Pyrite oxidation inhibition by a cross-linked lipid coating

The effect of a diacetylene-containing phospholipid on the oxidation of pyrite, FeS₂, was investigated. Earlier work reported by our research group showed that the adsorption of l,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine on pyrite suppressed the extent of its oxidation by about 75% over a specific time period. Results presented here show that the pre-exposure to UV radiation of this lipid after sorption onto pyrite results in a 90% suppression. Attenuated total reflection (ATR) Fourier transform infra-red spectroscopy (FTIR) suggests that the UV irradiation of the lipid does not result in degradation of the adsorbed layer. It is believed that the UV exposure results in the cross-linking and polymerization of the adsorbed phospholipid into a relatively impermeable barrier that separates the pyrite from the aqueous phase. The results of this study might have implications for the protection of pyrite from oxidation in the environment.     

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park,Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad™ AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad™ AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns.     

First results from the PROBA/CHRIS hyperspectral/multiangular satellite system over land and water targets

The Project for On-Board Autonomy (PROBA) platform developed by the European Space Agency was launched on October 22, 2001. The instrument payload includes the Compact High Resolution Imaging Spectrometer (CHRIS). The coupled system provides high spatial resolution hyperspectral/multiangular data, which represents a new-generation source of information for Earth observation purposes. The first results obtained from the preprocessing (noise removal and geometric/atmospheric correction) of two different datasets, collected over agricultural crops and inland waters, are presented in this letter. In situ measurements are used to assess the quality of the data and to validate the processing algorithms. The capabilities of this new kind of information for an improved analysis of the surface properties are shown, focusing on the advantages that the coupling between the spectral and the angular domains may have in future Earth observation systems.     

Theoretical variability of s1 in the tide generating potential

Summary The S₁ tidal wave arising from the second order tidal potential occurs in any geophysical data record. Since the frequency of S₁ is the same as that of earth’s rotation, many distortions are observed in real data sets. To isolate S₁ from its powerful neighbours,K ₁ and P₁ at least one-year hourly data series are required. Studies onS ₁ on an experimental basis, have been aimed mainly at a precise determination of its origin and mechanisms of variability. There are many hypotheses on its variability. In physical oceanography it is commonly accepted that the variability of S₁ is due to air-sea interaction processes. The authors review most existing hypotheses on the variability of S₁ They also show that the distortions of real data must be expected due to additional contributions from the second and third-order lunar potentials. An analysis is made to detect the sources of the additional contributions to the S₁ frequency.

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Theoretische schwankung der s 1 im gezeitenerzeugenden potential TIPAB-95

Zusammenfassung Die Gezeitenwelle (Partialtide) S₁ ist in jedem Datensatz gegenw?rtig, der unter dem Einfluβ der Gezei tenkr?fte aufgezeichnet wurde. Ihre Quelle ist das sonnent?gliche Gezeitenpotential zweiter Ordnung. Die Frequenz S₁ stimmt mit der der Erdrotation überein. In den beobachteten Datens?tzen treten aber viele St? rungen auf. Wenigstens ein Jahr stündlicher Beobachtungen ist erforderlich, um die S₁ von ihren beiden m?chtigen Nachbarn, n?mlich derK ₁ und P₁ ,trennen zu k?nnen. In l?ngeren Beobachtungsreihen tritt sie klar in Erscheinung. Viele Arbeiten über die S₁ haben sich damit besch?ftigt, ihren Ursprung und die Quelle ihrer Ver?nde rung genau zu bestimmen. Es wurden aber auch viele Hypothesen hinsichtlich der in den Beobachtungen vorgefundenen St?rungen aufgestellt. In dieser Arbeit wird eine neue Hypothese, die Ver?nderlichkeit der S₁ betreffend, aufgezeigt, deren Grundlage die theoretische Entwicklung “TIPAB-95” des gezeitenerzeugenden Potentials ist.

     

A new Tertiary borax deposit in the Andes

The Loma Blanca borate deposit was formed in the muds of playa-lake environments during the Late Miocene and is the fourth Tertiary commercial borax deposit discovered within the borate districts of the world. It is the only South American deposit known to contain any of the minerals colemanite, inyoite, ulexite, borax, tincalconite and teruggite with a unique and characteristic mineral sequence among the other Argentinian borate deposits. The Loma Blanca deposit is characterized by abundant Ca, Na and B, very low Cl and relatively high As, S and Mg concentrations compared with other borate deposits. Thermal springs and hydrothermal solutions associated with local volcanic activity are thought to be the source of the borates. The early colemanite, inyoite, ulexite, borax and teruggite nodules and crystals appear to have been formed directly from brines penecontemporaneously within the unconsolidated sediments, and they continued to grow as the sediments were compacted. Later generations of borate minerals occur in vughs, veins and as thin layers. Diagenetic alterations include the partial replacement of borax by ulexite and tincalconite; when weathered, borates are often almost completely replaced by calcite.     

