Deep Space 1 at comet 19P/Borrelly: Magnetic field and plasma observations

On September 22, 2001 the Deep Space 1 spacecraft performed a flyby at comet 19P/Borrelly at a solar distance of 1.36 AU leading the Earth by 74^° in longitude. The spacecraft-comet distance at closest approach was 2171 km. The bow shock had a magnetic compression ratio of 2.5 at a distance of 147 100 km from the nucleus. Deep Space 1 first entered the sheath region essentially from the north polar region. Fluctuations from the cometary ion pickup were present throughout the sheath region and even well upstream of the shock, as expected. The magnetic field pileup region had a peak field strength of 83 nT and was shown to be consistent with a pressure equal to the solar wind ram pressure. The peak field location was offset from the time of closest approach. It is uncertain whether this is a spatial or temporal variation. Draping of magnetic fields around the nucleus was sought, but evidence for this was not apparent in the data. A possible explanation is that the interplanetary solar wind was composed of turbulent short-scale fields, and thus the fields were not symmetric about the point of closest approach. During the flyby phase there were in general few intervals of ACE data where there were large scale Parker spiral fields. With the addition of plasma data, the shock properties are investigated. The characteristics of magnetic draping, pileup and fluctuations are explored. These comet 19P/Borrelly results are contrasted with other cometary flyby results.     

Since turtles cannot talk: what beak movement sensors can tell us about the feeding ecology of neritic loggerhead turtles,Caretta caretta

Understanding the role that consumers play in an ecosystem requires knowledge about food selection and intake rates. However, such basic data are often difficult to obtain, particularly for marine animals that are not easy to observe. To overcome this problem, a beak movement sensor was employed on a free‐ranging loggerhead turtle in a neritic foraging habitat at the Domitian littoral (SW Italy). In combination with gastrointestinal content analysis from six turtles found dead in the same area we sought to identify which beak movement patterns were associated with which prey type, and to quantify the ingestion of the various prey types. Brachyuran crabs (100% occurrence), in particular Liocarcinus vernalis, and small molluscs (66% occurrence) were found most frequently in the stomach and intestine of the turtles. Beak movements revealed average ingestion rates of (mean ± SE) 0.27 ± 0.13 food items per minute and that feeding occurred predominantly during dives >4 m and during early morning and evening. Interestingly, the time spent feeding amounted to only 2.2% of the total observation time, whereas feeding‐associated dives added up to just above 10% of the total time. We thus established that loggerhead turtles in this area are specialised on brachyuran crabs, on which they prey with high success during the short time dedicated to foraging. This information strengthens our knowledge about turtle–prey and turtle–habitat interactions, which are essential data to delineate the role that turtles play in this and similar marine ecosystems. Moreover, since the same area is also intensively used by the regional bottom trawl fishery, our results have important conservation implications, because they clearly show the time of day and water depths for which fishing activity should be regulated to reduce the number of turtles that are currently being incidentally caught in this area.     

First attempts towards an integrative concept for the ecological assessment of groundwater ecosystems

Healthy aquifers deliver important ecosystem services, e.g. the purification of infiltrating water and the storage of high-quality water over decades in significant quantities. The functioning of terrestrial and surface aquatic ecosystems directly depends on groundwater and vice versa. Nowadays, legislation has started to consider groundwater not only as a resource but as a living ecosystem. The assessment of ecosystems requires consideration of ecological criteria, which, so far, are not available for groundwater systems. In the framework of a project supported by the German Federal Environment Agency (UBA), a first concept for the ecological assessment of groundwater ecosystems is developed. Steps to be taken are introduced, with a strong focus on microbes as potential bioindicators. These include (1) the typology of groundwater ecosystems, (2) the derivation of natural background values, (3) the identification of potential bioindicators, and (4) the development of an assessment model. First successes and difficulties associated with these challenges, e.g. the lack of simple correlations between abiotic and biotic variables, are discussed on the basis of a data set from a local and regional aquifer in NE Germany. The need for collaboration between ecologists, hydrogeologists and geochemists, as well as the application of modern approaches such as multivariate statistics, is emphasized.     

