Liquid scintillation spectrometer optimization during alpha and beta emitters determination in waters

U disertaciji je izvršena optimizacija detektorskog IZ   sistema Quantulus 1220TM radi razvoja metoda za određivanje pojedinačnih radionuklida 3H, 222Rn i 90Sr, kao i ukupne alfa/beta aktivnosti u vodama. Predstavljeni su eksperimenti u svrhu kalibracije sistema, istraživanja uticaja relevantnih parametara na rezultate određivanja aktivnosti alfa i beta emitera, i podešavanja optimalnih vrednosti ovih parametara. Posebna pažnja je posvećena variranju  PSA diskriminatora, odnosno podešavanju analizatora oblika impulsa na optimalnu vrednost u svrhu optimalnog razdvajanja alfa od beta događaja, kao i ispitivanju efekata prigušenja u uzorcima i metodama njihove korekcije.  Predstavljene razvijene metode su brze, efikasne i jednostavne, što je naročito važno u slučaju radijacionog akcidenta, kada je potrebno brzo odrediti sadržaj radionuklida u  uzorcima vode, a njihova validnost je pokazana u okviru međunarodnih i međulaboratorijskih interkomparacija.Dissertation involves optimization of detector AB   system  Quantulus 1220TM for development of methods for determination of individual radionuclides 3H, 222Rn and 90Sr, as well as gross alpha/beta activity in waters. Presented experiments had purpose of calibration of the system,  investigation  of  relevant parameters  influence  on  activity  measurements  of alpha and beta emitters, as well as  setting the optimum values of  these parameters. Special attention  was devoted to  PSA  discriminator value  setting, i.e. adjusting the pulse shape analyzer level at optimum value for an optimal separation of alpha from beta events, as well as testing the effects of quenching in the samples and methods for quench  correction. Presented developed methods are fast, efficient and simple, which is especially important in the case of a radiation accident, when there is a need to quickly determine the content of radionuclides in water samples, and their validity has been demonstrated within the framework of international and inter-laboratory  ntercomparison measurements

BOOK REVIEW - TELEVISION AND NEW MEDIA AESTHETICS

Srnobrnja, Stanko. Television and New Media Aesthetics. Clio: Belgrade, 2010, p. 38

Direktna metoda za određivanje ukupne alfa/beta aktivnosti u vodama

Monitoring of environmental samples, drinking and surface waters, is continuously carried out, demanding development of methods that are both reliable and accurate on one side, but as simple and fast as possible, on the other. Screening tests such as gross alpha/beta activity measurements in water samples are one liquid scintillation counting (LSC) technique widely used as an efficient tool for radiological assesment and estimation whether water sample needs further analysis or not. In this paper, establishment of rapid gross alpha/beta screening technique in waters has been presented, which assumes modification of conventional ASTM D 7283-06 method, since samples were directly mixed with liquid scintillation cocktail, without any sample pretreatment. Method’s optimization involved sample-to-cocktail ratio determination based on the achieved detection limit and sample’s quench level. Optimal value of Pulse Shape Analysis (PSA) discriminator that considerably improves performance of LSC technique through alpha/beta spectra separation during radiological quality measurements of drinking waters has also been investigated. Results of calibration experiments and method’s validity measurements on spiked samples with 241Am and 90Sr/90Y aqueous standards are presented. Achieved detection limits for 300 minutes of counting are MDAα=0.294(11) Bq l-1 and MDAβ=0.405(5) Bq l-1, in alpha and beta window, respectively. Direct alpha/beta method provides deviations up to 40% from reference values, but it offers advantages over conventional alpha/beta measurements, it is ultra fast, simple and inexpensive test for efficient screening of water samples.Rutinski monitoring pijaćih i površinskih voda sprovodi se kontinuirano i nameće potrebu za razvojem metoda koje su, s jedne strane, pouzdane i tačne, ali istovremeno, jednostavne i brze. Screening testovi radi procene ukupne alfa/beta aktivnosti u uzorcima voda, jedna su od često primenjenih tehnika tečne scintilacione spektroskopije, kojima se efikasno može utvrditi da li uzorak zahteva dalju radiološku analizu ili ne. U radu je predstavljena optimizacija brze direktne metode za ispitivanje ukupne alfa/beta aktivnosti u vodama, uz prikaz i diskusiju postignutih granica detekcije. Ova metoda je modifikacija standardne test metode ASTM D 7283-06 za ispitivanje ukupne alfa i beta aktivnosti i podrazumeva direktno mešanje uzorka vode sa scintilacionim koktelom. Na taj način, uzorak je spreman za merenje bez prethodne pripreme koja, prema standardnim metodama, obično podrazumeva duge procedure poput uparavanja do suvog ostatka. Optimizacija metode sastoji se u određivanju optimalnog odnosa uzorak: scintilacioni koktel na osnovu granica detekcije (MDA) u alfa i beta kanalima, kao i nivoa prigušenja u uzorcima, uzimajući u obzir i maksimalni kapacitet određenog koktela. Podešena je vrednost PSA (Pulse Shape Analysis) diskriminatora u cilju optimalne separacije alfa i beta spektara i redukcije pozadinskih efekata. Kalibracija i validacija metode je izvršena standardnim referentnim materijalima, rastvorima 241Am i 90Sr/90Y. Utvrđeno je da za 300 minuta merenja tečnim scintilacionim brojačem, mogu se izmeriti koncentracije aktivnosti koje premašuju vrednosti MDAα=0,294(11) Bq l-1 i MDAβ=0,405(5) Bq l-1 u alfa i beta kanalima, respektivno. Rezultati validacije metode pokazuju da maksimalna relativna odstupanja mogu iznositi do 40%, što je prihvatljivo, uzimajući u obzir da metod nije predviđen za precizno merenje koncentracija aktivnosti pojedinih radionuklida, već za celokupnu procenu radiološke bezbednosti uzoraka voda.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин

