Concentrations of natural radionuclides in imported zirconium minerals

The natural radioactivity in imported zircon samples used as glaze for ceramic tiles in the ceramics industry has been presented in this paper. The measurements were made by gamma spectrometry with a high purity germanium detector. The average activity concentrations of 238U and 232Th determined in the measured samples (3250 Bq/kg, and 556 Bq/kg, respectively) are much higher than the concentrations found in the Earth’s crust. The activity concentration of 226Ra is also high in all analyzed samples, while 40K was not detected. The gamma index, I, the external hazard index, Hex, the internal hazard index, Hin, and the radium equivalent activity, Raeq, were calculated. Due to relatively high activity concentration level of uranium in imported zircon samples, specific regulations are necessary for zircon compound used in ceramic industry. It can be concluded that the investigated samples can be used as the component of ceramic glaze in the concentrations not above 3%

Control system modeling of hydraulic actuator with compressible fluid flow

U radu su tretirane Rimanove parcijalne diferencijalne jednačine u obliku izraza (1) gde je promenljiva μ definisana relacijom (2). Odgovarajući granièni uslovi definisani su u različitim oblicima, kao što su granični uslovi pritiska i protoka i to na fiksnim i na pokretnim granicama. Problem je formulisan sa ciljem da opiše kompletnu dinamiku hidrauličkog aktuatora, uključujući njegov stvarni protok i geometrijske karakteristike. U tu svrhu napravljen je poseban algoritam i odgovarajući računarski paket za simulaciju kompletne dinamike hidrauličkog aktuatora, uključujući i prisutne efekte talasa. Za rešenje problema korišćena je metoda karakteristika. Rezultati računarske simulacije dinamike hidrauličkog aktuatora predstavljeni su 3-D dijagramima.The paper treats Riemann's partial differential equations in the form (1), where variable μ is defined by relation (2). Corresponding boundary conditions are defined in various forms, such as boundary conditions of pressure and flow on the fixed and movable boundaries. Problem formulation is constructed in order to describe hydraulic actuator dynamics in a complete form, including its real flow and geometric characteristics. Special algorithm is generated and a corresponding computer package for simulation of the complete hydraulic actuator dynamics, including the existing wave effects, using the method of characteristics to obtain the desired problem solution. Results of computer simulation of hydraulic actuator dynamics are presented in 3-D diagrams

Control system modeling of hydraulic actuator with compressible fluid flow

U radu su tretirane Rimanove parcijalne diferencijalne jednačine u obliku izraza (1) gde je promenljiva μ definisana relacijom (2). Odgovarajući granièni uslovi definisani su u različitim oblicima, kao što su granični uslovi pritiska i protoka i to na fiksnim i na pokretnim granicama. Problem je formulisan sa ciljem da opiše kompletnu dinamiku hidrauličkog aktuatora, uključujući njegov stvarni protok i geometrijske karakteristike. U tu svrhu napravljen je poseban algoritam i odgovarajući računarski paket za simulaciju kompletne dinamike hidrauličkog aktuatora, uključujući i prisutne efekte talasa. Za rešenje problema korišćena je metoda karakteristika. Rezultati računarske simulacije dinamike hidrauličkog aktuatora predstavljeni su 3-D dijagramima.The paper treats Riemann's partial differential equations in the form (1), where variable μ is defined by relation (2). Corresponding boundary conditions are defined in various forms, such as boundary conditions of pressure and flow on the fixed and movable boundaries. Problem formulation is constructed in order to describe hydraulic actuator dynamics in a complete form, including its real flow and geometric characteristics. Special algorithm is generated and a corresponding computer package for simulation of the complete hydraulic actuator dynamics, including the existing wave effects, using the method of characteristics to obtain the desired problem solution. Results of computer simulation of hydraulic actuator dynamics are presented in 3-D diagrams

