Stellar dynamic spectroscopy

The dynamic spectrum, a three dimensional record of the radio intensity as a function both of time and frequency, has long been used as a probe of plasma processes in the solar corona. Beginning with the work of Wild and McCready (1950) dynamic spectroscopy has been used to distinguish between the multitude of radio wave emitting phenomena which occur in the solar corona and to infer the physical mechanisms responsible.Stellar dynamic spectroscopy has always been a tantalizing prospect. The vast body of experience with solar dynamic spectroscopy would prove invaluable in interpreting stellar dynamic spectra. Further, the new parameter regimes presented by stellar coronas would allow further insight to be gained in the physical processes at work in stellar coronas.Recently, Bastian and Bookbinder (1987) used the Very Large Array in spectral line mode at 1.4 GHz with a bandwidth of 50 MHz to obtain the first dynamic spectra of nearby flare stars. The spectral resolution was 3.125 MHz and the temporal resolution was 5 s. While the relative bandwidth was less than ideal (/ 5%), the spectra so obtained were sufficient to show the presence of narrowband structure in a radio outburst from the well-known dMe flare star UV Ceti.Several efforts are now underway to obtain stellar dynamic spectra, of both RS CVn binaries and dMe flare stars, with higher degrees of spectral and temporal resolution. Among these are use of a 1024 channel correlator with the 1000' telescope at Arecibo and use of the Berkeley Fast Pulsar Search Machine (Kulkarni et al. 1984) with the Green Bank 140' telescope.

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OpenGeoSys-ChemApp: a coupled simulator for reactive transport in multiphase systems and application to CO2 storage formation in Northern Germany

Sequestration of CO₂ into a deep geological reservoir causes a complex interaction of different processes such as multiphase flow, phase transition, multicomponent transport, and geochemical reactions between dissolved CO₂ and the mineral matrix of the porous medium. A prognosis of the reservoir behaviour and the feedback from large-scale geochemical alterations require efficient process-based numerical models. For this purpose, the multiphase flow and multicomponent transport code OpenGeoSys-Eclipse have been coupled to the geochemical model ChemApp. The newly developed coupled simulator was successfully verified for correctness and accuracy of the implemented reaction module by benchmarking tests. The code was then applied to assess the impact of geochemical reactions during CO₂ sequestration at a hypothetical but typical Bunter sandstone formation in the Northern German Basin. Injection and spreading of 1.48 × 10⁷ t of CO₂ in an anticline structure of the reservoir were simulated over a period of 20 years of injection plus 80 years of post-injection time. Equilibrium geochemical calculations performed by ChemApp show only a low reactivity to the geochemical system. The increased acidity of the aqueous solution results in dissolution of small amounts of calcite, anhydrite, and quartz. Geochemical alterations of the mineral phase composition result in slight increases in porosity and permeability, which locally may reach up to +0.02 and 0.1 %, respectively.     

Matching INSPIRE Quality of Service Requirements with Hybrid Clouds

A lot of effort has been invested in Spatial Data Infrastructures (SDIs) during the last decade regarding interoperable standards for services and data. But still the scalability and performance of SDI services is reported to be crucial especially if they are accessed concurrently by a high number of users. Furthermore, laws and provisions such as the INSPIRE directive specify challenging requirements regarding the performance, availability and scalability of SDI services. This article presents a Hybrid Cloud architecture for matching INSPIRE‐related Quality of Service (QoS) requirements, without investing in rarely used hardware in advance, by occupying external third‐party resources on a pay‐as‐you‐go basis. The presented Hybrid Cloud is a composition of a local IT‐infrastructure (Private Cloud) and the computational resources of third‐party vendors (Public Cloud). The local infrastructure is laid out to handle the average main load of a service and in lasting peak times additional resources of external providers are allocated and integrated on demand into the local infrastructure to provide sufficient service quality automatically. A proof‐of‐concept implementation of the proposed Hybrid Cloud approach is evaluated and benchmarked with respect to INSPIRE‐related QoS requirements.     

