Radio source calibration for the Very Small Array and other cosmic microwave background instruments at around 30 GHz

Accurate calibration of data is essential for the current generation of cosmic microwave background (CMB) experiments. Using data from the Very Small Array (VSA), we describe procedures which will lead to an accuracy of 1 per cent or better for experiments such as the VSA and CBI. Particular attention is paid to the stability of the receiver systems, the quality of the site and frequent observations of reference sources. At 30 GHz the careful correction for atmospheric emission and absorption is shown to be essential for achieving 1 per cent precision.
The sources for which a 1 per cent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC 7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ∼30 GHz is given for each.
Cas A, Tau A, NGC 7027 and Venus were examined for variability. Cas A was found to be decreasing at 0.394 ± 0.019 per cent yr⁻¹ over the period 2001 March to 2004 August. In the same period Tau A was decreasing at 0.22 ± 0.07 per cent yr⁻¹. A survey of the published data showed that the planetary nebula NGC 7027 decreased at 0.16 ± 0.04 per cent yr⁻¹ over the period 1967–2003. Venus showed an insignificant (1.5 ± 1.3 per cent) variation with Venusian illumination. The integrated polarization of Tau A at 33 GHz was found to be 7.8 ± 0.6 per cent at position angle =148°± 3°.     

Using the Fisher–Shannon method to characterize continuous seismic signal during volcanic eruptions: application to 2011–2012 El Hierro (Canary Islands) eruption

We investigated the dynamics of the continuous seismic signal recorded before and during the 2011–2012 El Hierro eruption (Canary Islands) using the innovative approach of the Fisher–Shannon method, a suitable statistical tool for detecting dynamic changes in complex systems. Our findings identify dynamic changes in the seismic signal that can be correlated with different stress states of the magmatic setting and the plumbing system in the volcano at El Hierro. The results contribute to the understanding of the fracturing pattern in the crust during a new intrusion and eruption of an overpressurized batch of magma.     

Effects of sewage pollution and bacterial load on growth and oxidative balance in the freshwater mussel Diplodon chilensis

The effect of chronic exposure to Escherichia coli on morphometrical parameters, different antioxidant defenses, lipid peroxidation and protein oxidation has been studied in digestive gland of the freshwater mussel Diplodon chilensis in the laboratory during 6 weeks. In, a parallel field study, we evaluated morphometrical and oxidative stress parameters in digestive glands of mussels collected from a sewage polluted area (SMA) and from a pristine area (control). Both sites were characterized by analyzing bacteriological and physic-chemical parameters. In the laboratory D. chilensis was able to filter bacteria at high concentrations with a clearing rate of 0.510 ± 0.036 L/h per gram of dry soft tissue mass. The digestive gland mass to shell length ratio (DGM/SL), reduced glutathione (GSH), lipid peroxidation, as concentration of thiobartituric acid reactive substances (TBARS), and glutathione-S-transferase (GST) activity of mussels fed with bacteria were significantly higher than those of control mussels after the fourth week. Fecal bacteria in lake water samples were undetectable in the control, and higher than 24,000 MPN (most probable number)/100 mL in SMA. DGM/SL was higher in SMA. No differences between sites were observed in total lipid and protein content, neither in superoxide dismutase activity. GSH content was higher in SMA, with no difference in the oxidized form. GST activity and MDA were significantly higher in SMA but protein oxidation was not affected.     

Aluminum coprecipitates with Fe (hydr)oxides: Does isomorphous substitution of Al for Fe in goethite occur?

Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitates were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with ?20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with ?25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with ?25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with ?30 mol% Al (at pH ∼2.25 for Fe³⁺ and at pH ∼4 for Al³⁺), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 mol% Al) in clustered arrangement (i.e., the formation of diaspore-like clusters) were in good agreement with available experimental data whereas optimized unit cell parameters for isolated Al atoms were not, and (ii) Al-substituted goethites with Al in diaspore-like clusters resulted in more energetically favored structures. Combined experimental and DFT results are consistent with the coprecipitation of Al with Fe (hydr)oxides and with the formation of diaspore-like clusters, whereas DFT results suggest isomorphous Al for Fe substitution within goethite is unlikely at ?8 mol% Al substitution.     

