Luminosity-Colours relations for thin disc main-sequence stars

In this study we present the absolute magnitude calibrations of thin disc main-sequence stars in the optical ($M_{V}$), and in the near-infrared ($M_{J}$). Thin disc stars are identified by means of Padova isochrones, and absolute magnitudes for the sample are evaluated via the newly reduced Hipparcos data. The obtained calibrations cover a large range of spectral types: from A0 to M4 in the optical and from A0 to M0 in the near-infrared. Also, we discuss the of effects binary stars and evolved stars on the absolute magnitude calibrations. The usage of these calibrations can be extended to the estimation of galactic model parameters for the thin disc individually, in order to compare these parameters with the corresponding ones estimated by $\chi{^2}_{min}$ statistics (which provides galactic model parameters for thin and thick discs, and halo simultaneously) to test any degeneracy between them. The calibrations can also be used in other astrophysical researches where distance plays an important role in that study.Comment: 8 pages, including 12 figures and 4 tables, accepted for publication in MNRA

The metallicity distributions in high-latitudes with SDSS

We present metallicities and their variations with different parameters for 36 high-latitude fields covering Galactic longitudes 0<l<360. The metallicities for relatively short vertical distances (z<2.5 kpc) show systematic fluctuations with Galactic longitude, similar to those of the thick-disc scaleheight, which may be interpreted as indicating a common origin, viz., the flare effect of the disc. This suggestion is supported by the metallicity variations which we find as functions of radial distance. The metallicity variation at larger vertical distances (6.5<z<9.5 kpc) is small but monotonic. Three different vertical metallicity gradients could be detected: d[M/H]/dz=-0.22(+/-0.03), d[M/H]/dz=-0.38 (+/-0.06), and d[M/H]/dz=-0.08 (+/-0.07) dex/kpc for the intervals z<3, 3<z<5, and 5<z<10 kpc, respectively. Since our data cover the whole Galactic longitude interval, the resulting metallicity gradients can be interpreted as properties of the larger-scale Galaxy. The first gradient confirms the dissipational formation of the disc at short z-distances. The steeper gradient corresponds to the transition region between different population components of the Galaxy, and finally, the lowest value provides an adequate description of the inner-halo metallicity gradient.Comment: 14 pages, 7 figures and 2 tables, accepted for publication in New Astronom

Anodized Nanoporous Titania Thin Films for Dental Application: Structure’ Effect on Corrosion Behavior

Nanostructured Titania layers formed on the surface of titanium and titanium alloys by anodic oxidation play an important role in the enhancement of their biocompatibility and osseointegration in the human body. For this purpose, we aimed to study in the current work the structural and electrochemical properties of amorphous and crystallized nanostructured TiO2 thin films elaborated on Ti6Al4V substrate by electrochemical anodization in fluoride ions (F–) containing electrolyte at 10 V during 15 min and heat treated in air at 550 °C for 2 h. The morphology, chemical composition and phase composition of synthesized layers were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The corrosion resistance improvement of both as-anodized and annealed titania layers was evaluated in 0.9 wt. % NaCl solution with pH = 6.4 at room temperature by means of open circuit potential (Eoc),potentiodynamic polarization (PDYN) and electrochemical impedance spectroscopy (EIS)

SDSS Absolute Magnitudes for Thin Disc Stars based on Trigonometric Parallaxes

We present a new luminosity-colour relation based on trigonometric parallaxes for thin disc main-sequence stars in SDSS photometry. We matched stars from the newly reduced Hipparcos catalogue with the ones taken from 2MASS All-Sky Catalogue of Point Sources, and applied a series of constraints, i.e. relative parallax errors ($\sigma_{\pi}/\pi\leq0.05$), metallicity ($-0.30\leq[M/H]\leq0.20$ dex), age ($0\leq t \leq 10$ Gyr) and surface gravity ($\log g>4$), and obtained a sample of thin disc main-sequence stars. Then, we used our previous transformation equations (Bilir et al. 2008a) between SDSS and 2MASS photometries and calibrated the $M_{g}$ absolute magnitudes to the $(g-r)_{0}$ and $(r-i)_0$ colours. The transformation formulae between 2MASS and SDSS photometries along with the absolute magnitude calibration provide space densities for bright stars which saturate the SDSS magnitudes.Comment: 7 pages, including 7 figures and 2 tables, accepted for publication in MNRA

