The electron screening in the d(d, p)t reaction has been studied for the deuterated metal Pt at a sample temperature T = 20 • C-340 • C and for Co at T = 20 • C and 200 • C. The enhanced electron screening decreases with increasing temperature, where the data agree with the plasma model of Debye applied to the quasi-free metallic electrons. The data represent the first observation of a temperature dependence of a nuclear cross section. We also measured the screening effect for the deuterated metal Ti (an element of group 4 of the periodic table) at T = −10 • C-200 • C: above 50 • C, the hydrogen solubility dropped to values far below 1 and a large screening effect became observable. Similarly, all metals of groups 3 and 4 and the lanthanides showed a solubility of a few per cent at T = 200 • C (compared to T = 20 • C) and a large screening also became observable. Within the Debye model, the deduced number of valence electrons per metallic atom agrees with the corresponding number from the Hall coefficient, for all metals investigated.

for converting on the lathe, my blueprints into pieces for the target chamber, and for his valuable help in mechanical issues.Jorge Rocha for doing the lithium implantations and for helping with his expertise in vacuum technology.Eng. Hugo Marques and Prof. Dr. Orlando Teodoro for taking the SIMS and XPS spectra and helping me in the analysis. Palavras chaveLítio primordial, reacções nucleares induzidas por partículas carregadas, secção eficaz, factor astrofísico S , distribuições angulares, blindagem electrónica, modelo de Debye. AbstractThis work presents the results of the experimental study of proton induced nuclear reactions in lithium, namely the He reactions were measured concurrently with seven and four targets, respectively. These targets were produced in order to obtain adequate and stable lithium depth profiles.In metallic environments, the measured electron screening potential energies are much higher than the predictions of atomic-physics models. The Debye screening model applied to the metallic conduction electrons is able to explain these high values. It is a simple model, but also very robust. Concerning primordial nucleosynthesis and stellar evolution models, these v vi results are very important as they show that laboratory measurements are well controlled, and the model inputs from these cross sections are therefore correct.

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Neurological examination of children includes the screening for soft neurological signs (NSS). There is little knowledge about their evolution during adolescence, except that their lasting presence has been associated with developmental, psychological, and cognitive disorders. We report the results of a NSS exam (assessing gross and fine motor function and the presence of hyperactivity and motor impersistence) over a 5‐year period, among a group of healthy children who were followed annually as part of a dental study. Their ages ranged from 11 to 15 years at onset to 14 to 18 years at the end. Participants were divided into four groups by age (younger and older) and sex. At the first evaluation there were 191 males and 150 females. NSS score diminished both with increasing age and follow‐up time in both groups, but at different rates in males and females. Females reached the lowest scores two years before the younger subgroup of males. These results show that NSS change rapidly in adolescence and at different rates in males and females, which must be taken into account in clinical contexts. The evolution of NSS suggests that they are a signature of neural development.