Phylogenetische Untersuchungen an Arten der Gräser-Gattung Aira L. anhand karyologischer und molekularbiologischer Methoden sowie In situ-Hybridisierungen

Innerhalb der Poaceae stellt die Gattung Aira einen Polyploidie-Komplex aus diploiden und tetraploiden Arten dar. Dieser ist für phylogenetische Verwandtschaftsforschungen interessant, da bei den durch Hybridisierung entstandenen tetraploiden Arten z.T. Unkenntnis über die parentalen Genome herrscht. Die Systematik der Gattung und die phylogenetischen Beziehungen der Arten zueinander wurden durch den Einsatz verschiedener Methoden untersucht. Da die Gattung durch gemeinsame morphologische Merkmale sehr stabil ist, erfolgt eine klare Differenzierung primär anhand karyologischer Daten. Die Sequenzierung der cpDNA bzw. nrDNA zeigt aufgrund einer geringen Divergenz einen begrenzten taxonomischen Wert, was sich in einer schlechten interspezifischen Abgrenzbarkeit widerspiegelt und auf eine spät stattgefundene Abtrennung der Arten hinweist. Durch RAPDs und der GISH konnten bei zwei Arten der allopolyploide Ursprung nachgewiesen und die parentalen Genome detektiert werden

Image resonance in the many-body density of states at a metal surface

The electronic properties of a semi-infinite metal surface without a bulk gap are studied by a formalism that is able to account for the continuous spectrum of the system. The density of states at the surface is calculated within the GW approximation of many-body perturbation theory. We demonstrate the presence of an unoccupied surface resonance peaked at the position of the first image state. The resonance encompasses the whole Rydberg series of image states and cannot be resolved into individual peaks. Its origin is the shift in spectral weight when many-body correlation effects are taken into account

Theory of inelastic lifetimes of low-energy electrons in metals

Electron dynamics in the bulk and at the surface of solid materials are well known to play a key role in a variety of physical and chemical phenomena. In this article we describe the main aspects of the interaction of low-energy electrons with solids, and report extensive calculations of inelastic lifetimes of both low-energy electrons in bulk materials and image-potential states at metal surfaces. New calculations of inelastic lifetimes in a homogeneous electron gas are presented, by using various well-known representations of the electronic response of the medium. Band-structure calculations, which have been recently carried out by the authors and collaborators, are reviewed, and future work is addressed.Comment: 28 pages, 18 figures, to appear in Chem. Phy

Sozialraeumliche Differenzierung in Freiburg im Breisgau eine faktorialoekologische Untersuchung von Stadtstrukturen, ihrer Veraenderung zwischen 1970 und 1980 und ihrer Bedeutung fuer die Wohnzufriedenheit

UuStB Koeln(38)-9Y5369 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

‘So long as there's hair there still’:displaying lack of interest as a practice for negotiating social norms of appearance for older women

ABSTRACTAlthough women's appearance is theorised as being central to their identity and social currency, much prior research has argued that as women age, other aspects of their lives assume a higher priority than their appearance. Nevertheless, they continue to invest time in appearance practices. In undertaking these various appearance practices, older women have to negotiate a range of conflicting social norms of age-appropriate appearance, such as managing the balancing act between ‘letting themselves go’, on the one hand, and looking like ‘mutton dressed as lamb’, on the other. This paper contributes to the growing literature on older women's attitudes to their appearance and related practices. Drawing on data from a two-year research project in a hair-salon catering primarily for older clients, I examine the question of the importance to women of their appearance through the lens of their hair-care practices. Focusing on a group of nine female clients aged 55–90 in a small hair-salon in southern England, I show how participants in their talk and embodied presentation display shifting orientations of investment/interest (or lack of interest) in their appearance. Comparing participants’ appearance practices, with their talk in two sequential environments in which a possible interest in appearance is made particularly salient, I argue that these shifting orientations reveal participants’ subtle negotiation of competing social norms of appearance for older women.</jats:p

“What we’re going to be doing”:Small stories and the “doing” of institutional identity by guides of working visitor attractions

A growing body of work charts and explicates the way participants in interactions constitute the context and their respective identities as ‘institutional’ through differences in a number of dimensions to ‘everyday’ talk. The role played by stories, particularly non-canonical or ‘small stories’, in this context-creating and identity-orientating work has been largely overlooked, although there is an expanding collection of studies into the affordances offered by different narrative types in terms of identity performance. Building on and combining existing research into institutional interaction on the one hand and narrative and identity on the other, the research discussed here starts to address the gap identified. Using fine-grained linguistic analysis and drawing on narrative positioning theory in a detailed analysis of two narratives recorded as part of a wider study, this paper aims to explicate the way participants — in this case guides in a working visitor attraction — may use different narrative types to orientate to their institutionally-ascribed identity of ‘guide’. The paper also highlights the benefits in terms of added nuance and depth of interpretation to be gained from using the tools of narrative analysis in investigating institutional contexts and identity.</jats:p