Context. Knowledge of the abundance distribution of star forming regions and young clusters is critical to investigate a variety of issues, from triggered star formation and chemical enrichment by ...nearby supernova explosions to the ability to form planetary systems. In spite of this, detailed abundance studies are currently available for relatively few regions. Aims. In this context, we present the analysis of the metallicity of the gamma Velorum cluster, based on the products distributed in the first internal release of the Gaia-ESO Survey. Methods. The gamma Velorum candidate members have been observed with FLAMES, using both UVES and Giraffe, depending on the target brightness and spectral type. In order to derive a solid metallicity determination for the cluster, membership of the observed stars must be first assessed. To this aim, we use several membership criteria including radial velocities, surface gravity estimates, and the detection of the photospheric lithium line. Results. Out of the 80 targets observed with UVES, we identify 14 high-probability members. We find that the metallicity of the cluster is slightly subsolar, with a mean Fe/H = −0.057 ± 0.018 dex. Although J08095427-4721419 is one of the high-probability members, its metallicity is significantly larger than the cluster average. We speculate about its origin as the result of recent accretion episodes of rocky bodies of ~60 M⊕ hydrogen-depleted material from the circumstellar disk.
Milky Way open clusters are very diverse in terms of age, chemical composition, and kinematic properties. Intermediate-age and old open clusters are less common, and it is even harder to find them ...inside the solar Galactocentric radius, due to the high mortality rate and strong extinction inside this region. NGC 6802 is one of the inner disk open clusters (IOCs) observed by the Gaia-ESO survey (GES). This cluster is an important target for calibrating the abundances derived in the survey due to the kinematic and chemical homogeneity of the members in open clusters. Using the measurements from Gaia-ESO internal data release 4 (iDR4), we identify 95 main-sequence dwarfs as cluster members from the GIRAFFE target list, and eight giants as cluster members from the UVES target list. The dwarf cluster members have a median radial velocity of 13.6 ± 1.9 km s-1, while the giant cluster members have a median radial velocity of 12.0 ± 0.9 km s-1 and a median Fe/H of 0.10 ± 0.02 dex. The color–magnitude diagram of these cluster members suggests an age of 0.9 ± 0.1 Gyr, with (m−M)0 = 11.4 and E(B−V) = 0.86. We perform the first detailed chemical abundance analysis of NGC 6802, including 27 elemental species. To gain a more general picture about IOCs, the measurements of NGC 6802 are compared with those of other IOCs previously studied by GES, that is, NGC 4815, Trumpler 20, NGC 6705, and Berkeley 81. NGC 6802 shows similar C, N, Na, and Al abundances as other IOCs. These elements are compared with nucleosynthetic models as a function of cluster turn-off mass. The α, iron-peak, and neutron-capture elements are also explored in a self-consistent way.
ABSTRACT We analyze the kinematics of ∼2000 giant stars in the direction of the Galactic bulge, extracted from the Gaia-ESO survey in the region − 10 ° 10 ° and − 11 ° b − 3 ° . We find distinct ...kinematic trends in the metal-rich ( M / H > 0 ) and metal-poor ( M / H < 0 ) stars in the data. The velocity dispersion of the metal-rich stars drops steeply with latitude, compared to a flat profile in the metal-poor stars, as has been seen previously. We argue that the metal-rich stars in this region are mostly on orbits that support the boxy-peanut shape of the bulge, which naturally explains the drop in their velocity dispersion profile with latitude. The metal-rich stars also exhibit peaky features in their line of sight velocity histograms, particularly along the minor axis of the bulge. We propose that these features are due to stars on resonant orbits supporting the boxy-peanut bulge. This conjecture is strengthened through the comparison of the minor axis data with the velocity histograms of resonant orbits generated in simulations of buckled bars. The "banana" or 2:1:2 orbits provide strongly bimodal histograms with narrow velocity peaks that resemble the Gaia-ESO metal-rich data.
