A digital camera acquires a first image in a sequence of images by loading it into a unified memory space of the digital camera in a first order and processing it in a second order. The impure feedstock is contacted with a selective hydrogenation catalyst in the presence of hydrogen in a selective hydrogenation zone maintained under selective hydrogenation conditions effective for selective hydrogenation of impurities containing reactive carbonyl groups thereby to hydrogenate the impurities to the corresponding alcohols. A portion of the first stripe is updated by writing updated data in a portion of a second stripe across the storage volume of the plurality of memory devices.