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Collisions involving 112 Sn and 124 Sn nuclei have been simulated with the Improved Quantum Molecular Dynamics transport model. The results of the calculations reproduce isospin diffusion data from two different observables and the ratios of neutron and proton spectra. By comparing these data to calculations performed over a range of symmetry energies at saturation density and different representations of the density dependence of the symmetry energy, constraints on the density dependence of the symmetry energy at sub-normal density are obtained. Results from present work are compared to constraints put forward in other recent analyses.

Carbon-supported Pd 4 Co nanoalloy samples (denoted as Pd 4 Co/C) have been synthesized by a modified polyol reduction process, involving a mixture of ethylene glycol (a polyol) and a small amount of sodium borohydride as reducing agents, and evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. The synthesis process offers Pd 4 Co nanoparticles with an average particle size of 4.6 nm and a narrow size distribution, which increases to 7.3 and 11.0 nm on annealing, respectively, at 350 and 500 C in 10% H 2 -90% Ar. Although the as-prepared Pd 4 Co/C sample exhibits instability during ORR, annealing at 350 and 500 C enhances the stability significantly due to an increasing degree of alloying between Pd and Co and increasing particle size. While both Pd/C and Pt/C exhibit a drastic decline in catalytic activity on annealing at 350 and 500 C due to a significant increase in particle size, the Pd 4 Co/C sample maintains high catalytic activity even after annealing at 350 C due to an increase in the degree of alloying. The Pd 4 Co/C catalyst offers an added advantage of excellent tolerance to methanol poisoning and lower cost compared to the conventional Pt/C catalyst.