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The procedure followed by the Laboratorio de Metrologia Nuclear in Sao Paulo, Brazil, for the standardization of {sup 242g} Am is described. The calibration system was composed of a 4 {pi} gas-flow proportional counter coupled to a pair of NaI(Tl) crystals operating in coincidence. The samples were produced by irradiating dried aliquots of {sup 241} Am with thermal and epithermal neutrons at the IEA-R1 research reactor. The efficiency tracer technique has been applied using {sup 60} Co as tracer. The beta detection efficiency was changed by external absorbers and extrapolated to unity by linear least square fitting applying covariance methodology. (author)

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The document describes the outcome of the CSN/CIEMAT-00 interlaboratory test comparison among environmental radioactivity laboratories. the exercise was organised according to the ISO-43 and the ISO/IUPAC/AOAC Harmonized Protocol for the proficiency testing of analytical laboratories. the test sample was a soil containing environmental levels of K-40, Ra-226, Ac-228, Sr-90, Cs-137, Cs-134, Pu (239-240) y Am-241. the Universidad Autonoma de Barcelona prepared the material and reported adequate statistical studies of homogeneity. The results of the exercise were computed for 30 participating laboratories, and their analytical performance was assessed using the u-score approach. A raised percentage of satisfactory laboratory performance has been obtained for all the analysis, being the best performance in gamma measurements. The exercise has drawn that several laboratories have difficulties in the evaluation of combined uncertainty, mainly in analysis involving radiochemical steps. The ...

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In the geologic formation where the oil deposits are located, diverse types of rocks perform functions as structural elements, storage containers for hydrocarbon water and calorific energy, as well as impermeable barriers and transport means of the energy and the fluids. Among the most important properties that are used to describe these functions are the porosity, the permeability, the compressibility of the pores volume, the formation resistivity factor, the saturation exponent, the velocity of acoustic waves P and S, the relative permeability, the capillary pressures, the elastic constants and other mechanical properties, the thermal expansion, coefficient, the thermal conductivity, the thermal diffusivity and the specific heat. The execution of an ample variety of activities related to the stages of exploration, location, evaluation and development of the oil deposits, depends strongly on having a good knowledge of the magnitude and the spatial variability of these properties. The ...

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Bowel infarction is a rare and typical condition of the elderly; despite improvements in diagnostic imaging and vascular surgery, bowel infarction remains a major cause of acute abdomen, with mortality rates ranging 70-80%. Diagnosis on often late because clinical signs, laboratory data and radiologic findings are a specific. The authors investigated radiographic and particular CT patterns of intestinal infraction in 56 patients submitted to surgery within 12 hours of admission. We also report the CT findings of 5 of these patients who had reversible mesenteric ischemia. CT is more sensitive than radiography and does not exhibit the limitations of angiography (i.e., invasiveness, radiation exposure and complex organization). Therefore CT can presently be considered the method of choice in patients with suspected bowel infarction. [Italian] L'infarto intestinale rappresenta una malattia rara e tipica del soggeto anziano; nonostante il notevole perfezionamento delle tecniche di ...