Spatial distribution of Belgrade air pollution

Belgrade air pollution has been monitored by two monitoring networks for more than a decade now, but no overall characterization of the pollution based on those results has been published so far. We give here seasonal spatial distributions of SO2, NO2, and BS (black smoke) over the city area, and discuss the characteristics in terms of likely sources and their seasonal contributions.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Detection of malathion by the CO2-laser

Possibilities of detecting the vapour of the pesticide malathion by a CO2-laser, using a photoacoustic technique developed in our laboratory were investigated. A set of vapor photoacoustic spectra of coincidence with this laser were obtained, the samples being: the commercial product available on the market, solvent, emulsifiers, and neat malathion. Relative contributions of the components in the product are discussed.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Optimizacija zapremine radioaktivnog obeleživača pri merenju zapreminskog protoka u zatvorenim cevovodima

In chemical processes it is essential that the flow in the process is accurately defined. Fluid velocity measurements are important for fluid flow quality performance in flow systems. This study focuses on determination of the volumetric flow rate and its standard (relative) deviation for calibration of conventional flow meters by using a radiotracer approach. The measurements for flow meter calibration were performed at a pilot-scale flow rig using Technetium-99 m (99mTc) as a radiotracer in the form of pertechnetate ion (99mTcO4-). The measured data were analyzed, and precision of the experimental setup was investigated under two different approaches – IAEA’s RTD software and sum approximation of raw data. For the first time, the variation of standard deviation of calculated flow rate with the injection volume and activity of the radiotracer was determined. Plug flow with axial dispersion was used to simulate the measured RTD curves and investigate the flow dynamics of the flowing water. The results of the study have shown the possibility of in situ calibration of flow meters with a relative error lower than 1 %. They also revealed a slight dependency of the precision of output results on the injection volume as well as similar results for manual and specialized RTD software data processing.U hemijskim procesima od suštinskog značaja je tačno definisan i precizan protok. Merenja brzine fluida su važna za karakterizaciju kvaliteta protoka tečnosti u sistemima. Ova studija se fokusira na određivanje zapreminskog protoka i standardnog (relativnog) odstupanja izmerenih vrednosti u cilju kalibracije konvencionalnih merača protoka korišćenjem metode radioaktivnog obeleživača. Merenja potrebna za kalibraciju merača protoka izvedena su na pilot postrojenju korišćenjem Tehnecijuma-99m (99mTc) kao radiotrejsera u obliku pertehnetatnog jona (99mTcO4-). Izmereni podaci su analizirani, a preciznost eksperimentalne postavke je ispitivana pomoću dva različita pristupa: upotrebom softvera za određivanje raspodele vremena zadržavanja (eng. residence time distribution, RTD) koga je razvila Međunarodna agencija za atomsku energiju i zbirne aproksimacije neobrađenih podataka. Po prvi put je utvrđena varijacija standardne devijacije izračunatog protoka u odnosu na zapreminu i u odnosu na aktivnost ubrizganog radioaktivnog obeleživača. Model protoka sa aksijalnom disperzijom je korišćen za simulaciju izmerenih RTD krivih i istraživanje dinamike protoka vode. Rezultati studije su pokazali mogućnost in situ kalibracije merača protoka sa relativnom greškom manjom od 1%. Takođe su pokazali malu zavisnost preciznosti izlaznih rezultata od količine ubrizganog obeleživača, kao i slične rezultate za manuelnu obradu i specijalizovanu obradu podataka upotrebom RTD softvera

Surface modifications of TiN coating by pulsed ir lasers: tea CO2 and HF laser

Interactions of a pulsed Transversely Excited Atmospheric (TEA) CO2 and chemical HF laser with polycrystalline titanium nitride (TiN) coating deposited on high quality steel AISI 316, were studied. It was shown that both lasers, at energy densities of 43 J/cm2 and 38.6 J/cm2, induce morphological changes on the target. The HF laser produces more pronounced damage than the TEA CO2 laser. The energy absorbed from either of these lasers is mainly converted into thermal energy.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Relationship between chromosomal and mitochondrial DNA variability of Drosophila subobscura population from the Lazar's river canyon