Importance of porosity and transfer of matter in the rock weathering processes: two examples in central Spain

Some physical properties (bulk and free porosity, pore size distribution), and the chemical composition and mass balance of two deeply weathered profiles one developed on Hercynian granodiorite and the other on pre-Cambrian slates were studied. Hydric and mercury porosimetry, nitrogen adsorption techniques, chemical analyses and XRD techniques were used. On granodiorite, weathering has created increased porosity with a pore diameter <5 μm, whereas on slates the weathering has produced of ca. 1 μm in diameter. These pore sizes have played an important role in the weathering processes. Assuming that weathering preserves volumes, except in the uppermost part of the profiles, it brought about a loss of matter of more than 12% (~300 kg/m³) on granodiorite and ca. 30% (~800 kg/m³) on slates. These changes are related to shifts in the mineralogical evolution, with the appearance of new 2:1 and 1:1 phyllosilicates and Fe oxy-hydroxides as the main authigenic minerals. The release of matter, at least since the upper Neogene until the present, has led to the lowering of relief in a more or less homogeneous way, giving rise to gentle hillsides and flat surfaces below which the current river networks are incised. Porosity studies have the potential to explain several specific landforms as well as affecting landscape development in general.     

The Bransfield current system

We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to describe the mesoscale variability observed in the Central Basin of the Bransfield Strait (Antarctica). The main mesoscale feature is the Bransfield Front and the related Bransfield Current, which flows northeastward along the South Shetland Island Slope. A laboratory model suggests that this current behaves as a gravity current driven by the local rotation rate and the density differences between the Transitional Zonal Water with Bellingshausen influence (TBW) and the Transitional Zonal Water with Weddell Sea influence (TWW). Below the Bransfield Front we observe a narrow (10 km wide) tongue of Circumpolar Deep Water all along the South Shetland Islands Slope. At the surface, the convergence of TBW and TWW leads to a shallow baroclinic front close to the Antarctic Peninsula (hereafter Peninsula Front). Between the Bransfield Front and the Peninsula Front we observe a system of TBW anticyclonic eddies, with diameters about 20 km that can reach 300 m deep. This eddy system could be originated by instabilities of the Bransfield Current. The Bransfield Current, the anticyclonic eddy system, the Peninsula Front and the tongue of Circumpolar Deep Water, are the dynamically connected components of the Bransfield Current System.     

Vertical Distribution of Radiation and Energy Balance Partitioning Within and Above a Lodgepole Pine Stand Recovering from a Recent Insect Attack

