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Search Results: 1 - 10 of 1196 matches for " Popovi? Dragana "
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Glassy dynamics of electrons near the metal-insulator transition
Dragana Popovi
Physics , 2011,
Abstract: This review first describes the evidence that strongly suggests the existence of the metal-insulator transition (MIT) in a two-dimensional electron system in Si regardless of the amount of disorder. Extensive studies of the charge dynamics demonstrate that this transition is closely related to the glassy freezing of electrons as temperature T->0. Similarities to the behavior of three-dimensional materials raise the intriguing possibility that such correlated dynamics might be a universal feature of the MIT regardless of the dimensionality.
Radon indoor concentrations and activity of radionuclides in building materials in Serbia
PopoviDragana,Todorovi? Dragana
Facta Universitatis Series : Physics, Chemistry and Technology , 2006, DOI: 10.2298/fupct0601011p
Abstract: The paper presents the results of radon indoor concentrations measurements in homes and public institutions (kindergardens) in Belgrade, as well as the results of the radionuclides content determination in building materials from Serbia, during the eighties and up to the mid-nineties of the 20th century. The activity of the radionuclides was determined on an HPGe detector (ORTEC relative efficiency 20%) by standard gamma spectrometry. Radon indoor concentrations on the grab samples of air were determined by alpha scintillation technique (Lucas scintilation cell with ZnS/Ag). Mean effective dose equivevalents of radon and its progenies in closed space were estimated at 0.074 mSv for radon and 1.22 mSv for its short-lived daughters, in total 1.3 mSv.
Mesoscopic Behavior Near a Two-Dimensional Metal-Insulator Transition
Dragana Popovi,S. Washburn
Physics , 1996, DOI: 10.1103/PhysRevB.56.R10048
Abstract: We study conductance fluctuations in a two-dimensional electron gas as a function of chemical potential (or gate voltage) from the strongly insulating to the metallic regime. Power spectra of the fluctuations decay with two distinct exponents (1/v_l and 1/v_h). For conductivity $\sigma\sim 0.1 e^{2}/h$, we find a third exponent (1/v_i) in the shortest samples, and non-monotonic dependence of v_i and v_l on \sigma. We study the dependence of v_i, v_l, v_h, and the variances of corresponding fluctuations on \sigma, sample size, and temperature. The anomalies near $\sigma\simeq 0.1 e^{2}/h$ indicate that the dielectric response and screening length are critically behaved, i.e. that Coulomb correlations dominate the physics.
Consequences of the Chernobyl disaster in the region of the Republic of Serbia
PopoviDragana,Spasi?-Joki? Vesna
Vojnosanitetski Pregled , 2006, DOI: 10.2298/vsp0605481p
Abstract:
Critical Behavior of a Strongly Disordered 2D Electron System: The Cases of Long-Range and Screened Coulomb Interactions
Ping V. Lin,Dragana Popovi
Physics , 2014, DOI: 10.1103/PhysRevLett.114.166401
Abstract: A study of the temperature (T) and density (n_s) dependence of conductivity \sigma(n_s,T) of a highly disordered, two-dimensional (2D) electron system in Si demonstrates scaling behavior consistent with the existence of a metal-insulator transition (MIT). The same critical exponents are found when the Coulomb interaction is screened by the metallic gate and when it is unscreened or long range. The results strongly suggest the existence of a disorder-dominated 2D MIT, which is not directly affected by the range of the Coulomb interactions.
Multi-axis integrated Hall magnetic sensors
Popovi? Radivoje S.,Kejik Pavel,Reymond Serge,PopoviDragana R.
Nuclear Technology and Radiation Protection , 2007, DOI: 10.2298/ntrp0702020p
Abstract: 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.
Active biomonitoring of air radioactivity in urban areas
PopoviDragana,Todorovi? Dragana,Ajti? Jelena,Nikoli? Jelena
Nuclear Technology and Radiation Protection , 2009, DOI: 10.2298/ntrp0902100p
Abstract: To assess the validity of the moss bag monitoring technique in the radioactivity control of ground level urban air, a study on radionuclide contents in moss was performed in the city of Belgrade, Serbia. From May 2006 to May 2007, moss (Sphagnum girgensohni, Dubna, Russia) was exposed to the aero pollution in a location in the central area of the city. The activity of 40K, 210Pb, and 137Cs was measured on an HPGe detector (Canberra, relative efficiency 23%) by standard gamma spectrometry. The activities 245 ± 25 Bq/kg for 40K, 315 ± 34 Bq/kg for 210Pb, and 28 ± 4 Bq/kg for 137Cs are in the range of values reported for the region; the differences are due to the moss species, local climate and measuring technique. Taking into consideration the time of the exposure and appropriate calibration procedure, moss bag biomonitoring could be used as a complementary method for determination of radionuclides in urban air.
