Timing noise and glitches

One of the most remarkable properties of radio pulsars is their rotational stability which allows many uses as clocks, For instance they enable us to determine the shapes and sizes of binary orbits, to study general relativistic effects in strong gravitational fields, to demonstrate the existance of gravitational radiation from binary systems, to permit the detection of extra solar planets, and also to put limits on the long period gravitational wave background. However, some display timing imperfections which tell us about the insides of neutron stars. This review describes the basic physics of slowdown and how period instabilities seem to be related to the rate of slowdown and the presence of internal superfluid liquid. Careful studies of glitches and the subsequent rotational behaviour of the pulsars can provide valuable information on the internal structure of neutron stars.     

Physicochemical conditions in coastal waters off Syndney, central NSW, Australia

The continental shelf off Sydney is narrow and characterized by extensive areas of rocky reef and sandy sediment. The overlying coastal waters are dynamic with a complex current structure. Important oceanographic processes include East Australian Current (EAC) activity, northward propagating coastal trapped waves, local wind driven currents and relatively high frequency internal tides and waves. These produce influences on a wide range of temporal and spatial scales. The activity of the EAC and its eddies has been associated with episodic incursions of waters which can quickly replace large parts of the shelf waters off Sydney. Thermal stratification and the episodic presence of cold, nutrient rich waters intruded from the continental slope are important features of the water column. Thermal stratification of up to 6°C generally exists for all but a few months of the year. Nutrient concentrations are generally low in surface waters but are higher and more variable at depth because of irregular intrusions of slope waters from depths greater than 150–200 m. The trace element levels in surface seawater entering the Sydney area are expected to be extremely low.     

Australia''s first deepwater sewage outfalls: Design considerations and environmental performance monitoring

The discharge of sewage to the ocean can be an issue of public and scientific concern. Such has been the case in Sydney over at least the past 25 years. In this paper, the history of Sydney's sewage discharge is outlined, and the decisions taken to address concerns about the environmental effects of shoreline discharge of large volumes of primary treated sewage effluent are described. Design criteria are described for deepwater outfall systems that, since 1990–1991, have discharged 80% of Sydney's sewage after primary treatment at North Head, Bondi and Malabar Sewage Treatment Plants (STP). The integrated elements of a comprehensive five year Environmental Monitoring Programme (EMP) are set out. Other papers in this volume describe the result of EMP component studies. The five year EMP was designed to provide the basis to assess the environmental performance of the new deepwater outfall systems during the first two years of their operation and to provide a baseline against which further change may be measured.     

Constraints on a plume in the mid-mantle beneath the Iceland region from seismic array data

Teleseismic P waves passing through low-wave-speed bodies in the mantle are refracted, causing anomalies in their propagation directions that can be measured by seismometer arrays. Waves from earthquakes in the eastern Pacific and western North America arriving at the NORSAR array in Norway and at seismic stations in Scotland pass beneath the Iceland region at depths of ∼ 1000–2000 km. Waves arriving at NORSAR have anomalous arrival azimuths consistent with a low-wave-speed body at a depth of ∼ 1500 km beneath the Iceland–Faeroe ridge with a maximum diameter of ∼250 km and a maximum wave-speed contrast of ∼ 1.5 per cent. This agrees well with whole-mantle tomography results, which image a low-wave-speed body at this location with a diameter of ∼ 500 km and a wave-speed anomaly of ∼ 0.5 per cent, bearing in mind that whole-mantle tomography, because of its limited resolution, broadens and weakens small anomalies. The observations cannot resolve the location of the body, and the anomaly could be caused in whole or in part by larger bodies farther away, for example by a body imaged beneath Greenland by whole-mantle tomography.     

Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano,Chile

Unconsolidated pyroclastic flow deposits of the 1993 eruption of Lascar Volcano, Chile, have, with time, become increasingly dissected by a network of deeply penetrating fractures. The fracture network comprises orthogonal sets of decimeter-wide linear voids that form a pseudo-polygonal grid visible on the deposit surface. In this work, we combine shallow surface geophysical imaging tools with remote sensing observations and direct field measurements of the deposit to investigate these fractures and their underlying causal mechanisms. Based on ground penetrating radar images, the fractures are observed to have propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to 1 cm/year⁻¹ occurred between 1993 and 1996 with continued subsidence occurring at a slower rate thereafter. In situ measurements show that 1 m below the surface, the 1993 deposits remain 5°C to 15°C hotter, 18 years after emplacement, than adjacent deposits. Based on the observed subsidence as well as estimated cooling rates, the fractures are inferred to be the combined result of deaeration, thermal contraction, and sedimentary compaction in the months to years following deposition. Significant environmental factors, including regional earthquakes in 1995 and 2007, accelerated settling at punctuated moments in time. The spatially variable fracture pattern relates to surface slope and lithofacies variations as well as substrate lithology. Similar fractures have been reported in other ignimbrites but are generally exposed only in cross section and are often attributed to formation by external forces. Here we suggest that such interpretations should be invoked with caution, and deformation including post-emplacement subsidence and fracturing of loosely packed ash-rich deposits in the months to years post-emplacement is a process inherent in the settling of pyroclastic material.     

Local and global in cyberspace: the geographical narratives of US food companies on the internet

Summary Internet websites provide a new are na in which companies can create images and representations with attendant geographical narratives. A case study of the websites of the 20 largest US-headquartered food, beverage and food service companies reveals an extensive use of geographical narratives that play on the particular spatial dimensions of the internet. The websites of many of these companies attempt to project and situate corporate activities within a stylized representation of the local and the global, thus providing a 'space' for corporate discourse within cyberspace. Insights gained from this case study highlight the importance of geography and geographical metaphors within the discursive lives of companies. The paper concludes that corporate websites portray idealized identities within idealized geographies.     

Enhanced visualization of the flat landscape of the Cambridgeshire Fenlands

The Fenlands of East Anglia, England, represent a subtle landscape, where topographic highs rarely exceed 30 m above sea level. However, the fens represent an almost full sequence of Quaternary deposits which, together with islands of Cretaceous and Jurassic outcrops, make the area of geological importance. This feature discusses the advantages of using 3D visualization coupled with high‐resolution topographical data, over traditional 2D techniques, when undertaking an analysis of the landscape. Conclusions suggest that the use of 3D visualization will result in a higher level of engagement, particularly when communicating geological information to a wider public.