Metallicity Determinations from Ultraviolet-Visual Spectrophotometry. I. The Test Sample

New visual spectrophotometric observations of non-supergiant solar neighborhood stars are combined with IUE Newly Extracted Spectra (INES) energy distributions in order to derive their overall metallicities, [M/H]. This fundamental parameter, together with effective temperature and apparent angular diameter, is obtained by applying the flux-fitting method while surface gravity is derived from the comparison with evolutionary tracks in the theoretical H-R diagram. Trigonometric parallaxes for the stars of the sample are taken from the Hipparcos Catalogue. The quality of the flux calibration is discussed by analyzing a test sample via comparison with external photometry. The validity of the method in providing accurate metallicities is tested on a selected sample of G-type stars with well-determined atmospheric parameters from recent high-resolution spectral analysis. The extension of the overall procedure to the determination of the chemical composition of all the INES non-supergiant G-type stars with accurate parallaxes is planned in order to investigate their atmospheric temperature structure

Synthetic Lick Indices and Detection of α-enhanced Stars. III. F, G, and K Stars with [Fe/H] > 0.00

A sample of 119 F, G, and K solar neighborhood stars, selected under the condition [Fe/H] > 0.00, is investigated in order to detect which of them, if any, present α-enhanced characteristics. According to the kinematics, the sample represents stars of the thin-disk component of the Galaxy. The search of α-enhanced characteristics is performed by adopting an already tested procedure that does not require previous knowledge of the stellar main atmospheric parameters. The analysis is based on the comparison of spectral indices in the Lick IDS system, coming from different observational data sets, with synthetic ones computed with solar-scaled abundances and with α-element enhancement. The main result of the analysis is the extreme paucity (likely just one in 119) of α-enhanced stars in our sample, thus suggesting [α/Fe] = 0.0 for thin-disk stars with [Fe/H] > 0.00. This result, which is in agreement with the standard evolutionary picture of the disk of the Galaxy, is compared with recent results from high-resolution analysis reported in the literature. The role of the atmospheric parameter assumptions in the analysis of high-resolution spectroscopic data is discussed, and a possible explanation of discrepant results about α-enhancement for stars with [Fe/H] > 0.00 is presented

Synthetic Lick Indices and Detection of α-enhanced Stars. II. F, G, and K Stars in the –1.0 < [Fe/H] < +0.50 Range

We present an analysis of 402 F, G, and K solar neighborhood stars, with accurate estimates of [Fe/H] in the range -1.0 to +0.5 dex, aimed at the detection of α-enhanced stars and at the investigation of their kinematical properties. The analysis is based on the comparison of 571 sets of spectral indices in the Lick/IDS system, coming from four different observational data sets, with synthetic indices computed with solar-scaled abundances and with α-element enhancement. We use selected combinations of indices to single out α-enhanced stars without requiring previous knowledge of their main atmospheric parameters. By applying this approach to the total data set, we obtain a list of 60 bona fide α-enhanced stars and of 146 stars with solar-scaled abundances. The properties of the detected α-enhanced and solar-scaled abundance stars with respect to their [Fe/H] values and kinematics are presented. A clear kinematic distinction between solar-scaled and α-enhanced stars was found, although a one-to-one correspondence to "thin disk" and "thick disk" components cannot be supported with the present data

UVES observations of QSO 0000-2620: oxygen and zinc abundances in the Damped Ly-alpha galaxy at z_abs=3.3901

Observations of the QSO 0000-2620 with UVES spectrograph at the 8.2m ESO KUEYEN telescope are used for abundance analysis of the damped Ly-alpha system at z_{abs}=3.3901. Several Oxygen lines are identified in the Ly_alpha forest and a measure for the oxygen abundance is obtained at [O/H]=-1.85 +/- 0.1 by means of the unsaturated OI 925 A and OI 950 A lines. This represents the most accurate O measurement in a damped Ly_alpha galaxy so far. We have also detected ZnII 2026 A and CrII 2056, 2062 A redshifted at about 8900 A and found abundances [Zn/H] = -2.07 +/- 0.1 and [Cr/H]=-1.99 +/- 0.1. Furthermore, previous measurements of Fe, Si, Ni and N have been refined yielding [Fe/H]=-2.04 +/- 0.1, [Si/H]=-1.90 +/- 0.1, [Ni/H]=-2.27 +/- 0.1, and [N/H]=-2.68 +/- 0.1. The abundance of the non-refractory element zinc is the lowest among the damped Ly-alpha systems showing that the associated intervening galaxy is indeed in the early stages of its chemical evolution. The fact that the Zn abundance is identical to that of the refractory elements Fe and Cr suggests that dust grains have not formed yet. In this Damped Ly-alpha system the observed [O,S,Si/Zn,Fe,Cr] ratios, in whatever combination are taken, are close to solar (i.e 0.1-0.2 dex) and do not show the [alpha-element/Fe] enhancement observed in Milky Way stars of comparable metallicity. The observed behavior supports a galaxy evolution model characterized by either episodic or low star formation rate rather than a Milky-Way-type evolutionary model.Comment: Accepted by Ap

