Sunday, November 29, 2015
ignalling processes in organisms are governed by specific extracellular and intracellular interactions and involve hundreds of different functionally highly versatile receptors situated in cell membranes. For scientists wishing to understand signalling processes the situation is made more complex by the receptors not only being unevenly distributed and often able to bind more than one ligand but also by the same type of receptor being able to bind a ligand strongly, weakly or not at all. New methods that allow precise quantifications of such complex interactions are urgently required.
When ESA launched its fifth and sixth Galileo navigation satellites, things went wrong. Because of a fault in the upper stage, both spacecraft ended up in elongated elliptical orbits instead of circular ones, making them unusable for navigation. Corrections of their orbits restored their function as navigation satellites, but their orbits still remained highly elliptical. To the satellite navigation engineers, this was a nuisance requiring changes in the software and the technology. But for physicists, the eccentric orbits offered an unexpected opportunity. Researchers at both Sytèmes de Référence Temps Espace and ZARM convinced ESA to use the satellites to test more extensively an effect predicted by Einstein's general relativity.
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