Proton transport model in the ionosphere .1. Multistream approach of the transport equations

The suprathermal particles, electrons and protons, coming from the magnetosphere and precipitating into the high-latitude atmosphere are an energy source of the Earth's ionosphere. They interact with ambient thermal gas through inelastic and elastic collisions. The physical quantities perturbed by these precipitations, such as the heating rate, the electron production rate, or the emission intensities, can be provided in solving the kinetic stationary Boltzmann equation. This equation yields particle fluxes as a function of altitude, energy, and pitch angle. While this equation has been solved through different ways for the electron transport and fully tested, the proton transport is more complicated. Because of charge-changing reactions, the latter is a set of two-coupled transport equations that must be solved: one for protons and the other for H atoms. We present here a new approach that solves the multistream proton/hydrogen transport equations encompassing the collision angular redistributions and the magnetic mirroring effect. In order to validate our model we discuss the energy conservation and we compare with another model under the same inputs and with rocket observations. The influence of the angular redistributions is discussed in a forthcoming paper.

Targeted drug delivery to the skin and deeper tissues: Role of physiology, solute structure and disease

1. Drug delivery through the skin has been used to target the epidermis, dermis and deeper tissues and for systemic delivery, The major barrier for the transport of drugs through the skin is the stratum corneum, with most transport occurring through the intercellular region, The polarity of the intercellular region appears to be similar to butanol, with the diffusion of solutes being hindered by saturable hydrogen bonding to the polar head groups of the ceramides, fatty acids and other intercellular lipids, Accordingly, the permeability of the more lipophilic solutes is greatest from aqueous solutions, whereas polar solute permeability is favoured by hydrocarbon-based vehicles. 2. The skin is capable of metabolizing many substances and, through its microvasculature, limits the transport of most substances into regions below the dermis. 3. Although the flux of solutes through the skin should be identical for different vehicles when the solute exists as a saturated solution, the fluxes vary in accordance with the skin penetration enhancement properties of the vehicle. It is therefore desirable that the regulatory standards required for the bioequivalence of topical products include skin studies. 4. Deep tissue penetration can be related to solute protein binding, solute molecular size and dermal blood flow. 5. Iontophoresis is a promising area of skin drug delivery, especially for ionized solutes and when a rapid effect is required. 6. In general, psoriasis and other skin diseases facilitate drug delivery through the skin. 7. It is concluded that the variability in skin permeability remains an obstacle in optimizing drug delivery by this route.