Coal fly ashes, long used as SCMs, are quite complex, consisting of a mixture of crystalline and amorphous phases. In this study, we aim to shed light on this complexity by fusing two highly ...complementary techniques: SEM-EDS and Raman spectroscopy. By closely analyzing hundreds of individual particles from 18 unique fly ashes, we report two major findings. Firstly, there is a distinct correlation between particle shape (roundness/circularity) and degree of crystallinity (FWHM of Raman peaks) where jagged particles happen to be almost always crystalline. Secondly, the mean position of the symmetric stretching Raman band of the silicate tetrahedra (between 600 and 1000 cm−1) is an indicator of the degree of polymerization of the glassy phase in any given particle. These results highlight the importance of understanding these complex systems at the individual particle level, where multiple phases intermixed at the micro-scale ultimately play a dominant role in governing macro-scale ash behavior.
We herein report on three cases of giant villous tumors of the rectum accompanied by electrolyte depletion syndrome (EDS) and review the related literature. In case 1, a giant villous tumor with a ...long axis of 15cm occupying the entire circumference of the upper rectum was detected on detailed examination performed for frequent diarrhea and EDS in an 81-year-old woman. In case 2, a 67-year-old woman presented with persistent watery diarrhea, and a 17×8cm villous tumor was discovered in the rectosigmoid colon. In case 3, a 10×10cm villous tumor was found in the upper rectum on detailed examination performed for the chief complaint of melena in a 73-year-old man. All cases had mucus production and EDS, and a villous tumor complicated by EDS was therefore suspected. EDS improved in these cases following surgery and the patients' postoperative course was uneventful. Villous tumors accompanied by EDS is relatively rare. Patients presenting with persistent watery diarrhea should be evaluated for a giant villous tumor complicated by EDS, as serious EDS may sometimes occur.
In the present study the phase changes in an ordinary concrete standing for 10years in a tidal zone were investigated with a range of techniques. From the exposed surface and inwards different zones ...had formed. SEM–EDS analysis of a polished section of the surface near region, showed a Mg rich layer with a thickness of 10–20μm, as well as the filling of cracks leading from the surface with a Mg rich phase, most likely brucite. In the outermost 2mm, an increase in the calcium carbonate content was identified by XRD and TGA. In the same zone SEM–EDS analyses indicated enrichment in ettringite and thaumasite. In the first 20mm calcium hydroxide leaching was observed using XRD and TGA. Chlorides appeared to have penetrated up to approx. 70mm from the surface. Part of the chlorides were found to be bound in alumina containing phases and in the C–S–H by SEM–EDS. These experimentally observed phase changes generally agreed with the predictions of a thermodynamic model.
A self-supporting 169Tm target was fabricated by rolling of 99.9% enriched 169Tm foil in the target laboratory of Inter-University Accelerator Centre, New Delhi. The sample was characterized using ...standard characterization techniques and confirmation of elemental purity was obtained. The XRD characterization shows that the target is crystalline in nature and free of strain. The prepared target was used to measure the lifetime of short lived excited states in 183Ir via Doppler Shift Attenuation Method.
O mineral ilmenita (FeTiO3) corresponde a um dos principais portadores de Ti, e perfaz 90% do consumo mundial desse elemento. China e Austrália detém 50% das reservas mundiais medidas de ilmenita. No ...Brasil, as principais jazidas estão localizadas nos municípios de Mataraca (PB), São Francisco de Itabapoana e São João da Barra (RJ), todas em ambiente do tipo placer. Os granitos e pegmatitos são importantes depósitos desse elemento e, no município de Bananal (SP), há registro dos granitos Bananal e Resgate. Os estudos foram realizados em três etapas: integração de dados geológicos, aerogeofísicos e geomorfológicos; realização de campanhas de campo, tendo a ilmenita sido identificada em cinco concentrados; e análise dos grãos de ilmenita por meio de MEV, visando à identificação qualitativa do mineral e de suas inclusões sólidas. Os grãos de ilmenita apresentaram dimensões entre 0.05mm e 2mm e composição química de 9,85% a 69,48% de Fe e de 5,99% a 26,18% de Ti. A presença de ilmenita está associada aos corpos graníticos Resgate e Granito Bananal. As assinaturas geofísicas em ambos os métodos indicam composições minerais e químicas heterogêneas ao longo dos corpos graníticos.
Glauconite is an authigenic clay mineral that is common in marine sedimentary successions. Dating of glauconite to determine the depositional age of sedimentary sequences has a long history but has ...fallen into disfavor due to the difficulty of obtaining “pure” glauconite separates. Recent advances in sedimentary petrography and reaction cell mass spectrometry permit rapid in situ Rb‐Sr dating of carefully screened glauconite grains. However, glauconite remains susceptible to burial alteration so that successful application of in situ Rb‐Sr glauconite geochronology requires improved, microscale constraints on the impact of postdepositional alteration on glauconite Rb‐Sr systematics and articulation of robust criteria for identifying grains suitable for geochronology. Here, we address these questions by combining SEM‐EDS mineral mapping, geochemical characterization, and in situ Rb‐Sr dating of glauconite grains in partially altered lower Cambrian sedimentary sequences from the Arrowie and Amadeus basins in Australia. Our approach provides information at high spatial resolution, representing new insights into the interplay between source material, burial fluids, and diagenetic processes. Among the different glauconite classes, which we classify based on alteration and inclusion type, only the primary apatite‐bearing “pristine” glauconite returns an age within the error of the expected stratigraphic age. We attribute the preservation of a depositional Rb‐Sr age to the influence of Sr‐rich, alteration‐resistant apatite and the limited permeability of the clay‐rich strata hosting these grains. We conclude that our combined petrographic–geochemical screening approach holds considerable potential for identifying the best preserved glauconite grains for in situ Rb‐Sr geochronology.
Key Points
New technology permits in situ Rb‐Sr dating of carefully screened glauconite grains
Apatite resists Sr exchange, and apatite‐bearing glauconite preserves primary Rb‐Sr age
Young and old ages are due to Sr exchange with burial fluids and uptake of radiogenic Sr in secondary carbonate inclusions, respectively
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