Transport and storage of heavy metals in the Sava river basin in Serbia

Selected heavy metals (Cu, Zn, Pb and Cd) in Sava River water and sediment in Serbia were investigated on three locations in the vicinity of industrial and urban settlements (Šabac, Obrenovac, Beograd) during the period spring 2007-autumn 2011. The fluxes of heavy metals from river water to sediment due to sedimentation and heavy metal re-suspension fluxes due to sediment re-suspension at a high flow were determined, by applying the model for assessment of the transport the pollutants through rivers. Those fluxes were attributed mainly to natural processes. [Projekat Ministarstva nauke Republike Srbije, br. 43009

Investigation of the mortar and concrete resistance in aggressive solutions

U radu je prikazan utjecaj dva agresivna rastvora – sulfata i nitrata na žbuku i beton. U eksperimentalnom radu ispitivane su prizme od žbuke s 5 % specijalnog dodatka. Četiri vrste betona su također izložene agresivnim rastvorima. Kemijska otpornost ispitivana je prema metodi Koch-Steinegger. Kako je uvjet za otpornost kod agresivnih rastvora da zatezna čvrstoća žbuke nije niža od 70 % u odnosu na referentne prizme njegovane u vodi, može se zaključiti da žbuka i beton izrađeni s kombinacijom cementa i dodataka, prikazani u ovom istraživanju, nisu otporni na rastvor amonijak nitrata ali jesu na sulfatnu koroziju.Testing the influence of two aggressive solutions - sulphate and nitrate on mortar and concrete was presented in this paper. Experimental work included testing of mortar prisms with 5 % special admixture. Also, four types of concrete were exposed to aggressive solutions. The chemical resistance was tested according to the Koch-Steinegger method. As a condition for resistance in aggressive solution means that flexural strength of mortar prisms is no less than 70 % of referent prisms cured in water it can be concluded that mortar and concrete made with combination of cement and admixture presented in this investigation are not resistant to ammonium nitrate solution, but are resistant to sulphate corrosion

Morphogenesis and anatomico-physiological characteristics of reproductive organs of walnut (Juglans regia L.)

