Accelerated oxidation of aluminides at intermediate temperatures

The aluminides NbAl3 and NiAl may show accelerated oxidation in a range of intermediate temperatures 600-1000 °C, especially at reduced oxygen pressures. Such pressures in the range 10-2 to 10-30 bar O2 have been established for exposures in ampoules with the specimens, by enclosing also buffer mixtures such as Cu-Cu2O, Fe3O4-Fe2O3, Ni-NiO etc. NbAl3 disintegrates into small particles (pesting) and NiAl shows internal oxidation, general or localized, and oxidation along grain boundaries. Auger analyses afier oxidation confirmed that oxygen penetrates into grain boundaries of NbAl3 and NiAl. The transport of oxygen through the outer oxide layer appears to be rate controlling, in the case of NbAl3 such transport is possible through Nb2O5 in the scale and in the case of NiAl through other defects caused by insufficient supply of oxygen in the exposures

Vietnam's socio-economic development : a social science review

The small-bodied hominin Homo jloresiensis was recently identified at Liang Bua, Flores, Indonesia. Some researchers have argued that H. jloresiensis represents pathological individuals from a behaviorally modern Homo sapiens population, arguing in part that the stone-tools found in association are too advanced to have been manufactured by a nonmodern hominin. Here we show that the Pleistocene stone-tools from Flores, including Liang Bua, are technologically and morphologically similar to the 1.2-1.9 Mya OldowaniDeveloped Oldowan tools from Olduvai Gorge in Africa. The Pleistocene lithic technology on Flores was therefore within the capabilities of small-brained, nonmodern hominins

Age and context of the oldest known hominin fossils from Flores

Recent excavations at the early Middle Pleistocene site of Mata Menge in the So'a Basin of central Flores, Indonesia, have yielded hominin fossils attributed to a population ancestral to Late Pleistocene Homo floresiensis. Here we describe the age and context of the Mata Menge hominin specimens and associated archaeological findings. The fluvial sandstone layer from which the in situ fossils were excavated in 2014 was deposited in a small valley stream around 700 thousand years ago, as indicated by 40Ar/39 Ar and fission track dates on stratigraphically bracketing volcanic ash and pyroclastic density current deposits, in combination with coupled uranium-series and electron spin resonance dating of fossil teeth. Palaeoenvironmental data indicate a relatively dry climate in the So'a Basin during the early Middle Pleistocene, while various lines of evidence suggest the hominins inhabited a savannah-like open grassland habitat with a wetland component. The hominin fossils occur alongside the remains of an insular fauna and a simple stone technology that is markedly similar to that associated with Late Pleistocene H. floresiensis