We have developed a macroscopic description of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays due to the presence of the geo-magnetic field. This description offers a simple and direct insight in the relation between the properties of the air shower and the time-structure of the radio pulse.

We study the adsorption and the dissociation of O molecules on the active sites of a boron-doped pyrolyzed Fe-N-C catalyst using density functional theory. Initially, we determine the possible structure of the FeN active site of the pyrolyzed Fe-N-C catalyst doped with a boron atom by considering the presence of a nitrogen atom as a metal-free site. The most stable configuration of the structure occurs when the boron and nitrogen atoms coalesce with the FeN site forming a complex site. This structure has higher stability compared to the undoped FeN site. The doped FeN possesses the unique ability to adsorb an oxygen molecule in a side-on mode due to the presence of the boron-nitrogen pair acting as a supporting site. One O atom of the O molecule sticks strongly to the top of the iron atom, while the other binds with the boron atom. This O side-on adsorption stretches the O-O bond length by 15%. Furthermore, the examined catalyst surface can dissociate the oxygen molecule easily with only half the energy barrier of the undoped FeN structure.

The interaction between neighbouring FeN4 and Psubs sites of a P-doped pyrolyzed Fe/N/C catalyst promotes four-electron reduction through associative and dissociative mechanisms.

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We investigate the interaction between zinc-porphyrin and oxygen molecule in zinc-porphy-rin(oxygen) complex using the first principles calculation. At first, we study the electronic and geometric structures of zinc-porphyrin and compare with other metalloporphyrin (metal = Mn, Fe, Co, and Ni). We demonstrate that the electronic structures of zinc-porphyrin are completely different with other metalloporphyrin, therefore its interaction with oxygen molecule is also different. In the ground state, the complex prefers the form 3 ( 1 ZnP-3 O 2 ). The singlet oxygen generation can be accessed through 1 (ZnP-O 2 ) complex. The excited singlet state of the complex prefers the form 1 ( 1 ZnP-1 O 2 ) and allows the interaction between ZnP and O 2 via charge transfer. Furthermore, we construct a mechanism for the quenching of 3 ZnP induced by 3 O 2 where ZnP-O 2 complexes act as the intermediate states.