The mechanism responsible for the irreversible deactivation of ceria-supported precious metals for the watergas-shift reaction has been investigated through accelerated aging tests. It is shown that deactivation of Pd/ ceria occurs more rapidly at 673 K compared to 523 K when operating with an integral reactor in 25 torr each of CO and H 2 O. By heating a fresh catalyst in H 2 , H 2 O, CO, or CO 2 , it was shown that deactivation occurs due to the presence of CO. Measurements of metal dispersion by CO adsorption and by x-ray diffraction show that deactivation on Pt/ceria and Pd/ceria catalysts in our studies was due to a loss of metal surface area. Finally, water-gas-shift rates on a series Pd/ceria catalysts with ceria crystallite sizes ranging from 7.2 to 40 nm and Pd loadings of either 1 wt% or 6 wt% demonstrated that rates were strictly proportional to the Pd surface area. Based on these observations, ceria-supported precious metals could be active and stable for the watergas-shift reaction if steps are taken to avoid metal particle-size growth. AbstractThe mechanism responsible for the irreversible deactivation of ceria-supported precious metals for the water-gas-shift reaction has been investigated through accelerated aging tests. It is shown that deactivation of Pd/ceria occurs more rapidly at 673 K compared to 523 K when operating with an integral reactor in 25 torr each of CO and H 2 O. By heating a fresh catalyst in H 2 , H 2 O, CO, or CO 2 , it was shown that deactivation occurs due to the presence of CO.Measurements of metal dispersion by CO adsorption and by x-ray diffraction show that deactivation on Pt/ceria and Pd/ceria catalysts in our studies was due to a loss of metal surface area. Finally, water-gas-shift rates on a series Pd/ceria catalysts with ceria crystallite sizes ranging from 7.2 to 40 nm and Pd loadings of either 1 wt% or 6 wt% demonstrated that rates were strictly proportional to the Pd surface area. Based on these observations, ceria-supported precious metals could be active and stable for the water-gas-shift reaction if steps are taken to avoid metal particle-size growth.

The substance P (SP)-preferring receptor neurokinin-1 receptor (NK-1R) has two forms: a full-length receptor consisting of 407 aa and a truncated receptor consisting of 311 aa. These two receptors differ in the length of the C terminus of NK-1R. We studied the undifferentiated and phorbol myristate acetate (

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