periodu od 2010. do 2013. godine u ekološkim uslovima Kraljeva proučavane su anatomske, morfološke i fiziološke osobine reproduktivnih organa kod pet sorti oraha (Šampion, Šejnovo, Gajzenhajmski 139, Gajzenhajmski 251 i Elit) i jednog spontanog sejanca. U radu je dat detaljan opis građe muških i ženskih cvetova na anatomskom i morfološkom nivou. Morfometrijska analiza resa, antera, polenovih zrna, ženskih cvetova, semenih zametaka i embrionovih kesica pokazala je da na neke morfometrijske parametre ne utiču značajno faktori spoljašnje sredine i da se oni mogu uspešno koristiti za determinaciju sorti. Procesi diferencijacije muških i ženskih cvetova, uključujući i procese formiranja muškog i ženskog gametofita, odvijali su se sukcesivno i istim redosledom kod svih ispitivanih genotipova i u svim godinama, a razlike po godinama i među genotipovima odnosile su se prvenstveno na vreme početka i dužinu trajanja pojedinih faza razvitka. U radu su definisane, detaljno opisane i fotodokumentovane karakteristične faze razvojnih procesa, a njihova dinamika prikazana je grafički za svaki genotip. Tip dihogamije ispoljio je značajan uticaj na dinamiku razvoja generativnih pupoljaka i cvetova. Između mikrofenofaza u razvitku muških i ženskih cvetova i stadijuma u formiranju spora i gameta u njima utvrđen je visok stepen podudarnosti, što omogućava da se na osnovu morfoloških promena na cvetovima prate histološke promene u sporogenim tkivima i gametofitima cvetova. Na morfološke osobine rodnog drveta (debljinu i dužinu rodnih letorasta i plodonosnih prirasta, broj nodusa i strukturu pupoljaka na grančicama i po nodusima) značajan uticaj ispoljili su genotip i faktori spoljašnje sredine. Na indukciju muških i ženskih cvasti značajno su uticali genotip, godina, razvijenost grančice i položaj pupoljka na grančici. Prisustvo ženskih cvetova ili mladih plodova na plodonosnim mladarima u nekim slučajevima imalo je negativan uticaj na indukciju novih generativnih pupoljaka na plodonosnim prirastima...Over the period of 2010-2013, under the environmental conditions of Kraljevo, the anatomical, morphological and physiological properties of reproductive organs were studied in five walnut cultivars ('Šampion', 'Sheinovo', 'Geisenheim 139', 'Geisenheim 251' and 'Elit') and one chance seedling. A detailed description of both the anatomical and the morphological structure of staminate and pistillate flowers is provided. The morphometric analysis of catkins, anthers, pollen grains, pistillate flowers, ovules and embryo sacs showed that some morphometric parameters are not significantly affected by environmental factors and that they can be successfully used for cultivar identification. The differentiation of staminate and pistillate flowers, including the formation of male and female gametophytes, occurred in successive stages following the same sequence of events in all genotypes studied and in all years, with differences across years and genotypes primarily regarding the onset time and length of particular developmental stages. Characteristic stages in the developmental processes are defined, detailed and photodocumented, and their dynamics is graphically presented for each genotype. The type of dichogamy exhibited a significant effect on the developmental dynamics of generative buds and flowers. A high degree of correspondence was determined between the microphenological phases of staminate and pistillate flowers and the stages of spore and gamete formation, which enables the observation of histological changes in sporogenous tissues and gametophytes based on changes in flower morphology. The morphological properties of the bearing wood (thickness and length of bearing shoots and bourse shoots, number of nodes, and structure of buds on the shoots and at nodes) were significantly affected by genotype and environmental factors. The induction of staminate and pistillate inflorescences was significantly affected by genotype, year, degree of shoot development and bud position on the shoot..

The measurement of tritium in water samples with electrolytic enrichment using liquid scintillation counter

Tritium (3H) present in the environment decreased in the last decades and nowadays it has low activity concentrations. Measurement of low-level tritium activities in natural waters, e. g. in precipitation, groundwater, and river water requires special techniques for water pretreatment and detection of low-level radioactivity. In order to increase the tritium concentration to an easily measurable level, electrolytic enrichment must be applied. This paper presents the enrichment method performed by electrolysis in a battery of 18 cells, giving an enrichment factor of 5.84 (calculated from 59 electrolyses). The calculated mean values of the separation factor and enrichment parameter were 4.10 and 0.84, respectively. Results for tritium activity in precipitation and surface water collected in Belgrade during 2008 and 2009 are presented. The Radiation and Environmental Protection Department of the Vinča Institute of Nuclear Sciences, participated in the IAEA TRIC2008 international intercomparison exercise. The participation in the intercomparisons for any laboratory doing low-level 3H measurements in the waters is very important and useful. It is considered the best way to check the entire procedure and methods of the measurements and the reliability of the standard used. The analysis of the reported 3H activity results showed that all results for five intercomparison samples, for which electrolytic enrichment were applied prior to the 3H measurement, are acceptable

MCL-1 promiscuity and the structural resilience of its binding partners

MCL-1 and its natural inhibitors, the BH3-only proteins PUMA, BIM, and NOXA regulate apoptosis by interacting promiscuously within an entangled binding network. Little is known about the transient processes and dynamic conformational fluctuations that are the basis for the formation and stability of the MCL-1/BH3-only complex. In this study, we designed photoswitchable versions of MCL-1/PUMA and MCL-1/NOXA, and investigated the protein response after an ultrafast photo-perturbation with transient infrared spectroscopy. We observed partial $\alpha$-helical unfolding in all cases, albeit on strongly varying timescales (1.6~ns for PUMA, 9.7~ns for the previously studied BIM, and 85~ns for NOXA). These differences are interpreted as a BH3-only-specific "structural resilience" to defy the perturbation while remaining in MCL-1's binding pocket. Thus, the presented insights could help to better understand the differences between PUMA, BIM, and NOXA, the promiscuity of MCL-1 in general, and the role of the proteins in the apoptotic network

