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Knowledge of the structural behavior of silicate melts and/or glasses at high pressures provides fundamental information for discussing the nature and properties of silicate magmas in the Earth's interior. The behavior of Si-O structures under high-pressure conditions has been widely studied, while the effect of cation atoms on the high-pressure structural behavior of silicate melts or glasses has not been well investigated. In this study, we investigated the structures of MgSiO3 and CaSiO3 glasses up to 5.4 GPa by in situ X-ray pair distribution function measurements to understand the effect of different cations (Mg2+ and Ca2+) on high-pressure structural behavior of silicate glasses. We found that the structural behavior of MgSiO3 and CaSiO3 glasses are different at high pressures. The structure of MgSiO3 glass changes by shrinking of Si-O-Si angle with increasing pressures, which is consistent with previous studies for SiO2 and MgSiO3 glasses. On the other hand, CaSiO3 glass shows almost no change in Si-Si distance at high pressures, while the intensities of two peaks at ~3.0 and ~3.5 Å change with increasing pressure. The structural change in CaSiO3 glass at high pressure is interpreted as the change in the fraction of the edge-shared and corner-shared CaO6-SiO4 structures. The different high-pressure structural behavior observed in MgSiO3 and CaSiO3 glasses may be the origin of differences in properties, such as viscosity between MgSiO3 and CaSiO3 melts at high pressures. This signifies the importance of different structural behaviors due to different cations in investigations of the nature and properties of silicate magmas in Earth's interior. [ABSTRACT FROM AUTHOR]

Bimodal behavior in the translational order of silicon's second shell in SiO2 liquid at high temperatures and high pressures has been recognized in theoretical studies, and the fraction of the S state with high tetrahedrality is considered as structural origin of the anomalous properties. However, it has not been well identified in experiment. Here we show experimental evidence of a bimodal behavior in the translational order of silicon's second shell in SiO2 glass under pressure. SiO2 glass shows tetrahedral symmetry structure with separation between the first and second shells of silicon at low pressures, which corresponds to the S state structure reported in SiO2 liquid. On the other hand, at high pressures, the silicon's second shell collapses onto the first shell, and more silicon atoms locate in the first shell. These observations indicate breaking of local tetrahedral symmetry in SiO2 glass under pressure, as well as SiO2 liquid. Understanding the structural origin of the anomalous properties of SiO2 liquid and glass at high pressures is fundamental in wide range of scientific fields. Here, the authors find experimental evidence of a bimodal behavior in the translational order of silicon's second shell and breaking of local tetrahedral symmetry in SiO2 glass under pressure. [ABSTRACT FROM AUTHOR]

A new experimental setup to continuously and automatically measure ultrasonic elastic wave velocities, X-ray radiography, and X-ray diffraction in large volume press is developed to explore structural change of amorphous materials at in situ high pressure and high temperature conditions. A continuous measurement for Zr50Cu40Al10 metallic glass is carried out during the heating process from 304 to 1102 K under high pressure conditions of 6.8–8.6 GPa. The sample length, elastic wave velocities, and Poisson's ratio show marked changes at 611, 745, 825, and 874 K, which are interpreted as glass transition temperature (Tg) at 611 K, two polyamorphic structural changes at 745 and 825 K, and crystallization above 874 K, respectively. We find that the 1.2Tg temperature (733 K at ∼8 GPa), where simulations study predicted occurrence of thermal rejuvenation, corresponds to the temperature of the polyamorphic structural change (745 K) in Zr50Cu40Al10 metallic glass. [ABSTRACT FROM AUTHOR]

The Accessible Silicate Earth (ASE) has a higher Nd/Nd ratio than most chondrites. Thus, if the Earth is assumed to have formed from these chondrites, a complement low-Nd/Nd reservoir is needed. Such a low-Nd/Nd reservoir is believed to have been derived from a melt in the early Earth and is called the Early Enriched Reservoir (EER). Although the major element composition of the EER is crucial for estimating its chemical and physical properties (e.g., density) and is also essential for understanding the origin and fate of the EER, which are both major factors that determine the present composition of the Earth, it has not yet been robustly established. In order to determine the major element composition of the EER, we estimated the age and pressure-temperature conditions to form the EER that would best explain its Nd isotopic characteristics, based on Sm-Nd partitioning and its dependence on pressure, temperature, and melting phase relations. Our estimate indicates that the EER formed within 33.5 Myr of Solar System formation and at near-solidus temperatures and shallow upper-mantle pressures. We then performed high-pressure melting experiments on primitive peridotite to determine the major element composition of the EER at estimated temperature at 7 GPa and calculated the density of the EER. The result of our experiments indicates that the near-solidus melt is iron-rich komatiite. The estimated density of the near-solidus melt is lower than that of the primitive peridotite, suggesting that the EER melt would have ascended in the mantle to form an early crust. Given that high mantle potential temperatures are assumed to have existed in the Hadean, it follows that the EER melt was generated at high pressure and, therefore, its composition would have been picritic to komatiitic. As the formation age of the EER estimated in our study precedes the last giant, lunar-forming impact, the picritic to komatiitic crust (EER) would most likely have been ejected from the Earth by the last giant impact or preceding impacts. Thus, the EER has been lost, leaving the Earth more depleted than its original composition. [ABSTRACT FROM AUTHOR]

The article discusses the effects of the conducted chemical treatment on food-borne pathogens found in cabbages using the combined solution of disinfectants sodium hypochlorite (NaClO) and calcinated calcium. It illustrates the results on the conducted study wherein the bactericidal activity of calcinated calcium was caused by the calcium's alkalinity. It presents the changes that took place regarding the bacterial count during the storage process after cabbages were treated.