Revealing the nature of central emission nebulae in the dwarf galaxy NGC 185

In this paper we present new optical observations of the galaxy NGC 185 intended to reveal the status of supernova remnants (SNRs) in this dwarf companion of the Andromeda galaxy. Previously, it was reported that this galaxy hosts one SNR. Our deep photometric study with the 2m telescope at Rozhen National Astronomical Observatory using narrow-band H$\alpha$ and [SII] filters revealed complex structure of the interstellar medium in the center of the galaxy. To confirm the classification and to study the kinematics of the detected nebulae, we carried out spectroscopic observations using the SCORPIO multi-mode spectrograph at the 6m telescope at the Special Astrophysical Observatory of the Russian Academy of Science, both in low- and high-resolution modes. We also searched the archival X-ray and radio data for counterparts of the candidate SNRs identified by our optical observations. Our observations imply the presence of one more SNR, one possible HII region previously cataloged as part of an SNR, and the presence of an additional source of shock ionization in one low-brightness PN. We detected enhanced [SII]/H_alpha and [NII]/H_alpha line ratios, as well as relatively high (up to 90 km s$^{-1}$) expansion velocities of the two observed nebulae, motivating their classification as SNRs (with diameters of 45 pc and 50 pc), confirmed by both photometric and spectral observations. The estimated electron density of emission nebulae is 30 - 200 cm$^{-3}$. Archival XMM-Newton observations indicate the presence of an extended, low-brightness, soft source in projection of one of the optical SNRs, whereas the archival VLA radio image shows weak, unresolved emission in the center of NGC 185.Comment: 15 pages, 14 figures, accepted for publication in A&

Beitrag zur interpretation und analyse von Kieferdeformitaten

U ovom radu autori nadograđuju svojevremeno objavljene podatke novim i originalnim spoznajama. Uvode dijagramski prikaz u interpretaciju i analizu deformacija čeljusti i na taj način daju svoj doprinos gnatološkim istraživanjima.In this paper the authors add to their formerly published information some new and original notions. They introduce the graphic presentation in the interpretation and analysis of the deformations of the jaws, giving thus a contribution to the gnathologic research.Die Autoren ergänzen die seinerzeit veröffentlichte Information mit neuen und originellen Erkentnissen. Die Deformitäten werden an Diagrammen dargestellt und damit ein neuer Beitrag zu gnathologischen Untersuchungen geliefert

Optical observations of NGC 1156 galaxy in narrowband [SII] and Hα filters

A

Kako učenici srednjih škola u Srbiji doživljavaju učenje na daljinu

Učenje na daljinu podrazumeva svaki kurikulum koji je predstavljen učenicima/ studentima bez neposrednog kontakta sa predavačem, usled prostorne i/ili vremenske distance (Sagheb-Tehrani, 2009:3). Na svom osnovnom nivou, učenje na daljinu se odvija kada su predavač (nastavnik, profesor) i učenici fizički odvojeni velikim rastojanjem i kada se za premošćavanje ovog jaza koristi digitalna tehnologija sa ciljem da se simulira komunikacija licem u lice (Ristić & Mandić, 2018). Nakon 19. veka modernizacija obrazovanja je započela ubrzano da se širi što se može povezati sa promenama koje su se dešavale u društvu (Maksimović & Osmanović, 2018: 92). Razvojem tehnologija medija i komunikacija menjala se i koncepcija učenja na daljinu, koja u savremenim okvirima podrazumeva učenje uz korišćenje računara i pametnih uređaja, Interneta i raznovrsnih digitalnih platformi i kanala koji omogućavaju razmenu nastavnih sadržaja i interaktivnu komunikaciju između predavača i učenika i učenika međusobno, kreiranjem on-line zajednice za učenje (Sun & Chen, 2016:158). Pregled relevantne literature ukazuje da su razvoj i veća primena modela učenja na daljinu doneli i veći broj termina koji definišu ovaj model učenja, pa se u literaturi nailazi na termine kao što su: on-line nastava, učenje na daljinu, daljinsko obrazovanje itd. I pored ekspanzije tehnologije, menjanja društva i politika obrazovanja često možemo čuti nedoumice po pitanju primene modela učenja na daljinu, kako od strane profesora, tako i od strane učenika/ studenata. Savremena istraživanja koja upoređuju učenje na daljinu i tradicionalno školovanje pokazuju da nastava i učenje na daljinu mogu biti jednako uspešni kao tradicionalna nastava ukoliko se koriste odgovarajući nastavni metodi i tehnologije, ukoliko postoji interakcija između učenika i ukoliko postoji blagovremena povratna veza između nastavnika i učenika (Ristić & Mandić 2018, prema Moore & Thompson, 1990; Verduin & Clark, 1991).XXVI Nаučnа konferencijа „Pedаgoškа istrаživаnjа i školskа prаksа

