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Applying radiocarbon (14C) dating using accelerator mass spectrometry (AMS) to the skeleton of a mammoth and the associated plant remains have been dated. The fossil of Zhalai Nur mammoth was dated to 43,500 +1000/–900 14C yr BP. The results of optically stimulated luminescence (OSL) dating, which show that a fluvially deposited gravel layer, from that the mammoth fossils were excavated, formed between 51,300±2100 and 26,600±1200 yr BP, place the new AMS 14C dates in a well-developed chronological framework. Through this study, it can be summarized that, firstly, using suitable sample material, it is possible to obtain reliable AMS 14C results, even when the ages of the target materials approach the upper limits of the method. Second, it reveals that a depositional hiatus exists during the Late Pleistocene, between ca. 26,000 yr BP and ca. 13,000 yr BP. Finally, large rivers and widely distributed areas of alluvial-fluvial deposits existed in this present-day desert area between ca. 51,000 and 26,000 yr BP. These results may shed new light on the study of the Mammuthus-Colelodonta-Bubalus fauna, the most important and fully developed fauna during the Late Pleistocene in northeastern China. They also deepen our understanding about the eco-environments of the region. [ABSTRACT FROM AUTHOR]

Ti2AlNb-based alloy with a dominated orthorhombic phase is one of the most promising high-temperature structural materials. In this work, the equilibrium volume, elastic, and thermodynamic properties of the ordered O phase with stoichiometric Ti2AlNb were predicted under different temperatures using first-principles calculations based on density functional theory combined with quasi-harmonic approximation (QHA). With the increase of temperature from 0 to 1300 K, the elastic properties decrease moderately and the bonding strength weakens slightly. The intrinsic properties of the Ti2AlNb O phase are ductile at all temperature considered. In order to explore the evolution mechanism of the temperature-dependent elastic properties further, the density of state (DOS) has been analyzed. The stoichiometric Ti2AlNb O phase shows good high-temperature mechanical and thermal stability, which is a kind of potential high-temperature alloy applied in aeronautics industries. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of FCC Al, HCP Sc, B2 AlSc, C15 AlSc, B8 AlSc, and L1 AlSc were studied using ab initio calculations based on density functional theory. The 0 K (−273 °C) total energies were calculated using the ab initio plane-wave pseudopotential method within the generalized gradient approximation. The ab initio calculations of the phonon dispersion curves and the density of state of FCC Al, HCP Sc, B2 AlSc, C15 AlSc, B8 AlSc, and L1 AlSc have been performed using the density functional theory and the direct method. Deduced from Helmholtz free energy, the thermal expansion, enthalpy, heat capacity, and entropy as a function of temperature were calculated and compared considerably with the experimental data and other computational results. Our calculations show that the enthalpies of formation are temperature-dependent, and the slope is about −3.4 J/mol/K for B2 AlSc, −2.3 J/mol/K for C15 AlSc, −0.8 J/mol/K for B8 AlSc, and −2.7 J/mol/K for L1 AlSc, respectively. [ABSTRACT FROM AUTHOR]