RESUMO
Abstract The purpose of this research was to discriminate soil fractions using mineralogical and elemental analyses and to show those fractions that present greater contribution to the soil mass attenuation coefficient (μ) as well as their partial cross-sections for photoelectric absorption (PA), coherent scattering (CS) and incoherent scattering (IS). Soil samples from different places of Brazil classified as Yellow Argisol, Yellow Latosol and Gray Argisol were submitted to elemental and mineralogical analyses through energy dispersive X-ray fluorescence (EDXRF) and Rietveld Method with X-ray diffraction data (RM-XRD). The mixture rule was utilized to calculate μ of each soil. The EDXRF analysis showed as predominant elements Si, Al, Fe and Ti oxides. The highest contents were Si (914.3 to 981.3 g kg-1) in the sand fractions, Al (507.9 to 543.7 g kg-1) and Fe (32.5 to 76.7 g kg-1) in the clay fractions, and Ti (18.0 to 59.0 g kg-1) in the silt fractions. The RM-XRD allowed identifying that the sand fractions are predominantly made of quartz (913.3 to 995.0 g kg-1), while the clay greatest portion is made of kaolinite (465.0 to 660.6 g kg-1) and halloysite (169.0 to 385.0 g kg-1). The main effect responsible for μ was IS (50 to 61.4%) followed by PA (28 to 40.1%) and CS (9.9 to 10.6%). By using the principal component analysis (PC-1: 57.5% and PC-2: 20.9%), the samples were differentiated through the discrimination between physical, chemical and mineralogical properties. The results obtained suggest that general information about the radiation interaction in soils can be obtained through the elemental and mineralogical analyses of their fractions.
Assuntos
Características do Solo/análise , Análise dos Mínimos Quadrados , Análise de Componente PrincipalRESUMO
Computed tomography (CT) is a technique that provides images of different solid and porous materials. CT could be an ideal tool to study representative sizes of soil samples because of the noninvasive characteristic of this technique. The scrutiny of such representative elementary sizes (RESs) has been the target of attention of many researchers related to soil physics field owing to the strong relationship between physical properties and size of the soil sample. In the current work, data from gamma-ray CT were used to assess RES in measurements of soil porosity (Ï). For statistical analysis, a study on the full width at a half maximum (FWHM) of the adjustment of distribution of Ï at different areas (1.2 to 1162.8 mm²) selected inside of tomographic images was proposed herein. The results obtained point out that samples with a section area corresponding to at least 882.1 mm² were the ones that provided representative values of Ï for the studied Brazilian tropical soil.
Assuntos
Solo , Tomografia Computadorizada por Raios X/métodos , PorosidadeRESUMO
Os autores fazem uma revisäo das necroses ósseas mais comuns na fase de crescimento, procurando enfocar os seguintes aspectos: freqüência, etiologia, clínica, radiologia, diagnóstico e tratamento
Assuntos
Humanos , Masculino , Feminino , Osteonecrose , Doença de Legg-Calve-Perthes , Necrose da Cabeça do Fêmur , OsteocondriteRESUMO
Os autores fazem uma análise retrospectiva do momento do partograma no acompanhamento do trabalho de parto de 500 pacientes, procurando evidenciar se a conduta médica esteve alicerçada no mesmo