(couleur) grey (Grande-Bretagne) , gray (USA) il fait gris it's a dull day, it's a grey day. faire grise mine to look morose. faire grise mine Ã  qn to give sb a cool reception.
In electrophilic aromatic substitution, the benzene ring acts as an electron donor (Lewis base or nucleophile) and reacts with an electron acceptor (Lewis acid or electrophile). The result of electrophilic aromatic substitution reactions is that an aromatic hydrogen is replaced by some other atom or functional group.
2.11.1 Introduction-Simple recombination model. recomb.gif. Fig.2.11.1 Carrier recombination mechanisms in semiconductors. Band-to-band recombination occurs when an electron falls from its state in the conduction band into the empty state in the valence band which is associated with the hole.This band-to-band transition is typically also a radiative transition in direct bandgap semiconductors. simple model for the recombination-generation mechanisms states that the recombination-generation rate is proportional to the excess carrier density. It acknowledges the fact that no recombination takes place if the carrier density equals the thermal equilibrium value.