Analysis of fully coupled thermomechanical behaviour around a rigid cylindrical heat source buried in clay

The problem of fully coupled consolidation and heat flow around a rigid cylindrical heat source buried in clay has been studied. The governing equations of the problem are summarized in the paper and a finite element time-marching scheme to obtain an approximate solution to the governing equations is described. The stress–strain behaviour of the skeleton of the saturated soil has been represented by both a linear elastic model and the modified Cam clay soil model. The results of a limited parametric study are presented with the aim of understanding the major mechanisms of soil behaviour close to buried canisters of hot radioactive waste. A range of soil properties has been included in the study, and the effects of soil disturbance during canister emplacement have also been considered.     

Open boundary conditions for regional tidal simulations

The performance of regional tide model simulations is examined in relation to the choice of open boundary conditions. Three barotropic open boundary conditions, clamped elevation, clamped normal velocity, and Flather, give similar results when the prescribed values are exact; however, Flather is much less sensitive to errors in the prescribed values. Of particular concern, it was found that with a phase error between the two boundaries, both the clamped conditions resulted in magnitude errors in the unclamped variable (although the simulation remained stable).A modified flow relaxation scheme for the depth-varying prognostic variables is presented. This implementation allows the transmission of a range of vertical modes while retaining realistic topography at the boundary. It was found to be an excellent internal tide boundary condition in tests comparing simulations of different domain length encompassing a ridge and sloping bottom, and in a comparison to an analytical solution. Mass is conserved without any artificial volume constraint.     

Methods for exploring management options to reduce greenhouse gas emissions from tropical grazing systems

Increasing atmospheric concentrations of greenhouse gases are expected to result in global climatic changes over the next decades. Means of evaluating and reducing greenhouse gas emissions are being sought. In this study an existing simulation model of a tropical savanna woodland grazing system was adapted to account for greenhouse gas emissions. This approach may be able to be used in identifying ways to assess and limit emissions from other rangeland, agricultural and natural ecosystems.GRASSMAN, an agricultural decision-support model, was modified to include sources, sinks and storages of greenhouse gases in the tropical and sub-tropical savanna woodlands of northern Australia. The modified model was then used to predict the changes in emissions and productivity resulting from changes in stock and burning management in a hypothetical grazing system in tropical northeastern Queensland. The sensitivity of these results to different Global Warming Potentials (GWPs) and emission definitions was then tested.Management options to reduce greenhouse gas emissions from the tropical grazing system investigated were highly sensitive to the GWPs used, and to the emission definition adopted. A recommendation to reduce emissions by changing burning management would be toreduce fire frequency if both direct and indirect GWPs of CO₂, CH₄, N₂O, CO and NO are used in evaluating emissions, but toincrease fire frequency if only direct GWPs of CO₂, CH₄ and N₂O are used. The ability to reduce greenhouse gas emissions from these systems by reducing stocking rates was also sensitive to the GWPs used. In heavily grazed systems, the relatively small reductions in stocking rate needed to reduce emissions significantly should also reduce the degradation of soils and vegetation, thereby improving the sustainability of these enterprises.The simulation studies indicate that it is possible to alter management to maximise beef cattle production per unit greenhouse gases or per unit methane emitted, but that this is also dependent upon the emission definition used. High ratios of liveweight gain per unit net greenhouse gas emission were found in a broadly defined band covering the entire range of stocking rates likely to be used. In contrast, high values of liveweight gain per unit anthropogenic greenhouse gas emission were found only at very low stocking rates that are unlikely to be economically viable.These results suggest that policy initiatives to reduce greenhouse gas emissions from tropical grazing systems should be evaluated cautiously until the GWPs have been further developed and the implications of emission definitions more rigorously determined.     

Fibre optics at the 4.2 m telescope (WHT)

We summarize some of the work on optical fibres carried out at the 4.2 m (WHT) telescope. We will briefly describe the Fibre Linked Experimental spectrograph.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Mobilising generosity, framing geopolitics: Narrating crisis in the homeland through diasporic media

This paper provides an account of the humanitarian interventions enacted by the Croatian–American diaspora during the secessionist conflicts in Yugoslavia during the 1990s. Whilst undeniably an act of generosity towards ‘distant strangers’, actions such as these also represent a much more complex reality – they are an outcome of a complex set of relations and processes, in which the ethical choices of individuals become bound up with nationalist ideologies, geopolitical questions and, crucially, knowledge and understanding of distant events. In particular, this paper considers the ways in which generosity is mobilised through the framing of Balkan geopolitics through diasporic media. In so doing, it becomes possible to deepen the dialogue between work on geography and ethics on the one hand, and critical geopolitics on the other. In particular, the paper argues that due attention needs to be paid to the ways in which such ‘networks of concern’ are constructed in a variety of banal and mundane ways.     

