Phototrophic biofilms and their potential applications

Phototrophic biofilms occur on surfaces exposed to light in a range of terrestrial and aquatic environments. Oxygenic phototrophs like diatoms, green algae, and cyanobacteria are the major primary producers that generate energy and reduce carbon dioxide, providing the system with organic substrates and oxygen. Photosynthesis fuels processes and conversions in the total biofilm community, including the metabolism of heterotrophic organisms. A matrix of polymeric substances secreted by phototrophs and heterotrophs enhances the attachment of the biofilm community. This review discusses the actual and potential applications of phototrophic biofilms in wastewater treatment, bioremediation, fish-feed production, biohydrogen production, and soil improvement

On the super-Rayleigh/subseismic elastodynamic indentation problem

The elastodynamic super-Rayleigh/subseismic indentation paradox is examined in this paper. Both the Craggs/Roberts steady-state problem and the Robinson/Thompson transient problem are reconsidered. Certain features of these solutions are discussed from a new point of view, by considering asymptotics at the end of the contact region, the influence of contact inequalities, energetics of the process and existence/uniqueness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42681/1/10659_2004_Article_BF00044967.pd

Ionization Mechanisms in Two-Temperature Air Plasmas

Investigations have been conducted to understand and experimentally validate the mechanisms of ionization in two-temperature atmospheric pressure air plasmas in which the electron temperature is elevated with respect to the gas temperature. The first part of the paper reports the results of numerical simulations performed with a new two-temperature chemical kinetic model, with reaction rate coefficients determined as weighted sums of elementary rate coefficients over the internal energy levels of atomic and molecular species. These calculations yield the surprising result that, for a given constant gas temperature, the steady-state electron number density exhibits an S-shaped dependence on the electron temperature. The middle limb of the S-shaped curve, which corresponds to electron number densities between approximately 10 13 and 10 17 e - /cm 3 , is found to be kinetically unstable. This S-shaped behavior is caused by competing ionization, charge transfer reactions, two-body dissociative recombination, and three-body electron recombination reactions, and therefore is characteristic of molecular plasmas. The numerical results are then interpreted in terms of macroscopic discharge parameters (electric field and current density) by means of Ohm's law and the electron energy equation. The resulting current density vs. electric field characteristic also exhibits an S-shaped dependence, which suggests that it may not possible to operate a stable discharge at electron number densities greater than 10 13 cm -3 by the sole use of a discharge operating at constant electric field. On the other hand, it may be possible to produce stable air plasmas by operating the electrical discharge at constant current density, as the electric field vs. current density characteristi..