A search for candidate radio supernova remnants in the nearby irregular starburst galaxies NGC 4214 and NGC 4395

We present the results of a search for new candidate radio su­pernova remnants (SNRs) in the nearby starburst irregular galaxies NGC 4214 and NGC 4395 using archived radio observations made with the Very Large Array (VLA) at the wavelengths of 3.5 cm, 6 cm and 20 cm for NGC 4214 and 6 cm and 20 cm for NGC 4395. These observations were analyzed as part of our ongoing search for candidate radio SNRs in nearby galaxies: the goal of this search is to prepare a large sample of candidate radio SNRs for the purpose of a robust statistical study of the properties of these sources. Based on our analysis, we have confirmed the nonthermal nature of the discrete radio sources α and β in NGC 4214 and classify these sources as candidate radio SNRs based on their positional coincidences with HII regions in that galaxy. We have measured the flux densities of the two candidate radio SNRs at each wavelength and calculated corresponding spectral indices: we have also measured flux densities of two other discrete radio sources in these galaxies - ρ in NGC 4214 and #3 in NGC 4395 which we suspect to be additional candidate radio SNRs based on their positional coincidences with other HII regions in these galaxies. However, the radio data presently available for these sources can­not confirm such a classification and additional observations are needed. We have also calculated the radio luminosities Lradio at the wavelength of 20 cm for these two candidate radio SNRs as well as the corresponding values for the minimum total energy Emin required to power these radio sources via synchrotron emission and the corresponding magnetic field strength Bmin. We have compared our mean calculated values for these properties with the mean values for populations of candidate radio SNRs in other starburst galaxies: while the values for Lradio and Bmin are roughly comparable to the values seen in other starburst galaxies, the mean value for Emin is higher than the mean value of any other starburst galaxy. Finally, we include these two candidate radio SNRs in a discussion of the Σ − D relation for extragalactic candidate radio SNRs and find that these sources are located on the shallower end of the master Σ − D relation for all extragalactic SNRs as derived by Urošević et al.(2005).published_or_final_versio

Prevalence of inducible clindamycin resistance among community-associated staphylococcal isolates in central Serbia

The emergence of resistance to most antimicrobial agents in staphylococci indicates the need for new effective agents in the treatment of staphylococcal infections. Clindamycin is considered to be one safe, effective and less costly agent. We analysed 482 staphylococcal isolates. Detection of inducible clindamycin resistance was performed by the D-test, while the presence of methylases genes: erm (A), erm (B) and erm (C), as well as, macrolide efflux gene mef was determined by polymerase chain reaction. Inducible clindamycin resistance phenotype was significantly higher in Staphylococcus aureus (S. aureus) strains then in coagulase-negative staphylococci (CNS). Among analysed S. aureus isolates, the predominance of the erm (C) gene, followed by the erm (A) gene were detected. These results indicate that the D-test should be routinely performed on each staphylococcal isolates

Mixed RF-VLC Relaying System with Radio-Access Diversity

We present a statistical analysis of a mixed radio-frequency (RF)-visible light communications (VLC) relaying system, where outdoor millimeter wave based RF links are utilized to provide backhaul connectivity for indoor VLC broadcasting. The multiple RF links are assumed to communicate with the VLC access point through decode-and-forward relay. Novel closed-form outage probability and average bit error rate expressions are derived and utilized to obtain numerical results. Monte Carlo simulations validate presented numerical results, which are further used to examine the effects of system and channel parameters on system performance.Comment: Presented at 2019 28th Wireless and Optical Communications Conference (WOCC

Uticaj parametara mlevenja na odnos amorfne i kristalne faze u jedinjenju Bi4Ti3O12

Poster presented at the XLVI Savetovanje srpskog hemijskog društva, Beograd, 29. mart (21. februar) 200