Do Regional Disparities in Research on Climate and Water Influence Adaptive Capacity?

As part of a long-term effort to both improve access to information on climate change and freshwater resources, and to understand the state of the science, we compiled an electronic bibliography of scientific literature in that area. We analyzed the distribution of information on climatic impacts on freshwater resources, with an emphasis on differences between developed and developing regions as well as differences in the types and focus of research carried out among regions. There has been more research overall in developed countries than in the developing world. Proportionally more of the available research on natural and human systems pertains to developed regions, while most of the analysis done in developing countries is limited to higher-level climatology and hydrology. We argue that scientific information and understanding are important elements of the ability to adapt to potential climatic changes. The distribution of the scientific literature in our database suggests that the types of science most directly relevant to adaptive capacity are skewed towards developed countries, which may exacerbate existing disparities in adaptive capacity, and ultimately worsen the consequences of climatic impacts in developing countries.     

A Modeling System for Studying Climate Controls on Mountain Glaciers with Application to the Patagonian Icefields

A modeling system for investigating meteorological controls on glacier mass balance is described and applied to the Southern Patagonian Icefield. Output from a mesoscale atmospheric model is used to drive a glacier mass balance model using model precipitation and turbulent fluxes adjusted to account for the unrealistically low surface elevations of the icefield in the atmospheric model. Simulations of January and July conditionsproduce glacier equilibrium line altitudes (ELAs) that are higher than the observed, but the ELA gradient is realistically simulated. The high ELAs are primarily due to underestimates of vertical temperature gradients in the atmospheric model and uncertainties in the ablation season length. The model shows that both winter and summerprecipitation, as well as summer temperatures, are important determinants of the mass balance of the Southern Patagonia glaciers. The position of the icefield on the continent is also relevant. On the western side of the icefield, precipitation rates are high and dominate the mass balance calculation. In the east, ablation is much more important for determining the mass balance, and this introduces an enhanced sensitivity to atmospheric temperature, wind speed, and atmosphericmoisture levels.     

The geopolitics of diaspora

In recent years there has been a growing body of work dealing with issues of diaspora and hybridity, both within geography and in other disciplines, such as cultural studies. This work tends to celebrate the potential of the hybrid and diasporic to transcend essentialist notions of identity and subjectivity. In this paper I argue that these approaches often fail to pay sufficient attention to two particular aspects of the diaspora experience: firstly, the geographical specificities of particular diasporas, and secondly, the ways in which essentialist modes of being are often reproduced within diasporic discourse. This is done by providing an overview of recent research into the Croatian diaspora in the United States (particularly their involvement in the Balkan conflicts of the 1990s), which begins to develop the notion of the geopolitics of diaspora.     

Linking hinterland evolution and continental basin sedimentation by using detrital zircon thermochronology: a study of the Khorat Plateau Basin, eastern Thailand

The effectiveness of detrital zircon thermochronology as a means of linking hinterland evolution and continental basin sedimentation studies is assessed by using Mesozoic continental sediments from the poorly understood Khorat Plateau Basin in eastern Thailand. New uranium lead (U‐Pb) and fission‐track (FT) zircon data from the Phu Kradung Formation identify age modes at 141 ± 17 and 210 ± 24 Ma (FT) and 2456 ± 4, 2001 ± 4, 251 ± 3, and 168 ± 2 Ma (U‐Pb), which are closely similar to data from the overlying formations. The FT data record post‐metamorphic cooling, whereas the U‐Pb data record zircon growth events in the hinterland. Comparison is made between detrital zircon U‐Pb data from ancient and modern sources across Southeast Asia. The inherent stability of the zircon U‐Pb system means that 250 Myr of post‐orogenic sedimentary recycling fails to change the regional zircon U‐Pb age signature and this precludes use of the U‐Pb approach alone for providing unique provenance information. Although the U‐Pb zircon results are consistent with (but not uniquely diagnostic of) the Qinling Orogenic Belt as the original source terrane for the Khorat Plateau Basin sediments, the zircon FT cooling data are more useful as they provide the key temporal link between basin and hinterland. The youngest zircon FT modes from the Khorat sequence range between 114 ± 6 (Phra Wihan Formation) and 141 ± 17 Ma (Phu Kradung Formation) that correspond to a Late Jurassic/Early Cretaceous reactivation event, which affected the Qinling Belt and adjacent foreland basins. The mechanism for regional Early Cretaceous erosion is identified as Cretaceous collision between the Lhasa Block and Eurasia. Thus, the Khorat Plateau Basin sediments might have originated from a reactivation event that affected a mature hinterland and not an active orogenic belt as postulated in previous models.