The Greco-Egyptian scientist Claudius Ptolemy referred to the larger island as great Britain (μεγάλης Βρεττανίας - megális Brettanias) and to Ireland as little Britain (μικρής Βρεττανίας - mikris Brettanias) in his work Almagest (147–148 AD). During what years did the British scientist Claudius Ptolemy complete his work, Almagest?