Dark-Age and Viking-Age pottery in the Hebrides, with special reference to the Udal, North Uist

This thesis is an examination of the evidence for Dark-age and Viking-age pottery in the Hebrides. A brief discussion of current knowledge of Hebridean ceramics shows how unusually ceramic-rich this area is in comparison with the rest of Scotland and much of the British Isles. But the Dark Age and Viking Age in the Hebrides and the pottery of those periods are very poorly known. The excavation of one major settlement site, the TJdal on North Uist, by I.A. Crawford, has allowed examination of stratified pottery groups of the period from c. 400 AD. to c. 1100 A.D. The stratigraphy, structures and chronology of this site are described briefly. The problems and methods involved in analysing a large handmade pottery assemblage are discussed in some detail. The stratified pottery from the Udal is described and the characteristic features of both Dark-age and Viking-age pottery assemblages are defined. Pottery from other sites in the Hebrides is then discussed and a series of sites with similar Dark-age pottery is listed. No close parallels have been found for this pottery outside the area. The Hebridean sites with Viking-age pottery are then described and pottery from other areas is examined in order to define the geographic range of this style. Close similarities can be seen with Souterrain Ware assemblages in northern Ireland and possibly with assemblages in the Faroes. This evidence suggests that the Dark-age style developed from the local Iron-age ceramics. The Viking-age style may indicate influence from Ireland and the interaction of Norse and native peoples in Scotland or Ireland. Further research, systematic fieldwork and excavation are now required to examine these hypotheses

Equivalence of the Siegert-pseudostate and Lagrange-mesh R-matrix methods

Siegert pseudostates are purely outgoing states at some fixed point expanded over a finite basis. With discretized variables, they provide an accurate description of scattering in the s wave for short-range potentials with few basis states. The R-matrix method combined with a Lagrange basis, i.e. functions which vanish at all points of a mesh but one, leads to simple mesh-like equations which also allow an accurate description of scattering. These methods are shown to be exactly equivalent for any basis size, with or without discretization. The comparison of their assumptions shows how to accurately derive poles of the scattering matrix in the R-matrix formalism and suggests how to extend the Siegert-pseudostate method to higher partial waves. The different concepts are illustrated with the Bargmann potential and with the centrifugal potential. A simplification of the R-matrix treatment can usefully be extended to the Siegert-pseudostate method.Comment: 19 pages, 1 figur

Probing the isovector transition strength of the low-lying nuclear excitations induced by inverse kinematics proton scattering

A compact approach based on the folding model is suggested for the determination of the isoscalar and isovector transition strengths of the low-lying ($\Delta S=\Delta T=0$) excitations induced by inelastic proton scattering measured with exotic beams. Our analysis of the recently measured inelastic $^{18,20}$O+p scattering data at $E_{\rm lab}=30$ and 43 MeV/nucleon has given for the first time an accurate estimate of the isoscalar $\beta_0$ and isovector $\beta_1$ deformation parameters (which cannot be determined from the (p,p') data alone by standard methods) for 2$^+_1$ and $3^-_1$ excited states in $^{18,20}$O. Quite strong isovector mixing was found in the 2$^+_1$ inelastic $^{20}$O+p scattering channel, where the strength of the isovector form factor $F_1$ (prototype of the Lane potential) corresponds to a $\beta_1$ value almost 3 times larger than $\beta_0$ and a ratio of nuclear transition matrix elements $M_n/M_p\simeq 4.2$.Comment: 5 pages, 3 figure

Climate and human forcing of Alpine river flow

River flow in Alpine environments is likely to be highly sensitive to climate change because of the effects of warming upon snow and ice, and hence the intra-annual distribution of river runoff. It is also likely to be influenced strongly by human impacts both upon hydrology (e.g. flow abstraction) and river regulation. This paper compares the river flow and sediment flux of two Alpine drainage basins over the last 5 to 7 decades, one that is largely unimpacted by human activities, one strongly impacted by flow abstraction for hydroelectricity. The analysis shows that both river flow and sediment transport capacity are strongly dependent upon the effects of temperature and precipitation availability upon snow accumulation. As the latter tends to increase annual maximum flows, and given the non-linear form of most sediment transport laws, current warming trends may lead to increased sedimentation in Alpine rivers. However, extension to a system impacted upon by flow abstraction reveals the dominant effect that human activity can have upon river sedimentation but also how human response to sediment management has co-evolved with climate forcing to make disentangling the two very difficult

Endovascular repair of an actively hemorrhaging gunshot injury to the abdominal aorta

