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Abstract  

A method based on neutron activation analysis was developed for the determination of fractions of milligrams of 2,4-D (2,4-dichlorophenoxy acetic acid) in aqueous solution in laboratory tests. The indirect determination of 2,4-D was based on the quantification of chlorine,38Cl, produced by neutron activation. The range of application was 0.01–100 mg l−1. No loss of38Cl by chemical effects of the nuclear reaction was found. The advantages of the proposed method include high precision and sensitivity of determination. Results were compared with those obtained by UV-Vis spectrophotometry, where concentrations less than 1 mg·l−1 were not detected.

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Exceptional geomagnetic storms were observed in late August and early September 1859. Auroras were observed around the world, and telegraph wires were damaged. Until now, there has been no evidence published of auroral observations in Spain during this famous space weather event. This paper presents Spanish observations that show the aspect of this great aurora from Spain, and the concurrent effects on European telegraph wires. We also computed the variation of the geomagnetic declination in Spain during recent centuries to put these records into context.

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Acta Chromatographica
Authors:
M. Rosales-Castro
,
R. F. González-Laredo
,
N. E. Rocha-Guzmán
,
J. A. Gallegos-Infante
,
J. Peralta-Cruz
,
J. Morré
, and
J. J. Karchesy

Summary

Crude acetone extracts (CE) from Quercus durifolia and Quercus eduardii barks were partially purified by liquid extraction with ethyl acetate into organic extracts (OE), and these were separated by a Toyopearl HW-40F column chromatography with acetone-water (3:2) into oligomeric fractions (OLF). OEs were analyzed by HPLC and OLF by HPLC-MS. Screening of the antioxidant capacity of CE, OE, and OLF were performed by scavenging 1,1′-diphenyl-2-picrylhydrazyl (DPPH) radical and ABTS·+ radical cations as well by β-carotene-linoleic acid model system assays. In the bark of both Quercus species the major compound identified in OE was catechin. In OLF the major compounds were monomeric and dimeric monogallate procyanidins, and monomeric, dimeric, trimeric, and tetrameric procyanidins. The best antioxidant capacity was shown by OLF from bark extracts of both species.

Open access
Community Ecology
Authors:
F. J. Fernandez-Maldonado
,
J. R. Gallego
,
A. Valencia
,
M. Gamez
,
Z. Varga
,
J. Garay
, and
T. Cabello

Cannibalism is a common phenomenon among insects. It has raised considerable interest both from a theoretical perspective and because of its importance in population dynamics in natural ecosystems. It could also play an important role from an applied perspective, especially when using predatory species in biological control programmes. The present paper aims to study the cannibalistic behaviour of Nabis pseudoferus Remane and the functional response of adult females. In a non-choice experiment, adult females showed clear acceptance of immature conspecifics as prey, with relatively high mortality values (51.89 ± 2.69%). These values were lower than those occurring for heterospecific prey, Spodoptera exigua Hübner, under the same conditions (80.00 ± 2.82%). However, the main result was that the rate of predation on heterospecific prey was reduced to 59.09 ± 7.08% in the presence of conspecific prey. The prey-capture behaviour of adult females differed when they hunted conspecific versus heterospecific prey. This was shown in the average handling time, which was 23.3 ± 3.3 min in the first case (conspecific) versus 16.6 ± 2.5 min in the second (heterospecific). Furthermore, the values increased in the former case and declined in the latter according to the order in which the prey were captured. The difference in handling time was not significant when adjusting the adult female functional response to conspecific nymphs. We argue that these results likely indicate risk aversion and a fear of reprisal among conspecifics.

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Community Ecology
Authors:
F.A. Rodríguez-Zaragoza
,
M. Ortiz
,
F. Berrios
,
L. Campos
,
A. de Jesús-Navarrete
,
J. Castro-Pérez
,
A. Hernández-Flores
,
M. García-Rivas
,
F. Fonseca-Peralta
, and
E. Gallegos-Aguilar

Banco Chinchorro is the largest reef in the Mexican Caribbean. Historically, spiny lobster, queen conch and over 20 other reef species have been exploited here. Multispecies intervention management from an ecosystem perspective has been developed in this area; however, an assessment of the effects of such practices on ecosystem health is required. Five quantitative trophic models were constructed using Ecopath with Ecosim. The results show that, in terms of biomass, benthic autotrophs are the dominant group in all communities. Ecosystem Network Analysis indices showed that Cueva de Tiburones was the most mature, developed, complex and healthy subsystem, but, El Colorado and La Baliza were the subsystems most resistant to disturbances. The fisheries mainly concentrate on primary (La Baliza and Cueva de Tiburones sites) and secondary consumers (La Caldera, Chancay, and El Colorado). The greatest propagation of direct and indirect effects, estimated by Mixed Trophic Impacts and Ecosim simulations, were generated by the benthic autotrophs, small benthic epifauna, benthic-pelagic carnivorous fish and benthic carnivorous fish, among others. In contrast, the System Recovery Time showed different patterns among subsystems, indicating several compartments that reduce resilience. Considering the structure, dynamics, trophic functioning and ecosystem health of Banco Chinchorro, its ecological heterogeneity highlights the need for the design of a specific (by subsystem) management strategy, particularly because different species or functional groups present greater sensitivity to human interventions in each community.

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