Varijante i transkripcija gena koji kodiraju komponente leptinskog signalnog puta, inflamacije i antioksidativne zaštite u patogenezi multiple skleroze

Multipla skleroza (MS) je hronična autoimunska bolest centralnog nervnog sistema (CNS) čiji osnovni patogenetski mehanizmi obuhvataju neuroinflamaciju, demijelinizaciju i neurodegeneraciju. Glavno patofiziološko obeležje MS je hiperaktivacija određenih komponenti imunskog sistema, koja dovodi do nastajanja i akumulacije strukturno-funkcionalnih oštećenja CNS kao posledice hronične inflamacije i oksidativnog stresa. Adipocitokin i hormon leptin potencijalni je molekularni marker MS, budući da učestvuje u patogenezi ove bolesti delovanjem na regulaciju imunskog i odgovora na oksidativni stres. Varijante i promene u transkripciji gena koji kodiraju komponente leptinskog signalnog puta, i sa njima povezane komponente inflamacije i antioksidativne zaštite, asocirane su sa nastankom i/ili kliničkim tokom MS kao i odgovorom na terapiju. Danas u Srbiji ima preko 9000 obolelih od MS, a samo 1 od 10 pacijenata dobija trenutno dostupnu konvencionalnu imunomodulatornu terapiju. Mogućnost modulisanja nivoa cirkulišućeg leptina sugeriše njegov potencijalni značaj u budućem razvoju personalizovanog pristupa u lečenju MS baziranog na poboljšavanju efekata ili supstituciji postojeće konvencionalne terapije.Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) with underlying pathogenetic mechanisms that include neuroinflammation, demyelination and neurodegeneration. The main pathophysiological feature of MS is the hyperactivation of certain immune system components, which leads to formation and accumulation of structural and functional damage in the CNS as a result of chronic inflammation and oxidative stress. The adipocytokine and hormone leptin is a potential molecular marker of MS, since it participates in the pathogenesis of this disease by acting on the regulation of immune system and response to oxidative stress. Variants and transcriptional changes of genes coding for components of the leptin signaling pathway, and associated components of inflammation and antioxidant protection, are associated with the onset and/or clinical course of MS as well as response to therapy. Today, there are over 9,000 MS patients in Serbia, and only 1 out of 10 patients receives currently available conventional immunomodulatory therapy. The possibility of modulating the level of circulating leptin suggests its potential importance in the future development of a personalized approach in treatment of MS based on improving the effects or substituting the existing conventional therapy

MANAGER’S ROLE IN RAISING THE LEVEL OF JOB SATISFACTION

Organizations, as a complex systems, in the structure of their subsystems have the human or social subsystem. It is a subsystem that has a significant influence on the functioning of the organization and its competitiveness. The quality of the social organizational subsystem is determined by the quality of the different variables that the subsystem includes. Job satisfaction is one of these variables. It is a variable that can have an adequate impact on the effectiveness and efficiency of the organization, as well as on its performance. The aim of the authors of this paper is to point out the nature, the significance, causes and consequences of job satisfaction, as well as the role of managers in raising the level of these organizational variables. Key words:  job satisfaction, staff, management, organizatio