The chemical gradient of oxygen in the Galaxy from planetary nebulae (PNe) has been closely investigated using a recent extensive fully homogenous set of chemical determinations (up to end of 2001) ...and various distant scales. The found gradient is quite flatter than believed so far, amounting to about −0.016 ± 0.008 log(O/H) kpc−1 insensitive to the distance scales, when all PNe of types I, II, III of Peimbert are used. The value is −0.02 ± 0.01 if only type II PNe are considered, thus reducing the ambiguity introduced by the mixing up of progenitors coming from a large spread in mass. A second control set made by the chemical oxygen abundances determined by all studies between 2002 and 2005, with a data base of some 200 objects, provides a similar result. Since previous determinations do have a spread in the slope of the galactocentric oxygen gradient from PNe between −0.07 and −0.01, further work is required to assess the matter. If our low value will be confirmed, the suggestion arises that type II PNe, due to mixing processes, might have lost their ability to be good tracers of oxygen abundance in the interstellar medium at the time of formation of the progenitors.
ABSTRACT
Bradykinin (BK) mediates inflammation and contributes to angiogenesis. We assessed the mechanisms for BK contribution to angiogenesis. Nanomolar concentrations of BK induced angiogenesis in ...rabbit corneas in absence of inflammation. The effect was dose‐dependent and mediated by the B1 receptor. B2 receptor stimulation failed to directly promote vascular growth unless inflammation was induced. Anti‐fibroblast growth factor‐2 (FGF‐2) antibody blocked the effect of BK or B1 receptor agonist. In postcapillary venular endothelial cells (CVEC), B2 receptor activation induced inositol phosphate turnover and calcium transients, whereas the B1 receptor was coupled to nitric oxide synthase (NOS) up‐regulation and activation and cGMP increase. Differential RT‐PCR and Western blot analysis revealed FGF‐ 2 up‐regulation in cells exposed to BK or to the selective B1 agonist, whereas the B2 agonist was without effect. Consistently, BK and the B1 but not the B2 agonist exerted a proliferative effect on CVEC, which was prevented by anti‐FGF‐2 antibody and by NOS inhibition. These results demonstrate that BK is angiogenic despite its proinflammatory activity and that the B1 receptor is involved. The B1 receptor is coupled to NOS activation and FGF‐2 up‐regulation, events not shared by the B2 receptor activation.
c-fos-induced growth factor/vascular endothelial growth factor D (Figf/Vegf-D) is a secreted factor of the VEGF family that binds to the vessel and lymphatic receptors VEGFR-2 and VEGFR-3. Here we ...report that Figf/Vegf-D is a potent angiogenic factor in rabbit cornea in vivo in a dose-dependent manner. In vitro Figf/Vegf-D induces tyrosine phosphorylation of VEGFR-2 and VEGFR-3 in primary human umbilical cord vein endothelial cells (HUVECs) and in an immortal cell line derived from Kaposi's sarcoma lesion (KS-IMM). The treatment of HUVECs with Figf/Vegf-D induces dose-dependent cell growth. Figf/VEGF-D also induces HUVEC elongation and branching to form an extensive network of capillary-like cords in three-dimensional matrix. In KS-IMM cells Figf/Vegf-D treatment results in dose-dependent mitogenic and motogenic activities. Taken together with the previous observations that Figf/Vegf-D expression is under the control of the nuclear oncogene c-fos, our data uncover a link between a nuclear oncogene and angiogenesis, suggesting that Figf/Vegf-D may play a critical role in tumor cell growth and invasion.
The young open cluster NGC3293 is included in the observing program of the Gaia-ESO survey (GES). The radial velocity values provided have been used to assign cluster membership probabilities by ...means of a single-variable parametric analysis. These membership probabilities are compared to the results of the photometric membership assignment of NGC3293, based on UBVRI photometry. The agreement of the photometric and kinematic member samples amounts to 65 per cent, and could increase to 70 per cent as suggested by the analysis of the differences between both samples. A number of photometric PMS candidate members of spectral type F are found, which are confirmed by the results from VPHAS photometry and SED fitting for the stars in common with VPHAS and GES data sets. Excesses at mid- and near-infrared wavelengths, and signs of Hα emission, are investigated for them. Marginal presence of Hα emission or infilling is detected for the candidate members. Several of them exhibit moderate signs of U excess and weak excesses at mid-IR wavelengths. We suggest that these features originate from accretion discs in their last stages of evolution.