The current outbreak of mountain pine beetle (MPB) that started in the late 1990s in British Columbia, Canada, is the largest ever recorded in the north American native habitat of the beetle. The killing of trees is expected to change the vertical distribution of net radiation ( $Q^*$ Q ? ) and the partitioning of latent ( $Q_\mathrm{E}$ Q E ) and sensible ( $Q_\mathrm{H}$ Q H ) heat fluxes in the different layers of an attacked forest canopy. During an intensive observation period in the summer of 2010, eddy-covariance flux and radiation measurements were made at seven heights from ground level up to 1.34 times the canopy height in an MPB-attacked open-canopy forest stand $(\hbox {leaf area index} = 0.55~\mathrm{{m}}^{2}\ \mathrm{{m}}^{-2})$ ( leaf area index = 0.55 m 2 m - 2 ) in the interior of British Columbia, Canada. The lodgepole pine dominated stand with a rich secondary structure (trees and understorey not killed by the beetle) was first attacked by the MPB in 2003 and received no management. In this study, the vertical distribution of the energy balance components and their sources and sinks were analyzed and energy balance closure (EBC) was determined for various levels within the canopy. The low stand density resulted in approximately 60 % of the shortwave irradiance and 50 % of the daily total $Q^*$ Q ? reaching the ground. Flux divergence calculations indicated relatively strong sources of latent heat at the ground and where the secondary structure was located. Only very weak sources of latent heat were found in the upper part of the canopy, which was mainly occupied by dead lodgepole pine trees. $Q_\mathrm{H}$ Q H was the dominant term throughout the canopy, and the Bowen ratio ( $Q_\mathrm{H}/Q_\mathrm{E}$ Q H / Q E ) increased with height in the canopy. Soil heat flux ( $Q_\mathrm{G}$ Q G ) accounted for approximately 4 % of $Q^*$ Q ? . Sensible heat storage in the air ( $\Delta Q_\mathrm{S,H}$ Δ Q S , H ) was the largest of the energy balance storage components in the upper canopy during daytime, while in the lower canopy sensible heat storage in the boles ( $\Delta Q_\mathrm{S,B}$ Δ Q S , B ) and biochemical energy storage ( $\Delta Q_\mathrm{S,C}$ Δ Q S , C ) were the largest terms. $\Delta Q_\mathrm{S,H}$ Δ Q S , H was almost constant from the bottom to above the canopy. $\Delta Q_\mathrm{S,C}$ Δ Q S , C , $\Delta Q_\mathrm{S,B}$ Δ Q S , B and latent heat storage in the air ( $\Delta Q_\mathrm{S,E}$ Δ Q S , E ) varied more than $\Delta Q_\mathrm{S,H}$ Δ Q S , H throughout the canopy. During daytime, energy balance closure was high in and above the upper canopy, and in the lowest canopy level. However, where the secondary structure was most abundant, ${\textit{EBC}} \le 66\,\%$ EBC ≤ 66 % . During nighttime, the storage terms together with $Q_\mathrm{G}$ Q G made up the largest part of the energy balance, while $Q_\mathrm{H}$ Q H and $Q_\mathrm{E}$ Q E were relatively small. These radiation and energy balance measurements in an insect-attacked forest highlight the role of secondary structure in the recovery of attacked stands.     

Clay mineral occurrence and burial transformations: reservoir potential of the Permo‐Triassic sediments of the Iberian Range

The diagenetic evolution of Permian (Autunian and Saxonian) and Triassic (Buntsandstein) sandstones and mudrocks have been studied over 1000 m sequence from the Sigüenza 44‐3 drill core in the Iberian Range, Spain. We compare and contrast the diagenetic processes in these different lithologies and the timing of clay mineral formation. Moreover, we establish the relationship between clay mineral diagenesis and reservoir potential. Both the Permian and Triassic successions are characterised by conglomerates, sandstones and interbedded mudstones of fluvial origin that change upwards into distal deposits of a fluvio‐deltaic system. The clay minerals are illite, illite‐smectite mixed layers, kaolinite and dickite. The illite content in all sequences is not related to diminished feldspars; it is owing to the initial detrital mineralogical composition of the Autunian sandstones. The effect of feldspar alteration to kaolin minerals has a strong influence on the lost of porosity‐permeability in the Saxonian facies. In contrast, illite and mixed layers illite‐smectite are the main clay rims preserving porosity in the Buntsandstein sandstones. However, fibrous illite is the dominant pore‐filling in the Permian Autunian facies, closing porosity and permeability. Kaolinite and dickite show opposite trends: dickite increases yet kaolinite decreases from Triassic to Permian sandstones. Dickite replaced kaolinite during burial‐thermal evolution of the succession. The δD and δ¹⁸O isotopic signatures from silt and clay fractions indicate a mixture of meteoric and marine waters, and suggest a minimum temperature range between 60 and 150 °C for diagenetic pore fluids. The Permian δD values (?24‰ to ?44‰) are relatively similar to Buntsandstein values (?24‰ to ?37‰). However, the Permian δ¹⁸O values (+7.6 and +15.3, average of +13.3‰) are generally higher by ca. 6.2‰ compared to the Buntsandstein data (4.8–10.1‰, average +7.1‰). Such a variation is interpreted as the result of mesodiagenetic pore fluid changes. The extensive dickitisation of kaolinite is attributed to increased hydrogen ions resulting from maturation of organic matter. The vitrinite reflectance of organic matter and the modelled thermal history suggest a maximum burial of 3400 m, accomplished 70 Ma ago. The Permo‐Triassic reached the gas window shortly before major uplift, at 65 Ma, when further maturation and hydrocarbon expulsion ceased.