Examining access to GP services in rural Ireland using microsimulation analysis

This paper analyses the effect accessibility has on General Practitioner (GP) utilisation rates at the sub-national level for Ireland. Specifically, the aim of this paper is to estimate whether there is an urban–rural differential in GP utilisation rates. We do this by simulating micro-level healthcare data. Using this synthetic data, simple logit models are employed to estimate the likelihood that individuals in different jurisdictions will attend a GP surgery. These individual logit estimates are then inputted into a spatial interaction model to highlight areas with low GP accessibility given their health status. The policy implications of these results are discussed in relation to both the healthcare literature and current Irish healthcare policy.     

Exploring the marine biotic index (AMBI): variations on a theme by Ángel Borja

The results of manipulating the input data to AMBI are explored using various transformations of numerical species abundance (NAMBI), biomass (BAMBI) and production (PAMBI) from a variety of stations on the NE Atlantic shelf at which the pollution/disturbance status is known. There is a close agreement between the proportions of species in the five AMBI ecological groups and a phylum level meta-analysis axis of increasing environmental impact. All AMBI measures provide a better monotonic relationship with the impact axis than do traditional species diversity measures, which show higher diversity at intermediate levels of disturbance. A marginally better relationship with the impact axis of the meta-analysis is achieved by a moderate (square root) transformation of the data. ‘Production’ data (an appropriate combination of abundance and biomass information) provide only a marginal improvement on abundance data, but are ecologically and functionally much more relevant. Severe transformation of the data, culminating in presence/absence, degrades the relationship with the impact axis, but if only simple species lists are available then these may still be useable in making an environmental assessment.     

A general-purpose parallel raster processing programming library test application using a geographic cellular automata model

A general-purpose parallel raster processing programming library (pRPL) was developed and applied to speed up a commonly used cellular automaton model with known tractability limitations. The library is suitable for use by geographic information scientists with basic programming skills, but who lack knowledge and experience of parallel computing and programming. pRPL is a general-purpose programming library that provides generic support for raster processing, including local-scope, neighborhood-scope, regional-scope, and global-scope algorithms as long as they are parallelizable. The library also supports multilayer algorithms. Besides the standard data domain decomposition methods, pRPL provides a spatially adaptive quad-tree-based decomposition to produce more evenly distributed workloads among processors. Data parallelism and task parallelism are supported, with both static and dynamic load-balancing. By grouping processors, pRPL also supports data–task hybrid parallelism, i.e., data parallelism within a processor group and task parallelism among processor groups. pSLEUTH, a parallel version of a well-known cellular automata model for simulating urban land-use change (SLEUTH), was developed to demonstrate full utilization of the advanced features of pRPL. Experiments with real-world data sets were conducted and the performance of pSLEUTH measured. We conclude not only that pRPL greatly reduces the development complexity of implementing a parallel raster-processing algorithm, it also greatly reduces the computing time of computationally intensive raster-processing algorithms, as demonstrated with pSLEUTH.     

The inclusion of differentially assessed lands in urban growth model calibration: a comparison of two approaches using SLEUTH

This research sought to understand the role that differentially assessed lands (lands in the United States given tax breaks in return for their guarantee to remain in agriculture) play in influencing urban growth. Our method was to calibrate the SLEUTH urban growth model under two different conditions. The first used an excluded layer that ignored such lands, effectively rendering them available for development. The second treated those lands as totally excluded from development. Our hypothesis was that excluding those lands would yield better metrics of fit with past data. Our results validate our hypothesis since two different metrics that evaluate goodness of fit both yielded higher values when differentially assessed lands are treated as excluded. This suggests that, at least in our study area, differential assessment, which protects farm and ranch lands for tenuous periods of time, has indeed allowed farmland to resist urban development. Including differentially assessed lands also yielded very different calibrated coefficients of growth as the model tried to account for the same growth patterns over two very different excluded areas. Excluded layer design can greatly affect model behavior. Since differentially assessed lands are quite common through the United States and are often ignored in urban growth modeling, the findings of this research can assist other urban growth modelers in designing excluded layers that result in more accurate model calibration and thus forecasting.     

