A modified hyperbolic tangent equation to determine equilibrium shape of headland bay beaches

When designing any artificial beach, it’s desirable to avoid (or minimise) future maintenance commitments by arranging the initial beach planshape so that it remains in equilibrium given the incident wave climate. Headlands bays, or embayments, where a sandy beach is held between two erosion resistant headlands, tend to evolve to a stable beach planshape with little movement of the beach contours over time. Several empirical bay shape equations have been derived to fit curves to the shoreline of headland bay beaches. One of the most widely adopted empirical equations is the parabolic bay shape equation, as it is the only equation that directly links the shoreline positions to the predominant wave direction and the point of diffraction. However, the main limitation with the application of the parabolic bay shape equation is locating the downcoast control point. As a result of research presented in this paper a new equation, based on the hyperbolic tangent shape equation was developed, which eliminates the requirement of placing the down coast control point and relies on defining a minimum beach width instead. This modified equation was incorporated into a new ArcGIS tool

Erosion and the sediment conveyor in central Australia

Why are the Neogene sedimentary fills across central Australia generally thin and discontinuous? One long-standing explanation is that sluggish tectonism and intensified aridity have combined to suppress rates of erosion and sediment production yielding a landscape crowded with inherited, preMiocene forms. Quantifying rates of sediment production, residence time and transport is possible with numerous methods, but the recent growth of cosmogenic nuclide (CN) analysis has provided unprecedented quantitative insights to rates of landscape evolution. Measurements of in situ produced cosmogenic 10Be and 26Al integrate rates of surface processes over million-year timescales—the last part of the Neogene in which aridity has strengthened across the continental interior. We present a compilation of ~600 published and unpublished 10Be and 26Al measurements from central Australia with a focus on the Neogene Eyre Basin and its periphery. Outlying and inlying bedrock uplands serve as engines of sediment production via erosion of bedrock. Surrounding the bedrock outcrops are vast sediment conveyors of varying efficiency and tempo: hillslopes, pediments, and alluvial fans are interim storage/burial zones for sediment in transit to the network of low-gradient rivers, dunes, and playas towards base level. Interactions between fluvial and aeolian processes are especially pertinent to sediment flux in the Eyre Basin. Major rivers such as the Cooper and Finke traverse dunefields in their lower reaches where quantities of alluvia are recirculated into dunes and vice versa. Tracking the trajectories of sediment from source-to-sink (including aeolian recirculation) remains a major challenge, but is central to unravelling the sedimentary dynamics of central Australia's Neogene basins. Based on the CN compilation we estimate 1) spatially averaged erosion rates at the scale of a hillslope or river catchment; 2) pointbased erosion rates on bedrock surfaces; 3) residence time of sediment in hillslope regolith and alluvial fans; and 4) cumulative burial history of sediments in transit. Catchment-scale erosion rates (n~100) are consistently low (<10 m/Myr) and include some of the lowest rates ever measured (~0.3 m/Myr); however, a small group of catchments in the Flinders Ras yield higher erosion rates (~30–60 m/Myr). Bedrock hillslopes (n~200) tend to erode even slower (<5 m/Myr), with a subset of Flinders Ras sites again being the exception (~10–30 m/Myr) and suggesting the influence of recent tectonism. Several CN depth-profiles measured on hillslopes and alluvial fans indicate sediment residence times >0.5 Myr, and high-resolution sampling along three hillslopes with differing morphology (linear, convex, and concave) reveals major variations in sediment production and transport rates that hint at the long-term evolution. In the rivers, fluvial sediments show a weak tendency to increase cumulative burial history downstream (1–2 Myr), consistent with the expanding accommodation space for storage and burial. Dune sediments sampled in the Simpson and Tirari dunefields (n~16) contain cumulative burial histories (up to 1.5 Myr) similar to that of the intersecting rivers. This points to an intimate mix of fluvial and aeolian processes in areas approaching base level. Curiously, these sediments occur in the lowest part of the continent and contain the longest histories of cumulative burial, yet do not form part of the thickest sedimentary fills in the Eyre Basin

Percutaneous Coronary Intervention Versus Medical Therapy for Chronic Total Occlusion of Coronary Arteries:A Systematic Review and Meta-Analysis

PURPOSE OF REVIEW: Chronic total occlusion (CTO) of the coronary arteries is a significant clinical problem and has traditionally been treated by medical therapy or coronary artery bypass grafting. Recent studies have examined percutaneous coronary intervention (PCI) as an alternative option. RECENT FINDINGS: This systematic review and meta-analysis compared medical therapy to PCI for treating CTOs. PubMed and Embase were searched from their inception to March 2019 for studies that compared medical therapy and PCI for clinical outcomes in patients with CTOs. Quality of the included studies was assessed by Newcastle-Ottawa scale. The results were pooled by DerSimonian and Laird random- or fixed-effect models as appropriate. Heterogeneity between studies and publication bias was evaluated by I2 index and Egger's regression, respectively. Of the 703 entries screened, 17 studies were included in the final analysis. This comprised 11,493 participants. Compared to PCI, medical therapy including randomized and observational studies was significantly associated with higher risk of all-cause mortality (risk ratio (RR) 1.99, 95% CI 1.38-2.86), cardiac mortality (RR 2.36 (1.97-2.84)), and major adverse cardiac event (RR 1.25 (1.03-1.51)). However, no difference in the rate of myocardial infarction and repeat revascularization procedures was observed between the two groups. Univariate meta-regression demonstrated multiple covariates as independent moderating factors for myocardial infarction and repeat revascularization but not cardiac death and all-cause mortality. However, when only randomized studies were included, there was no difference in overall mortality or cardiac death. In CTO, when considering randomized and observational studies, medical therapy might be associated with a higher risk of mortality and myocardial infarction compared to PCI treatment

Continuity and change in the institution of town and country planning: modelling the role of ideology

The institution of town and country planning rests upon ideas and concepts which will always be contested. Such concepts include ‘liberty’, ‘community’, ‘society’ and ‘the state’. It is a function of political ideology to seek to fix the meanings of contested concepts and thus exert control over political reality. By analysing the particular conceptual structure of the ideologies which seek to influence planning from positions of political power, the analyst can show how these ideologies are related to shifts in the conceptual and institutional structure of planning. The paper illustrates this analytical method in the context of the transition from the ideology of New Labour to the ideology of the Conservative-led Coalition government in England after 2010