Endovascular stents have had a limited role in the management of trauma and vascular emergencies involving active hemorrhage. We describe a patient with delayed rupture of the infrarenal aorta after intra-abdominal sepsis caused the breakdown of a primary aortic repair. A stent-graft repair was performed, as concomitant injuries did not allow anterior access to the aorta. This report describes the successful endovascular repair of an actively hemorrhaging penetrating abdominal aortic injury. Endovascular approaches to aortic injuries may be valuable in settings where a hostile abdomen precludes traditional open repair

Detection range and efficiency of acoustic telemetry receivers in a connected wetland system

Acoustic telemetry is an important tool for assessing the behavioural ecology of aquatic animals, but the performance of receivers can vary spatially and temporally according to changes in environmental gradients. Studies testing detection efficiency and/ or detection range are therefore important for data interpretation, although the most thorough range-testing approaches are often costly or impractical, such as the use of fixed sentinel tags. Here, stationary tag data (from study animals that had either died or expelled their tags) provided a substitute for the long-term monitoring of receiver performance in a wetland environment and was complemented by periodic boat-based range testing, with testing of the effects of environmental variables (water temperature, conductivity, transparency, precipitation, wind speed, acoustic noise) on detection efficiency (DE) and detection range (DR). Stationary tag DE was highly variable temporally, the most influential factors being water temperature and precipitation. Transparency was a strong predictor of DR and was dependent on chlorophyll concentration (a surrogate measure of algal density). These results highlight the value of stationary tag data in assessments of acoustic receiver performance. The high seasonal variability in DE and DR emphasises the need for long-term receiver monitoring to enable robust conclusions to be drawn from telemetry data

Widths of Isobaric Analog Resonances: a microscopic approach

A self-consistent particle-phonon coupling model is used to investigate the properties of the isobaric analog resonance in $^{208}$Bi. It is shown that quantitative agreement with experimental data for the energy and the width can be obtained if the effects of isospin-breaking nuclear forces are included, in addition to the Coulomb force effects. A connection between microscopic model predictions and doorway state approaches which make use of the isovector monopole resonance, is established via a phenomenological ansatz for the optical potential.Comment: 18 pages, 1 figure. To appear on Phys. Rev. C (tentatively scheduled for June 1998

Movements of common bream Abramis brama in a highly-connected, lowland wetland reveal spatially discrete sub-populations with diverse migration strategies

1. Freshwater ecosystems are increasingly characterised by high levels of fragmentation that restrict the movements of mobile fauna. Yet studies also suggest the migratory behaviours of potamodromous fishes can be highly variable in barrier-free systems, where differing migratory behaviours enable populations to exploit a wide range of food and space resources. This intra-population divergence in spatial and temporal resource use is important to our ecological understanding of distribution patterns and population structure. 2. Common bream Abramis brama (‘bream’) is a potentially strong model species for testing the importance of divergent migration patterns in lowland rivers, but existing studies have been largely restricted to spatially confined and/or anthropogenically- modified systems. This study’s principal focus was to examine the diversity of bream migration behaviour in a highly-connected, lowland system using passive acoustic telemetry, which provided continuous, multi-year data on the movements of 181 bream across a tidally-influenced, lowland wetland in eastern England (~60 km of continuous river length plus numerous interconnected shallow lakes and dykes). Tracked bream were grouped according to their initial location and timing of tagging. 3. Bream migratory behaviours varied considerably between tagging groups, but with greater consistency within groups. There was little mixing of groups outside of spawning periods, with season and tidal phase being significant predictors of movements. Rates of movement and swimming speeds were highest in spring, with movements also generally occurring in the direction of tidal flows. 4. For fish tagged just prior to spawning, there was considerable diversity in their post- spawning movements, with some remaining in the immediate vicinity and others that moved to areas ~ 25 km away. These spatially discrete patterns remained until the following spawning period, with high individual consistency in movement behaviour between years. 5. These results suggest this lowland fish population is comprised of several distinct, semi-independent subpopulations that only share space resources in their spawning period. This indicates the importance of connectivity in lowland freshwater systems for enabling and maintaining high phenotypic diversity in the migration behaviours of potamodromous fishes

Ground--state energies and widths of 5^5He and 5^5Li

We extract energies and widths of the ground states of $^5$He and $^5$Li from recent single--level R--matrix fits to the spectra of the $^3$H$({\rm d},\gamma$)$^5$He and the $^3$He$({\rm d},\gamma$)$^5$Li reactions. The widths obtained differ significantly from the formal R--matrix values but they are close to those measured as full widths at half maxima of the spectra in various experiments. The energies are somewhat lower than those given by usual estimates of the peak positions. The extracted values are close to the S--matrix poles calculated previously from the multi--term analyses of the N-$^4$He elastic scattering data.Comment: 3 pages, no figures, uses revtex.sty, accepted for publication in PRC, uuencoded postscript and tex-files available at ftp://is1.kph.tuwien.ac.at/pub/ohu/fwidth.u