The purpose of the present paper is to suggest a method for determining the235U abundance in uranium samples (compounds, metallic alloys or other uranium materials, where this element may be natural or
not) through a particular application of neutron activation analysis, based on the fission interference by molybdenum. The
method lies on an a priori calibration with natural uranium, thus it does not require235U certified standards.
The present paper describes an attempt to create a reliable and easy to use system for neutron activation with short-lived nuclides, suitable to be used with several irradiation and counting procedures in instrumental neutron activation analysis (INAA) at the Portuguese Research Reactor. This system can become very useful for a large community within LNETI, as well as other national institutes and universities, particularly for those involved in studies where the analysis of a large number of samples is required. Selenium determination has been performed, through the short-lived nuclide77mSe, as an example of the reliability of the system.
The resonance neutron self-shielding factor, Gres, is required in neutron metrology and activation data analysis. In a previous paper, the authors have shown that a dimensionless
variable can be introduced which converts the dependence of Gres on the physical and nuclear properties of the material samples into an universal curve, valid for the isolated resonances
of any nuclide. This work presents a methodology based on the universal curve, which enables to calculate Gres for a group of isolated resonances by weighting its individual contributions. A good agreement was reached with results calculated
by the MCNP code and with experimental values for Mo foils and wires.
The interpretation of the sample activation in a nuclear reactor requires the knowledge of two corrective parameters: the
thermal neutron self-shielding factor, Gth, and the resonance neutron self-shielding factor, Gres. The authors established a universal curve of Gres for isolated resonances and various geometries. The present paper deals with the description of Gth in foils, wires, spheres and cylinders by means of a universal curve on the basis of a dimensionless variable which includes
the physical, nuclear and geometrical properties of the sample. The universal curve is in good agreement with the experimental
and calculated values obtained from the literature.
Authors:J. Piedade-Guerreiro, M. Carmo Freitas and E. Martinho
The neutron activation analysis (NAA) was applied to the multielement analysis of the mediterranean fruit fly, Ceratitis capitata Wied., taken from a stock produced at the Tropical Scientific Research Institut (IICT) in Lisbon, and to its artificial food. Dry samples were irradiated in the OSIRIS reactor, within a work performed at the Laboratoire d'Analyse par Activation Pierre Süe (CEA/CEN-Saclay). The contents of Ca, K, Mg, Cl, Na, Fe, Zn, Al, Mn, Ba, Rb, Br, Co and Cs for the cases of Ceratitis capitata Wied. eggs, larvae, pupae, males and females and of its artificial food are reported.
Authors:M. Gouveia, M. Prudencio, M. Freitas, E. Martinho and J. Cabral
A numerical procedure is given to correct for the interference of U in the determination of the light rare earths, Zr, and Ru. The corresponding interference factors were calculated and their values compared with experimental results. The agreement is favourable in most cases.
Authors:J.P. Duarte, Manuel Coelho-e-Silva, V. Severino, D. Martinho, L. Luz, J.R. Pereira, R. Baptista, J. Valente-dos-Santos, A.M. Machado-Rodrigues, V. Vaz, A. Cupido-dos-Santos, J. Martín-Hernández, S.P. Cumming and R.M. Malina
The study was aimed to investigate the reproducibility of performance parameters obtained from 10-s maximal cycling effort against different braking forces in young adult athletes. The sample (n = 48) included male athletes aged 18.9–29.9 years (175.5 ± 6.9 cm, 76.2 ± 10.1 kg). The exercise protocol was performed in a cycle-ergometer against a random braking force (4% to 11% of body mass). Intra-individual variation was examined from repeated tests within one week. Descriptive statistics were computed and differences between sessions were tested using paired t-test. The coefficient of correlation between repeated measures, technical error of measurement (TEM), coefficient of variation and ICC were calculated. Agreement between trials was examined using the Bland-Altman procedure. Mean values of peak power were relatively stable when obtained from sampling rates of 50 Hz and ranged between 1068 watt and 1082 watt (t(47) = 1.149, p = 0.256, ES-r = 0.165) or while corresponding to a sampling rate of 1 Hz (t(47) = 0.742, p = 0.462, ES-r = 0.107). Correlations between repeated measures were high (+0.907, 95% CI: +0.839 to +0.947) and TEM about 59.3 watt (%CV = 5.52%; ICC = 0.951, 95% CI: 0.912 to 0.972). The present study suggests that reproducibility of peak power in male adult athletes tended to be acceptable and within individual error appeared unrelated to braking force.