Shoreline Evolution around a River Entrance

Bacterial Evolution: What Goes Around Comes Around

Over 3 billion years ago, cellular life began anaerobically. A new study now establishes a key link between oxidative stress and proliferation of wall-less bacteria known as L-forms. The finding provides insights into both the origin of life and the potential threat posed by pathogenic L-forms.

Orbital evolution around irregular

The new prooles of the space missions aimed at asteroids and comets, moving from y{bys to rendez{ vous and orbiting, call for new spaceeight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the rst images of as...

Evolution of river dolphins.

The world's river dolphins (Inia, Pontoporia, Lipotes and Platanista) are among the least known and most endangered of all cetaceans. The four extant genera inhabit geographically disjunct river systems and exhibit highly modified morphologies, leading many cetologists to regard river dolphins as an unnatural group. Numerous arrangements have been proposed for their phylogenetic relationships t...

Debris Disk Evolution around a Stars

We report 24 and/or 70 μm measurements of ∼160 A-type main-sequence stars using the Multiband Imaging Photometer for Spitzer (MIPS). Their ages range from 5 to 850 Myr based on estimates from the literature (cluster or moving group associations) or from the H-R diagram and isochrones. The thermal infrared excess is identified by comparing the deviation (∼3% and ∼15% at the 1-σ level at 24 and 7...

A Simple Model for River Network Evolution