Zavisnost efikasnosti germanijumskih detektora od gustine uzoraka u spektrometriji gama zračenja

The effect of the density of environmental samples on the counting efficiency of Ge detectors used in gamma-spectrometry was studied. The dependence εff(ρ) was determined for two HPGe detectors (relative efficiencies 18% and 20%) using five radioactive standard reference materials (silicone resins, epoxy resin, milk powder, soil) with different matrix densities (0.45-1.22 g/cm3) in Marinelli beakers (V = 500 cm3). The dependence of efficiency vs. density was found to be linear and the regression parameters for energies in the range of 60-2000 keV were determined, too. The effect of variation in density on the counting efficiency of Ge detectors is dominant in the range of lower energies (60-600 keV) and de creases with energies in the higher energy range.Ispitivan je uticaj gustine uzoraka iz životne sredine na efikasnost brojanja germanijumskih detektora u spektrometriji gama zračenja. Zavisnost εff(ρ) određena je za dva HPGe detektora (relativnih efikasnosti 18% i 20%) za različite radioaktivne standardne referentne materijale (silikonske smole epoksi smolu, mleko u prahu, zemlju) različitih gustina (0,45-1,22 g/cm3) u Marineli posudama zapremine V = 500 cm3. Utvrđena je linearna zavisnost efikasnosti brojanja od gustine uzoraka pri čemu su određeni parametri linearne regresije za niz energija iz intervala od 60-2000 keV. Efekt promene gustina na efikasnost brojanja germanijumskih detektora dominantan je u intervalu nižih energija (60-600 keV) i smanjuje se sa porastom energije u intervalu viših energija

Supplementary data for article: Relić, D.; Đorđević, D. S.; Popović, A. R. Assessment of the Pseudo Total Metal Content in Alluvial Sediments from Danube River, Serbia. Environmental Earth Sciences 2011, 63 (6), 1303–1317. https://doi.org/10.1007/s12665-010-0802-1

Supplementary material for: [https://doi.org/10.1007/s12665-010-0802-1]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1170

Multi-axis integrated Hall magnetic sensors

Conventional Hall magnetic sensors respond only to the magnetic field component perpendicular to the surface of the sensor die. Multi-axis sensing capability can be provided in the following two ways: (a) by integrating magnetic flux concentrators on the die, and (b) by using vertical Hall devices. Here we review the most important two-and three-axis integrated Hall magnetic sensors based on these concepts. Their applications include mapping of magnetic fields and sensing angular position

Specijacija odabranih mikro- i makroelemenata u uzorcima lignita termoelektrane 'Nikola Tesla A' (Obrenovac, Srbija)

Four samples of milled lignite used in the "Nikola Tesla A" power plant located in Obrenovac near Belgrade, were subjected to a five-step sequential extraction, comprising of the following phases: distilled water, 1M ammonium acetate, 0.2M ammonium oxalate/0.2M oxalic acid, acidic solution of H2O2and a 6M solution of HCl. The concentrations of the different elements obtained in the extractions were statistically analyzed. The majority of the examined elements were found to be most probably associated with inorganic fractions of lignite, only aluminum, silicon, chromium and arsenic have a larger extractable organic/sulfide fraction than an extractable inorganic fraction. Alumosilicates of magnesium (carriers of arsenic, zinc, lead, copper and chromium), silicates of potassium (scavengers of lead and nickel), mixed aluminates of iron and magnesium (carriers of arsenic, zinc, copper and chromium) and compounds of iron that do not contain aluminum and magnesium (scavengers of manganese) were dissolved in the fifth phase of the sequential extraction. Copper is a substrate of alumosilicates of potassium and magnesium, while zinc and chromium are substrates of compounds of iron leached in the third phase of the sequential extraction. Interphase correlation revealed that the adsorbed and ion-exchangeable fractions of most of the examined elements do not exhibit preferential binding to the components of the inorganic matrix of lignite ash.Četiri uzorka mlevenog lignita korišćenog u Termoelektrani "Nikola Tesla A" u Obrenovcu u Beograda su podvrgnuta sekvencijalnoj ekstrakcija koja se sastojala od pet faza: u prvoj je korišćena destilovana voda, u drugoj 1M amonijum-acetat, u trećoj 0,2M amonijum-oksalat i 0,2M oksalna kiselina, u četvrtoj kiseo rastvor H2O2 i u petoj 6M rastvor HCl. Dobijene koncentracije izabranih elemenata su statistički analizirane, kako bi se utvrdile veze između različitih elemenata. Najveći deo ispitivanih elemenata je uglavnom asociran sa ekstrahovanom neorganskom fazom uglja, samo aluminijum silicijum, hrom i arsen imaju unutar ekstraktibilnog dela elemenata veću organsku/sulfidnu frakciju od neorganske. Od jedinjenja rastvornih u petoj fazi ekstrakcije uglja, alumosilikati magnezijuma su nosilac arsena, cinka olova, bakra i hroma, silikati kalijuma nosilac olova i nikla, mešoviti aluminati gvožđa i magnezijuma nosilac arsena, cinka, bakra i hroma, a jedinjenja gvožđa koja nisu povezana sa aluminatima ni magnezijumom nosilac mangana. U trećoj fazi ekstrakcije uglja se rastvaraju alumosilikati kalijuma i magnezijuma asocirani sa bakrom, dok su jedinjenja gvožđa rastvorna u trećoj fazi ekstrakcije asocirana sa cinkom i hromom. Interfazna korelaciona analiza je pokazala da se adsorbovana i jonoizmenjiva frakcija većine ispitivanih elemenata ne vezuje preferencijalno za delove neorganske matrice čestica pepela

