The high flux of cosmic rays onto the unshielded surface of Mars poses a significant hazard to the survival of martian microbial life. Here, we determined the survival responses of several bacterial strains to ionizing radiation exposure while frozen at a low temperature characteristic of the martian near-subsurface. Novel psychrotolerant bacterial strains were isolated from the Antarctic Dry Valleys, an environmental analogue of the martian surface, and identified by 16S rRNA gene phylogeny as representatives of Brevundimonas, Rhodococcus, and Pseudomonas genera. These isolates, in addition to the known radioresistant extremophile Deinococcus radiodurans, were exposed to gamma rays while frozen on dry ice (-79°C). We found D. radiodurans to exhibit far greater radiation resistance when irradiated at -79°C than was observed in similar studies performed at higher temperatures. This greater radiation resistance has important implications for the estimation of potential survival times of microorganisms near the martian surface. Furthermore, the most radiation resistant of these Dry Valley isolates, Brevundimonas sp. MV.7, was found to show 99% 16S rRNA gene similarity to contaminant bacteria discovered in clean rooms at both Kennedy and Johnson Space Centers and so is of prime concern to efforts in the planetary protection of Mars from our lander probes. Results from this experimental irradiation, combined with previous radiation modeling, indicate that Brevundimonas sp. MV.7 emplaced only 30 cm deep in martian dust could survive the cosmic radiation for up to 100,000 years before suffering 10⁶ population reduction.

The direct borohydride fuel cell (DBFC) has attracted increasing interest as a potential high power source for mobile and portable applications. Engineering design plays an important role in the development of the DBFC. This paper reports data for the selection of anode, cathode, and membrane materials for the DBFC. The best DBFC performance is achieved with a Au anode, a Pt cathode, and a 3541P ion exchange membrane. The use of non‐precious catalysts, e.g., Ag, leads to promising results.

Proton-exchange-membrane fuel cells (PEMFCs) have received considerable interest as a reliable power source due to their ability to attain high power densities with high energy efficiency. 1 A vital component of the PEMFC is the proton exchange membrane (PEM), which provides the ionic path between the anode and the cathode while separating the two reactant gases. The PEM material most frequently used for this type of application is Nafion ® due to its chemical and mechanical stability and its commercial availability. Since Nafion is relatively costly, much research is being directed toward developing less expensive membrane materials. 2 One such alternative class of membrane derives from studies of radiation-grafted polymerization of styrene monomer into matrices such as fluorinated ethylene propylene (FEP), ethylenetetrafluoroethylene (ETFE), and poly(vinylidene fluoride) (PVDF) with subsequent sulfonation of the polystyrene. 3-6 The grafting and sulfonation processes allow the introduction of ionic conductivity while maintaining the mechanical characteristics of the base polymer. The process uses prefabricated commercial films and thus circumvents difficulties in obtaining thin films of uniform thickness. Parameters such as cross-linking density and membrane thickness can also be controlled. 3,7 The first step in the radiation-grafting technique is irradiation of the base polymer membrane usually with a gamma-source or electron-beam to form radicals on the polymer backbone. This is followed by introduction of the monomer, subsequent copolymerization, and concurrent attachment to the base polymer as a graft chain. Finally, the grafted chains are sulfonated. 3 Scherer's group has studied the radiation grafting approach extensively. They have explored the influence of synthetic conditions on the degree of grafting, structure, and physicochemical properties of FEP-g-polystyrenesulfonic acid (PSSA) films and evaluated their performance, stability, and degradation in PEMFCs. 3,4,7-9 From these studies they have been able to identify important membrane properties, for example: optimum thickness, cross-linking density, and specific resistance required for fuel-cell applications. 3 The performance of PEMFCs is dependent on many factors, but three are prominent and involve the PEM: (i) the ohmic overpotential due to membrane resistance, (ii) the activation overpotential due to slow kinetics of the oxygen reduction reaction (ORR) at the electrode/membrane interface, and (iii) the concentration overpotential due to mass-transport limitations of oxygen to the electrode surface. 10 In order to understand fully the applicability of PEMs in PEMFCs, it is important that the materials be systematically investigated to establish correlations between membrane composition and electrochemical properties. A better understanding of these properties at a fundamental level should lead to further advances in membrane development for applications in PEMFCs.Lehtinen et al. have studied the electrochemical properties of PVDF-g-PSSA membrane...

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