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In this paper, different types of rocks exploited in a quarry located in the Limeira region (São Paulo State, Brazil) were studied to investigate its main petrographic characteristics, physical–mechanical (apparent specific weigh ρa, apparent porosity ηa, water absorption αa and uniaxial compressive strength UCS) and thermoanalytical properties, whose curves of each of the rocks were obtained from thermogravimetry (TG), differential thermal analysis and thermomechanical analysis (TMA). Four main petrographic types were evaluated: an aphanitic rock (APH), a diabase (DIA) and two monzodiorites with distinct granulations designated as MOMM and MONMC. In terms of mineralogical composition APH is the only rock that presents volcanic glass, while for the other rocks the main mineralogy was always associated with plagioclases, clinopyroxenes and opaque minerals. The results of the physical and mechanical characterization indicate the good aptitude of these materials to be used as aggregates in engineering works. The obtained values of apparent porosity (ηa) were less than 1% for all rocks. The value of resistance rates for all samples showed that the APH has the larger value, which is attributed to the grain size of the rock. The TG curves of each of the four samples contain small mass losses between the initial temperature and around 105 °C, which attributed to the water absorption. Besides, the APH sample had a mass loss attributed to the carbonate compound. The TMA curves showed that form DIA and MOMM are similar between them, while the APH differ from both. Further, the MONMC has not presented an appreciable thermal expansion. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect(s) of mineral trioxide aggregate (MTA) on in vitro RANKL-mediated osteoclast-dependent bone resorption events and the influence of Ca2+ and Al3+ on the osteoclastogenesis inhibition by MTA. Materials and methods: Two types of osteoclast precursors, RAW 264.7 (RAW) cell line or bone marrow cells (obtained from BALB/c mice and stimulated with recombinant (r) macrophage colony stimulation factor (M-CSF), were stimulated with or without recombinant (r) activator of nuclear kappa B ligand (RANKL), in the presence or absence of MTA for 6 to 8 days. White Angelus MTA and Bios MTA (Angelus, Londrina, Paraná, Brazil) were prepared and inserted into capillary tubes (direct contact surface = 0.50 mm2 and 0.01 mm2). Influence of MTA on these types of osteoclast precursors was measured by the number of differentiated tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells (RAW and bone marrow cells), TRAP enzyme activity (RAW cells), cathepsin K gene expression (RAW cells), and resorptive pit formation (RAW cells) by mature osteoclasts. Besides, RAW cells were also stimulated with Ca2+ and Al3+ to evaluate the influence of these ions on MTA anti-osteoclastogenic potential. Results: In bone marrow and RAW cells, the number of TRAP-positive mature osteoclast cells induced by rRANKL was significantly inhibited by the presence of MTA compared with control rRANKL stimulation without MTA (p < 0.05), along with the reduction of TRAP enzyme activity (p < 0.05) and the low expression of cathepsin K gene (p < 0.05). In contrast, to control mature osteoclasts, the resorption area on dentin was significantly decreased for mature osteoclasts incubated with MTA (p < 0.05). rRANKL-stimulated RAW cells treated with Ca2+ and Al3+ decreased the number of osteoclasts cells. Besides, the aluminum oxide was the dominant suppressor of the osteoclastogenesis process. Conclusions: MTA significantly suppressed RANKL-mediated osteoclastogenesis and osteoclast activity and, therefore, appears able to suppress bone resorption events in periapical lesions. This process might be related to Ca2+ and Al3+ activities. Clinical relevance: MTA is an important worldwidely acknowleged biomaterial. The knowledge about its molecular activities on osteoclasts might contribute to improving the understanding of its clinical efficacy. [ABSTRACT FROM AUTHOR]

Dissolution cavities in weathered pebbly quartzite of the ~2.5-Ga Moeda Formation at Capanema, Quadrilátero Ferrífero of Minas Gerais, Brazil, are decorated with suspended filaments of opaline silica. The filaments sustain xenotime-hematite aggregates in the open space. Xenotime occurs as inclusions in buds and botryoidal aggregates of hematite. The filamentous structures consist of strand-forming buds, hypha-like extensions, and thin strands that compose mat-like arrangements. They resemble microbial filaments that were replaced by opaline silica and fossilized. The occurrence of spherical hematite as protuberances on hematite-free opaline hyphae is interpreted as accretion of dissolved iron onto extracellular polymers. Phosphate sites in polymeric substances expelled from the microbial filaments might have adsorbed yttrium and heavy rare-earth elements from groundwater to the iron-accreting polymers. These would have resulted in botryoidal aggregates of hematite with xenotime inclusions. The presence of authigenic xenotime in the weathering zone opens a new possibility to constrain the evolution of lateritic profiles by xenotime geochronology. [ABSTRACT FROM AUTHOR]