Trace and major element pollution originating from coal ash suspension and transport processes

Coal ash obtained by coal combustion in the “Nikola Tesla A” power plant in Obrenovac, near Belgrade, Yugoslavia, is mixed with water of the Sava river and transported to the dump. In order to assess pollution caused by leaching of some minor and major elements during ash transport through the pipeline, two sets of samples (six samples each) were subjected to a modified sequential extraction. The first set consisted of coal ash samples taken immediately after combustion, while the second set was obtained by extraction with river water, imitating the processes that occur in the pipeline. Samples were extracted consecutively with distilled water and a 1 M solution of KCl, pH 7, and the differences in extractability were compared in order to predict potential pollution. Considering concentrations of seven trace elements as well as five major elements in extracts from a total of 12 samples, it can be concluded that lead and cadmium do not present an environmental threat during and immediately after ash transport to the dump. Portions of zinc, nickel and chromium are released during the ash transport, and arsenic and manganese are released continuously. Copper and iron do not present an environmental threat due to element leaching during and immediately after the coal ash suspension and transport. On the contrary, these elements, as well as chromium, become concentrated during coal ash transport. Adsorbed portions of calcium, magnesium and potassium are also leached during coal ash transport

Ranking and similarity of conventional, microwave and ultrasound element sequential extraction methods

This study aims to compare three extraction techniques of four sequential element extraction steps from soil and sediment samples that were taken from the location of the Pancevo petrochemical industry (Serbia). Elements were extracted using three different techniques: conventional, microwave and ultrasound extraction. A novel procedure sum of the ranking differences (SRD) - was able to rank the techniques and elements, to see whether this method is a suitable tool to reveal the similarities and dissimilarities in element extraction techniques, provided that a proper ranking reference is available. The concentrations of the following elements Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Si, Sn, Sr, V and Zn were determined through ICP OES. The different efficiencies and recovery values of element concentrations using each of the three extraction techniques were examined by the CRM BCR-701. By using SRD, we obtained a better separation between the different extraction techniques and steps when we rank their differences among the samples while lower separation was obtained according to analysed elements. Appling this method for ordering the elements could be useful for three purposes: (i) to find possible associations among the elements; (ii) to find possible elements that have outlier concentrations or (iii) detect differences in geochemical origin or behaviour of elements. Cross-validation of the SRD values in combination with cluster and principal component analysis revealed the same groups of extraction steps and techniques.The peer-reviewed version: [http://cer.ihtm.bg.ac.rs/handle/123456789/2934

Reversed-phase thin-layer chromatography behavior of aldopentose derivatives

Quantitative structure-retention relationships (QSRR) have been used to study the chromatographic behavior of some aldopentose. The behavior of aldopentose derivatives was investigated by means of the reversed-phase thin-layer chromatography (RP TLC) on the silica gel impregnated with paraffin oil stationary phases. Binary mixtures of methanol-water, acetone-water and dioxane-water were used as mobile phases. Retention factors, RM0, corresponding to zero percent organic modifier in the aqueous mobile phase was determined. Lipophilicity C0 was calculated as the ratio of the intercept and slope values. There was satisfactory correlation between them and log P values calculated using different theoretical procedures. Some of these correlations offer very good predicting models, which are important for a better understanding of the relationships between chemical structure and retention. The study showed that the hydrophobic parameters RM0 and C0 can be used as a measures of lipophilicity of investigated compounds

Supplementary data for the article: Sakan, S.; Popović, A.; Škrivanj, S.; Sakan, N.; Đorđević, D. Comparison of Single Extraction Procedures and the Application of an Index for the Assessment of Heavy Metal Bioavailability in River Sediments. Environmental Science and Pollution Research 2016, 23 (21), 21485–21500. https://doi.org/10.1007/s11356-016-7341-6

Supplementary material for: [https://doi.org/10.1007/s11356-016-7341-6]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2347

Universal Behavior of the Resistance Noise across the Metal-Insulator Transition in Silicon Inversion Layers

Studies of low-frequency resistance noise show that the glassy freezing of the two-dimensional (2D) electron system in the vicinity of the metal-insulator transition occurs in all Si inversion layers. The size of the metallic glass phase, which separates the 2D metal and the (glassy) insulator, depends strongly on disorder, becoming extremely small in high-mobility samples. The behavior of the second spectrum, an important fourth-order noise statistic, indicates the presence of long-range correlations between fluctuators in the glassy phase, consistent with the hierarchical picture of glassy dynamics.Comment: revtex4; 4+ pages, 5 figure

Supplementary material for the article: Relić, D.; Héberger, K.; Sakan, S.; Škrbić, B.; Popović, A.; Đorđević, D. Ranking and Similarity of Conventional, Microwave and Ultrasound Element Sequential Extraction Methods. Chemosphere 2018, 198, 103–110. https://doi.org/10.1016/j.chemosphere.2017.12.200

Supplementary material for: [https://doi.org/10.1016/j.chemosphere.2017.12.200]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2109]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3250