RESUMEN

The anomalously fast growth of the silicon oxide layer at room temperature has been reported for the Cu/Si system. However, the systematical exploration of such a reaction under humidity conditions has not yet been carried out. Through one combination of the experiments and first-principle density functional theory (DFT) simulations, here, we investigate the influence of the imparted Cu atoms in Cu/Si on the oxidation of Si with the presence of H2O. The Cu addition causes the geometric distortion of the Si lattice, which alters the charge transfer to absorbed H2O and decreases its dissociation energy. This results in the experimental formation of much defective SiOx for the Cu/Si system than bare Si under humidity conditions. Furthermore, the presence of such an oxide structure and the catalytic effect of Cu provide the suitable diffusion channels and adsorption sites for the H2O transport and its dissociation. This enhances the oxidation rate of Si consequently and results in the fast growth of the oxide layer on Cu/Si at room temperature.

RESUMEN

Advertisement calls potentially represent honest signals for delimiting species and sexual selection. Quantitative statistics of individual variation in advertisement call properties can be used to predict female preferences for particular signal properties. In this study, advertisement call properties and their individual variation was analyzed in two endemic treefrog species, Liuixalus hainanus and L. ocellatus. Together with the description of the advertisement calls, our goals included determining whether call properties can be used to distinguish between the two species on the field, which acoustic properties are likely play a role in species or individual recognition, and whether they could predict the signaler's body size. We found that the dominant frequency, call duration, inter-call interval, and note number of monosyllabic calls in L. hainanus were significantly higher or longer than those in L. ocellatus. The dominant frequency was classified as a static property; the call duration, inter-call interval, inter-note interval, and note number were classified as dynamic properties in both species. The inter-note interval of multisyllabic calls was correlated with body mass, and the pulse number of monosyllabic calls was correlated with snout-vent length in L. ocellatus. These results indicate that the dominant frequency strongly contributed to species recognition of L. hainanus and L. ocellatus males. Acoustic properties reflected the signaler's body size in L. ocellatus but did not in L. hainanus. The difference in advertisement call characteristics between the two species may be due to the different reproductive strategies associated with different selection pressures and may promote the sharing of similar habitats by the two species.

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RESUMEN

Mating patterns exhibit considerable intra- and interspecific variation. Sexual selection can lead to the occurrence of random and assortative mating in different populations of the same species. Thus, understanding variation in mating decisions is crucial to understanding variation in the direction of sexual selection. We investigated natural mating patterns in Black-spectacled toads (Duttaphrynus melanostictus), an explosive-breeding species that breeds throughout the year. We captured amplectant pairs (137) and non-amplectant males (212) during breeding seasons from November 2016 to April 2017 in tropical-island population of southern China. Our study found no significant difference in snout-vent length (SVL) between amplectant and non-amplectant males. Female and male SVL were positively correlated with each other. Small females were paired more frequently with small males, less frequently with large males, but had no preference for or against medium males. Medium females exhibited no preference. Large females showed no preference for large males, but were paired less frequently with small males. These data suggested that successful amplectant males had body sizes representative of the entire population. Both random and size-assortative mating were present simultaneously in the same population and within the same breeding season. Female choice was important in shaping the mating behavior of Black-spectacled toads, promoting genotype-frequency stabilization and body-size diversity in the population.

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