From Ge I lines in the near-ultraviolet, germanium abundances are deduced for the Sun, one metal-poor subgiant, and nine turnoff stars spanning a range of metallicities. The abundance of germanium with respect to iron varies widely among the stars, and is always at or below its solar proportion. In four stars, one mildly and the rest extremely metal-poor, Ge is deficient by [ges ]0.5 dex. The nearby elements Zn and Zr show nearly scaled-solar abundances. The Ge deficiency persists when heavy r-process elements such as platinum are extremely enhanced. Among this small sample, Ge deficiency correlates with Al deficiency, of similar size.

A large body of theoretical and computational work shows that jets - modelled as magnetized disk winds - exert an external torque on their underlying disks that can efficiently remove angular momentum and act as major drivers of disk accretion. These predictions have recently been confirmed in direct HST measurements of the jet rotation and angular momentum transport in low mass protostellar systems. We review the theory of disc winds and show that their physics is universal and scales to jets from both low and high mass star forming regions. This explains the observed properties of outflows in massive star forming regions, before the central massive star generates an ultracompact HII region. We also discuss the recent numerical studies on the formation of massive accretion disks and outflows through gravitational collapse, including our own work on 3D Adaptive Mesh simulations (using the FLASH code) of the hydromagnetic collapse of an initial rotating, and cooling Bonner-Ebert sphere. Magnetized collapse gives rise to outflows. Our own simulations show that both a jet-like disk wind on sub AU scales, and a larger scale molecular outflow occur (Banerjee & Pudritz 2005).

We present here the first results (on NGC 2808 and NGC 6752) of a program that studies the anticorrelation between Na and O in a sample of Galactic Globular Clusters, using GIRAFFE spectra obtained with UVES@VLT.

We investigate the main differences between static 1D and 3D time-dependent model stellar atmospheres of red giants at very low metallicities. We focus in particular on the impact of 3D LTE spectral line formation on the derivation of elemental abundances for the extremely metal-poor ([Fe/H] $\approx-$5.3) red giant HE 0107-5240.

We have computed updated models of population II stars on the Spite plateau. We focus here on the light elements abundance predictions when the new tachocline mixing process is accounted for.

Spectroscopic abundances of s- and r-process enriched very metal-poor stars are interpreted as the result of mass transfer in a binary system from an AGB companion assuming an initial composition of the parental cloud pre-enriched in r elements. The spectroscopic determination of [Na/Fe], [Mg/Fe] and [ls/Fe] permits an estimate of the initial AGB stellar mass, while a value [Zr/Nb] ≈ 0 is a nuclear indicator of an extrinsic AGB in a binary system.

We have studied the lithium abundance in 18 extremely metal-poor main-sequence turnoff stars as a function of [Fe/H] and $T_{\rm eff}$, using high-quality VLT/UVES spectra. The sample covers the range $-3.3\le [{\rm Fe}/{\rm H}]\le -2.5$, with half of the stars below [Fe/H] = −3.0. $T_{\rm eff}$ is determined from H$\alpha$ line profiles as well as from B-V, V-K, J-H and J-K colours. The behaviour of A(Li) as a function of metallicity is markedly different when different temperature scales are adopted. However, even when applying standard depletion corrections, it is a robust result that the Li abundance in extremely metal poor dwarfs is far below the prediction of standard big bang nucleosynthesis using a baryonic density consistent with the WMAP data.

PN G 135.9 +55.9 is an extraordinary nebula discovered recently in the Galactic halo (Tovmassian et al. 2001). The first studies estimated its oxygen abundance to be 1/100 of the solar value or even less.

Being extremely metal-poor, PNG 135.9+55.9 offers an unprecedented opportunity to check our understanding of the evolution of intermediate-mass stars at very low metallicity, by complementing the data obtained from metal-poor giants (Spite et al 2005). Indeed, PNG 135.9+55.9 and some of those stars are snapshots of the evolution of very similar stars at different times.