Nature of the diffuse emission sources in the H I supershell in the galaxy IC 1613

We present a study of the nearby low-metallicity dwarf galaxy IC 1613, focusing on the search for massive stars and related feedback processes, as well as for faint supernova remnants (SNR) in late stages of evolution. We obtained the deepest images of IC 1613 in the narrow-band H{\alpha}, He II and [S II] emission lines and new long-slit spectroscopy observations using several facilities (6-m BTA, 2.5m SAI MSU, and 150RTT telescopes), in combination with the multi-wavelength archival data from MUSE/VLT, VLA, XMM-Newton, and Swift/XRT. Our deep narrow-band photometry identifies several faint shells in the galaxy, and we further investigate their physical characteristics with the new long-slit spectroscopy observations and the archival multi-wavelength data. Based on energy balance calculations and assumptions about their possible nature, we propose that one of the shells is a possible remnant of a supernova explosion. We study five out of eight Wolf-Rayet (WR) star candidates previously published for this galaxy using the He ii emission line mapping, MUSE/VLT archival spectra, and new long-slit spectra. Our analysis discards the considered WR candidates and finds no new ones. We found P Cyg profiles in H{\alpha} line in two stars, which we classify as Luminous Blue Variable (LBV) star candidates. Overall, the galaxy IC 1613 may have a lower rate of WR star formation than previously suggested

Comparison of Microbially Induced Healing Solutions for Crack Repairs of Cement-Based Infrastructure

Reinforced concrete crack repair and maintenance costs are around 84% to 125% higher than construction costs, which emphasises the need to increase the infrastructure service life. Prolongation of the designed service life of concrete structures can have significant economic and ecological benefits by minimising the maintenance actions and related increase of carbon and energy expenditure, making it more sustainable. Different mechanisms such as diffusion, permeation and capillary action are responsible for the transport of fluids inside the concrete, which can impact on the structure service life. This paper presents data on microbially induced repair and self-healing solutions for cementitious materials available in the contemporary literature and compares results of compressive strength test and capillary water absorption test, which are relevant to their sealing and mechanical characteristics. The results of the repair and self-healing solutions (relative to unassisted recovery processes) were “normalized.” Externally applied bacteria-based solutions can improve the compressive strength of cementitious materials from 13% to 27%. The internal solution based solely on bacterial suspension had 19% improvement efficacy. Results also show that “hybrid” solutions, based on both bio-based and non-bio-based components, whether externally or internally applied, have the potential for best repair results, synergistically combining their benefits

Galactic and Extragalactic Samples of Supernova Remnants: How They Are Identified and What They Tell Us

Supernova remnants (SNRs) arise from the interaction between the ejecta of a supernova (SN) explosion and the surrounding circumstellar and interstellar medium. Some SNRs, mostly nearby SNRs, can be studied in great detail. However, to understand SNRs as a whole, large samples of SNRs must be assembled and studied. Here, we describe the radio, optical, and X-ray techniques which have been used to identify and characterize almost 300 Galactic SNRs and more than 1200 extragalactic SNRs. We then discuss which types of SNRs are being found and which are not. We examine the degree to which the luminosity functions, surface-brightness distributions and multi-wavelength comparisons of the samples can be interpreted to determine the class properties of SNRs and describe efforts to establish the type of SN explosion associated with a SNR. We conclude that in order to better understand the class properties of SNRs, it is more important to study (and obtain additional data on) the SNRs in galaxies with extant samples at multiple wavelength bands than it is to obtain samples of SNRs in other galaxiesComment: Final 2016 draft of a chapter in "Handbook of Supernovae" edited by Athem W. Alsabti and Paul Murdin. Final version available at https://doi.org/10.1007/978-3-319-20794-0_90-