18 research outputs found

    A systolic inequality for geodesic flows on the two-sphere

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    For a Riemannian metric g on the two-sphere, let lmin(g) be the length of the shortest closed geodesic and lmax(g) be the length of the longest simple closed geodesic. We prove that if the curvature of g is positive and sufficiently pinched, then the sharp systolic inequalities lmin(g)2≤π Area(S2,g)≤lmax(g)2, hold, and each of these two inequalities is an equality if and only if the metric g is Zoll. The first inequality answers positively a conjecture of Babenko and Balacheff. The proof combines arguments from Riemannian and symplectic geometry

    Coral skeletons provide historical evidence of phosphorus runoff on the Great Barrier Reef

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    Recently, the inshore reefs of the Great Barrier Reef have declined rapidly because of deteriorating water quality. Increased catchment runoff is one potential culprit. The impacts of land-use on coral growth and reef health however are largely circumstantial due to limited long-term data on water quality and reef health. Here we use a 60 year coral core record to show that phosphorus contained in the skeletons (P/Ca) of long-lived, near-shore Porites corals on the Great Barrier Reef correlates with annual records of fertiliser application and particulate phosphorus loads in the adjacent catchment. Skeletal P/Ca also correlates with Ba/Ca, a proxy for fluvial sediment loading, again linking near-shore phosphorus records with river runoff. Coral core records suggest that phosphorus levels increased 8 fold between 1949 and 2008 with the greatest levels coinciding with periods of high fertiliser-phosphorus use. Periods of high P/Ca correspond with intense agricultural activity and increased fertiliser application in the river catchment following agricultural expansion and replanting after cyclone damage. Our results demonstrate how coral P/Ca records can be used to assess terrestrial nutrient loading of vulnerable near-shore reefs

    Kisten ras mutations in patients with colorectal cancer: the “RASCAL II” study.

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    This collaborative study suggests that not only is the presence of a codon 12 glycine to valine mutation important for cancer progression but also that it predispose to more aggressive biological behaviour in patients with advanced colorectal cancer
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