimise the architectural design and the size and location of ventilation openings. The needs for further research and engineering development are outlined. Finally to operate effectively and energy efficiently, natural and mixed ventilation requires an appropriately sensitive sensor to measure very low pressure differences at different building heights for the optimum control of mechanical ventilation system operation. The development of such a sensor is described.

Development of inductively coupled plasma atomic emission spectrometry for palladium and rhodium determination in platinum-based alloy

Inductively coupled plasma atomic emission spectroscopy (ICP-AES) with internal standardization was applied for the analysis of an in-house reference platinum alloy containing palladium and rhodium (approximately 5% by weight). In order to compensate for variations in signal recovery due to matrix interferences, and therefore to improve the precision, platinum, the major component, was chosen as an internal standard. Quantitative analysis was based on calibration using a set of matrix-matched calibration standards with and without employing the internal standard. These results were compared with those obtained by X-ray fluorescence (XRF) spectroscopy. The results for both techniques were in a good agreement, although the precision was slightly better in the ICP-AES technique, with or without the internal standard.

Numerical analysis of glulam beams reinforced with CFRP plates

AbstractThis paper presents an analysis of bending behaviour of glued laminated timber (glulam) beams reinforced with carbon fibre reinforced polymer (CFRP) plates, based on finite element numerical modelling. Nonlinear 3-dimensional model was developed and validated by experimental tests carried out on unreinforced beams and beams reinforced with two different reinforcement arrangements. Suitable constitutive relationships for each material were utilised in the model, as well as anisotropic plasticity theory for timber in compression. Adhesive bond between CFRP plate and timber was modelled as a perfect connection. Beam failure in the model was defined by maximum stress criterion. The predicted behaviour of beams has shown good agreement with the experimental results in relation to load-deflection relationship, ultimate load, elastic stiffness and strain profile distribution. The non-linear behaviour of reinforced beams before failure was also achieved in the numerical analysis, confirming the finite ele...

Forensic application of phylogenetic analyses – Exploration of suspected HIV-1 transmission case

Transmission of human immunodeficiency virus (HIV) between individuals may have important legal implications and therefore may come to require forensic investigation based upon phylogenetic analysis. In criminal trials results of phylogenetic analyses have been used as evidence of responsibility for HIV transmission. In Serbia, as in many countries worldwide, exposure and deliberate transmission of HIV are criminalized. We present the results of applying state of the art phylogenetic analyses, based on pol and env genetic sequences, in exploration of suspected HIV transmission among three subjects: a man and two women, with presumed assumption of transmission direction from one woman to a man. Phylogenetic methods included relevant neighbor-joining (NJ), maximum likelihood (ML) and Bayesian methods of phylogenetic trees reconstruction and hypothesis testing, that has been shown to be the most sensitive for the reconstruction of epidemiological links mostly from sexually infected individuals. End-point limiting-dilution PCR (EPLD-PCR) assay, generating the minimum of 10 sequences per genetic region per subject, was performed to assess HIV quasispecies distribution and to explore the direction of HIV transmission between three subjects. Phylogenetic analysis revealed that the viral sequences from the three subjects were more genetically related to each other than to other strains circulating in the same area with the similar epidemiological profile, forming strongly supported transmission chain, which could be in favour of a priori hypothesis of one of the women infecting the man. However, in the EPLD based phylogenetic trees for both pol and env genetic region, viral sequences of one subject (man) were paraphyletic to those of two other subjects (women), implying the direction of transmission opposite to the a priori assumption. The dated tree in our analysis confirmed the clustering pattern of query sequences. Still, in the context of unsampled sequences and inherent limitations of the applied methods, we cannot unambiguously prove that HIV-1 transmission occurred directly between two individuals. Further exploration of the known and suspected transmission cases is needed in order to define methodologies and establish their reliability.

The use of the solar energy in photochemical and photocatalytic processes

The increasing use of the Earth’s natural resources has generated increasing disposal of waste products and contamination of the environment. Many of these products are organic chemicals. Characteristic examples of waste products in the atmosphere, hydrosphere and soil are insecticides, herbicides and pesticides used to protect crops, accidental leakages and spills, and the continual discharge of waste by products in effluent streams from petrochemical and essential industries. To purify these contaminated atmospheres, hydrosphere and soil a procedure and process has been developing with minimal specific consumption energy from a renewable energy source. This paper will provide a survey and analysis of the parameters, thermal efficiency and conversion energy in the use of solar energy in the photochemical and photocatalytic degradation processes of organic effluents. As a consequence of the use of solar energy in the degradation of these effluents, a conceptual solution of a technical–technological and ph...