The dependence of Ge detectors efficiency on the density of the samples in gamma-ray spectrometry
Vuka?inovi? Ivana,Todorovi? Dragana,PopoviDragana R.
Nuclear Technology and Radiation Protection , 2007, DOI: 10.2298/ntrp0702058v
Abstract: 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.
EMERGENCY CONTRACEPTION
Milena Veljkovi?,Jasmina Popovi,Dragana Panti?
Acta Medica Medianae , 2007,
Abstract: Emergency contraception refers to any device or drug that is used as an emergency procedure to prevent pregnancy after unprotected sexual intercourse.The first method of emergency contraception was high dose of estrogen. Concern about side effects led to subsequent development of the so-called Yuzpe regimen which combined ethinil estradiol with levonorgestrel and levonorgestrel alone. Less convenient to use is the copper intauterine contraceptive device.It is known that in some women sexual steroids may inhibit or delay ovulation and may interfere with ovum and sperm transport and implantation. Copper intrauterine device causes a foreign-body effect on the endometrium and a direct toxic effect to sperm and blastocyst.The Yuzpe regimen reduces the risk of pregnancy after a single act of sexual intercourse by about 75% and the levonorgestrel alone by about 85%. The copper intrauterine device is an extremely effective method for selected patients.Nausea and vomiting are common among women using the Yuzpe regimen and considerably less common among women using levonorgestrel alone regimen.Emergency contraception is relatively safe with no contraindications except pregnancy. It is ineffective if a woman is pregnant. There is no need for a medical hystory or a phisical examination before providing emergency contraceptive pills. They are taken long before organogenesis starts, so they should not have a teratogenic effect.Counseling should include information about correct use of the method, possible side effects and her preferences for regular contraception.Unintended pregnancy is a great problem. Several safe, effective and inexpensive methods of emergency contraception are available including Yuzpe regimen, levonorges-trel-only regimen and copper intrauterine device.
Different Roles of a Rat Cortical Thymic Epithelial Cell Line In Vitro on Thymocytes and Thymocyte Hybridoma Cells: Phagocytosis, Induction of Apoptosis, Nursing and Growth Promoting Activities
Dragana Vu evi ,Miodrag oli ,Petar Popovi ,Sonja Ga i
Clinical and Developmental Immunology , 2002, DOI: 10.1080/1044667021000003934
Abstract: In this work, the interaction between a rat cortical thymic epithelial cell (TEC) line (R-TNC.1) with nursing activity and thymocytes as well as BWRT 8 thymocyte hybridoma (TH) cells has been studied. The R-TNC.1 cell line significantly bound thymocytes and TH. Binding was stronger during the first 30 min of cell incubation and was followed by a progressive deadhesion. Among adherent thymocytes the proportion of apoptotic cells increased with culture time which was a consequence of higher capacity of the line for binding of apoptotic than viable cells and induction of apoptosis in a subset of adherent thymocytes. Emperiopolesis activity of this thymic nurse cell (TNC) line was manifested by engulfment of thymocytes as well as TH cells. A subset of viable intra-TNC thymocytes has been triggered to die by apoptosis, whereas other internalized thymocytes have been stimulated to proliferate, as measured by an increase in the percentage of cells in mitosis and higher incorporation of bromodeoxyuridine (BrdU), in comparison to thymocytes cultivated alone. A significant stimulation of proliferation of engulfed TH cells was also observed. The R-TNC.1 cell line efficiently phagocytosed both apoptotic thymocytes and TH, and the process is followed by intra-TNC destruction of ingested cells. Cumulatively, these results suggest different role of the R-TNC.1 clone: phagocytosis of apoptotic cells; induction of apoptotic cell death in a subset of both bound and internalized thymocytes and stimulation of proliferation of a subset of intra-TNC thymocytes or TH cells.
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