Geological constraints on mesoscale coastal barrier behaviour

Barrier/lagoon systems occupy a significant part of the world’s coast. They are diverse in size, morphology, geological and oceanographic setting, and morphodynamic behaviour. Understanding the behaviour of barriers at 101 to 102 year and 101 to 102 kilometre scales (mesoscale) is an important scientific and societal goal, not least because of the preponderance of intensive coastal development in a time of global climate change. Such understanding presents significant challenges. Challenges in describing mesoscale system behaviour relate largely to the incomplete evidence base of (i) morphological change in system components, (ii) dynamic and internal forcing factors (drivers) and (iii) geological constraints. These shortcomings curtail the development of baseline datasets against which to test models. Understanding observed changes and thereby predicting future behavioural patterns demands assumptions and simplifications regarding the linkages between initial state, dynamic drivers, system feedbacks and a multiplicity of geological constraints that are often location-specific. The record of mesoscale change is improving with the acquisition of long-term morphological datasets. Advances in technology and chronological control mean that geological investigations can now provide decadal to century-scale temporal resolution of morphological change. In addition, exploratory modelling is improving understanding of the influence of various dynamic and geological factors. Straightforward linking of dynamic forcing and response is seldom able to account for observed mesoscale behaviour. Geological factors exert a significant or even dominant control on barrier behaviour at decadal to century timescales. Whereas these geological controls can be quantified to some extent by detailed investigations of contemporary barrier/lagoon morphology and constituent materials, underlying geology and topography and sediment supply, in all but a few locations, such data are absent. This sets an unavoidable constraint on efforts to quantitatively predict the future behaviour of barrier systems, which are strongly site-specific in terms of their geological setting and morphology. Geological controls exist in a network of interactions that individually and collectively influence mesoscale barrier behaviour. Dominant, first-order controls are: • Basement slope; • Basement irregularity and erodibility; • External sediment supply; • Orientation; and • Shoreline lithification (beachrock and aeolianite) An important intermediate level of geological control is exerted by shoreface morphology. Shorefaces are themselves influenced by underlying geological factors, but they are dynamic at longer timescales than barriers. Geological influences are in most cases unquantified and are usually disregarded when conceptualizing and modelling barrier evolution. Consideration of the geological influences is, however, essential in efforts to predict future behaviour at mesoscale (management) timescales

Community-based DOTS and family member DOTS for TB control in Nepal: costs and cost-effectiveness

<p>Abstract</p> <p>Background</p> <p>Two TB control strategies appropriate for South Asia (a community-based DOTS [CBD] strategy and a family-based DOTS [FBD] strategy) have been shown to be effective in Nepal in meeting the global target for the proportion of registered patients successfully treated. Here we estimate the costs and cost-effectiveness of the two strategies. This information is essential to allow meaningful comparisons between these and other strategies and will contribute to the small but growing body of knowledge on the costs and cost-effectiveness of different approaches to TB control.</p> <p>Methods</p> <p>In 2001–2, costs relating to TB diagnosis and care were collected for each strategy. Structured and semi-structured questionnaires were used to collect costs from health facility records and a sample of 10 patients in each of 10 districts, 3 using CBD and 2 using FBD. The data collected included costs to the health care system and social costs (including opportunity costs) incurred by patients and their supervisors. The cost-effectiveness of each strategy was estimated.</p> <p>Results</p> <p>Total recurrent costs per patient using the CBD and FBD strategies were US$76.2 and US$84.1 respectively. The social costs incurred by patients and their supervisors represent more than a third of total recurrent costs under each strategy (37% and 35% respectively). The CBD strategy was more cost-effective than the FBD strategy: recurrent costs per successful treatment were US$91.8 and US$102.2 respectively.</p> <p>Discussion</p> <p>Although the CBD strategy was more cost-effective than the FBD strategy in the study context, the estimates of cost-effectiveness were sensitive to relatively small changes in underlying costs and treatment outcomes. Even using these relatively patient-friendly approaches to DOTS, social costs can represent a significant financial burden for TB patients.</p

New detections of HC5N towards hot cores associated with 6.7 GHz methanol masers

We present new detections of cyanodiacetylene (HC5N) towards hot molecular cores, observed with the Tidbinbilla 34 m radio telescope (DSS–34). In a sample of 79 hot molecular cores, HC5N was detected towards 35. These results are counter to the expectation that long chain cyanopolyynes, such as HC5N, are not typically found in hot molecular cores, unlike their shorter chain counterpart HC3N. However, it is consistent with recent models which suggest HC5N may exist for a limited period during the evolution of hot molecular cores