the morphological river evolution at long-time (centuries and even millennia) and large spatial scale (watersheds of several square kilometres) can be described by means of simplified 1d models, able to simulate the variation of bed elevation and grain size composition at non-detailed scales, involving a reduced computational effort. the erosion and deposition phenomena acting along rivers can ...

The lifetimes of chromospheric active regions and active region complexes (\active longitudes") for 35 lower main sequence stars observed at Mount Wilson Observatory are estimated from the relative distribution of pooled variance at diierent time scales. The time scale of active region evolution (i.e., the lifetime of large active regions) is approximately 50 days, while the lifetime of active ...

Over evolutionary time, the morphology of angiosperm pollen has evolved toward an increasing number of apertures, among other things. From a neo-Darwinian point of view, this means that (i) some polymorphism for aperture number must exist and (ii) there must be some fitness increase associated with increasing the aperture number. Pollen types with different aperture numbers often occur in the s...