Modelling Abduction in Science by means of a Modal Adaptive Logic

Scientists confronted with multiple explanatory hypotheses as a result of their abductive inferences, generally want to reason further on the different hypotheses one by one. This paper presents a modal adaptive logic MLA ^s that enables us to model abduction in such a way that the different explanatory hypotheses can be derived individually. This modelling is illustrated with a case study on the different hypotheses on the origin of the Moon.     

High brightness electron beam from a multi-walled carbon nanotube

Carbon nanotubes can act as electron sources with very rigid structures, making them particularly interesting for use as point electron sources in high-resolution electron-beam instruments. Promising results have been reported with respect to some important requirements for such applications: a stable emitted current and a long lifetime. Two parameters of an electron source affect the resolution of these instruments: the energy spread of the emitted electrons and a parameter called the reduced brightness, which depends on the angular current density and the virtual source size. Several authors have measured a low energy spread associated with electron emission. Here we measure the reduced brightness, and find a value that is more than a factor of ten larger than provided by state-of-the-art electron sources in electron microscopes. In addition, we show that an individual multi-walled carbon nanotube emits most current into a single narrow beam. On the basis of these results, we expect that carbon nanotube electron sources will lead to a significant improvement in the performance of high-resolution electron-beam instruments.