[en] The long-range transfer processes (range, R approx. 20-50 A) of excess electrons produced by radiolysis of molecular solids are analyzed in terms of an orbital overlap model. A united atom approximation makes possible the separation of angular and radial factors. The angular dependence is used to treat the effect of the relative orientation of donor and acceptor molecules on the transfer rate; variations of up to a factor of approx. 1000 are predicted. A distinction is drawn between reactions of electrons with scavengers (or transfer between additives), where the significant overlap is localized around donor and acceptor sites, and recombination with a cation produced by the radiolysis, where the overlap is largely spread out over the intervening volume. In the former case, interference due to nodes in the wave functions is significant, while in the latter, various powers of R appear in the preexponential factor. The role of the Franck--Condon principle in determining the effective barrier height is discussed. Electronic interaction is also important in determining transfer rates for different donors and acceptors. 3 figures, 2 tables

[en] On the Alba Patera volcanic shield of Mars, a Hesperian flood-lava phase was followed by the extrusion of sheet lavas and tube-fed lavas emerging in many cases from the flanking fissures of rising domes. These events were followed by the eruption of additional sheet and tube-fed lavas from linear vents which formed complex flow fields. Later, Amazonian volcanism at Alba involved long, narrow flows from two complex summit calderas; the thermal energy outflow for some individual flows would have been substantially greater than the annual heat loss of the earth through volcanism, implying that the process of patera-building represented substantial Martian geological heat-loss during the planet's early volcanic-centralization stages. 40 refs

[en] It has recently been demonstrated that the dramatic effects of plasma precipitation and convection on the composition and dynamics of the polar thermosphere and ionosphere include a number of strong interactive, or feedback, processes. To aid the evaluation of these feedback processes, a joint three dimensional time dependent global model of the Earth's thermosphere and ionosphere was developed in a collaboration between University College London and Sheffield University. This model includes self consistent coupling between the thermosphere and the ionosphere in the polar regions. Some of the major features in the polar ionosphere, which the initial simulations indicate are due to the strong coupling of ions and neutrals in the presence of strong electric fields and energetic electron precipitation are reviewed. The model is also able to simulate seasonal and Universal time variations in the polar thermosphere and ionospheric regions which are due to the variations of solar photoionization in specific geomagnetic regions such as the cusp and polar cap