Bimetallic Cobalt/Rhenium Systems: Preferred Position of Rhenium Through an Interdisciplinary Approach

Some commercial type Fischer–Tropsch catalysts are based on rhenium-doped cobalt. In an attempt to elucidate the preferred position of rhenium in the cobalt matrix, we have carried out experimental Low Energy Ion Scattering investigations of oxidized and reduced catalyst samples and computational DFT investigations of bimetallic Co/Re clusters. The results indicate that rhenium preferentially occupies subsurface sites, where it can coordinate to a maximum number of cobalt atoms.     

Psychophysical model of chromatic perceptual transparency based on substractive color mixture

Variants of Metelli's episcotister model, which are based on additive color mixture, have been found to describe the luminance conditions for perceptual transparency very accurately. However, the findings in the chromatic domain are not that clear-cut, since there exist chromatic stimuli that conform to the additive model but do not appear transparent. We present evidence that such failures are of a systematic nature, and we propose an alternative psychophysical model based on subtractive color mixture. Results of a computer simulation revealed that this model approximately describes color changes that occur when a surface is covered by a filter. We present the results of two psychophysical experiments with chromatic stimuli, in which we directly compared the predictions of the additive model and the predictions of the new model. These results show that the color relations leading to the perception of a homogeneous transparent layer conform very closely to the predictions of the new model and deviate systematically from the predictions of the additive model.