Dust Emission from Herbig Ae/Be stars - Evidence for Disks and Envelopes

IR and mm-wave emission from Herbig Ae/Be stars has produced conflicting conclusions regarding the dust geometry in these objects. We show that the compact dimensions of the mm-wave emitting regions are a decisive indication for disks. But a disk cannot explain the spectral energy distribution (SED) unless it is embedded in an extended envelope that (1) dominates the IR emission and (2) provides additional disk heating on top of the direct stellar radiation. Detailed radiative transfer calculations based on the simplest model for envelope-embedded disks successfully fit the data from UV to mm wavelengths and show that the disks have central holes. This model also resolves naturally some puzzling results of IR imaging.Comment: 9 pages, 2 figures. accepted to ApJ

Ispitivanje pasivnog imuniteta kod prasadi poreklom od krmača vakcinisanih Kina sojem virusa klasične kuge svinja

An experimental study was conducted to investigate the course of classical swine fever (CSF) infection in piglets originating from sows vaccinated with China strain vaccine. The experiment was carried out on 24 piglets (age 28, 35, 44 and 54 days) from vaccinated sows and on 11 non vaccinated piglets, originated from non CSF vaccinated sows. Two piglets from the each age group originating from vaccinated sows were challenged by intramuscular injection with CSF virus. Four piglets of the same age from vaccinated sows, and two piglets derived from unvaccinated sows were added to the challenged group to determine contact (horizontal) infection. After challenge, clinical examination and blood sampling from every animal was carried out on day 0, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29. Blood samples were examined for CSF virus specific antibodies by ELISA test, and for viral antigen i. e. viral RNA by RT-PCR technique. After death or sacrifice pathomorphological changes, presence and distribution of CSF virus antigen were detected in piglet tissue samples by ELISA test. On the basis of the obtained results it can be concluded that not all piglets born to vaccinated sows have maternal antibodies at a detectable level, and the issue of the efficiency of passive immunization needs to be evaluated in the future.Ova istraživanja su izvršena u cilju praćenja toka oboljenja nakon infekcije prasadi virusom klasične kuge svinja (KKS) poreklom od krmača vakcinisanih Kina sojem virusa KKS. Ogled je obavljen na 24 praseta (uzrasta 28, 35, 44 i 54 dana) poreklom od vakcinisanih krmača i na 11 nevakcinisane prasadi poreklom od nevakcinisanih krmača. Po dva praseta iz svake starosne grupe, poreklom od vakcinisanih krmača, su veštački inficirana intramuskularnom aplikacijom virusa KKS. U cilju ustanovljavanja kontaktne (horizontalne) infekcije, direktno inficiranim jedinkama su dodata po četiri praseta istog uzrasta poreklom od vakcinisanih krmača i dva praseta poreklom od nevakcinisanih krmača. Nakon veštačke infekcije, vršen je klinički pregled i uzorkovanje krvi od svake životinje 0, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 i 29 dana ogleda. Uzorci krvi su ispitivani ELISA testom na prisustvo specifičnih antitela protiv virusa KKS, na prisutvo antigena virusa KKS odnosno virusne RNA metodom RT-PCR. Nakon uginuća ili žrtvovanja, vršen je patomorfološki pregled i utvrđivanje prisustva i distribucije antigena virusa u uzorcima tkiva ELISA testom. Na osnovu postignutih rezultata istraživanja može se zaključiti da pojedina prasad, poreklom od vakcinisanih krmača, nemaju detektabilna specifična antitela što nameće razmatranje pitanja efikasnosti pasivne imunizacije

Improvement possibilities of the I-V characteristics of PIN photodiodes damaged by gamma irradiation

This paper presents the behavior of PIN photodiodes after combined gamma and neutron irradiation. Different types of PIN photodiodes have been exposed first to gamma and then to neutron irradiation. I-V characteristics (current dependence on voltage) of photodiodes have been measured after each of these irradiations. It has been noted that the photocurrent level after the neutron irradiation is higher than before it, which is not consistent with the current theories about the effects of neutron radiation on semiconductors. In order to explain this behavior of the photodiodes, the Monte Carlo simulation of photon transport through the material has been used. It is proposed that a possible cause for current enhancement are defects in semiconductor created by gamma irradiation and effects of neutron irradiation on these defects. The results can be explained by an intercentre transfer of charge between defects in close proximity to each other. The aim of this paper is to investigate the improvement possibilities of the I-V characteristics of PIN photodiodes, and photodetectors in general, damaged by gamma irradiation. [Projekat Ministarstva nauke Republike Srbije, br. 171007

