5 resultados para Barbara--Amber waves of grain
em Biblioteca Digital da Produção Intelectual da Universidade de São Paulo (BDPI/USP)
Resumo:
The sphene-centered ocellar texture consists of leucocratic ocelli with sphene (titanite) crystals at the center, enclosed in a biotite-rich matrix. This texture has been recognized worldwide in hybrid intermediate rocks. On the basis of structural, petrological, and geochronological data from selected outcrops of the Variscan Ribadelago pluton (NW Iberian Massif), we propose that the ocelli were formed by migration and accumulation of a residual melt through a plagioclase- and biotite-dominated crystalline framework. At the late stage of crystallization, the magma acted as a hyperdense suspension and reacted to the pressure gradient caused by the regional stress field, entering the domain of grain-supported flow. Microstructures reveal that aligned crystal domains arose in the crystal framework from the shearing and compaction of the crystal mush and behaved as magmatic microshears. Relative displacement of adjacent crystal clusters along these microshears corresponded to the onset of Reynolds dilatancy that generated an expansion of the crystal mush, involving melt migration and pore aperture. The mineralogy of the ocelli, dominated by andesine and sphene, represents the composition of the migrating melt. The chemistry of this late, Ti-rich melt stems from the incongruent melting of biotite. Magmatic sphene from the ocelli yields a U-Pb age of 317 +/- 1 Ma, which represents the final crystallization of the hybridized magmatic system. Moreover, this texture offers an opportunity to better understand the rheological behavior of highly crystallized magmas.
Resumo:
Ilha Comprida is a regressive barrier island located in southeastern Brazil that was formed essentially by Quaternary sandy sediments. Ilha Comprida sediments were analyzed to assess heavy mineral indices and grain size variables. The spatial variation of heavy minerals and grain size was interpreted in terms of the present barrier dynamics and the barrier`s evolution since the Middle Holocene. These analyses allowed for the identification of the main factors and processes that control the variation of heavy minerals and grain size on the barrier. Rutile and zircon (RZi) and tourmaline and hornblende (THi) are significantly sensitive to provenance and exhibit the contributions of the Ribeira de Iguape River sediments, which reach the coast next to the northeastern end of Ilha Comprida. In addition to the influence of provenance, TZi responds mainly to hydraulic sorting processes. This agrees with a sediment transport pattern characterized by a divergence of two resultant net alongshore drifts southwest of the barrier. The sediments from the Ribeira de Iguape River reach the barrier directly through the river mouth and indirectly after temporary storage in the inner shelf. The combination of grain size and heavy mineral analyses is a reliable method for determining sediment transport patterns and provenance. (C) 2010 Elsevier Ltd. All rights reserved.
Resumo:
The aim of this study was to investigate the effects of nutrients (nitrogen, zinc and boron) on fungal growth and fumonisins production in corn samples obtained at the beginning of grain formation and at harvest. Three nitrogen doses were applied to the corn plants through soil in combination with three zinc doses and two boron doses during sowing. Mycological analysis of grains, using Dichloran Rose-Bengal Chloramphenicol Agar, collected at the beginning of formation demonstrated a fungal population predominantly of yeasts. Analysis of freshly harvested corn revealed a higher frequency of Penicillium spp. (72%) and F verticillioides (27%). High Performance Liquid Chromatography analysis revealed that 100% of grains were contaminated with fumonisins B, at levels ranging from 0.3 to 24.3 mg/kg and 93% contaminated with fumonisin B(2) at levels ranging from 0.05 to 5.42 mg/kg. Nitrogen (50 kg/ha) in combination with boron (0.5 kg/ha) resulted in an increased fumonisin B2 production. (c) 2007 Elsevier Ltd. All rights reserved.
Resumo:
Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by hypogammaglobulinemia and recurrent infections. Herein we addressed the role of unfolded protein response (UPR) in the pathogenesis of the disease. Augmented unspliced X-box binding protein 1 (XBP-1) mRNA concurrent with co-localization of IgM and BiP/GRP78 were found in one CVID patient. At confocal microscopy analysis this patient`s cells were enlarged and failed to present the typical surface distribution of IgM, which accumulated within an abnormally expanded endoplasmic reticulum. Sequencing did not reveal any mutation on XBP-1, neither on IRE-1 alpha that could potentially prevent the splicing to occur. Analysis of spliced XBP-1, IRE-1 alpha and BiP messages after LPS or Brefeldin A treatment showed that, unlike healthy controls that respond to these endoplasmic reticulum (ER) stressors by presenting waves of transcription of these three genes, this patient`s cells presented lower rates of transcription, not reaching the same level of response of healthy subjects even after 48 h of ER stress. Treatment with DMSO rescued IgM and IgG secretion as well as the expression of spliced XBP-1. Our findings associate diminished splicing of XBP-1 mRNA with accumulation of IgM within the ER and lower rates of chaperone transcription, therefore providing a mechanism to explain the observed hypogammaglobulinemia. (C) 2008 Elsevier Ltd. All rights reserved.
Resumo:
The count intercept is a robust method for the numerical analysis of fabrics Launeau and Robin (1996). It counts the number of intersections between a set of parallel scan lines and a mineral phase, which must be identified on a digital image. However, the method is only sensitive to boundaries and therefore supposes the user has some knowledge about their significance. The aim of this paper is to show that a proper grey level detection of boundaries along scan lines is sufficient to calculate the two-dimensional anisotropy of grain or crystal distributions without any particular image processing. Populations of grains and crystals usually display elliptical anisotropies in rocks. When confirmed by the intercept analysis, a combination of a minimum of 3 mean length intercept roses, taken on 3 more or less perpendicular sections, allows the calculation of 3-dimensional ellipsoids and the determination of their standard deviation with direction and intensity in 3 dimensions as well. The feasibility of this quick method is attested by numerous examples on theoretical objects deformed by active and passive deformation, on BSE images of synthetic magma flow, on drawing or direct analysis of thin section pictures of sandstones and on digital images of granites directly taken and measured in the field. (C) 2010 Elsevier B.V. All rights reserved.