Human motivation and professional practice: of knights, knaves and social workers

Efforts to improve the efficiency and responsiveness of public services by harnessing the self-interest of professionals in state agencies have been widely debated in the recent literature on welfare state reform. In the context of social services, one way in which British policy-makers have sought to effect such changes has been through the "new community care" of the 1990 NHS and Community Care Act. Key to this is the concept of care management, in which the identification of needs and the provision of services are separated, purportedly with a view to improving advocacy, choice and quality for service users. This paper uses data from a wide-ranging qualitative study of access to social care for older people to examine the success of the policy in these terms, with specific reference to its attempts to harness the rational self-interest of professionals. While care management removes one potential conflict of interests by separating commissioning and provision, the responsibility of social care professionals to comply with organizational priorities conflicts with their role of advocacy for their clients, a tension rendered all the more problematic by the perceived inadequacy of funding. Moreover, the bureaucracy of the care management process itself further negates the approach's supposedly client-centred ethos. The definitive version is available at www.blackwell-synergy.com

Release currents of IP₃ receptor channel clusters and concentration profiles

We simulate currents and concentration profiles generated by Ca2+ release from the endoplasmic reticulum (ER) to the cytosol through IP3 receptor channel clusters. Clusters are described as conducting pores in the lumenal membrane with a diameter from 6 nm to 36 nm. The endoplasmic reticulum is modeled as a disc with a radius of 1–12 mm and an inner height of 28 nm. We adapt the dependence of the currents on the trans Ca2+ concentration (intralumenal) measured in lipid bilayer experiments to the cellular geometry. Simulated currents are compared with signal mass measurements in Xenopus oocytes. We find that release currents depend linearly on the concentration of free Ca2+ in the lumen. The release current is approximately proportional to the square root of the number of open channels in a cluster. Cytosolic concentrations at the location of the cluster range from 25 μM to 170 μM. Concentration increase due to puffs in a distance of a few micrometers from the puff site is found to be in the nanomolar range. Release currents decay biexponentially with timescales of < 1 s and a few seconds. Concentration profiles decay with timescales of 0.125–0.250 s upon termination of release.

Exact solutions for cluster-growth kinetics with evolving size and shape profiles

In this paper we construct a model for the simultaneous compaction by which clusters are restructured, and growth of clusters by pairwise coagulation. The model has the form of a multicomponent aggregation problem in which the components are cluster mass and cluster diameter. Following suitable approximations, exact explicit solutions are derived which may be useful for the verification of simulations of such systems. Numerical simulations are presented to illustrate typical behaviour and to show the accuracy of approximations made in deriving the model. The solutions are then simplified using asymptotic techniques to show the relevant timescales of the kinetic processes and elucidate the shape of the cluster distribution functions at large times.