The First Galaxies: Clues from Element Abundances

It has recently become possible to measure directly the abundances of several chemical elements in a variety of environments at redshifts up to z = 5. In this review I summarise the latest observations of Lyman break galaxies, damped Lyman alpha systems and the Lyman alpha forest with a view to uncovering any clues which these data may offer to the first episodes of star formation. The picture which is emerging is one where the universe at z = 3 already included many of the components of today's galaxies--even at these early times we see evidence for Populations I and II stars, while the `smoking gun' for Population III objects may be hidden in the chemical composition of the lowest density regions of the IGM, yet to be deciphered.Comment: 15 pages, LaTex, 8 Postscript Figures. To appear in the Philosophical Transactions of The Royal Society, Series

Si and Mn Abundances in Damped Lya Systems with Low Dust Content

We have measured the abundances of Zn, Si, Mn, Cr, Fe, and Ni in three damped Lyman alpha systems at redshifts z < 1 from high resolution echelle spectra of QSOs recorded with the Keck I telescope. In all three cases the abundances of Cr, Fe, and Ni relative to Zn indicate low levels of dust depletions. We propose that when the proportion of refractory elements locked up in dust grains is less than about 50 percent, it is plausible to assume an approximately uniform level of depletion for all grain constituents and, by applying a small dust correction, recover the intrisic abundances of Si and Mn. We use this approach on a small sample of damped systems for which it is appropriate, with the aim of comparing the metallicity dependence of the ratios [Si/Fe] and [Mn/Fe] with analogous measurements in Milky Way stars. The main conclusion is that the relative abundances of both elements in distant galaxies are broadly in line with expectations based on Galactic data. Si displays a mild enhancement at low metallicities, as expected for an alpha-capture element, but there are also examples of near-solar [Si/Fe] at [Fe/H] < -1. The underabundance of Mn at low metallicities is possibly even more pronounced than that in metal-poor stars, and no absorption system has yet been found where [Mn/Fe] is solar. The heterogeneous chemical properties of damped Lyman alpha systems, evident even from this limited set of measurements, provide further support for the conclusion from imaging studies that a varied population of galaxies gives rise to this class of QSO absorbers.Comment: 29 pages, LaTex, 7 Postscript Figures. Accepted for Publication in the Astrophysical Journa

Influence of stored aqueous ceftriaxone solutions on colony formation by neutrophil and macrophage precursor cells

Aqueous solutions of ceftriaxone in concentrations similar to those achieved in man and stored at temperatures of 4°C, 22°C and 37°C for up to four weeks were tested in methylcellulose cultures of normal bone marrow from ten donors. No significant differences were detected between the colony formation by neutrophil and macrophage precursors in control cultures and in cultures containing stored ceftriaxone. It is concluded that aqueous ceftriaxone solutions stored for up to four weeks at temperatures up to 37°C are not altered to such an extent that they adversely affect colony formation by bone marrow progenitor cells from healthy donor

s/alpha/Fe Abundance Ratios in Halo Field Stars: Is there a Globular Cluster Connection?

We try to understand the s- and r-process elements vs Ti/Fe plots derived by Jehin et al. (1999) for mildly metal-poor stars within the framework of the analytical semi-empirical models for these elements by Pagel & Tautvaisiene (1995, 1997). Jehin et al. distinguished two Pop II subgroups: IIa with alpha/Fe and s-elements/Fe increasing together, which they attribute to pure SNII activity, and IIb with constant alpha/Fe and a range in s/Fe which they attribute to a prolonged accretion phase in parent globular clusters. However, their sample consists mainly of thick-disk stars with only 4 clear halo members, of which two are `anomalous' in the sense defined by Nissen & Schuster (1997). Only the remaining two halo stars (and one in Nissen & Schuster's sample) depart significantly from Y/Ti (or s/alpha) ratios predicted by our model.Comment: 6 pages, 5 figures To appear in: Roma-Trieste Workshop 1999: `The Chemical Evolution of the Milky Way: Stars vs Clusters', Vulcano Sept. 1999. F. Giovanelli & F. Matteucci (eds), Kluwer, Dordrech

Occupational closure in nursing work reconsidered: UK health care support workers and assistant practitioners: a focus group study

In healthcare, occupational groups have adopted tactics to maintain autonomy and control over their areas of work. Witz described a credentialist approach to occupational closure adopted by nursing in the United Kingdom during the 19th and early 20th centuries. However, the recent advancement of assistant, ‘non-qualified’ workers by governments and managers forms part of a reconfiguration of traditional professional work. This research used focus groups with three cohorts of healthcare support workers undertaking assistant practitioner training at a London university from 2011-13 (6 groups, n=59). The aim was to examine how these workers positioned themselves as professionals and accounted for professional boundaries. A thematic analysis revealed a complex situation in which participants were divided between articulating an acceptance of a subordinate role within traditional occupational boundaries and a usurpatory stance towards these boundaries. Participants had usually been handpicked by managers and some were ambitious and confident in their abilities. Many aspired to train to be nurses claiming that they will gain recognition that they do not currently get but which they deserve. Their scope of practice is based upon their managers’ or supervisors’ perception of their individual aptitude rather than on a credentialist claim. They ‘usurp’ nurses claim to be the healthcare worker with privileged access to patients, saying they have taken over what nursing has considered its core work, while nurses abandon it for largely administrative roles. We conclude that the participants are the not unwilling agents of a managerially led project to reshape the workforce that cuts across existing occupational boundaries

Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron

In this article we study the galactic evolution of the LiBeB elements within the framework of a detailed model of the chemical evolution of the Galaxy that includes galactic cosmic ray nucleosynthesis by particles accelerated in superbubbles. The chemical composition of the superbubble consists of varying proportions of ISM and freshly supernova synthesized material. The observational trends of 6 LiBeB evolution are nicely reproduced by models in which GCR come from a mixture of 25% of supernova material with 75% of ISM, except for 6 Li, for which maybe an extra source is required at low metallicities. To account for 7 Li evolution several additional sources have been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars). The model fulfills the energetic requirements for GCR acceleration.Comment: 25 pages, 9 figures. Accepted for publication in the Astrophysical Journa

Chemical Compositions of Four Metal-poor Giants

We present the chemical compositions of four K giants CS 22877-1, CS 22166-16, CS22169-35 and BS 16085 - 0050 that have [Fe/H] in the range -2.4 to -3.1. Metal-poor stars with [Fe/H] < -2.5 are known to exhibit considerable star - to - star variations of many elements. This quartet confirms this conclusion. CS 22877-1 and CS 22166-16 are carbon-rich. There is significant spread for [$\alpha$/Fe] within our sample where [$\alpha$/Fe] is computed from the mean of the [Mg/Fe], and [Ca/Fe] ratios. BS 16085 - 0050 is remarkably $\alpha$ enriched with a mean [$\alpha$/Fe] of $+$0.7 but CS 22169-35 is $\alpha$-poor. The aluminium abundance also shows a significant variation over the sample. A parallel and unsuccessful search among high-velocity late-type stars for metal-poor stars is described.Comment: 14 pages (text), 4 tables, 3 figures, Accepted for publication in PAS

Data systems for improvement of reindeer production

This paper presents a calf selection program, a recording and a database system developed as a part of a joint Swedish - Norwegian development project where one of the main objectives is to improve identification, handling and production recording systems. The systems are used in a reindeer flock in the south parts of the reindeer area in Sweden. The additional marking system has been used in this flock since 1981 and procedures for identification of the mothers of the calves has been used since 1986