Barium lines in high-quality spectra of two metal-poor giants in the Galactic halo

Context. Theoretical results showed the possibility that neutron capture elements were produced in the early Universe by two different sources: a frequent s-process source hosted by rotating massive stars, and a rare r-process source hosted most likely by neutron star mergers. The two sources produce barium with different isotopic compositions. Aims. We aim to investigate the lines of barium in two halo stars, HD 6268 and HD 4306. The spectra present an exquisite quality, both in terms of resolution (R > 100 000) and signal-to-noise (~400). Due to hyperfine splitting (hfs) effects, barium lines are expected to show slightly different profiles depending on the barium isotopic fraction. Methods. We applied a standard local thermodynamic equilibrium synthesis of the barium lines. We compared the synthetic results assuming an s-process isotopic pattern or an r-process isotopic pattern for the two barium lines for each star that exhibited hfs. We also applied a methodology, less dependent on the accuracy of the theoretical Ba hfs structure, that transforms the lines of HD 4306 into those we would observe if its atmospheric parameter values (i.e. Teff, log g, micro- and macro-turbulence, V sin i, and Ba abundance) were the same as those of HD 6268. Results. With both methods, our results show that the barium lines with hfs effects of HD 4306 are in agreement with an s-process composition and the lines in HD 6268 have a different profile, which is most likely linked to the presence of an r-process isotopic pattern. Conclusions. Two lines of barium of HD 6268 and HD 4306 seem to confirm the theoretical expectation that both r-process events and also s-process contribution by rotating massive stars have polluted the ancient halo of our Galaxy

Synthesis and evaluation of thymol-based synthetic derivatives as dual-action inhibitors against different strains of h. pylori and AGS cell line

Following a similar approach on carvacrol-based derivatives, we investigated the synthesis and the microbiological screening against eight strains of H. pylori, and the cytotoxic activity against human gastric adenocarcinoma (AGS) cells of a new series of ether compounds based on the structure of thymol. Structural analysis comprehended elemental analysis and 1H/13C/19F NMR spectra. The analysis of structure-activity relationships within this molecular library of 38 structurally-related compounds reported that some chemical modifications of the OH group of thymol led to broad-spectrum growth inhibition on all isolates. Preferred substitutions were benzyl groups compared to alkyl chains, and the specific presence of functional groups at para position of the benzyl moiety such as 4-CN and 4-Ph endowed the most anti-H. pylori activity toward all the strains with minimum inhibitory concentration (MIC) values up to 4 µg/mL. Poly-substitution on the benzyl ring was not essential. Moreover, several compounds characterized by the lowest minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values against H. pylori were also tested in order to verify a cytotoxic effect against AGS cells with respect to 5-fluorouracil and carvacrol. Three derivatives can be considered as new lead compounds alternative to current therapy to manage H. pylori infection, preventing the occurrence of severe gastric diseases. The present work confirms the possibility to use natural compounds as templates for the medicinal semi-synthesis

PKCε-dependent signalling in cardiac differentiation

The Protein kinase C (PKC) family, composed by 12 different isoforms, plays a pivotal role in many biological contexts such as cell differentiation, proliferation and survival. PKCe has been demonstrated to be relevant for cardio-protection as well as in ischemia-reperfusion injury (Budas et al. 2010). Transgenic mice over-expressing a constitutively active PKCε show concentric hypertrophy (Takeishi et al. 2000) suggesting negative effects of a permanently active PKCε in cardiac cells. Although the effects of PKCε over-expression have been analyzed both from the physiological and morphological points of view, molecular studies of its consequences on early cardiac marker gene expression are still lacking. On the other side Bone Marrow Mesenchymal Stem Cells (BMMSCs) can be induced to acquire a cardiac fate by treatment with 5-azacytidine (5-AZ) (Wakitani et al. 1995), representing a good in vitro model for cardiac differentiation studies. We addressed the role of in vivo PKCε over-expression on early cardiac genes (namely, nkx2.5 and gata4) regulation. Our results suggest a negative role of PKCε, mediated by ERK1/2, on expression of these two genes both in vivo and in ex-vivo rat BMMSCs, showing that this protein is a fine tuner of precursor cardiac cells