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