Extended plasticity in commercial-purity zinc

90% rolling-reduction of annealed commercial-purity zinc sheet (grain size 100 - 150 μ) results in the fragmentation of the large grains into, finally, stable micro-grains, 1 - 211 in diameter. The stability of the micro-grains is due to the presence of soluble and insoluble impurities which prevent recrystallization. This micro-grain material is strain-rate sensitive, and elongations of 200% have been obtained at room temperature. Although this as-rolled, 90% reduction zinc sheet is not super-plastic according to the current definition, its behaviour has led to the coining of the phase 'extended plasticity'. Evidence of grain-boundary sliding is found on examination of the surface by scanning electron microscopy, while the examination of thin foils and activation energy measurements support the dynamic softening (recovery) theory; thus, both these mechanisms must be operating, to a greater or less extent, to confer on this material the observe mechanical behaviour. It is finally concluded that it is dangerous to draw conclusions regarding the mechanism of plastic deformation from surface observations alone

On the structure of the scalar mesons f0(975)f_0(975) and a0(980)a_0(980)

We investigate the structure of the scalar mesons $f_0(975)$ and $a_0(980)$ within realistic meson-exchange models of the $\pi\pi$ and $\pi\eta$ interactions. Starting from a modified version of the J\"ulich model for $\pi\pi$ scattering we perform an analysis of the pole structure of the resulting scattering amplitude and find, in contrast to existing models, a somewhat large mass for the $f_0(975)$ ($m_{f_0}=1015$ MeV, $\Gamma_{f_0}=30$ MeV). It is shown that our model provides a description of $J/\psi\rightarrow\phi\pi\pi/\phi KK$ data comparable in quality with those of alternative models. Furthermore, the formalism developed for the $\pi\pi$ system is consistently extended to the $\pi\eta$ interaction leading to a description of the $a_0(980)$ as a dynamically generated threshold effect (which is therefore neither a conventional $q\overline{q}$ state nor a $K\overline{K}$ bound state). Exploring the corresponding pole position the $a_0(980)$ is found to be rather broad ($m_{a_0}=991$ MeV, $\Gamma_{a_0}=202$ MeV). The experimentally observed smaller width results from the influence of the nearby $K\overline{K}$ threshold on this pole.Comment: 25 pages, 15 Postscript figure

'They are all dead that i could ask': Indigenous Innovation and the Micropolitics of the Field in Twentieth-century Southern Africa

Recovering the agency, skill and innovation of archaeological field assistants from historical encounters is essential to interrogating processes of knowledge production, but is often hampered by access to appropriate archival sources and methods. We detail a field project from early twentieth-century Basutoland (modern-day Lesotho) that is unique both for its aim to salvage details of rock-art production as a dying craft and for its archive chronicling the project's intellectual journey from experiment to draft manuscripts to published work over more than three decades. We argue that critical historiographic attention to this archive offers a guide for examining the intimate dynamics of fieldwork and the effects of these micropolitics on the archaeological canon. We demonstrate how sustained attention to long processes of knowledge production can pinpoint multiple instances in which the usability of field assistants' scientific knowledge is qualified, validated, or rejected, and in this case how an African assistant is transformed into an ethnographic interlocutor. For rock-art studies especially, this represents a need for interrogating the epistemic cultures - not just the content - of foundational historical data

Caught in the cROssfire: GSH Controls T Cell Metabolic Reprogramming

T cell activation and proliferation critical for protective immunity depend on appropriate rewiring of cellular metabolism. In this issue of Immunity, Mak et al. (2017) show that the antioxidant gluthathione (GSH) controls reactive oxygen species (ROS)-dependent engagement of metabolic signaling pathways that lead to protective T cell responses

‘Spunkles’, Donors, and Fathers: Men, Trans/Masculine and Non-Binary People’s Accounts of Sperm Donors and their Relationships to Children

Across the world, growing numbers of men, trans/masculine and non-binary people are bearing children, some of whom utilise known donor sperm in order to conceive. How this diverse population understand the role of known donors, both in the lead up to conception and in terms of the lives of children conceived of their donations has, to date, received little attention. This chapter focuses on a subsample of nine individuals drawn from a larger international study of 51 men, trans/masculine or non-binary who were gestational parents. The nine participants whose narratives are examined in this chapter all used known donor sperm to conceive, and in their interviews discussed their thoughts about the role of donors in their children’s lives, exploring topics such identifying potential donors, the incorporation (or not) of donors into existing kinship narratives, and the need to create opportunities for children to negotiate their own relationships with donors in the future. The findings highlight the potentially unique social scripting needs of men, trans/masculine and non-binary people who conceive using donor sperm. The chapter concludes by providing suggestions for how this diverse group of people may be assisted in developing scripts for disclosing donor conception to their children, and for negotiating the role of donors in children’s lives in the context of legislatures where such disclosure is required

Men, Trans/Masculine and Non-Binary People’s Views About Pregnancy

Drawing on focus groups conducted with 18 young men, trans/masculine, and non-binary people across three countries, in this chapter we argue that essentialist beliefs about reproduction very much impact the experiences of this diverse group of young people. In the sections that follow we first provide an overview of the limited body of literature in this area. We then briefly describe the background to our project, before presenting the findings of our thematic analysis of the focus group data. We conclude the chapter by exploring what our findings mean for a trans reproductive justice approach