The persistence with which adult male rats investigated a juvenile conspecific was significantly reduced following preexposure to either the juvenile or chemosensory stimuli (soiled bedding or urine) from that juvenile. The reduced persistence did not occur when the chemosensory stimulus came from a juvenile different from the one with which the subject was subsequently tested, which suggests the presence of a chemosensorily mediated social memory. It is suggested that any such memory may have adaptive value in that it permits a male rat to more readily identify a novel conspecific. Also, the lack of reduced persistence of social investigatory behavior in castrated subjects demonstrates the importance of male gonadal hormones in the formation, storage, and/or retrieval of the proposed chemosensorily mediated social memory.
Ni/hydrotalcite catalysts are synthesized by the coprecipitation method. Synthesis times are decreased and activation is performed with just a reductive calcination under mild conditions without the usual air‐calcination step. Compared with the other reported catalysts made of Ni/hydrotalcite, in terms of space–time yield (STY), the best synthesized catalyst is the most efficient one (STY = 137.19 mol CH4 h−1 L−1 at 300 °C) and this high efficiency is kept at low temperature (STY = 132.67 mol CH4 h−1 L−1 at 250 °C). Results show that the amount of reduced Ni, created upon the mild reduction, increases with the Ni loading and the Ni0 amount correlates with the catalytic activity. CO2 adsorption capacity remarkably increases with the Ni content but this trend does not correlate with the conversion. Surface areas, neither pore sizes, do not show a correlation with catalytic results. The most important result is the very high activity observed at temperatures below 300 °C. Characterization results indicate that the outstanding low‐temperature performance must be due to the presence of high amounts of small and reduced Ni crystallites with low interaction with the support. Developed catalysts are stable for 28 h at 300 °C.
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