“Dead Zone” dynamics in Lake Erie: the importance of weather and sampling intensity for calculated hypolimnetic oxygen depletion rates

Calculated hypolimnetic oxygen depletion (HOD) rates depend not only on environmental factors but also logistical ones. In particular, lack of understanding of the effects of weather in addition to how sampling effort determines calculated HOD rates complicates ecological understanding and environmental management of lake ecosystems. To better determine the roles of weather and sampling effort, we combined (1) weekly measurements of temperature and dissolved oxygen (DO) concentrations from seven stations in the Sandusky subbasin of Lake Erie’s central basin during 2005, (2) contemporaneous measures of storm activity and tributary discharge, and (3) a two-dimensional coupled hydrodynamic, chemical, and biological model of Lake Erie to investigate (1) how increased storm activity and tributary discharge affected short- (daily) and long-term (seasonal) dynamics of hypolimnetic hypoxia, and (2) how spatial (number of sites sampled) and temporal (sampling frequency) sampling effort affected calculated HOD rates. Our model closely replicated field-observed DO dynamics. When comparing baseline modeled dynamics to those in a second simulation with twice the number of days with high winds, however, we found that with more storm activity (1) periods of entrainment became more frequent, (2) the hypolimnion was warmer, (3) thermal stratification occurred 1 month later, whereas autumnal turnover occurred at least 1 week earlier shortening the duration of stratification by 1–2 months, and (4) HOD rates increased 12%. Further, spatial and temporal sampling intensity also affected calculated HOD rates. Consequently, adequately quantifying actual HOD rates requires sufficient sampling effort and the particular role of weather should be assessed with rigorous field and simulation studies, especially if HOD rates are used to indicate management success.     

Hubble observations of Jupiter’s north–south conjugate ultraviolet aurora

Comparisons of the northern and southern far ultraviolet (UV) auroral emissions of Jupiter from the Hubble Space Telescope (HST) or any other ultraviolet imager have mostly been made so far on a statistical basis or were not obtained with high sensitivity and resolution. Such observations are important to discriminate between different mechanisms responsible for the electron acceleration of the different components of the aurora such as the satellite footprints, the «main oval» or the polar emissions. The field of view of the ACS and STIS cameras on board HST is not wide enough to provide images of the full jovian disk. We thus compare the morphology of the north and south aurora observed 55 min apart and we point out similarities and differences. On one occasion HST pointed successively the two polar regions and auroral images were seen separated by only 3 min. This makes it possible to compare the emission structure and the emitted FUV power of corresponding regions. We find that most morphological features identified in one hemisphere have a conjugate counterpart in the other hemisphere. However, the power associated with conjugate regions of the main oval, diffuse or discrete equatoward emission observed quasi-simultaneously may be different in the two hemispheres. It is not directly nor inversely proportional to the strength of the B-field as one might expect for diffuse precipitation or field-aligned acceleration with equal ionospheric electron density in both hemispheres. Finally, the lack of symmetry of some polar emissions suggests that some of them could be located on open magnetic field lines.     

Geological and thermochronological studies of the Dashui gold deposit, West Qinling Orogen, Central China

The Dashui gold deposit is a structurally controlled, Carlin-type gold deposit hosted by recrystallised limestone in the West Qinling Orogen of Central China. The major, structurally late east-trending Dashui Fault forms the hanging wall to the gold mineralisation at the Dashui mine and defines the contact between Middle Triassic limestone and a steeply dipping overlying succession of Middle Triassic argillaceous limestone, dolomite, and sandstone. Multiple carbonate veins and large-scale supergene enrichment, represented by hematite, goethite, limonite and jarosite, characterise the deposit. Detailed geochronological investigation using zircon SHRIMP U-Pb dating reveals that volcanic rocks closely associated with the Dashui gold deposit were synchronous with the Ge’erkuohe Granite and pre-date mineralisation. The igneous dyke sample from the hanging wall has the same U-Pb zircon age as the footwall, ca. 213 Ma. (U-Th)/He thermochronology on dykes in the hanging wall and footwall of the Dashui Fault yields identical (U-Th)/He zircon ages of ca. 210 Ma but distinct (U-Th)/He apatite ages of ca. 136 and 211 Ma, respectively. Therefore, the hanging wall and footwall are interpreted as having distinct post-mineralisation exhumation histories. Reverse fault movement exhumed the hanging wall ~2 to 4 km since the Late Triassic with the main component of faulting taking place between the Late Triassic and Early Cretaceous. These relationships suggest a Late Triassic to Early Cretaceous age for the primary gold mineralisation at the Dashui gold deposit, with the corollary that any ‘missing portion’ of the deposit, previously hypothesised to exist in the hanging wall of the Dashui Fault, has been eroded away. The mineralisation in the footwall may have been supergene enriched soon after the primary mineralisation was emplaced, because it has been located at shallow depth since the Late Triassic. Semi-quantitative results obtained in this study also constrain the maximum depth of formation of the Dashui gold at no more than 2 km.     

