Research plans in Europe for radiation health hazard assessment in exploratory space missions.

The European Space Agency (ESA) is currently expanding its efforts in identifying requirements and promoting research towards optimizing radiation protection of astronauts. Space agencies use common limits for tissue (deterministic) effects on the International Space Station. However, the agencies have in place different career radiation exposure limits (for stochastic effects) for astronauts in low-Earth orbit missions.

Adsorption properties of oligo(fluorooxetane)-b-poly(ethylene oxide)-b-oligo(fluorooxetane) triblock copolymers at the air-water interface: comparison of hydroxyl and acetate end groups.

ABA triblock copolymers, where A is an oligo(fluorooxetane) and B is poly(ethylene oxide) (PEO), are prepared easily using an alpha,omega-dihydroxy PEO initiator and cationic, ring-opening polymerization of a fluorinated oxetane monomer. Terminal hydroxyl groups can be converted readily and quantitatively to acetate groups using acetic anhydride. Both types of triblock copolymers are surface active in water.

Synthesis, characterization, adsorption, and interfacial rheological properties of four-arm anionic fluorosurfactants.

Four-arm oligo(fluorooxetane) tetraols containing -CF3 and -C2F5 groups were prepared in reasonable yields by cationic, ring-opening polymerization of fluorinated oxetane monomers using a tetrafunctional, alkoxylated polyol as initiator and BF3.THF as catalyst. The tetraols were then converted to ammonium sulfate salts using oleum followed by neutralization with ammonium hydroxide in excellent yields.

Effect of binding of an oligomeric cationic fluorosurfactant on the dilational rheological properties of gelatin adsorbed at the air-water interface.

The effect of binding of an oligomeric cationic fluorooxetane surfactant on the interfacial properties of adsorbed gelatin-fluorooxetane complexes has been studied using dynamic surface tension and dilational rheological measurements. Adsorption kinetics of gelatin-fluorooxetane complexes are reminiscent of a mixed (barrier/diffusion limited) process, while the dilational rheological properties of the interface exhibit a strong dependence on surfactant concentration. At low surfactant concentrations, dilational surface moduli as well as phase angles are relatively insensitive to the presence of the fluorooxetane.