Browsing by Author "Martinez, G"

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    Induction of settlement and metamorphosis of the scallop Argopecten purpuratus Lamarck by excess K+ and epinephrine
    (1999) Martinez, G; Aguilera, C; Campos, EO
    Settlement and metamorphosis of marine invertebrate larvae is known to be triggered by specific environmental cues. Neuroactive compounds, particularly some monoamines, have been implicated in this process, and depolarization of receptor cell membranes has been suggested to occur as a response to them. An increase of extracellular K+ in seawater has been used as an effective inducer of these processes for some species. This study describes work designed to assay effects of epinephrine and excess K+ as inducers of settlement and metamorphosis of larvae of the scallop Argopecten purpuratus. Epinephrine and excess K+ increased the percentages of settlement, metamorphosis, and survival of these larvae. Responses were dose-dependent, with a maxima under 10(-5) M (epinephrine) and 10 mM (K+). In the case of epinephrine, the responses did not vary significantly with the time of exposure. An analysis of size and energy content of larvae induced to metamorphosis by the different methods showed that larvae induced with epinephrine produced postlarvae that were significantly smaller in size and energetically weaker than postlarvae produced using excess K+ or no added exogenous inducer.
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    Non-universality of phase separation in two-dimensional critical binary-fluid mixtures
    (1997) Goncalves, S; Martinez, G; Iglesias, JR
    The domain growth in the late-time regime of phase-separating two-dimensional A-B critical fluid mixtures is investigated with molecular-dynamics simulations. Growth exponents are found to depend not only on temperature, as was previously shown, but also on the particular pair interaction potential. We study this dependence for two different molecular pair potentials with reduced strength among unequal particles and discuss possible mechanisms for the coarsening process as a function of temperature. At the low-temperature quenching regime the phase separation shows percolating patterns not previously reported, where a sequential aggregation of clusters gives rise to a possible multi-scaling behaviour.