PVC pipes in gas distribution: still going strong!

In the Netherlands (impact-modified) PVC is the preferred material for low-pressure (30 and 100 mbar) gas distribution systems. More than 50% of the total length (about 122,000 km) of this system is rigid PVC or impact-modified PVC. The installation of rigid PVC (uPVC) pipelines started about 50 years ago. Presently, about 22,500 km of rigid PVC is still in operation. In this paper the good experiences with rigid PVC gas distribution systems in the Netherlands will be illustrated by results of regular leak surveys and test results on pipe samples taken from the gas grid. It will be shown that the leakage rate of uPVC pipe systems is very low and about equal to that of PE and steel pipe systems. Impact tests show no significant decrease in ductility with respect to time of use. Furthermore, the ductility of the PVC pipeline materials which have been in use for many years is shown to be mainly dependent on the (initial) quality (degree of gelation). The good performance of PVC gas pipeline systems is also proven by modelling studies. It will be shown that the long-term failure behaviour of uPVC is determined by the ability to yield. Failure will occur if a certain critical value of the plastic strain is surpassed. Using this model the long-term behaviour under internal pressure of rigid PVC pipes can be predicted quantitatively

Proton-neutron alignment in the yrast states of 66^{66}Ge and 68^{68}Ge

The $^{66}$Ge and $^{68}$Ge nuclei are studied by means of the shell model with the extended $P+QQ$ Hamiltonian, which succeeds in reproducing experimentally observed energy levels, moments of inertia and other properties. The investigation using the reliable wave-functions predicts T=0, J=9 one-proton-one-neutron ($1p1n$) alignment in the $g_{9/2}$ orbit, at high spins ($14_1^+$, $16_1^+$ and $18_1^+$) in these $N \approx Z$ even-even nuclei. It is shown that a series of the even-$J$ positive-parity yrast states (observed up to $26_1^+$ for $^{68}$Ge) consists of the ground-state band and successive three bands with different types of particle alignments (two-neutron, $1p1n$, two-proton-two-neutron) in the $g_{9/2}$ orbit.Comment: 4 pages, 5 figures, to be published in Pyhs. Rev.

Engendering objects

Engendering objects explores social and cultural dynamics among Maisin people in Collingwood Bay (Papua New Guinea) through the lens of material culture. Focusing upon the visually stimulating decorated barkcloths that are used as male and female garments, gifts, and commodities, it explores the relationships between these cloths and Maisin people. The main question is how barkcloth, as an object made by women, engenders people’s identities, such as gender, personhood, clan and tribe, through its manufacturing and use. This book describes in detail how barkcloth (tapa) not only visualizes and expresses, but also materializes and defines, people’s multiple identities. By ‘following the object’ and how it is made and used in the performance of life-cycle rituals, in exchanges and in church festivities, this interaction between people and things, and how they are mutually constituted, becomes visible. How are women’s bodies and minds linked with the production of barkcloth? How do cloths produced by women both establish and contest clan identity? In what ways is the commodification of barkcloth related to gender dynamics? Barkcloth and its associated designs show how gender ideologies and the socio-material constructions of identity are performed and, as such, developed, established and contested. The narratives of both men and women reveal the ways in which barkcloth provides a link with the past and dreams for the future. The author argues that the cloths and their designs embody dynamics of Maisin culture and in particular of Maisin gender relations. In contributing to the current debates on the anthropology of ‘art’, this study offers an alternative way of understanding the significance of an object, like decorated barkcloth, in shaping and defining people’s identities within a local colonial and postcolonial setting of Papua New Guinea