Implementation of GIS technologies in assessment and protection of natural values of Tara National Park

Mount Tara is among the most important centers of Balkan and European ecosystem and species biodiversity. It is characterized by diversified and well-maintained communities of old deciduous and mixed coniferous forests (beech/fir/spruce). They represent a unique example of well preserved forests in SE Europe with numerous endemic and relict species of indigenous flora and fauna. The geographical information system (GIS) that we have created has proved an excellent tool for valorization and protection of all natural values and potentials of Tara National Park.Geografski informacioni sistem je: organizovan skup računarskog hardvera softvera, geografskih podataka i kadra, dizajniran da efikasno prikuplja smešta, nadgrađuje, manipuliše, analizira i prikazuje sve forme geografski referencirane informacije. Za ekologe GIS je otvorio nove mogućnosti za istraživanja i aplikaciju sakupljenih informacija. Zbog same kompleksnosti sistema životne sredine mi najčešće nastojimo da ih proučavamo koristeći redukcionistički pristup, fokusirajući ce na male, diskretne pojednostavljene aspekte. Međutim većina problema u životnoj sredini su više faktorijalni i zahtevaju razmatranje širokog spektra izvora informacija pitanja i interesa. Za većinu ekoloških studija potrebne su nam eksplicitnije i kvalifikovanije terenske informacije vezane za faktore koji bi mogli da objasne posmatranu ekosistemsku, faunističku i florističku raznovrsnost u dimenziji prostorne i vremenske distribucije uključujući i podatke o geologiji, klimi, pedologiji, distribuciji i ponašanju istrživanih vrsta. Ovde svoju ulogu pronalaze geografski informacioni sistemi (GIS). Nacionalni park Tara obuhvata najveći deo planine Tare u zapadnoj Srbiji prosečne nadmorske visine 1000-1200 m na 180 km od Beograda. Ukupna površina zaštićenog područja Nacionalnog parka je 19.175 ha, a 37.584 ha predstavlja zaštitnu zonu oko Nacionalnog parka. Pripada opštini Bajina Bašta. Planina Tara predstavlja jednu od vrućih tačaka specijskog i ekosistemskog diverziteta sa 35 različitih šumskih zajednica lišćarskog, mešovito četinarskog tipa, kao i 19 opisanih livadskih zajednica. Mnoge od njih posebno one sa Pančićevom omorikom, imaju reliktan ili endemoreliktan karakter. U tom smislu sasvim je opravdano što se Tara danas našla na listi područja značajnih za očuvanje ptičijeg sveta (IBA) i dnevnih leptira Evrope (PBA), a u toku je njeno uključivanje u međunarodnu listu područja značajnog za očuvanje svetske flore (IPA). Kako se gazdovanje i upravljanje praktično svim prirodnim potencijalima NP Tara, do sada dominantno zasnivalo na principima šumarske tehnologije i inženjeringa ovaj rad ima svoju punu naučnu opravdanost u pokušaju implementacije savremenih naučnih saznanja iz oblasti zaštite biodiverziteta, konzervacione ekologije geografije i prostornog planiranja u mehanizam upravljanja prirodnim nacionalnim resursima. Ovaj tip vrednovanja i zaštite otvara mogućnost primene održivog/usklađenog korišćenja resursa NP Tara. Tokom 2002. i 2003. godine formirane su teme GIS NP Tara koje obuhvataju prirodne (geomorfologija, geologija, pedologija, hidrologija, vegetacija, flora fauna), korišćene (eksploatacija šuma) i veštačke (antropogene) sadržaje (puteve, brane, naselja, turističke sadržaje i granice). Geografski informacioni sistem koji je formiran za NP Taru sa temama koje ga čine da prati okvire sličnih projekata rađenih u Evropi i svetu i jedan je od tipičnih geografskih informacionih sistema (iz oblasti ekologije, zaštite životne sredine, šumarstva, itd), koji sadrži gotovo sve vrste podataka (izuzev satelitskih snimaka) u GIS (rasterske, vektorske, DEM, baza podataka i aerofotogrametrijske snimke).Projekat ministarstv