Doctors' thinking about the system as a threat to patient safety

‘Systems thinking’ is an important feature of the emerging ‘patient safety’ agenda. As a key component of a ‘safety culture’, it encourages clinicians to look past individual error to recognise the latent factors that threaten safety. This paper investigates whether current medical thinking is commensurate with the idea of ‘systems thinking’ together with its implications for policy. The findings are based on qualitative semistructured interviews with specialist physicians working within one NHS District General Hospital in the English Midlands. It is shown that, rather then favouring a 'person-centred’ perspective, doctors readily identify ‘the system’ as a threat to patient safety. This is not necessarily a reflection of the prevailing safety discourse or knowledge of policy, but reflects a tacit understanding of how services are (dis)organised. This line of thinking serves to mitigate individual wrong-doing and protect professional credibility by encouraging doctors to accept and accommodate the shortcomings of the system, rather than participate in new forms of organisational learning.

DNA charge neutralisation by linear polymers II: reversible binding

We model the way in which polymers bind to DNA and neutralise its charged backbone by analysing the dynamics of the distribution of gaps along the DNA. We generalise existing theory for irreversible binding to construct new deterministic models which include polymer removal, movement along the DNA and allow for binding with overlaps. We show that reversible binding alters the capacity of the DNA for polymers by allowing the rearrangement of polymer positions over a longer timescale than when binding is irreversible. When the polymers do not overlap, allowing reversible binding increases the number of polymers adhered and hence the charge that the DNA can accommodate; in contrast, when overlaps occur, reversible binding reduces the amount of charge neutralised by the polymers.

Two-dimensional Stokes flow driven by elliptical paddles

A fast and accurate numerical technique is developed for solving the biharmonic equation in a multiply connected domain, in two dimensions. We apply the technique to the computation of slow viscous flow (Stokes flow) driven by multiple stirring rods. Previously, the technique has been restricted to stirring rods of circular cross section; we show here how the prior method fails for noncircular rods and how it may be adapted to accommodate general rod cross sections, provided only that for each there exists a conformal mapping to a circle. Corresponding simulations of the flow are described, and their stirring properties and energy requirements are discussed briefly. In particular the method allows an accurate calculation of the flow when flat paddles are used to stir a fluid chaotically.