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Any finite generic set of points on the unit circle corresponds to a permutation in a canonical way. We characterise and enumerate the permutations that arise from this correspondence.
A monotone grid class is a permutation class (i.e., a downset of permutations under the containment order) defined by local mono-tonicity conditions. We give a simplified proof of a result of Mur-phy and Vatter that monotone grid classes of forests are partially well-ordered.
A selection of points drawn from a convex polygon, no two with the same vertical or horizontal coordinate, yields a permutation in a canonical fashion. We characterise and enumerate those permutations which arise in this manner and exhibit some interesting structural properties of the permutation class they form. We conclude with a permutation analogue of… (More)
BACKGROUND Carotid endarterectomy (CEA) reduces the risk of stroke in patients with internal carotid stenosis of 50-99 per cent. This study assessed national surgical practice through audit of CEA procedures and outcomes. METHODS This was a prospective cohort study of UK surgeons performing CEA, using clinical audit data collected continuously and… (More)
OBJECTIVE Guidelines recommend that patients suffering an ischaemic transient ischaemic attack (TIA) or stroke caused by carotid artery stenosis should undergo carotid endarterectomy (CEA) within 14 days. METHOD The degree to which UK vascular units met this standard was examined and whether rapid interventions were associated with procedural risks. The… (More)