We first argue that the collective behaviour of the Cooper pairs created by thermal fluctuations well above the superconducting transition temperature, T C , is dominated by the uncertainty principle which, in particular, leads to a welldefined temperature, T C , above which the superconducting coherence vanishes. On the grounds of the BCS approach, the corresponding reduced-temperature, ε C ≡ ln(T C /T C ), is estimated to be around 0.55, i.e., above T C ≃ 1.7 T C coherent Cooper pairs cannot exist. The implications of these proposals on the superfluid density are then examined using the Gaussian-Ginzburg-Landau approximation. Then we present new measurements of the thermal fluctuation effects on the electrical conductivity and on the magnetization in different lowand high-T C superconductors with different dopings which are in excellent agreement with these proposals and that demonstrate the universality of ε C . 74.20.-z Theories and models of superconducting state 74.20.De Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) 74.40.+k Fluctuations (noise, chaos, nonequilibrium superconductivity, localization, etc.)

The capacity of carbohydrate and ketone bodies metabolism in brain and liver was evaluated in fed and food-deprived Atlantic salmon (Salmo salar) in a time period covering from 1 to 7 days (Experiment I), and in Atlantic salmon food deprived for 6 weeks, and food deprived for 4 weeks and refed for 2 weeks (Experiment II). The results obtained demonstrate for the first time in a teleost the existence of changes in brain metabolism due to food deprivation. Thus, decreased glucose levels in plasma are reflected in the brain by an increased mobilization of glycogen reserves, and by a decreased glycolytic capacity. Also, ketone bodies appear to increase their importance as a metabolic fuel from day 7 of food deprivation onwards. A possible increase in the gluconeogenic potential in brain simultaneously is not discarded. All these metabolic changes are reversed under refeeding conditions.

By using high quality single crystals and epitaxial thin films, the in-plane paraconductivity in almost optimally doped YBa 2 Cu 3 O 7Ϫ␦ , with T c0 տ92 K, was determined well inside the so-called short-wavelength fluctuation regime, which corresponds to reduced temperatures, ⑀ϵln(T/T c0 ), above typically ⑀ϭ0.1. It is then shown that these data may be explained in terms of the Gaussian-Ginzburg-Landau approach for bilayered superconductors by introducing a total energy cutoff, instead of the momentum cutoff approximation always used until now. These results seem to confirm the absence of appreciable pseudogap effects on the in-plane resistivity in optimally doped YBa 2 Cu 3 O 7Ϫ␦ superconductors.

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By using two randomly oriented polycrystalline YBa2Cu3O7 − δ samples with masses as big as 0.63 g and 0.90 g, but almost optimally doped (Tc0 ≃ 90.8 K and 92.0 K) and with excellent stoichiometric homogeneity, the in-plane fluctuation-induced diamagnetism was determined, for the first time in any superconductor, well inside the so-called short wavelength regime in the zero-magnetic-field limit, which corresponds to reduced temperatures, ϵ ≡ ln (T/Tc0), above typically ϵ = 0.1. It is then shown that these measurements may be explained in terms of the Schmidt limit of the Gaussian-Ginzburg-Landau approach for bilayered superconductors by introducing a total-energy cut-off in the fluctuation spectrum.