On poloidal mode coupling in the continuous spectrum of 2D equilibria

The continuous spectrum of linear ideal MHD is determined analytically in 2D magnetostatic models for coronal loops and arcades by means of a perturbation expansion. Poloidal mode coupling, induced by non-circularity of the cross-sections of the magnetic surfaces and/or variation of the plasma density along the magnetic field lines, is shown to occur in first order. The coupling is most pronounced on and near rational surfaces for particular poloidal and toroidal mode numbers and produces gaps in the continuous spectrum of ideal MHD.     

ALH 82102: An Antarctic meteorite embedded partly in ice

Abstract We measured the concentrations of F, Cl, Br and I in two different aliquots of the meteorite ALH 82102. This H5 chondrite was recovered at the Allan Hills region, while it was partially embedded in the ice. One aliquot was taken from that part of the surface of the meteorite that was still in the ice, and the other one was taken from the side, which was poking out of the ice. Both aliquots are highly, and nearly to the same degree, contaminated with halogens. The observed enrichments occurred mainly during the time the meteorite was lying on the surface of the ice by deposition and/or adsorption of aerosols, salts, and gaseous components. A contamination during the time it was covered by the ice is unlikely. We conclude, therefore, that this meteorite was not always buried in the ice during its “residence time” on Earth. In order to accumulate the observed contamination, it had to be on the surface of the ice part of the time between its fall onto the Earth and its collection. The age of the ice surrounding the meteorite cannot be equal to the measured terrestrial age of ALH 82102.     

Does the Fornax dwarf spheroidal have a central cusp or core?

The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at ∼1 kpc from its centre. In a cuspy cold dark matter halo the globulars would sink to the centre from their current positions within a few Gyr, presenting a puzzle as to why they survive undigested at the present epoch. We show that a solution to this timing problem is to adopt a cored dark matter halo. We use numerical simulations and analytic calculations to show that, under these conditions, the sinking time becomes many Hubble times; the globulars effectively stall at the dark matter core radius. We conclude that the Fornax dwarf spheroidal has a shallow inner density profile with a core radius constrained by the observed positions of its globular clusters. If the phase space density of the core is primordial then it implies a warm dark matter particle and gives an upper limit to its mass of ∼0.5 keV, consistent with that required to significantly alleviate the substructure problem.     

3D fold growth rates

Geological folds are inherently 3D structures; therefore, they also grow in three dimensions. Here, fold growth in all three dimensions is quantified by numerically simulating upright single‐layer folds in 3D Newtonian media. Horizontal uniaxial shortening leads to a buckling instability, which grows from a point‐like initial perturbation in all three dimensions by fold amplification (vertical), fold elongation (parallel to fold axis) and sequential fold growth (parallel to shortening direction) of secondary (and further) folds adjacent to the initial isolated fold. The two lateral directions exhibit similar averaged growth rates, leading to bulk fold structures with aspect ratios in map view close to 1. However, fold elongation is continuous with increasing bulk shortening, while sequential fold growth exhibits jumps whenever a new sequential fold appears and the bulk fold structure therefore suddenly occupies more space. Compared with the two lateral growth directions, fold amplification exhibits a slightly higher growth rate.     

Managing coastal evolution in a more sustainable manner. The Conscience approach

This paper summarises the main findings of the Conscience research project, whose primary objective was to define and validate, through pilot applications, a methodology to support the implementation, for European coasts, of concepts such as coastal resilience, favorable sediment status, strategic sediment reservoirs and coastal sediment cells. The Conscience conceptual framework to managing coastal erosion has proved to be an efficient tool, because it provides a consistent approach where objective (data) and subjective (desired status) information are analyzed and compared from the standpoint of a consensus target (objective). Moreover, this is done using the best available knowledge and observations, considering always their level of uncertainty, to conduct a sustainable management policy for coastal erosion. The methodology has been tested in field cases from The Netherlands, Poland, Romania, Spain, United Kingdom and Ireland, to cover different time and space scales, together with a wide range of processes and different management objectives.     