Context. Determination and calibration of the ages of stars, which heavily rely on stellar evolutionary models, are very challenging, while representing a crucial aspect in many astrophysical areas. ...Aims. We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. Methods. We perform a homogeneous analysis of eight open clusters using the Gaia-DR1 TGAS catalogue for bright members and information from the Gaia-ESO Survey for fainter stars. Cluster membership probabilities for the Gaia-ESO Survey targets are derived based on several spectroscopic tracers. The Gaia-ESO Survey also provides the cluster chemical composition. We obtain cluster parallaxes using two methods. The first one relies on the astrometric selection of a sample of bona fide members, while the other one fits the parallax distribution of a larger sample of TGAS sources. Ages and reddening values are recovered through a Bayesian analysis using the 2MASS magnitudes and three sets of standard models. Lithium depletion boundary (LDB) ages are also determined using literature observations and the same models employed for the Bayesian analysis. Results. For all but one cluster, parallaxes derived by us agree with those presented in Gaia Collaboration (2017, A&A, 601, A19), while a discrepancy is found for NGC 2516; we provide evidence supporting our own determination. Inferred cluster ages are robust against models and are generally consistent with literature values. Conclusions. The systematic parallax errors inherent in the Gaia DR1 data presently limit the precision of our results. Nevertheless, we have been able to place these eight clusters onto the same age scale for the first time, with good agreement between isochronal and LDB ages where there is overlap. Our approach appears promising and demonstrates the potential of combining Gaia and ground-based spectroscopic datasets.
New determinations of chemical abundances for He, N, O, Ne, Ar and S are derived for all galactic planetary nebulae (PNe) so far observed with a relatively high accuracy, in an effort to overcome ...differences in these quantities obtained over the years by different authors using different procedures. These include: ways to correct for interstellar extinction, the atomic data used to interpret the observed line fluxes, the model nebula adopted to represent real objects and the ionization corrections for unseen ions. A unique ‘good quality’ classical-type procedure, i.e. making use of collisionally excited forbidden lines to derive ionic abundances of heavy ions, has been applied to all individual sets of observed line fluxes in each specific position within each PN. Only observational data obtained with linear detectors, and satisfying some ‘quality’ criteria, have been considered. Such observations go from the mid-1970s up to the end of 2001. The observational errors associated with individual line fluxes have been propagated through the whole procedure to obtain an estimate of the accuracy of final abundances independent of an author's ‘prejudices’. Comparison of the final abundances with those obtained in relevant multi-object studies on the one hand allowed us to assess the accuracy of the new abundances, and on the other hand proved the usefulness of the present work, the basic purpose of which was to take full advantage of the vast amount of observations done so far of galactic PNe, handling them in a proper homogeneous way. The number of resulting PNe that have data of an adequate quality to pass the present selection amounts to 131. We believe that the new derived abundances constitute a highly homogeneous chemical data set on galactic PNe, with realistic uncertainties, and form a good observational basis for comparison with the growing number of predictions from stellar evolution theory. Owing to the known discrepancies between the ionic abundances of heavy elements derived from the strong collisonally excited forbidden lines and those derived from the weak, temperature-insensitive recombination lines, it is recognized that only abundance ratios between heavy elements can be considered as satisfactorily accurate. A comparison with theoretical predictions allowed us to assess the state of the art in this topic in any case, providing some findings and suggestions for further theoretical and observational work to advance our understanding of the evolution of low- and intermediate-mass stars.
Vascular endothelial growth factor (VEGF) is a secreted protein that is a specific growth factor for endothelial cells. We have recently demonstrated that nitric oxide (NO) donors and vasoactive ...peptides promoting NO-mediated vasorelaxation induce angiogenesis in vivo as well as endothelial cell growth and motility in vitro; in contrast, inhibitors of NO synthase suppress angiogenesis. In this study we investigated the role of NO in mediating the mitogenic effect of VEGF on cultured microvascular endothelium isolated from coronary postcapillary venules. VEGF induced a dose-dependent increase in cell proliferation and DNA synthesis. The role of NO was determined by monitoring proliferation or guanosine 3',5'-cyclic monophosphate (cGMP) levels in the presence and absence of NO synthase blockers. The proliferative effect evoked by VEGF was reduced by pretreatment of the cells with NO synthase inhibitors. Exposure of the cells to VEGF induced a significant increment in cGMP levels. This effect was potentiated by superoxide dismutase addition and was abolished by NO synthase inhibitors. VEGF stimulates proliferation of postcapillary endothelial cells through the production of NO and cGMP accumulation.
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