A numerical modelling and experimental study of flow width dynamics on alluvial fans

Alluvial fans are dynamic landforms, the evolution of which is controlled by both external environmental forcing (climate, tectonics and base level change) and internal process‐form feedbacks. The latter include changes in flow configuration (between sheetflow and channelized flow states), driven by aggradation and degradation, which may in turn promote changes in sediment transport capacity. Recent numerical modelling indicates that such feedbacks may lead to dramatic and persistent fan entrenchment in the absence of external forcing. However, the parameterization of flow width within such models is untested to date and is subject to considerable uncertainty. This paper presents results from an experimental study of flow width dynamics on an aggrading fan in which spatial and temporal patterns of fan inundation are monitored continuously using analysis of digital vertical photography. Observed flow widths are compared with results from a simple theoretical model developed for non‐equilibrium (aggradational) conditions. Results demonstrate that the theoretical model is capable of capturing the first‐order characteristics of width adjustment over the course of the experiment, and indicate that flow width is a function of fan aggradation rate. This illustrates that models of alluvial flow width derived for equilibrium conditions may have limited utility in non‐equilibrium situations, despite their widespread use to date. Copyright © 2009 John Wiley & Sons, Ltd.     

Estimating suspended sediment concentrations from turbidity measurements and the calibration problem

In situ turbidity meters are being increasingly used to generate continuous records of suspended sediment concentration in rivers. However, the usefulness of the information obtained depends heavily on the existence of a close relationship between fluctuations in suspended sediment concentration and turbidity and the calibration procedure that relates suspended sediment concentration to the turbidity meter's signal. This study assesses the relationship between suspended sediment concentration and turbidity for a small (1·19 km²) rural catchment in southern Brazil and evaluates two calibration methods by comparing the estimates of suspended sediment concentration obtained from the calibrated turbidity readings with direct measurements obtained using a USDH 48 suspended sediment sampler. With the first calibration method, the calibration relationship is derived by relating the turbidity readings to simultaneous measurements of concentration obtained from suspended sediment samples collected from the vicinity of the turbidity probe during flood events. With the second method, the calibration is based on the readings obtained from the turbidity meter when the probe immersed in samples of known concentration prepared using soils collected from the catchment. Overall, there was a close link between fluctuations in suspended sediment concentration and turbidity in the stream at the outlet of the catchment, and the estimates of sediment concentration obtained using the first calibration method corresponded closely with the conventionally measured sediment concentrations. However, use of the second calibration method introduced appreciable errors. When the estimated sediment concentrations were compared with the measured values, the mean errors were ± 122 mg l^?1 and + 601 mg l^?1 for the first and second calibration procedures respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

The architecture, eruptive history, and evolution of the Table Rock Complex, Oregon: From a Surtseyan to an energetic maar eruption

The Table Rock Complex (TRC; Pliocene–Pleistocene), first documented and described by Heiken [Heiken, G.H., 1971. Tuff rings; examples from the Fort Rock-Christmas Lake valley basin, south-central Oregon. J. Geophy. Res. 76, 5615-5626.], is a large and well-exposed mafic phreatomagmatic complex in the Fort Rock–Christmas Lake Valley Basin, south-central Oregon. It spans an area of approximately 40 km², and consists of a large tuff cone in the south (TRC1), and a large tuff ring in the northeast (TRC2). At least seven additional, smaller explosion craters were formed along the flanks of the complex in the time between the two main eruptions. The first period of activity, TRC1, initiated with a Surtseyan-style eruption through a 60–70 m deep lake. The TRC1 deposits are dominated by multiple, 1-2 m thick, fining upward sequences of massive to diffusely-stratified lapilli tuff with intermittent zones of reverse grading, followed by a finely-laminated cap of fine-grained sediment. The massive deposits are interpreted as the result of eruption-fed, subaqueous turbidity current deposits; whereas, the finely laminated cap likely resulted from fallout of suspended fine-grained material through a water column. Other common features are erosive channel scour-and-fill deposits, massive tuff breccias, and abundant soft sediment deformation due to rapid sediment loading. Subaerial TRC1 deposits are exposed only proximal to the edifice, and consist of cross-stratified base-surge deposits. The eruption built a large tuff cone above the lake surface ending with an effusive stage, which produced a lava lake in the crater (365 m above the lake floor). A significant repose period occurred between the TRC1 and TRC2 eruptions, evidenced by up to 50 cm of diatomitic lake sediments at the contact between the two tuff sequences. The TRC2 eruption was the last and most energetic in the complex. General edifice morphology and a high percentage of accidental material suggest eruption through saturated TRC1 deposits and/or playa lake sediments. TRC2 deposits are dominated by three-dimensional dune features with wavelengths 200–500 m perpendicular to the flow, and 20–200 m parallel to the direction of flow depending on distance from source. Large U-shaped channels (10–32 m deep), run-up features over obstacles tens of meters high, and a large (13 m) chute-and-pool feature are also identified. The TRC2 deposits are interpreted as the products of multiple, erosive, highly-inflated pyroclastic surges resulting from collapse of an unusually high eruption column relative to previously documented mafic phreatomagmatic eruptions.