The genetic structure of Drosophila subobscura population from the Lazar’s River Canyon (Serbia) was studied with respect to restriction site polymorphism of mitochondrial DNA and chromosomal inversion polymorphism. The aim was to shed more light on the role of cytonuclear interactions in shaping mitochondrial DNA variability in this species. Similar to other populations of D. subobscura two main haplotypes (I and II) were found, as well as less common ones that appeared at very low frequencies. The frequency distribution of haplotypes did not depart from neutrality. We did not find statistically significant linkage disequilibrium between the haplotypes belonging to haplogroups I and II and any of the chromosomal arrangements. However, when we compared the data in hereby analyzed population and two previously analyzed populations we observed that haplotype I is more frequent in populations where standard inversion arrangements are less frequent. Pattern of the observed mitochondrial variability could be influenced either directly by environmental variability or through environmentally specific cytonuclear coadaptation.U ovom radu analizirana je genetička varijabilnost restrikcionih mesta mitohondrijalne DNK, kao i varijabilnost inverzionog polimorfizma u populaciji Drosophila subobscura sakupljenoj u kanjonu Lazareve reke. Cilj je bio rasvetljavanje uloge citonuklearnih interakcija u oblikovanju varijabilnosti mitohondrijalne DNK. Utvrđeno je prisustvo dva dominantna haplotipa (I i II) kao i dva haplotipa niske učestalosti. Nije utvrđena statistički značajna neravnoteža vezanosti između haplotipova grupisanih u haplogrupe I i II i nijednog od hromozomskih aranžmana. Međutim, upoređivanjem podataka prethodno analiziranih populacija i populacije analizirane u ovom radu, primećuje se povećanje učestalosti haplotipa I sa smanjenjem učestalosti standardnih hromozomskih aranžmana. Ovakav obrazac ukazuje ili na direktan uticaj sredinskih činilaca na varijabilnost mitohondrijalne DNK ili na sredinski zavisnu citonuklearnu koadaptaciju.Projekat ministarstva br. 17301

IR laser-induced changes to L-adrenaline-D-hydrogentartrate incorporated in KBr matrices

Changes in the pharmaceutical L-adrenaline-D-hydrogentartrate, incorporated in KBr matrices, induced by a pulsed carbon-dioxide Transversely Excited Atmospheric (TEA) laser, were observed. Modifications of the sample were monitored via infrared spectra. Special attention was devoted to the dependence of the sample changes on the laser energy density used. The irradiation of the pharmaceutical has been performed with two laser lines at wavelengths of about 10.6 mum. The laser lines coincide well with the absorption band of the pharmaceutical, which is assigned to the ring vibrations/ out-of-plane OH deformation vibrations, within the carboxyl (COOH) group of L-adrenaline-D-hydrogentartrate. Laser energy densities of 1.20 and 1.70 J/cm(2) modified the pharmaceutical/compound. It was found that this modification is in essence a thermal effect. The level of change showed a dependence on the laser energy density, number of accumulated laser pulses and temporal shape of the pulse

Intra-species differentiation among Drosophila subobscura from different habitats in Serbia

Adaptation to different environmental conditions is a natural phenomenon that potentially leads to population subdivision. We surveyed genetic differentiation in inversion polymorphism within populations of Drosophila subobscura sampled in three ecologically different forest communities. The analysis of inversion polymorphism revealed significant differences between some pairs of samples in some gene arrangement frequencies of the A, U, and E chromosomes and some karyotype combination frequencies of the U chromosome, but significant differentiation within populations was not observed. It cannot be decided which evolutionary forces are responsible for the observed variability in inversion polymorphism.Adaptacija na različite sredinske uslove može uticati na diferencijaciju u okviru populacija. U ovom radu analizirana je genetička diferencijacija po inverzionom polimorfizmu u okviru populacija D. subobscura sakupljenih u tri ekološki različita staništa. Utvrđene su značajne razlike u učestalosti pojedinih hromozomskih aranžmana A, U i E hromozoma, i učestalosti pojedinih kombinacija kariotipova U hromozoma, ali nije utvrđena diferencijacija u okviru populacija. Razmatrani su evolutivni faktori koji bi mogli da budu odgovorni za uočenu varijabilnost u inverzionom polimorfizmu.Projekat ministarstva br. 14301

