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Different bulk transition-metal oxides (NiO, CuO, Mn 2 O 3 , Cr 2 O 3 , and Co 3 O 4 ) were prepared, by precipitation from nitrate precursors, and tested for the combustion of methane-air lean mixtures (1000-5000 ppmv of CH 4 ). Catalyst performances were compared in terms of both intrinsic activity and resistance to self-deactivation. Methane combustion experiments were carried out at ambient pressure and a space velocity of 62 h -1 [weight hourly space velocity (WHSV)]. The activity of the studied catalysts (determined by the recording of light-off curves in the interval of 250-600 °C) decreases in the order:However, deactivation studies, carried out both at constant temperature (620 °C) and in hysteresis experiments, reveal that Mn 2 O 3 is the most stable catalyst.

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Mitochondrial DNA analysis confirms that Maragatos from Spain are a genetically isolated human group. Genetic distances between Maragatos and the comparison samples are significantly different even with the Leo  n sample (P50.001) which shares the same geographic area as the Maragatos. Although the northAfrican haplogroup U6 is present in them, their attributed Berber origin is weakened, as this haplogroup is also detected in surrounding populations with which, in addition, Maragatos have the smaller genetic distances. These U6 haplotypes are ascribed to a pre-historic African colonisation that influenced all the Iberian Peninsula. The presence of Neolithic haplogroups in this sample suggests that their isolation culture was not absolute until recent times. European Journal of Human Genetics (2001) 9, 708 ± 716.