Induction in arbitrarily shaped oceans VI, oceans of variable depth

We present calculations of t he electric currents induced in a model ocean by the 24 hr Sq variation. The model has realistic bathymetry and represents a further step of a consistent approach to oceanic induction in which we have introduced various complexities in order of priority. The solution obtained is compared with our previously published results for the case of an ocean of realistic shape and uniform depth. It is found that the major shelf-seas considerably modify the pattern of elect ric current circu­ lation in the oceans of the southern hemisphere. The consistent nature of the method of matched outer and inner expansions which we have used is also discussed. It seems probable that other methods, not limited to finding an outer solution and consequently more complicated, will at best only produce an outer solution since, in practice, the relatively coarse mesh necessarily used in the computation of realistic global problems precludes a fine resolution of the coastal bathymetry. Finally , the meaning of the internal and external Legendre coefficients and their relationship to Sq over the oceans is briefly discussed

Induction in arbitrarily shaped oceans. V, the circulation of Sq-induced currents around land masses

The model ocean used in previous papers in this series is refined to allow for five separate land masses. The ocean is taken to be of uniform depth, and insulated from the mantle which is modelled by an infinitely conducting core at uniform depth. The fast method of solution introduced in Paper IV enables the electric currents induced by Sq to be calculated on a 2° x 2° global mesh. The 'outer' solution away from the coast is calculated. The 'inner' solution will be a coastal correction different for every coastal configuration. The current is allowed to circulate round isolated land masses, giving markedly different patterns from those in Paper IV. For some harmonics it appears necessary to differentiate even between Australia and New Zealand, although the world-wide effect of the remote island of Spitz­ bergen is minimal. Current distributions are shown for periods of 6, 8, 12 and 24 hr, and a value is set on the current streaming between the various land masses for all the Legendre harmonics considered

Induction in arbitrarily shaped oceans. IV, sq for a simple case

World curves are presented of electric currents induced in electrically insulated oceans by Sq using a perfectly conducting sphere to simulate the underlying mantle. The curves are valid everywhere away from those coastal regions at which the sea bed rises steeply. In such cases an edge correction may be needed. The numerical computations are for periods of 6, 8, 12 and 24 hr and comparison is made with results obtained by others for a 24-hr period. Circulation conditions around the island are ignored in this note

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee

Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. METHODS: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. FINDINGS: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. INTERPRETATION: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin