877 research outputs found
Sequestration of noble gases in giant planet interiors
The Galileo probe showed that Jupiter's atmosphere is severely depleted in
neon compared to protosolar values. We show, via ab initio simulations of the
partitioning of neon between hydrogen and helium phases, that the observed
depletion can be explained by the sequestration of neon into helium-rich
droplets within the postulated hydrogen-helium immiscibility layer of the
planet's interior. We also demonstrate that this mechanism will not affect
argon, explaining the observed lack of depletion of this gas. This provides
strong indirect evidence for hydrogen-helium immiscibility in Jupiter
Grazers and diggers: exploitation competition and coexistence among foragers with different feeding strategies on a single resource
A mathematical model is presented that describes a system where two consumer species compete exploitatively for a single renewable resource. The resource is distributed in a patchy but homogeneous environment; that is, all patches are intrinsically identical. The two consumer species are referred to as diggers and grazers, where diggers deplete the resource within a patch to lower densities than grazers. We show that the two distinct feeding strategies can produce a heterogeneous resource distribution that enables their coexistence. Coexistence requires that grazers must either move faster than diggers between patches or convert the resources to population growth much more efficiently than diggers. The model shows that the functional form of resource renewal within a patch is also important for coexistence. These results contrast with theory that considers exploitation competition for a single resource when the resource is assumed to be well mixed throughout the system.Shane A. Richards, Roger M. Nisbet, William G. Wilson, and Hugh P. Possingha
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