Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO 3-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO 3 glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; [3] O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO 3 melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO 3 melt toward deeper part of the Earth's lower mantle.silicate melts at high pressure ͉ tricluster oxygen T he nature of silicate melts at high pressure and temperature governs magmatic processes in the Earth's interior and it probably dominated the differentiation of Earth in the Hadean magma ocean where significant fractions of the Earth were melts (1-3). It has been suggested that the potential presence of silicate melts, primarily in MgSiO 3 composition, at the top of the transition zone (4-6) and in the core-mantle boundary (7,8) significantly contributes to the seismic heterogeneity of the regions. Pressure-induced structural changes in the silicate melts play an important role in the macroscopic thermodynamic, transport, and electronic properties at high pressure (e.g., refs. 9-13). Despite their importance and implications for global geophysical processes in the Earth's interior as precursors to crystalline MgSiO 3 phases, including perovskite and postperovskite (14, 15), the high-pressure structures of MgSiO 3 glass and melt remain enigmatic because of their inherent structural disorder and the lack of suitable experimental probes at high pressures. In other binary alkali and ternary aluminosilicate glasses, the densification mechanism is mostly associated with an increase, either gradual or abrupt, in the coordination number of the framework cations, such as Si and Al from 4 to 5 and 6 at the expense of the nonbridging oxygen (NBO) (11,12,(16)(17)(18)(19)(20). However, pressure dependence of the coord...

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The pasting viscosity, morphological properties, and swelling properties of potato starch and waxy maize starch mixtures at different ratios were investigated. Pasting analysis of the starch mixtures (7% solids in water, w/w) using a Rapid Visco Analyser showed linear changes in peak viscosity and pasting temperature according to the mixing ratios of both starches, but not in breakdown and setback. The pasting profile revealed that the starches rendered mutual effects during pasting, more significantly when the amounts of potato and waxy maize starches were similar. The volume fraction of swollen granules and the presence of amylose appeared to be important parameters in the mutual effects of both starched during pasting. Under a light microscope, the swelling of potato starch granules was delayed by the presence of waxy maize starch. Overall results indicate that new pasting properties can be generated by mixing starches of different botanical sources.

Knowledge of the extent of chemical and topological disorder in topological disordered oxide glasses and melts is essential for understanding the atomistic origins of their macroscopic properties. Here, we report the high-resolution B-11 and O-17 triple quantum magic angle spinning (3QMAS) NMR spectra for binary borogermanate glasses. The NMR results, together with quantum chemical calculations of cluster energy difference, allow us to estimate the extent of chemical disorder and topology variation with composition. The B-11 NMR result shows that the boroxol ring fraction decreases nonlinearly with increasing mole fraction of Ge and is smaller than that in binary borosilicate glasses, suggesting that the Ge/Si content influences the topological changes. Whereas oxygen clusters are not well resolved in O-17 NMR spectra, the Ge-O-Ge fraction apparently increases with increasing GeO(2) content. The estimated degree of framework disorder (Q) in borogermanate glasses is approximately 0.4, according to quantum chemical calculations based on density functional theory. This is halfway between chemical order (Q = 1) and a random distribution (Q = 0). In contrast, Q is approximately -0.6 for borosilicate glasses, indicating a moderate tendency toward complete phase separation (Q = -1). This result confirms that the degree of framework disorder shows a strong dependence on the type of framework cations (Si or Ge). The predicted configurational enthalpy of borogermanate glasses, explicitly considering both chemical and topological disorder, shows a negative deviation as predicted from the positive Q value. The results demonstrate that the macroscopic properties of topologically disordered noncrystalline solids can be established from the detailed quantification of topological and chemical disorder.