A model for multiphase flow and transport in porous media including a phenomenological approach to account for deformation—a model concept and its validation within a code intercomparison study

Multiphase flow processes in unsaturated cohesive soils are often affected by deformation due to swelling and shrinking as a result of varying water contents. This paper presents a model concept which is denoted ‘phenomenological’ in terms of the processes responsible for soil deformation, since the effects of deformation on flow and transport are only considered by constitutive relations that allow an adaptation of the hydraulic properties. This new model is validated in a detailed intercomparison study with two state-of-the-art models that are capable of explicitly describing the processes relevant for the deformation. A ‘numerical experiment’ with a state-of-the-art reference model is used to produce ‘measurement data’ for an inverse-modelling-based estimation of the model input parameters for the phenomenological concept.     

Influence of Redox Mediators and Electron Donors on the Anaerobic Removal of Color and Chemical Oxygen Demand from Textile Effluent

Color removal was evaluated in anaerobic assays using synthetic (SE) and real (RE) effluents containing the dye Direct Black 22 (DB22). The focus was on the individual influence of two electron donors (EDs), sucrose and ethanol; and their combination with two redox mediators (RMs), lawsone and riboflavin. In addition to SE assays, the EDs were combined with sulfate which was present in the RE. Distinct behavior was observed with both assays. In the case of SE, using the EDs sucrose and ethanol resulted in DB22 removal efficiency of 93 and 83%, respectively; but only 27% in the control. The respective removal rates were 27.8‐ and 4.4‐fold higher than that of the control. Using the EDs with the RM lawsone resulted in color removal higher than that with riboflavin. Interestingly, in the ethanol + sulfate assay, late release of the last was observed, possibly due to the desulfonation reaction of the aromatic structures during the DB22 molecule breakdown. In the case of RE, no improvement was observed with either EDs; and some combinations with the RMs even resulted in decreased color removal. Therefore, the used EDs and RMs showed positive effect on color removal in SEs; but unexpectedly not in REs.     

Brittle-plastic deformation in initially dry rocks at fluid-present conditions: transient behaviour of feldspar at mid-crustal levels

We present detailed microstructural and chemical analyses from an initially dry anorthositic rock deformed during wet amphibolite facies conditions. Three different domains representing the microstructural variation of the deformed samples are investigated in detail in terms of fracture morphology and mode, grain characteristics and chemistry of present phases. Results show transient deformational behaviour where a close interaction between brittle, plastic and fluid-assisted deformation mechanisms can be observed. Our analysis allows us to describe the succession, interrelationships and effects of active mechanisms with progressively increasing strain in three so-called stages. In Stage 1, initial fracturing along cleavage planes promoted fluid influx that caused fragmentation and chemical reactions, producing fine-grained mineral assemblages in the fractures. Deformation twins and dislocations developed in clast pieces due to stress relaxation. Passive rotation of conjugate fracture sets and interconnection of intracrystalline fractures formed micro-shear-zones, constituting Stage 2. Microstructures and grain relationships indicate the activity and fluctuation between fracturing, dissolution-precipitation creep, grain boundary sliding and locally dislocation creep, reflecting the transient behaviour of brittle and plastic deformation mechanisms. Further rotation and widening of fractures into overall foliation parallel shear-bands (Stage 3) promoted strain partitioning into these areas through increased fluid influx, influence of fluid-assisted grain boundary sliding, phase mixing and presence of weak phases such as white mica. We suggest that local differences in fluid availability, volume fraction of weak phases produced by fluid present metamorphic reactions coupled with volume increase and local variations in stress concentration induced transient brittle-plastic behaviour. The studied shear-zone represents an example of the transformation of a rigid dry rock to a soft wet rock during deformation through syntectonic fracturing.     