Sequences of thrusts and displacement transfer in the superposed duplexes of the Esla Nappe Region (cantabrian zone, nw spain)

In a cross-section through the southern arm of the Cantabrian Zone, several duplexes have been identified below the Esla Nappe, which is the uppermost and main thrust sheet of the area. The folds deforming the Esla Nappe are culmination walls linked to frontal and lateral ramps belonging to the lower thrust sheets. The thrust sequence can be established on the basis of quantitative analysis of displacement transfer and out of sequence thrusting. The primitive footwall ramps of the Esla Nappe Region were often subsequently broken by décollements developed in successively lower stratigraphic levels of these footwalls. The kinematics of the lowest duplex are more complicated than those of typical duplexes described elsewhere: some thrusts transfer only part of their displacement to the roof thrust, while the remaining part is accommodated along the higher thrusts of previously emplaced duplexes, cutting out of sequence one or more floor or roof thrusts. Cumulative displacement of the thrusts in this region is about 90 km, giving a present thickness 3 times that of the original pre-orogenic sequence, together with a translation of at least 60 km, for the synorogenic basin.     

Analysis of the goodness of empirical approaches in predicting explosive detonation parameters

Goodness of empirical models for predicting explosive detonation velocity and pressure was analysed using 3 databases consisting of experimental velocity and pressure measurements for different explosives. The first database was used to estimate experimental errors for detonation velocity and pressure measurements. The second database was used to compare residuals obtained by the experimental models and by various thermochemical codes. Finally, the third database, consisting of some 600 data on 130 explosive substances, was used to estimate residual bias and dispersion resulting from the application of the experimental models. Also analysed was model coherence with the ideal detonation theory. Our main conclusion is that all the models introduce bias in their predictions depending on the density and oxygen balance values of the explosive. Of those analysed, the Xiong model was notable for its good results, with residual dispersion comparable to that obtained from application of the best thermochemical codes. Our results would indicate that the Xiong model is the only model that may be compatible with the ideal detonation theory. The pressure equation derived from the ideal detonation theory and calibrated with experimental data had excellent predictive capacity.     

Wind and wave height climate from two decades of altimeter records on the Chilean Coast (15°–56.5° S)

Ocean Dynamics - In order to look for climatological changes on significant wave height and wind magnitude distributions, two decades of altimeter data were analyzed in a monthly 1° ×...     

New active galactic nuclei science cases with interferometry

Infrared (IR) interferometry has made widely recognised contributions to the way we look at the dusty environment of supermassive black holes on parsec scales. It finally provided direct evidence for orientation-dependent unification of active galaxies, however it also showed that the classical “torus” picture is oversimplified. New scientific opportunities for AGN have been suggested, and will soon be carried out, focusing on the dynamical aspects of spectrally and spatially resolved interferometry, as well as the potential to employ interferometry for cosmology. This will open interferometry to new scientific communities.     

Historical analysis of heavy metal pollution in three estuaries on the north coast of Galicia (NW Spain)

This research focuses on the development of metal pollution in sediment cores from three estuaries in Northwest Spain: Viveiro, Ortigueira and Barqueiro. Pb, Cu, Co, Cr, Cd and Zn and total organic carbon were assessed using principal component analysis (PCA) in order to obtain background values, measure pollution levels and identify pollution sources. Results were interpreted by considering the local industrial history, grain size and C/N relationship. The pollution levels obtained bear a strong resemblance to those documented for of a moderately industrialised area. PCA identifies factors that reflect mainly temporal associations with metals. Sedimentation rates between 0.9 and 1.1 cm/year were determined. In Viveiro core levels of Cr pollution are associated with tanneries. In Ortigueira, high core levels of Cu and Co are linked to mining, and Cr levels to adjacent ultramafic rocks. Erosion of Holocene sediment causes high values of Co and Cr in the Barqueiro core. Cu increase in the three estuaries is related to fungicide use since 1910. Sea level rise appears to be affecting the marine characteristics of the sediments in Barqueiro. In Viveiro, the nature of the sediment reflects engineering work and land reclamation.