Heat generation during plunge stage in friction stir welding

This paper deals with the heat generation in the Al alloy Al2024-T3 plate under different rotating speeds and plunge speeds during the plunge stage of friction stir welding. A 3-D finite element model is developed in the commercial code ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson- Cook material law, and Coulomb's Law of friction. The heat generation in friction stir welding can be divided into two parts: frictional heat generated by the tool and heat generated by material deformation near the pin and the tool shoulder region. Numerical results obtained in this work indicate a more prominent influence from the friction-generated heat. The slip rate of the tool relative to the workpiece material is related to this portion of heat. The material velocity, on the other hand, is related to the heat generated by plastic deformation. Increasing the plunging speed of the tool decreases the friction-generated heat and increases the amount of deformation-generated heat, while increasing the tool rotating speed has the opposite influence on both heat portions. Numerical results are compared with the experimental ones, in order to validate the numerical model, and a good agreement is obtained

Optimization of injected radiotracer volume for flow meter calibration in closed conduits

In chemical processes it is of essential for flow in the process to be accurate and well defined. Fluid velocity measurements are important for fluid flow quality performance in the systems. This study focuses on determination of volumetric flow rate measurement and on calibration of conventional flowmeter using industrial radiotracer approach. In this work, the application of radiotracer method for RTD measurement in flow meter calibration for chemical industry is described. The experiments in pilot-scale flow rig were performed using Technetium-99 m ( 99mTc) as a radiotracer in the form of pertechnetate ion (99mTcO4 - ) to calibrate flow meter. The data were evaluated using plug flow with axial dispersion model of RTD software. The optimization of the parameters included input signal of radiotracer, concentration of radiotracer and position of detectors. The measured data were analyzed, and precision of experimental setup was investigated under two different approaches. A plug flow with axial dispersion was used to simulate the measured RTD curves and investigate flow dynamics of the flowing water. The results of the study, showed that there might be an optimum injection volume range of the tracer for each specific application. The optimum range in this study was determined from 300 to 700 µL. In this range, relative standard deviation was around 1% for both calculation methods, which is lower than with other available injection volumes. Bias of the initial flow rate was lower using summation approximation, resulting in ca 9% in the area of interest. In case of RTD software, bias values were between 10 and 11%. For the first time the variation of standard deviation of calculated flow rate with injection volume and activity of radiotracer was determined. The results of the study may help in injection volume optimization as well as give a guide on how to process data without RTD software, as the results obtained by both methods were in great agreement. They also revealed a slight dependency of the precision of output results on the injection volume as well as similar results for manual and specialized RTD software data processing. The study that investigated the change of standard deviation of calculated flow rate with injection volume and activity of used radiotracer was conducted for the first time in literature

Spektrofotometrijsko ispitivanje reakcije zlata(III) sa kalijum-jodidom

The equilibria of the complex formation between AuCl4-n(OH)n- and I- was studied spectrophotometrically in aqueous solutions containing KI:Au(III)≤2 in the acidity range from 1 M HCl to pH 7 at 25 ºC. From the hydrogen ion and Cl- ion dependence of the absorption spectra, it was found that AuCl2I2- and Au(OH)2I2- complexes were formed. The equilibrium constants of complex formation were determined.Ravnoteže obrazovanja kompleksa između AuCl4-n(OH)n i KI ispitivane su spektrofotometrijski u vodenim rastvorima pri odnosu koncentracija KI:Au(III) ≤ 2 u oblasti kiselosti od 1 M HCl do pH 7 na 25 ºC. Iz promene apsorpcionih spektara u zavisnosti od kiselosti sredine i koncentracije Cl- jona nađeno je da se obrazuju kompleksi AuCl2I2- i Au(OH)2I2-. Određene su konstante ravnoteže odgovarajućih reakcija. PR Projekat Ministarstva nauke Republike Srbije