Incorporating prior knowledge improves detection of differences in bacterial growth rate

BACKGROUND: Robust statistical detection of differences in the bacterial growth rate can be challenging, particularly when dealing with small differences or noisy data. The Bayesian approach provides a consistent framework for inferring model parameters and comparing hypotheses. The method captures the full uncertainty of parameter values, whilst making effective use of prior knowledge about a given system to improve estimation. RESULTS: We demonstrated the application of Bayesian analysis to bacterial growth curve comparison. Following extensive testing of the method, the analysis was applied to the large dataset of bacterial responses which are freely available at the web-resource, ComBase. Detection was found to be improved by using prior knowledge from clusters of previously analysed experimental results at similar environmental conditions. A comparison was also made to a more traditional statistical testing method, the F-test, and Bayesian analysis was found to perform more conclusively and to be capable of attributing significance to more subtle differences in growth rate. CONCLUSIONS: We have demonstrated that by making use of existing experimental knowledge, it is possible to significantly improve detection of differences in bacterial growth rate

Transient pulsed radio emission from a magnetar

Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >1e14 G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal -- and at >20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars.Comment: accepted by Nature; some new data and significantly revised discussio

Steam reforming of crude glycerol with in situ CO(2) sorption.

Steam reforming of the crude glycerol by-product of a biodiesel production plant has been evaluated experimentally at atmospheric pressure, with and without in situ CO(2) sorption, in a continuous flow fixed-bed reactor between 400 degrees C and 700 degrees C. The process outputs were compared to those using pure glycerol. Thermodynamic equilibrium calculations were used to assess the effect on the steam reforming process of the main crude impurities (methanol and four fatty acid methyl esters). The crude glycerol and steam conversions and the H(2) purity reached 100%, 11% and 68%, respectively at 600 degrees C. No CH(4) was found at and above 600 degrees C. Steam reforming of crude glycerol with in situ CO(2) removal is shown to be an effective means of achieving hydrogen purity above 88% in pre-CO(2) breakthrough conditions