THIS ISSUE

摘要

Atmospheric aerosol particles are crucial to the existence of clouds as we know them. It is thought that the aerosol can affect the ability of clouds to form precipitation and in turn cloudiness. But how, in detail, do clouds -and through them the radiative forcing of the global climate system - depend on the aerosol? Bjorn Stevens and Graham Feingold propose that past difficulties in untangling relationships between the aerosol, clouds and precipitation reflect in part a failure to take into account the many processes that act to buffer cloud and precipitation responses to aerosol perturbations. To counter this, say Stevens and Feingold, research needs to focus on understanding specific regimes of aerosol, cloud and precipitation. [Review p. 607]rnDeregulation of the Wnt pathway, a signalling system involved in embryogenesis and in many other processes in living cells, is implicated in many cancers, making it an attractive target for anticancer therapies. But while inhibitors of Notch and Hedgehog pathways have reached the clinical trial stage, 'drugable' targets for Wnt inhibitors have proved elusive. Now, using a chemical genetics approach, a small molecule inhibitor of the Wnt pathway has been identified and its target and mechanism of action characterized.