Normal pressure modifications and tentative high-pressure phases of the nitridosilicates MSiN2 with M = Be, Mg, or Ca have been thoroughly studied by density functional methods. At ambient pressure, BeSiN2 and MgSiN2 exhibit an ordered wurtzite variant derived from idealized filled β-cristobalite by a C1-type distortion. At ambient pressure, the structure of CaSiN2 can also be derived from idea...

Building upon and complementing recent results on the rigidity theory of periodic bar-and-joint frameworks, this paper studies tetrahedral structures modeled on specific crystalline materials: quartz, cristobalite and tridymite. The general theory predicts at least three infinitesimal degrees-of-freedom. Here, we investigate the actual deformations of these structures. We show that quartz and c...

We show that the pseudorelativistic physics of graphene near the Fermi level can be extended to three dimensional (3D) materials. Unlike in phase transitions from inversion symmetric topological to normal insulators, we show that particular space groups also allow 3D Dirac points as symmetry protected degeneracies. We provide criteria necessary to identify these groups and, as an example, prese...

Mouse peritoneal macrophages were used to evaluate the relative cytotoxicity of a series of diatomaceous earth products in vitro. The amorphous and crystalline silica content of the products was determined by a combination of infrared spectroscopy and x ray powder diffraction techniques. The cytotoxicities of the high cristobalite content flux calcined materials were similar to that of the stan...

Abstract We report the results of an experimental multianalytical characterisation industrial cristobalite powders, used as raw materials for artificial stone production. Cristobalite is considered a serious threat to human health. The study was carried out through X-ray diffraction (XRD), scanning electron microscopy with energy dispersive microanalysis (SEM/EDS), continuous-wave (cw) and puls...

Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical stu...

In our previous study, we investigated ammonia-free phosphate-bonded investments using Mg (H2PO4)2 powder. The purpose of the present study was to attempt usage of 50 wt% Mg (H2PO4)2 solution instead of powder. Magnesium oxide (MgO) was prepared as a binder and cristobalite was selected as a refractory. After arranging six kinds of experimental investments (A-F) with different cristobalite/MgO ...

Barrett, Edward G., Carl Johnston, Günter Oberdörster, and Jacob N. Finkelstein. Silica-induced chemokine expression in alveolar type II cells is mediated by TNF-ainduced oxidant stress. Am. J. Physiol. 276 (Lung Cell. Mol. Physiol. 20): L979–L988, 1999.—We have shown previously that epithelial cells may contribute to the inflammatory response in the lung after exposure to crystalline silica th...

Abstract This work investigates the phase transformations in silica (SiO 2 ) during heating to a target temperature between 1700 °C and 1900 effect of SiO polymorphs on reduction reaction 2SiO + SiC = 3SiO CO silicon production. Different rates up have been used achieve different compositions quartz, amorphous cristobalite. The had minor final composition, longer time at temperatures > 1400 ...

A variety of artificial fibers extensively employed as lining in high-temperature apparatus may undergo a devitrification process that leads to significant changes in the chemical-physical properties of the materials. Among them, the crystallization of carcinogenic minerals, such as cristobalite, has already been documented for alumino-silicate ceramic fibers. Five fibrous samples with differen...