Search Results

You are looking at 1 - 10 of 91 items for

  • Author or Editor: M. Rodríguez x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The effect of sediment size, pH, temperature and conductivity on the transfer of uranium from sediment to water has been studied. The uranium concentration and the234U/238U,235U/238U activity ratios were measured in water, sediments and suspended matter sampled from Jucar River, using low level alpha-spectrometry. Distribution factors were obtained from these measurements. A more detailed sampling was done in the neighbourhood of the Cofrentes Nuclear Plant (Valencia, Spain). Total uranium activity,234U/238U activity ratio and distribution factors for234U and238U were found to vary with pH. Leaching and dilution, which depend on pH and salinity, are the probable mechanisms for these changes.

Restricted access

Abstract  

A study is presented on the distribution of thorium and radium isotopes in sediments, suspended matter and water collected along Jucar river (East of Spain), using low-level α-spectrometry. The first aim of this work is to study the thorium and radium activity in water, sediment and suspended matter and their dependence on pH, temperature, conductivity and sediment sizes along Jucar river. The analysis of activity variation with these parameters will provide information about the dynamics of these radionuclides in rivers. The values obtained for the distribution factors between suspended matter and water (K d) are also discussed.

Restricted access

Abstract  

A new method for the determination of low-level radium and thorium isotopes in environmental samples by -spectrometry is described. Thorium and radium isotopes were chemically separated from the same sample, by using the same tracer (229Th). Two different ways were explored for the concentration process in water samples, obtaining a chemical yield for Ra isotopes between 70–90% in both cases using KMnO4 as carrier and BaCl2 and FeCl3, respectively. The method can also be directly applied for uranium measurements, but in this case there is a limitation on the range of uranium isotopes that can be analyzed.

Restricted access

Abstract  

The uranium concentration and the234U/238U,235U/238U activity ratios were studied in water samples from Jucar River, using low-level -spectrometry. The effects of pH, temperature and salinity were considered and more detailed sampling was done in the neighbourhood of Cofrentes Nuclear Plant (Valencia, Spain). Changes were observed in the uranium concentration with the salinity and the234U/238U activity ratio was found to vary with pH. Leaching and dilution, which depend on pH and salinity, are the probable mechanisms for these changes in the concentration of uranium and the activity ratios.

Restricted access

In many occasions descriptive analysis consists of product-specific training where the samples to be measured are used during the training. Towards the end of the training period it is common practice to present these samples and reach a consensus on their profiles, which we have called Training Consensus Profiles (TCP). Following the TCP, the samples are scored by each assessor and the results are statistically analysed to obtain statistical profiles. The objective of the present work was to compare the TCP with the statistical profiles in samples from three different food categories: fernet (an herb-based alcoholic drink), mayonnaise, and spaghetti. General Procrustes analysis showed that the TCP and statistical profiles were similar. A case is made, that if this type of training and measurement are to be followed, the statistical measuring stage could be left aside, directly reporting the results obtained from the TCP. Advantages and limitations on reporting these TCP profiles are discussed.

Restricted access
Acta Alimentaria
Authors: L. Hernández Rodríguez, D. Afonso Morales, E.M. Rodríguez-Rodríguez, and C. Díaz Romero

Proximate composition was determined in 19 wheat cultivars from the Canary Islands in order to establish differences between them and contribute to their characterization. All parameters analysed showed significant differences between cultivars; and also many parameters were affected by the species and subspecies of wheat. Triticum aestivum had higher mean moisture, protein, and fibre and lower mean starch, sucrose, and amylose concentrations than Triticum turgidum. Low starch content and high fibre content could be due to the transformation of starch into resistant starch during desiccation process. An important contribution of complex carbohydrates, including fibre as well as protein and phenolic compounds, was observed for the consumption of wheat.

Restricted access

Abstract  

The intercalation compounds Ti(C3H7NH2)(HPO4)2·H2O (18.4 Å) (-TiP/n-Pr) and Ti(C4H9NH2)(HPO4)2·H2O (20.5 Å) (-TiP/n-Bu) have been prepared using -titanium phosphate, Ti(HPO4)2·2H2O (11.6 Å), as precursor. The retention of UO 2 2+ , in aqueous solutions by -TiP is very low being only a superficial adsorption phenomenon. When the intercalated materials are used, the retention is quantitative until 95% of the cation exchange capacity in the -TiP/n-Pr case (c.e.c.=6.30 mequiv./g), and over 80% for the -TiP/n-Bu compound (c.e.c.=6.04 mequiv./g).

Restricted access

Abstract  

The signal processing of the experimental output produced by simultaneous injection of two liquids in a flow microcalorimeter allows, besides the determination of the mixture energy, to obtain information about the mixture thermokinetics. Starting from this information, a model of space-time behaviour of the mixture dissipation is proposed. The simulations carried out explain that an increase of the injection flow produces an increase in the dissipation length which could be located out of the detection zone.

Restricted access

Abstract  

In this paper, it is made a study of the accuracy of an isothermal titration calorimeter in the operating mode of ‘continuous injection’. The experimental equipment has been a TAM2277-201/2250 by Thermometric AB and the liquid mixtures used in the calibration have been the mixture cyclohexane+benzene and the mixture water+ethanol. The calibration contemplates different effects that affect the uncertainty in the determination of the sensitivity, the effect of the liquid injection, the treatment of the calorimetric signal, the variation of the experimental baseline and the different noises included in the calorimetric signal.

Restricted access