Rockfalls detached from a lateral moraine during spring season. 2010 and 2011 events observed at the Rebaixader debris-flow monitoring site (Central Pyrenees, Spain)

Instability processes at glacial deposits represent an important hazard in mountainous areas. During the spring seasons of 2010 and 2011, two falls of large boulders (18 and 55? m³) initiated in a lateral moraine in the Rebaixader catchment (Central Pyrenees, Spain). Detailed information was gathered due to the debris-flow monitoring system installed along the torrent. Meteorological data showed that the two rockfalls were triggered without important rainfall amounts. Field surveys, ground vibration acquired at geophones and the movie recorded with a video camera provided unique information on the rockfall occurrence and dynamics. In addition, the information gave an excellent opportunity to show the importance of monitored data for the calibration of model parameters for runout simulations. The analysis focussed on the 2011 event and showed that the boulder passed rolling and bouncing through the monitored torrent reach. The velocity estimates in this reach range from 3 to 9 ?m/s. The 2011 rockfall was also back-analysed by a two-dimensional physically based model, which was fitted by the monitored and field data. The results of the simulation coincided well with recorded measurements, although the output could be improved by the application of a three-dimensional model.     

Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO ₃ ^– ), iron (Fe²⁺), manganese (Mn²⁺), and sulfate (SO ₄ ^2– ). Redox conditions were evaluated also based on methane (CH₄), excess nitrogen gas (N₂) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100?m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.     

Full‐scale Applications of Membrane Filtration in Municipal Wastewater Treatment Plants

The performance of one pilot‐scale and two full‐scale membrane bioreactors (MBR) were evaluated based on the control of main operational parameters, composition of microbial community and pathogens concentration in the treated outlet. Plants were designed for 0.75 m³/day (A), 60 m³/day (B) and 30 m³/day (C). Inlet and outlet samples were monitored for chemical oxygen demand (COD), biological oxygen demand, total suspended solids, ammonia nitrogen concentration (NH₄–N), nitrate nitrogen concentration, total Kjeldahl nitrogen, total phosphorus and phosphate phosphorus concentration concentrations. Plants showed good COD removal: 91.9% for Plant A, 97.8% for Plant B and 94.2% for Plant C. The targeted nitrogenous ion was NH₄–N due to the requirements for outlet limits. NH₄–N removal was moderate for Plant A (73.3%) and Plant B (86.1%) and excellent for Plant C (>99%). Excellent phosphorus removal was achieved by Plant A (average outlet concentration was 0.7 mg/L, efficiency 84.7%). Unsatisfactory results for phosphorus removal were achieved at the full‐scale plants due to operational problems. The dependency between the extracellular polymeric substances increase and decreasing mixed liquor volatile suspended solids for both lab and full‐scale plants was confirmed. Soluble microbial product concentrations were reduced by 65–68% after coagulant dosage for Plant A. Outlets from the MBR plants were monitored for the presence of pathogens (thermotolerant coliforms, Escherichia coli, intestinal Enterococci and culturable microorganisms at 22 and 37°C). The treated effluent from Plant A, B and C met Czech national legislation regarding reuse criteria (standards) for environment, irrigation and swimming purposes. Plants B and C were not able to achieve requirements for potable water and personal hygiene quality standards.     

Influence of plankton concentration on gametogenesis and spawning of the black lip pearl oyster Pinctada margaritifera in Ahe atoll lagoon (Tuamotu archipelago, French polynesia)

Pearl culture industry represents one of the dominant business sector of French Polynesia. However, it still entirely relies on unpredictable spat collection success. Our aim was to assess the influence of natural plankton concentration fluctuations on maturation and spawning of the black lip pearl oyster Pinctada margaritifera, during a 4months survey conducted in Ahe atoll lagoon. Plankton concentration was assessed by chlorophyll a extraction and by microscope counts while gonadic index, gonado-visceral dry weights and histology were used to measure pearl oysters reproduction activity. We found that (i) plankton concentration fluctuations were mainly related to wind regime, (ii) gametogenesis rate was mainly related to plankton concentration, (iii) spawning occurred when maximal gonad storage was reached, (iv) plankton concentration was the main spawning synchronizing factor. These results contribute explaining P. margaritifera spat collection variability in French Polynesian atoll lagoon.