Diffusion and solubility of hydrogen and water in periclase

Cylinders of synthetic periclase single crystals were annealed at 0.15–0.5 GPa and 900–1200 °C under water-saturated conditions for 45 min to 72 h. Infrared spectra measured on the quenched products show bands at 3,297 and 3,312 cm^?1 indicating V _OH ^? centers (OH-defect stretching vibrations in a half-compensated cation vacancy) in the MgO structure as a result of proton diffusion into the crystal. For completely equilibrated specimens, the OH-defect concentration, expressed as H₂O equivalent, was calculated to 3.5 wt ppm H₂O at 1,200 °C and 0.5 GPa based on the calibration method of Libowitzky and Rossmann (Am Min 82:1111–1115, 1997). This value was confirmed via Raman spectroscopy, which shows OH-defect-related bands at identical wavenumbers and yields an H₂O equivalent concentration of about 9 wt ppm using the quantification scheme of Thomas et al. (Am Min 93:1550–1557, 2008), revised by Mrosko et al. (Am Mineral 96:1748–1759, 2011). Results of both independent methods give an overall OH-defect concentration range of 3.5–9 (+4.5/?2.6) ppm H₂O. Proton diffusion follows an Arrhenius law with an activation energy E _a = 280 ± 64 kJ mol^?1 and the logarithm of the pre-exponential factor logD_o (m² s^?1) = ?2.4 ± 1.9. IR spectra taken close to the rims of MgO crystals that were exposed to water-saturated conditions at 1,200 °C and 0.5 GPa for 24 h show an additional band at 3,697 cm^?1, which is related to brucite precipitates. This may be explained by diffusion of molecular water into the periclase, and its reaction with the host crystal during quenching. Diffusion of molecular water may be described by logD_H2O (m² s^?1) = ?14.1 ± 0.4 (2σ) at 1,200 °C and 0.5 GPa, which is ~ 2 orders of magnitude slower than proton diffusion at identical P-T conditions.     

Geomorphic coupling between hillslopes and channels in the Swiss Alps

The coupling relationships between hillslope and channel network are fundamental for the understanding of mountainous landscapes' evolution. Here, we applied dendrogeomorphic methods to identify the hillslope–channel relationship and the sediment transfer dynamics within an alpine catchment, at the highest possible resolution. The Schimbrig catchment is located in the central Swiss Alps and can be divided into two distinct geomorphic sectors. To the east, the Schimbrig earth flow is the largest sediment source of the basin, while to the west, the Rossloch channel network is affected by numerous shallow landslides responsible for the supply of sediment from hillslopes to channels. To understand the connectivity between hillslopes and channels and between sources and sink, trees were sampled along the main Rossloch stream, on the Schimbrig earth flow and on the Rossloch depositional area. Geomorphic observations and dendrogeomophic results indicate different mechanisms of sediment production, transfer and deposition between upper and lower segments of the channel network. In the source areas (upper part of the Rossloch channel system), sediment is delivered to the channel network through slow movements of the ground, typical of earth flow, shallow landslides and soil creep. Contrariwise, in the depositional area (lower part of the channel network), the mechanisms of sediment transfer are mainly due to torrential activity, floods and debris flows. Tree analysis allowed the reconstruction of periods of high activity during the last century for the entire catchment. The collected dataset presents a very high temporal resolution but we encountered some limitations in establishing the source‐to‐sink connectivity at the catchment‐wide scale. Despite these uncertainties, for decennial timescales the results suggest a direct coupling between hillslopes and neighbouring channels in the Rossloch channel network, and a de‐coupling between sediment sources and sink farther downstream, with connections possible only during extraordinary events. Copyright © 2012 John Wiley & Sons, Ltd.     

Implications of EU-Water Framework Directive for the East German Postmining Landscape Lausitz: Coping with a sparse knowledge of the underground

Mining dumps are major sources of pollutants within the mining area of Lausitz, especially sulphate and iron. Their existence in catchment areas comprising groundwater bodies or lakes often imposes negative effects on the water quality. The European Union Water Framework Directive [EU-WFD, 2000. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy. The European Parliament and Council, L327/1, p. 72] aims to achieve ‘good quality’ status for all water bodies across Europe by 2015. Consequently, predicting the development of ground and lake water quality is necessary and must be based on the geochemical composition of the mining dumps. Therefore, the dumps need to be quantified as pollutant sources.A method to calculate the amount of sulphate in mine dumps is presented. It is based on historic geological and geochemical data characterising the pre-mining situation. Additional information on the dump body, derived from the vertical extension of mining activities and the current Digital Elevation Model (DEM), allows the composition of the dump to be determined. This procedure is demonstrated for the Bärwalde site. An average total sulphur content of 0.62% (5.9 million tonnes) was calculated for the Bärwalde dump. About 40% of it is estimated to be pyrite sulphur. Applying an average pyrite oxidation rate for the whole dump body of 7% led to an additional water-soluble mass of 0.18 million tonnes of sulphate sulphur.Applying this technique to all mine dumps managed by the postmining administration company LMBV, will improve our knowledge of the catchment area for the different lakes of Lausitz and will form an essential basis for reactive transport calculations.