Anatomy of a high-silica eruption as observed by a local seismic network: the June 2011 Puyehue–Cordón Caulle event (southern Andes, Chile)

High-silica explosive eruptions are one of the most dangerous natural phenomena, yet it is unclear which processes are involved in this infrequent kind of event. We present the first systematic characterization of near-field seismicity associated with a large high-silica eruption analyzing data recorded before, during and after the 4 June 2011 rhyolitic eruption of Puyehue–Cordón Caulle Volcanic Complex (PCCVC). Results of a first-level data processing, developed by the Southern Andean Volcano Observatory (OVDAS) to monitor unrest and the evolution of the eruption, are complemented here with the relocation of hypocenters into a local 1D velocity model, the time series of the b value and the computation of the focal mechanism. This information allows us to define several phases before and after the onset of the eruption, describing details of the space–time evolution of seismicity, defining and characterizing the seismic sources, and identifying the structural control of the magmatic intrusion and stress variations during the eruption. Our results illuminate several underlying processes, with emphasis on the possible role that basement structures had on the storage, transport and evacuation of magma. Integrating our results with previous findings based on satellite geodesy and petrology of erupted materials, we discuss general conceptual models regarding destabilization of structurally controlled acidic magmatic systems, the pass from unrest to eruption, and changes in eruptive style and waning phases of eruptions, with broader implications for monitoring and forecast of violent silicic eruptions.</p

Uptake of copper (II) ions from acidic aqueous solutions using a continuous column packed with microcapsules containing a β-hydroxyoximic compound

In this paper, the uptake of Cu(II) ions from an acidic aqueous solution using a continuous column packed with microcapsules containing the chelating extractant LIX-860 N-IC was examined. A simple, economical method was employed to synthesise the microcapsules' polymeric matrix consisting of an in situ radical polymerisation method followed by the subsequent impregnation of the extractant compound 5-nonylsalicylaldoxime. The microcapsules had a spherical shape with a rough surface and a strong hydrophobic character that assured that the organic extractant was immobilised on the microspheres' porous structure. During the metal sorption experiments, three different columns were used, and the aqueous feed solution circulated through them at different flow rates in repetitive sorption-desorption cycles. The results of these experiments revealed that the metal extractability was improved when the flow rate of the feed phase decreased and when the largest column was used, likely because of

Chemical structure and biological properties of sulfated fucan from the sequential extraction of subAntarctic Lessonia sp (Phaeophyceae)

This work is related to the structural characterization of the sulfated polysaccharide from Lessonia sp and the study of its antioxidant and antiparasitic properties. Sequential extraction afforded D-mannitol as the only low MW sugar alcohol. Extraction with 2% CaCl2 afforded in 3.0% yield, a sulfated fucan (SF). Its major fraction (48.5% yield), isolated by ion-exchange chromatography corresponds to a linear polymer of α-l-fucopyranosil residues linked 1→3, sulfated at the O-4 and partially at O-2 positions. By alkaline extraction, sodium alginate (10.3% yield) was obtained. The antioxidant capacity of SF by ESR showed high elimination index (IC50, mg/mL) of hydroxyl (0.27), alkoxy (10.05), and peroxyl (82.88) radicals in relation to commercial mannitol. SF showed activity against the epimastigote form of Trypanosoma cruzi parasite (250 μg/mL) and low cytotoxicity in murine cells (367 μg/mL). The elimination capacity of radicals in aqueous medium of SF would allow its potential biomedical application.status: publishe

Chemical structure and biological properties of sulfated fucan from the sequential extraction of subAntarctic Lessonia sp (Phaeophyceae)

© 2018 Elsevier Ltd This work is related to the structural characterization of the sulfated polysaccharide from Lessonia sp and the study of its antioxidant and antiparasitic properties. Sequential extraction afforded D-mannitol as the only low MW sugar alcohol. Extraction with 2% CaCl2 afforded in 3.0% yield, a sulfated fucan (SF). Its major fraction (48.5% yield), isolated by ion-exchange chromatography corresponds to a linear polymer of α-L-fucopyranosil residues linked 1→3, sulfated at the O–4 and partially at O–2 positions. By alkaline extraction, sodium alginate (10.3% yield) was obtained. The antioxidant capacity of SF by ESR showed high elimination index (IC50, mg/mL) of hydroxyl (0.27), alkoxy (10.05), and peroxyl (82.88) radicals in relation to commercial mannitol. SF showed activity against the epimastigote form of Trypanosoma cruzi parasite (250 μg/mL) and low cytotoxicity in murine cells (367 μg/mL). The elimination capacity of radicals in aqueous medium of SF would allo