Transformations between WISE, 2MASS, SDSS and BVRI photometric systems: I. Transformation equations for dwarfs

We present colour transformations for the conversion of the W1 and W2 magnitudes of WISE photometric system to the Johnson-Cousins' BVRI, SDSS (gri), and 2MASS (JHK_s) photometric systems, for dwarfs. The W3 and W4 magnitudes were not considered due to their insufficient signal to noise ratio (S/N). The coordinates of 825 dwarfs along with their BVRI, gri, and JHK_s data, taken from Bilir et al. (2008) were matched with the coordinates of stars in the preliminary data release of WISE (Wright et al., 2010) and a homogeneous dwarf sample with high S/N ratio have been obtained using the following constraints: 1) the data were dereddened, 2) giants were identified and excluded from the sample, 3) sample stars were selected according to data quality, 4) transformations were derived for sub samples of different metallicity range, and 5) transformations are two colour dependent. These colour transformations, coupled with known absolute magnitudes at shorter wavelenghts, can be used in space density evaluation for the Galactic (thin and thick) discs, at distances larger than the ones evaluated with JHK_s photometry.Comment: 16 pages, including 5 figures and 7 tables, accepted for publication in MNRA

Microwave-Assisted Synthesis of Some 1H-1,2,4-Triazol-3-one Derivatives

4-Amino-5-(methyl/ethyl)-2,4-dihydro-3H-1,2,4-triazol-3-one were synthesized from the reaction of (methyl/ethyl)-ester ethoxycarbonyl hydrazone with hydrazine hydrate and then, converted to corresponding Schiff bases using 9H-fluorene- 3-carbaldehyde. Ester, hydrazide and oxadiazole derivatives were synthesized starting from Schiff bases in three steps. All reactions occurred under conventional conditions and microwave irradiation. The obtained results were compared.KEYWORDS Triazole, oxadiazole, hydrazine hydrate, microwave irradiation

A Universal Vertical Stellar Density Distribution Law for the Galaxy

We reduced the observational logarithmic space densities in the vertical direction up to 8 kpc from the galactic plane, for stars with absolute magnitudes (5,6], (6,7] and [5,10] in the fields #0952+5245 and SA114, to a single exponential density law. One of three parameters in the quadratic expression of the density law corresponds to the local space density for stars with absolute magnitudes in question. There is no need of any definition for scaleheights or population types. We confirm with the arguments of non-discrete thin and thick discs for our Galaxy and propose a single structure up to several kiloparsecs from the galactic plane. The logarithmic space densities evaluated by this law for the ELAIS field fit to the observational ones. Whereas, there are considerable offsets for the logarithmic space densities produced by two sets of classical galactic model parameters from the observational ones, for the same field.Comment: 9 pages, 1 figure and 10 tables, accepted for publication in Astrophysics & Space Scienc

Classical r-matrix of the su(2|2) SYM spin-chain

In this note we straightforwardly derive and make use of the quantum R-matrix for the su(2|2) SYM spin-chain in the manifest su(1|2)-invariant formulation, which solves the standard quantum Yang-Baxter equation, in order to obtain the correspondent (undressed) classical r-matrix from the first order expansion in the ``deformation'' parameter 2 \pi / \sqrt{\lambda}, and check that this last solves the standard classical Yang-Baxter equation. We analyze its bialgebra structure, its dependence on the spectral parameters and its pole structure. We notice that it still preserves an su(1|2) subalgebra, thereby admitting an expression in terms of a combination of projectors, which spans only a subspace of su(1|2) \otimes su(1|2). We study the residue at its simple pole at the origin, and comment on the applicability of the classical Belavin-Drinfeld type of analysis.Comment: 14 pages, LaTeX, no figures; corrections made, further analysis of the residue and references adde