26,243 research outputs found
Local electromigration model for crystal surfaces
We analyze the dynamics of crystal surfaces in the presence of
electromigration. From a phase field model with a migration force which depends
on the local geometry, we derive a step model with additional contributions in
the kinetic boundary conditions. These contributions trigger various surface
instabilities, such as step meandering, bunching and pairing on vicinal
surfaces. Experiments are discussed
Carbon in soils
Carbon is the fourth most common element in the galaxy(by mass) but does not even rank in the twelve most abundant elements on Earth. By far the most abundant source of carbon on Earth is in the crust as inorganic rocks such as calcite and limestone in marine and sedimentary deposits. These rocks have taken many millions of years to form. Other major inorganic sources are in the oceans and atmosphere
Nitrogen, soils and environment
The article discusses the risk of damaging the environment brought by nitrogen fertilisers which are used for increasing agricultural productivity. The oxidation of ammonium allows for the formation of nitrate. Troposphere ozone and aerosols are produced through the increase of reactive nitrogen in the atmosphere
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