ANALYSIS OF MACHIAVELLIAN BEHAVIOR OF STUDENTS IN THE REPUBLIC OF SERBIA

Using the "Mach IV Scale", this paper analyses the level of Machiavellian behavior among the student population in the Republic of Serbia. The obtained results were compared with the outcome of similar studies conducted in the United States and Indonesia. Results indicated that Machiavellianism level, manifested among the student population in the Republic of Serbia, is higher than Machiavellianism level manifested among students in the United States and Indonesia. The mixed results of this study point to the conclusion that economic development of a certain country (expressed by GDP per capita) could not be a base for reliable conclusion regarding the potential expression level of Machiavellian behavior of state’s population. These results can be useful for managers, in general, and for managers in the Republic of Serbia, particularly, in the process of recruiting and selecting new candidates, and in the course of delegating tasks to existing members of the organization.Key words: machiavellianism, economic development, students, managemen

Long-term outcome of strabismus and ptosis surgery in a mother and daughter with congenital fibrosis of extraocular muscles

Background. Congenital fibrosis of extraocular muscles (CFEOM) is a very rare congenital condition, characterized by variable amounts of restriction of the extraocular muscles, with or without ptosis. The aim of this report was to deseribe a severe, atypical, exposure-induced corneal stromal lysis in two patients. Case report. A mother and a daughter with a severe CFEOM were presented. The surgery of both extraocular muscles and ptosis led to a fair outcome in mother even 30 years after, and a very good outcome in daughter 4 years after the treatment. Conclusion. Though frequently challenging and disappointing the outcome of surgery of both extraocular muscles and ptosis in CFEOM can be favorable even in rather severe cases. To the best of our knowledge, the atypical keratolysis we described has not been highlighted in the literature on CFEOM so far

Zinc oxide-based materials with enhanced sunlight-driven photo- and photo-electro-catalytic activity

Current trend in photocatalysis is to develop efficient semiconductors which can be activated by absorbing sunlight. Which wavelength of sunlight will be absorbed depends on the semiconductor band gap; semiconductors with a wide band gap (> 3 eV) can absorb only UV light (5% of sunlight), while those with a narrow band gap (< 3 eV) can be activated by visible light (45% of sunlight). Zinc oxide (ZnO) is promising semiconductor with band gap of 3.37 eV. Various approaches have been applied to modify its optical properties, for example: incorporation of different metal and nonmetal ions or defects into the crystal structure, particles’ surface sensitization or hydrogenation. In this study, we examined the influence of different defects present in ZnO particles on their photo- and photo-electro-catalytic properties. Processing of ZnO particles were carried out in order to introduce: (1) lattice defects, through microwave procedure, (2) surface defects, through mechanical activation, and (3) surface defects, trough composite with polyethylene oxide. Synthesized particles were characterized by XRD, FESEM, laser diffraction particle size analyzer, Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopy. The results of achieved photo- and photo-electro-catalytic tests indicate that both, structural and surface, defects enhanced sunlight-driven activity of ZnO particles

Synthesis of LiCrxMn2-xO4 (x~0.18) by glycine-nitrate method

LiCr0.18Mn1.82O4 spinel has been successfully synthesized by glycine-nitrate method. As a cathode material for lithium batteries it shows initial discharge capacity of 107.1 mAh/g and capacity retention of 93.3% after ten cycles.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Synthesis and characterization of Na0.4MnO2 as cathode material for aqueous sodium-ion batteries

The application of rechargeable batteries is growing significantly and there is a need for developing cheaper batteries with good performances. Sodium-ion batteries could be a viable option due to higher abundance of sodium against lithium mineral resources, its low price and similar principles intercalate Na+ ions as Li+ ions in lithium-ion batteries. Different materials as manganese oxides and vanadium oxide are used as electrode materials in sodium batteries. Na0.44MnO2 was regarded as one of the most promising cathode materials for sodium-ion batteries due to its high specific capacity and good cyclability. In this work, Na0.4MnO2 was synthesized using glycine-nitrate method (GNM). The structure of synthesized powder was characterized by X-Ray Diffraction (XRD), while the particles morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elemental mapping was performed by energy-dispersive Xray spectroscopy (EDS). XRD results showed that the phase structure of Na0.4MnO2 was orthorhombic with tunnel structure. TEM and SEM micrographs of obtained powder material showed uniformed rod-like shape particles with the average lengths and widths of 300 nm and 80 nm, respectively and EDS analysis confirmed that the sample contains Na, Mn, and O in an appropriate ration. The electrochemical behavior of Na0.4MnO2 was investigated by cyclic voltammetry (CV) in a saturated aqueous solution of NaNO3 at scan rates from 20 to 400 mV•s-1. The initial discharge capacity of Na0.4MnO2 in NaNO3 solution was 50 mA•h•g- 1, while after 15 cycles its value increased for 9%. while the efficiency (the ratio of the capacity charge and discharge) was amounting to ~ 95%. This indicates that material synthesized by GNM can be used as cathode material in aqueous sodium-ion batterie