Abstract. We analyse the hypothesis that predictable gradients occur in plant–pollinator interactions along altitudinal gradients due to thermal constraints on insect body size and floral traits being selected for by pollinators. Pollinators’ size should follow Bergmann's rule in mountains (larger body size at higher altitudes) and selection should, in turn, lead to larger flower size at higher altitudes. The study focuses on the flower and pollinator size variation in 11 Cytisus scoparius populations located between 680 and 1300 m a.s.l., and on the relationship between flower size and pollination success of plants in each population. Significant differences among populations were found in flower size, pollinator size and fruiting success (anova, P < 0.001 in all cases). Regression models show that (i) pollinator size increases significantly with altitude, (ii) a parallel quadratic increase in flower size and (iii) a quadratic decrease in pollination success with altitude. Moreover, there is a tendency of plants with smaller flowers in each population to have a higher percentage of flowers initiating development into fruits (ancova, P < 0.05). All these observations support the presence of the predicted gradient in the studied species and they suggest the possibility of it to be somewhat common among plants that occupy large altitudinal ranges due to the simple basis on which it could be rooted.
The electrical characteristics of anodic oxide films formed on tantalum are investigated in anodes oxidized in the standard electrolytes for low-voltage (0.01% H3PO4in water) and high-voltage (same plus ethylene glycol) applications. It is found that small additions (about 0.1%) of certain organic acids such as citric acid to the above electrolytes greatly improves the leakage current, the scintillation voltage and the dielectric losses of tantalum capacitors. Furthermore, the use of these organic acids makes it possible to extend to higher voltages the use of the low-voltage electrolyte, and allows, in the case of the high-voltage electrolyte, a substantial diminution in the ethylene glycol concentration without impairing the characteristics of the resulting capacitors. Finally, the effect of the citric acid and the ethylene glycol in the anodizing electrolytes is discussed.
An electronic method, based on the differentiation of the potential curve during anodization at a constant current, is presented for evaluating the number of breakdown events in the scintillation of anodic oxides. This simple method facilitates the study of the breakdown phenomenon in anodic oxides as a function of the anodization current density, nature and resistivity of the electrolyte, etc. The results are briefly discussed according to a proposed model of the scintillation mechanism.8. F. Forlani and N. Minnaja, "Electrical Breakdown in Thin
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