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  • Author or Editor: A. Rodriguez x
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Abstract  

A calorimetric sensor has been developed to measure surface heat dissipations in the human body. An experimental prototype has been built in order to study its performance and a simple model that represents acceptably the experimental system has been proposed.

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Abstract  

Simultaneous DTA-TG has been carried out on a set of natural vermiculite samples. Based on their dehydration behaviour the samples can be divided in two groups: (a) those with DTA endothermic peak temperatures at 140°–150°C and 240°–270°C (pure vermiculties) and (b) those with peak temperatures at 95°–115°C (vermiculite with mica or mica-vermiculite interstratifications). The low temperature at which the endothermic effect in group (b) appears is discussed on the basis of dilution due to the inert layers of mica, differences in chemical composition, and lowering of interlamellar water bond energy.

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Abstract  

Instrumental neutron activation analysis (INAA) is a well-known analytical method for nondestructive, sensitive and accurate determination of elemental composition of geological samples. In the present work twenty-two elements were determined by INAA in nine rhyolitic geological samples from a wolframium ore body Lela, located in the territory of Isla de la Juventud, Cuba. The obtained results are important for the preliminary geochemical evaluation of the studied rocks.

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Abstract  

Instrumental neutron activation analysis (INAA) and gamma spectrometric analysis (GSA) were used for the determination of twenty-one elements in pegmatites of Loma Venturilla area, in Central Cuba. The application of both methods allowed the determination of K, Co, Cr, Sc, Rb, Cs, Ba, Ta, Hf, Th, U, La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu. The results were obtained with good precision and accuracy. The knowledge of such concentrations is particularly useful for geochemical investigations. The obtained concentration values can be used in studies on the petrogenesis of those rocks. The results facilitate the evaluation and estimation of the main process involved in the generation and differentiation of the melts from which the pegmatites were formed.

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Abstract  

The state of trace concentrations of95Zr–95Nb and134Cs was studied at an initial pH>13 in an uranyl triperoxidate medium using the electromigration method. OH ions governing the potential are adsorbed on the colloidal Nb(V)-hydroxide which leads to an increase in its negative electric charge; while95Zr did not move during the procedure. However, the electrophoretic mobility of the134Cs could be explained in terms of their agglomerations attributed to the interaction of Cs+ ions with water molecules to give larger aggregations.

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Abstract  

An effective modification of the chemical processes has been obtained to dissolve uranium(IV) and extract it as uranium triperoxocomplex, which facilitates its manipulation and final conversion into uranium nitrate as a high purity concentrate.

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Abstract  

It has been established that the coexistence of chemical species structurally different from cerium, is a direct consequence of the time taken for its preparation. Its practical applications, within the scope of purifying uranium, may constitute the most important technological aspect in the process of ionic exchange, to separate141Ce from uranium.

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