How peculiar is the ‘peculiar variable’ DZ Crucis (Nova Cru 2003)?

The variable star DZ Cru was thought to be a nova when it was discovered in eruption in 2003 August. This explanation was later challenged, however, when the first spectra of the object were reported. We present near-infrared spectroscopy of DZ Cru obtained at the New Technology Telescope on three occasions, starting ∼1.5 yr after outburst, with the aim of establishing the nature of the object. The spectra display H i, O i, [N i] emission lines, together with He i P Cygni lines superposed on a dust continuum. These observations suggest the ‘peculiar variable in Crux’ is a classical nova

A near-infrared survey of Miras and the distance to the Galactic Centre

We report the results of a near-infrared survey for long-period variables in a field of view of 20 arcmin by 30 arcmin towards the Galactic Centre (GC). We have detected 1364 variables, of which 348 are identified with those reported in Glass et al. (2001). We present a catalogue and photometric measurements for the detected variables and discuss their nature. We also establish a method for the simultaneous estimation of distances and extinctions using the period-luminosity relations for the JHKs bands. Our method is applicable to Miras with periods in the range 100--350 d and mean magnitudes available in two or more filter bands. While J-band means are often unavailable for our objects because of the large extinction, we estimated distances and extinctions for 143 Miras whose H- and Ks-band mean magnitudes are obtained. We find that most are located at the same distance to within our accuracy. Assuming that the barycentre of these Miras corresponds to the GC, we estimate its distance modulus to be 14.58+-0.02(stat.)+-0.11(syst.) mag, corresponding to 8.24+-0.08(stat.)+-0.42(syst.) kpc. We have assumed the distance modulus to the LMC to be 18.45 mag, and the uncertainty in this quantity is included in the systematic error above. We also discuss the large and highly variable extinction. Its value ranges from 1.5 mag to larger than 4 mag in A(Ks) except towards the thicker dark nebulae and it varies in a complicated way with the line of sight. We have identified mid-infrared counterparts in the Spitzer/IRAC catalogue of Ramirez et al. (2008) for most of our variables and find that they follow rather narrow period-luminosity relations in the 3.6 to 8.0 micrometre wavelength range.Comment: Accepted for publication in MNRAS, 22 pages (28 tables, 11 figures). Figure 7 and tables 6, 7 and 9 will be published in full online onl

The Large Magellanic Cloud and the Distance Scale

The Magellanic Clouds, especially the Large Magellanic Cloud, are places where multiple distance indicators can be compared with each other in a straight-forward manner at considerable precision. We here review the distances derived from Cepheids, Red Variables, RR Lyraes, Red Clump Stars and Eclipsing Binaries, and show that the results from these distance indicators generally agree to within their errors, and the distance modulus to the Large Magellanic Cloud appears to be defined to 3% with a mean value of 18.48 mag, corresponding to 49.7 Kpc. The utility of the Magellanic Clouds in constructing and testing the distance scale will remain as we move into the era of Gaia.Comment: 23 pages, accepted for publication in Astrophysics and Space Science. From a presentation at the conference The Fundamental Cosmic Distance Scale: State of the Art and the Gaia Perspective, Naples, May 201

Investigation of Adhesion and Tribological Behavior of Borided AISI 310 Stainless Steel

In the present study, the effects of the boriding process on adhesion and tribological properties of AISI 310 steel were investigated. Boriding was performed in a solid medium consisting of Ekabor-II powders at 1123 and 1323K for 2 and 6 h. The boride layer was characterized by optical microscopy, the X-ray diffraction technique and the micro-Vickers hardness tester. The X-ray diffraction analysis of the boride layers on the surface of the steels revealed the existence of FexBy, CrxBy and NixBy compounds. Depending on the chemical composition of substrates, the boride layer thickness on the surface of the AISI 310 steel was found to be 56.74 μm. The hardness of the boride compounds formed on the surface of the AISI 310 steel ranged from 1658 to 2284 HV0,1, whereas the Vickers hardness value of the untreated steel AISI 310 was 276 HV0,1. The wear tests were carried out in a ball-disc arrangement under a dry friction condition at room temperature with an applied load of 10N and with a sliding speed of 0.3 m/s, at a sliding distance of 1000m. The wear surfaces of the steel were analyzed using an SEM microscopy and X-ray energy dispersive spectroscopy EDS. It was observed that the wear rate of unborided and borided AISI 310 steel ranged from 4.57 to 71.42 mm3/Nm

Cytogenetic and molecular responses of ammonium sulphate application for tolerance to extreme temperatures in Vicia faba L.

Effects of ammonium sulphate [(NH4)(2)SO4] on mitosis, cell cycle and chromosomes in Vicia faba L. seeds exposed to extreme temperatures were investigated using flowcytometric and cytogenetic analysis. Seeds germinated at high and low temperatures showed a significant decrease in mitotic index as compared to those of optimum temperature conditions. Application of 50 and 1000 mu M (NH4)(2)SO4 were successful in alleviating the negative effects of low and high temperature on mitotic activity, respectively. 50 mu M (NH4)(2)SO4 showed the most positive effect on cell cycle at the extreme temperatures. This concentration increased the cell division removing or decreasing the negative effects of temperature stress. Namely, the highest G2/M and S phase percentages under stress conditions were obtained with application of 50 mu M (NH4)(2)SO4. Chromosomal aberrations were not observed in cells of seeds germinated in distilled water and also at any temperatures. However, the frequency of chromosomal aberrations increased significantly by increasing (NH4)(2)SO4 concentration. The highest aberration frequency in all temperature degree tested was found at 1000 mu M (NH4)(2)SO4 concentration.Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP)Suleyman Demirel University [1636-YL-08]The authors thank the Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP) for the financial support of the project SDUBAP (1636-YL-08). Thanks also to Dr. Gulderen Yanikkaya DEMIREL and Mehtap OZDEMIR (Istanbul Centro Laboratory Flowcytometry Department, Istanbul, Turkey) for its help in flow cytometric study

Cytogenetic and molecular responses of ammonium sulphate application for tolerance to extreme temperatures in Vicia faba L.

Effects of ammonium sulphate [(NH4)(2)SO4] on mitosis, cell cycle and chromosomes in Vicia faba L. seeds exposed to extreme temperatures were investigated using flowcytometric and cytogenetic analysis. Seeds germinated at high and low temperatures showed a significant decrease in mitotic index as compared to those of optimum temperature conditions. Application of 50 and 1000 mu M (NH4)(2)SO4 were successful in alleviating the negative effects of low and high temperature on mitotic activity, respectively. 50 mu M (NH4)(2)SO4 showed the most positive effect on cell cycle at the extreme temperatures. This concentration increased the cell division removing or decreasing the negative effects of temperature stress. Namely, the highest G2/M and S phase percentages under stress conditions were obtained with application of 50 mu M (NH4)(2)SO4. Chromosomal aberrations were not observed in cells of seeds germinated in distilled water and also at any temperatures. However, the frequency of chromosomal aberrations increased significantly by increasing (NH4)(2)SO4 concentration. The highest aberration frequency in all temperature degree tested was found at 1000 mu M (NH4)(2)SO4 concentration.Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP)Suleyman Demirel University [1636-YL-08]The authors thank the Department of Scientific Research Project Management of Suleyman Demirel University (SDUBAP) for the financial support of the project SDUBAP (1636-YL-08). Thanks also to Dr. Gulderen Yanikkaya DEMIREL and Mehtap OZDEMIR (Istanbul Centro Laboratory Flowcytometry Department, Istanbul, Turkey) for its help in flow cytometric study