We present our most recent abundance analysis for this object, providing stringent limits on the abundances of C, N, O, and Ne, to be confronted with the predictions for the yields of low metallicity intermediate mass stars.

Star formation at very low metallicity is expected to produce only massive stars. This is a result of the low cooling rate. Hydrodynamical simulations of star formation from zero metallicity gas suggest that the first stars had masses in excess of about 102 M[odot]. These stars can not be observed because of their large redshift and their very short lifetime. However, a similar (but not the same) effect might be observable in regions of star formation close to very luminous radiation sources, where intense radiation may destroy dust and CO molecules in starforming clouds. Such clouds will be warmer than in normal metal rich star forming regions because of the reduced cooling, which is then predominantly due to H2 and atomic C and O. Under those conditions star formation may result in the formation of high mass stars without the normal large numbers of accompanying low mass stars. Observations show that this process may occur close to the centre of the interacting galaxy M51, where the intense radiation of the nuclear starburst and the small dust content destroyed molecular CO in star forming regions. HST observations of this region show the presence of about 30 massive stars, of $25\textlessM\textless 150 M\odot$, without the accompanying clusters of low mass stars.

The enrichment of the intergalactic medium (IGM) with heavy elements provides us with a record of past star formation and with an opportunity to study the interactions between galaxies and their environments. We summarize current data analysis methods and observational constraints on abundances in the diffuse, high-redshift (z>2) IGM. This review is targeted at interested outsiders and attempts to answer the following questions: Why should you care? What do we want to measure? How do we do it? What do we know? What are the common misconceptions?

We present the first metallicity distribution (MDF) derived for the bulge of M31. We have used HST WFPC2 V and I images to construct the color-magnitude diagram of a field located at 1.55 kpc from the center of M31. We have translated the RGB star colors into abundances. We describe the M31 bulge MDF properties, compare them to those of the M31 halo. We discuss the analogy with our Galaxy and the implications for the formation of spiral galaxies.

Low mass AGB Stars are the main contributors to the Galactic s-process enrichment. We present new theoretical results obtained by adopting a full network from H to Bi coupled with the physical evolution of the stellar structure. We describe the formation of a 13C pocket as a consequence of H diffusion from the envelope into the He-rich intershell. Such 13C is burnt during the interpulse phase and provides the main neutron source in these stars. We computed two models with the same total mass (that is 2 M[odot]) but two different initial chemical composition, namely (Y=0.269 – Z=0.015) and (Y=0.245 – Z=0.0001), representative of disk and halo stars respectively. We evaluate the differences in the final s-process surface composition and compare the results with the available observational data.

The rare light elements — Li, Be, and B — have a unique and highly coupled history in the Universe. A coordinated analysis of their abundances in very low metallicity stars can help us understand the inner workings of stars and can constrain models of Galactic chemical evolution. We measure the Be abundances of nine stars and the Li isotopic ratio of ten stars. We find three stars with interesting Be abundances and three stars with detectable $^6$Li.

Carbon stars found in the Small Magellanic Cloud and the Sagittarius Dwarf Spheroidal galaxy have been chemically analysed. We found that the abundance ratios derived between elements belonging to the first and the second s-process abundance peaks agree remarkably well with the theoretical predictions of low mass metal-poor AGB nucleosynthesis models. Together with their estimated luminosities, their derived abundances and their carbon isotopic ratio we speculate on the evolutionary status of these carbon stars.

The chemical composition of high-redshift galaxies is an important property that gives clues to their past history and future evolution. Measuring abundances in distant galaxies with current techniques is often a challenge, and the canonical metallicity indicators can often not be applied. I discuss currently available metallicity indicators based on stellar and interstellar absorption and emission lines, and assess their limitations and systematic uncertainties. Recent studies suggest that star-forming galaxies at redshift around 3 have heavy-element abundances already close to solar, in agreement with predictions from cosmological models.

