Metal-poor dwarf galaxies in the SIGRID galaxy sample. I. HII region observations and chemical abundances

In this paper we present the results of observations of seventeen HII regions in thirteen galaxies from the SIGRID sample of isolated gas rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [OIII] 4363A line, from which we calculate the electron temperature, Te, and gas-phase oxygen abundance. Five of the objects are blue compact dwarf (BCD) galaxies, of which four have not previously been analysed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [NII] {\lambda}{\lambda} 6548,6584A lines, suggesting a particularly low metallicity (< Zsolar/30). We compare the electron temperature based abundances with those derived using eight of the new strong line diagnostics presented by Dopita et al. (2013). Using a method derived from first principles for calculating total oxygen abundance, we show that the discrepancy between the Te-based and strong line gas-phase abundances have now been reduced to within ~0.07 dex. The chemical abundances are consistent with what is expected from the luminosity-metallicity relation. We derive estimates of the electron densities and find them to be between ~5 and ~100 cm-3. We find no evidence for a nitrogen plateau for objects in this sample with metallicities 0.5 > Zsolar > 0.15.Comment: 46 pages, 15 figures, 6 tables, 1 appendix. Accepted for publication in the Astrophysical Journa

A study of pulsed thermography for life assessment of thin EB-PVD TBCs undergoing oxidation ageing

This paper presents an assessment of ageing for thin Thermal Barrier Coatings (TBC) using active thermography. As TBCs undergo ageing during their service life, sintering changes the porosity, elements migrate from the substrate, and micro-cracks build up in the structure of the material, exhibiting a change in thermal conductivity and diffusion properties. As the material ages and these properties change over time, it is possible to exploit trends in this change for characterisation of coating ageing, which would provide a diagnostics tool to estimate remaining useful life. In this study, through-depth diffusivity measurement has been applied to thin EB-PVD coatings which are artificially aged via oxidation furnace cycles. In order to address the difficulties of capturing a fast thermal event in a thin coating, a novel parametric study approach has been carried out to optimise data capture and analysis, maximising available frames for the model fitting step. Through-depth diffusivities have been measured during ageing for six samples, yielding a repeatable trend in thermal diffusivity measurements, with three features, which can be exploited for ageing characterisation of thin EB-PVD TBCs, and used as an alarm of imminent failure

The diary of Robert John Mullins (1833-1913)

Summary of Content: This volume offers its readers extracts from the diary and the correspondence of Robert John Mullins, Anglican missionary, priest and in due time principal of what was called the Kafir Institution in Grahamstown and as such a pioneer in the field of western education to black South Africans. After his marriage to Jennie Roe he was assisted in all that he undertook by a loyal and devoted wife. The editors have made use of the earlier diaries and manuscripts because of the light they shed on the conditions in the eastern Cape frontier in the crucial years before and after the cattle-killing. While Mullins' own observations are those of a young missionary his remarks and the record of his experiences are themselves to be viewed in the light of the recent scholarship in regard to the cattle-killing which reveals the multisidedness of an appalling social tragedy. What Mullins wrote records, for better or for worse, episodes which show how South Africans of different origins have in the past regarded one another. Mullins was a committed Christian eager to offer to all whom he could reach the salvation of Christ in which he so fervently believed.He was often intolerant of Xhosa customs he could not understand as well as often perplexed and discouraged. But the overwhelming impact of this record is what it took to be a missionary: courage, commitment, humour, resilience, a capacity to endure physical hardship and enjoy physical activity. All these were qualities which Robert John Mullins possessed in abundance. As his diary shows they were the qualities the frontier demanded. Working over a long period of time Nancy Charton and Brenda Nicholls (who became a coeditor in 1991) have transcribed the diary entries and the correspondence working with the help of the sites of some of the missionary activity. The help of members of the Mullins family (notably Judy Sturrock and her husband) is gratefully acknowledged. Earlier generous contributions made it possible to obtain a typescript from which the editors could work. Every effort has been made to identify the individuals (Xhosa, Tembu and white) and events (both in South Africa and abroad) which are alluded to in the diary. This was a time consuming task and the editors are grateful to all who helped them with it. The book consists of an introduction and eleven chapters. The introduction describes the material and the methods of the editors, discusses the religious and social conditions of the time, addresses the problems of interpartition presented by the cattle-killings, turns attention to the dilemmas of missionaries and then focusses the attention of readers on the diarist Robert John Mullins (with Jennie as later stand-in) as well as the value of the diary. There is much to interest the educationist, the theologian, the economist, and the historian. Chapter 1 deals with Mullins' voyage to the Cape in 1854 and the extracts record the experiences of an exuberant as well as a dedicated lad of sixteen. Chapter 2 deals with the arrival at the Cape in 1854. Chapter 3 gives us a picture of Mullins' experience of Graham's Town in 1854. Chapter 4 deals with Mullins' experience at St Luke's Mission. Chapter 5 covers the period of 1856-57 when Mullins was at Balotwa and the cattle-killing frenzy developed. Chapter 6 describes the hunger and turmoil which followed in the wake of the cattle-killing. Chapter 7 describes the founding of a new station, St Peter's Gwytyu. Chapter 8 is concerned with life at St Peter's in the early months of 1858. Chapter 9 covers the last months at St Peter's and his journey to the Bashee. Chapters 10 and 11 cover the early years in the married life of Robert John Mullins and his wife Jennie. The Mullins' delight in family life is strongly evident in their joy in each other's company and their anxious joy over their first-born baby. Chapter 11 gives the reader the texts of letters written by Robert John and his wife Jennie in the years which marked the end of Mullins' career as a frontier missionary, and the opening to him of the opportunity to become Principal of the Kafir Institution. A map carefully prepared by Mr Oakley West of the Geography Department, with the assistance of Deby Brody, enables the reader to trace the frontier journeys of Robert John Mullins and his wife Jennie who were among the pioneers of frontier societies who did their best to make available to others what they believed to be the eternal benefits of the Christian faith, and the accompanying mores of the 'western' culture of their day