Proučavanje procesa domestikacije u Srbiji - domestikacija goveda u neolitu

The neolithic settlement Belovode, situated between the two important centres of prehistoric culture: Vinča and Rudna Glava has been only partly investigated. In this study, the Belovode zoological collection was examined with the aim of providing data concerning the character of domesticated and transitional animals and wild ancestral forms inhabiting the Central Balkans during neolithic times. A total of 3487 animal bone fragments have been excavated at the site, so far. It was established that the bone remnants chronologically belong to the period of about 5500 - 4800 years B.C. by radiocarbon dating. Morphological comparison showed that almost 42% of the bone remnants were of bovine origin. In order to define the character of the domesticated or wild ancestors of cattle in East Serbia at that time, the bovine collection was further examined in detail. The total of 18 horns/horn bases allowed morphological comparison and morphometric analysis. The data obtained showed that two different ancestors of domesticated cattle were exploited in Belovode: Bos primigenius and Bos brachyceros. Among the archaeological findings were zoomorphic figurines including ox sculptures the shape and details of wich also indicated cattle farming activity in neolithic Belovode.Neolitsko naselje Belovode, koje se nalazi između dva značajna preistorijska kulturna centra: Vinče i Rudne Glave je do sada samo delimično istraženo. Ispitivanje paleozoološke kolekcije dobijene dosadašnjim iskopavanjem Belovoda je sprovedeno sa ciljem da se utvrdi status domestikacije tokom neolita u Srbiji i Centralnom Balkanu i opišu odomaćeni i/ili divlji preci domaćih životinja. Do sada je na nalazištu iskopano ukupno 3487 ostataka kostiju životinja. Procenjeno je da osteološki artefakti potiču iz perioda između 5 500 i 4 800 godina pre nove ere. Morfološkom analizom je utvrđeno da 42% ostataka kostiju potiče od goveda. U cilju boljeg poznavanja neolitskih predaka goveda na staništima istočne Srbije, preduzeto je istraživanje ostataka goveda metodom morfološke komparacije. Nalaz 18 rogova i baza rogova je omogućio veoma informativnu komparaciju i morfometrijske analizu. Dobijeni rezultati ukazuju da su u Belovodu bila zastupljena dva pretka domaćih goveda: Bos primigenius i Bos brachyceros. Arheološki nalaz zoomorfnih figurina, pre svega goveda, relnih oblika i izvajanih detalja takođe ukazuju na razvijeni uzgoj goveda u naselju Belovode

Natural and artificial (90Sr) radionuclides in some carbonated mineral waters used in Serbia

A radiological characterization of 7 different carbonated mineral water samples collected in the local supermarkets in the area of Belgrade (produced in Serbia) was carried out. Analysis included determination of gross alpha and gross beta activities. The obtained results showed that the natural activity concentrations of alpha and beta emitting radionuclides in carbonated mineral water samples were within World Health Organization recommended levels, except for the Heba Strong and Kiseljak samples where the beta activity exceeds 1 Bq/L. For these two water samples gamma spectrometry analysis was performed as well as determination of 90Sr by oxalic method. The instrumentation used to count the gross alpha and gross beta activities, as well as for 90Sr, was a/b low level proportional counter Thermo Eberline FHT 770 T. Gamma spectrometric measurements were performed using a HPGe Canberra detector with a counting efficiency of 20%. The annual effective dose equivalent due to ingestion of investigated waters was calculated for age group >17, and obtained values are lower than 0.1 mSv recommended reference level. Finally, a comparison of the investigated waters with worldwide data was made. [Projekat Ministarstva nauke Republike Srbije, br. III43009