AMS (Alpha Magnetic Spectrometer) is a particle detector designed to operate at the International Space Station. Starting in 2008, its purpose is to perform accurate, high statistics, long duration measurements of energetic (0.1 GeV to $\sim$TeV) charged cosmic ray spectra in space, providing fundamental information about key ingredients in the spallation reactions taking place in the interstellar medium. We present here the characteristics of this experiment and the extense collaboration supporting the project.

We have derived Mn abundances for more than 200 stars in nineteen globular clusters. In addition, Mn abundance determinations have been made for a comparable number of halo field stars possessing an overlapping range of metallicities and stellar parameters. The primary data set was comprised of high resolution spectra previously-acquired at the McDonald, Lick and Keck Observatories. Additional data were obtained from several other investigators. Data were analyzed using synthetic spectra of the 6000 Å Mn I triplet. Hyperfine structure parameters were included in the synthetic spectra computations. Our analysis shows that over the metallicity range $-0.7>[Fe/H]-2.7$ field stars have a mean relative abundance of $<[Mn/Fe]>=-0.36$ identical to that of the nineteen globular clusters $<[Mn/Fe]>=-0.36$. Our Mn abundance results viewed in conjunction with the globular cluster Cu abundances of Simmerer et al. (2003) suggest the following possibilities: one, the production of these elements is highly metallicity-dependent or two, these elements were manufactured in the Galactic halo prior to formation of present-day globular clusters.

Motivated by the WMAP results indicating an early epoch of reionization, we consider alternative cosmic star formation models which are capable of reionizing the early intergalactic medium. We develop models which include an early burst of massive stars (with several possible mass ranges) combined with standard star formation, in the framework of the hierarchical scenario of structure formation. We compute as a function of redshift the stellar ionizing flux of photons, the supernova rates and the chemical evolution, both in the intergalactic medium and in the interstellar medium of forming galaxies. We apply constraints from the cosmic observed star formation rate and the observed abundances in the Lyman $\alpha$ forest and in Damped Lyman $\alpha$ clouds in conjunction with the ability of the models to produce the required degree of reionization.

We determine the carbon isotopic ratios in the atmospheres of some evolved stars in both globular clusters and the disk of our Galaxy. Analysis of 12CO and 13CO bands at 2.3 micron was carried out using fits to observed spectra of red giants and Sakurai's object (V4334 Sgr). The dependence of theoretical spectra on the various input parameters was studied in detail. The computation of model atmospheres and a detailed abundance analysis was performed in a self-consistent fashion. A special procedure for determining the best fits to observed spectra was used. We show, that globular cluster giants with [Fe/H]$\,{<}\,{-}$1.3 have a low 12C/13C = 4 ±1 abundance ratios. In the spectra of Sakurai's object (V4334 Sgr) taken between 1997-98, the 2.3 micron spectral region is veiled by hot dust emission. By fitting UKIRT spectra we determined 12C/13C = 4 ±1 for the July, 1998 spectrum. CO bands in the spectra of ultracool dwarfs are modelled as well.

Although carbon is, together with oxygen and nitrogen, one of the most important elements in the study of galactic chemical evolution its production sites are still poorly known and have been much debated (see e.g. Gustafsson et al. 1999; Chiappini et al. 2003). To trace the origin and evolution of carbon we have determined carbon abundances from the forbidden [C I] line at 8727 Å and made comparisons to oxygen abundances from the forbidden [OI] line at 6300 Å in a sample of 51 nearby F and G dwarf stars. These data and the fact that the forbidden [C I] and [O I] lines are very robust abundance indicators (they are essentially insensitive to deviations from LTE and uncertainties in the stellar parameters, see, e.g., Gustafsson et al. 1999; Asplund et al. 2005) enable us to very accurately measure the C/O ratio as well as individual C and O abundances. Our first results indicate that the time-scale for the main source that contribute to the carbon enrichment of the interstellar medium operate on the same time-scale as those that contribute to the iron enrichment (and can possibly be AGB stars…)