The recognition of multiple magmatic events and pre-existing deformation zones in metamorphic rocks as illustrated by CL signatures and numerical modelling: examples from the Ballachulish contact aureole, Scotland

The combination of cathodoluminescence (CL) analysis, temperature and temperature–time calculations, and microstructural numerical modelling offers the possibility to derive the time-resolved evolution of a metamorphic rock. This combination of techniques is applied to a natural laboratory, namely the Ballachulish contact aureole, Scotland. Analysis of the Appin Quartzite reveals that the aureole was produced by two distinct magmatic events and infiltrated by associated fluids. Developing microstructures allow us to divide the aureole into three distinct regions. Region A (0–400?m, 663°C?<?T _max?<?714°C) exhibits a three-stage grain boundary migration (GBM) evolution associated with heating, fluid I and fluid II. GBM in region B (400–700?m, 630°C?<?T _max?<?663°C) is associated with fluid II only. Region C (>700?m of contact, T _max?<?630°C) is characterised by healed intragranular cracks. The combination of CL signature analysis and numerical modelling enables us to recognise whether grain size increase occurred mainly by surface energy-driven grain growth (GG) or strain-induced grain boundary migration (SIGBM). GG and SIGBM result in either straight bands strongly associated with present-day boundaries or highly curved irregular bands that often fill entire grains, respectively. At a temperature of ~620°C, evidence for GBM is observed in the initially dry, largely undeformed quartzite samples. At this temperature, evidence for GG is sparse, whereas at ~663°C, CL signatures typical for GG are commonplace. The grain boundary network approached energy equilibrium in samples that were at least 5?ka above 620°C.     

Estuarine ecological risk based on hepatic histopathological indices from laboratory and in situ tested fish

Juvenile Senegalese soles were exposed through 28-day laboratory and field (in situ) bioassays to sediments from three sites of the Sado estuary (W Portugal): a reference and two contaminated by metallic and organic contaminants. Fish were surveyed for ten hepatic histopathological alterations divided by four distinct reaction patterns and integrated through the estimation of individual histopathological condition indices. Fish exposed to contaminated sediments sustained more damage, with especial respect to regressive changes like necrosis. However, differences were observed between laboratory- and field-exposed animals, with the latest, for instance, exhibiting more pronounced fatty degeneration and hepatocellular eosinophilic alteration. Also, some lesions in fish exposed to the reference sediment indicate that in both assays unaccounted variables produced experimental background noise, such as hyaline degeneration in laboratory-exposed fish. Still, the field assays yielded results that were found to better reflect the overall levels of contaminants and physico-chemical characteristics of the tested sediments.     

Forest–savanna–morichal dynamics in relation to fire and human occupation in the southern Gran Sabana (SE Venezuela) during the last millennia

The southern Gran Sabana (SE Venezuela) holds a particular type of neotropical savanna characterized by the local occurrence of morichales (Mauritia palm swamps), in a climate apparently more suitable for rain forests. We present a paleoecological analysis of the last millennia of Lake Chonita (4°39′N–61°0′W, 884 m elevation), based on biological and physico-chemical proxies. Savannas dominated the region during the last millennia, but a significant vegetation replacement occurred in recent times. The site was covered by a treeless savanna with nearby rainforests from 3640 to 2180 cal yr BP. Water levels were higher than today until about 2800 cal yr BP. Forests retreated since about 2180 cal yr BP onwards, likely influenced by a higher fire incidence that facilitated a dramatic expansion of morichales. The simultaneous appearance of charcoal particles and Mauritia pollen around 2000 cal yr BP supports the potential pyrophilous nature of this palm and the importance of fire for its recent expansion. The whole picture suggests human settlements similar to today – in which fire is an essential element – since around 2000 yr ago. Therefore, present-day southern Gran Sabana landscapes seem to have been the result of the synergy between biogeographical, climatic and anthropogenic factors, mostly fire.