The Vinča Institute of Nuclear science is a nuclear physics research institution near Belgrade, Serbia. Since its founding, the institute has also conducted research in the fields in physics, chemistry and biology. The scholarly institute is part of the University of Belgrade. Wikipedia.
Suljovrujic E.,Vinca Institute of Nuclear Sciences
Radiation Physics and Chemistry | Year: 2010
The post-irradiation dielectric behaviour of different polyethylenes (PEs) has been studied by means of dielectric loss (tanδ) analysis over the wide temperature (25-325. K) and frequency (1. kHz-1. MHz) ranges. For this reason, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) samples were previously gamma irradiated in air to absorbed dose of 300. kGy. The irradiated samples were divided into two groups, and for the first one annealing treatment which can substantially reduce the concentration of free radicals were employed. For the second group, e.g. samples stored in air at room temperature after irradiation, post-irradiation evolution in free radical concentration, dielectric relaxation spectra and carbonyl content was investigated as a function of storage time, up to 90 days. Dielectric relaxation behaviour is related to differences in the initial structures of PEs (such as branching, crystallinity, etc.) and to the radiation-induced effects; carbonyl groups that were introduced by irradiation and/or delayed (post-irradiation) oxidation were regarded as tracer groups. Electron spin resonance (ESR), differential scanning calorimetry (DSC), infrared (IR) spectroscopy and gel measurements were used to determine the changes in free radical concentration, crystal fraction, oxidation and degree of network formation, respectively. © 2010 Elsevier Ltd.
Suljovrujic E.,Vinca Institute of Nuclear Sciences
Radiation Physics and Chemistry | Year: 2013
If a large amount of polymer free radicals remain trapped after irradiation of polymers, the post-irradiation effects may result in a significant alteration of physical properties during long-term shelf storage and use. In the case of polyethylenes (PEs) some failures are attributed to the post-irradiation oxidative degradation initiated by the reaction of residual free radicals (mainly trapped in crystal phase) with oxygen. Oxidation products such as carbonyl groups act as deep traps and introduce changes in carrier mobility and significant deterioration in the PEs electrical insulating properties. The post-irradiation behaviour of three different PEs, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) was studied; previously, the post-irradiation behaviour of the PEs was investigated after the irradiation in air (Suljovrujic, 2010). In this paper, in order to investigate the influence of different irradiation media on the post-irradiation behaviour, the samples were irradiated in air and nitrogen gas, to an absorbed dose of 300. kGy. The annealing treatment of irradiated PEs, which can substantially reduce the concentration of free radicals, is used in this study, too. Dielectric relaxation behaviour is related to the difference in the initial structure of PEs (such as branching, crystallinity etc.), to the changes induced by irradiation in different media and to the post-irradiation changes induced by storage of the samples in air. Electron spin resonance (ESR), differential scanning calorimetry (DSC), infra-red (IR) spectroscopy and gel measurements were used to determine the changes in the free radical concentration, crystal fraction, oxidation and degree of network formation, respectively. © 2013 Elsevier Ltd.
Plecas I.B.,Vinca Institute of Nuclear Sciences
Progress in Nuclear Energy | Year: 2010
Transport phenomena involved in the leaching of a radioactive material from a cement composite matrix are investigated using an empirical method employing a polynomial equation. To assess the safety for disposal of radioactive waste-cement composition, the leaching of 137Cs and 60Co, from a waste composite into a surrounding fluid has been studied. Leaching tests were carried out in accordance with a method recommended by IAEA. Determination of retardation factors, KF and coefficients of distribution, kd, using a simplified mathematical model for analyzing the migration of radionuclides, have been developed. Transport phenomena involved in the leaching of a radioactive material from a cement composite matrix are investigated using an empirical method employing a polynomial equation. In our experiment we have analized mechanism of 137Cs and 60Co leaching values during a period of 60 days. Results presented in this paper are examples of results obtained in a 25-year mortar and concrete testing project, which will influence the design of the engineered trenches system for a future central Serbian radioactive waste storage center. © 2010 Elsevier Ltd. All rights reserved.
Maric N.P.,University of Belgrade |
Adzic M.,Vinca Institute of Nuclear Sciences
Psychiatria Danubina | Year: 2013
One of the most consistent biological findings in major depression (MDD) is the altered activity of the hypothalamic-pituitaryadrenal (HPA) axis. It is not surprising that glucocorticoid receptor (GR), the common mechanism for stress-related changes in brain function, is a potential target of antidepressant drugs and therapies. All effective antidepressant treatments should trigger and maintain GR-related cellular processes necessary for recovery from MDD. Classic antidepressants act indirectly, by affecting the dynamic interplay between serotonin neurotransmission and HPA. On the other hand, certain compounds acting at suprahypothalamic, HPA axis, glucocorticoid receptors, and post-receptor levels are being considered as new therapeutic options with the potential to modulate the aforementioned system in affective disorders directly. Different classes of drugs pharmacologically modify the HPA axis. This article summarizes the efficacy of classic antidepressants, as well as drugs classified as "antiglucocorticoids" (GR agonists, GR antagonists, dehydroepiandrosterone- DHEA, steroid synthesis inhibitors drugs, etc) in their capacity to heal glucocorticoid-mediated damage in depression. New avenues investigating the potential therapeutic benefits of antiglucocorticoids in affective disorders are at the proof-of-concept stage and future developments in this area deserve the full attention of psychiatrists and neuroscientists, as the current pharmacological treatment of MDD is far from perfect. © Medicinska naklada-Zagreb, Croatia.
Cvijovic D.,Vinca Institute of Nuclear Sciences
Physica A: Statistical Mechanics and its Applications | Year: 2010
Lee, in a series of papers, described a unified formulation of the statistical thermodynamics of ideal quantum gases in terms of the polylogarithm functions, Lis (z). It is aimed here to investigate the functions Lis (z), for s = 0, - 1, - 2, ..., which are, following Lee, referred to as the polypseudologarithms (or polypseudologs) of order n ≡ - s. Various known results regarding polypseudologs, mainly obtained in widely differing contexts and currently scattered throughout the literature, have been brought together along with many new results and insights and they all have been proved in a simple and unified manner. In addition, a new general explicit closed-form formula for these functions involving the Carlitz-Scoville higher tangent numbers has been established. © 2009 Elsevier B.V. All rights reserved.