Carbon dioxide dissolution in structural and stratigraphic traps

The geologic sequestration of carbon dioxide (CO[subscript 2]) in structural and stratigraphic traps is a viable option to reduce anthropogenic emissions. While dissolution of the CO[subscript 2] stored in these traps reduces the long-term leakage risk, the dissolution process remains poorly understood in systems that reflect the appropriate subsurface geometry. Here, we study dissolution in a porous layer that exhibits a feature relevant for CO[subscript 2] storage in structural and stratigraphic traps: a finite CO[subscript 2] source along the top boundary that extends only part way into the layer. This feature represents the finite extent of the interface between free-phase CO[subscript 2] pooled in a trap and the underlying brine. Using theory and simulations, we describe the dissolution mechanisms in this system for a wide range of times and Rayleigh numbers, and classify the behaviour into seven regimes. For each regime, we quantify the dissolution flux numerically and model it analytically, with the goal of providing simple expressions to estimate the dissolution rate in real systems. We find that, at late times, the dissolution flux decreases relative to early times as the flow of unsaturated water to the CO[subscript 2] source becomes constrained by a lateral exchange flow though the reservoir. Application of the models to several representative reservoirs indicates that dissolution is strongly affected by the reservoir properties; however, we find that reservoirs with high permeabilities (k ≥ 1 Darcy) that are tens of metres thick and several kilometres wide could potentially dissolve hundreds of megatons of CO[subscript 2] in tens of years.United States. Dept. of Energy (Grant DE-SC0003907)United States. Dept. of Energy (Grant DE-FE0002041)MIT Masdar ProgramMartin Family Fellowship for Sustainabilit

The late Frasnian rhynchonellid genus <i>Pammegetherhynchus</i> (Brachiopoda)in Poland, and its relevance to the Kellwasser Crisis

The rhynchonellid species, Pammegetherhynchus kowalaensis sp. n., occurs in the late Frasnian (Early to Late Palmatolepis rhenana, and possibly early Palmatolepis linguiformis conodont zones) marly-bituminous succession at Kowala (various outcrops) in the Gałęzice Syncline, south of Kielce in the Holy Cross Mountains, Poland. The only other known species of this genus is the type species, Pammegetherhynchus merodae Sartenaer, 1977, from the late Frasnian (somewhere in the Early and Late Palmatolepis rhenana Zones) of the French Fagne (dark shales of `Matagne' aspect), and, probably, of the Eifel (`Büdesheimer Goniatitenschiefer'). P. kowalaensis sp. n. occurred in level-bottom pioneer assemblages, thriving in reef downslope, mostly poorly-oxygenated habitats of the Kellwasser interval. The species finally disappeared near the Frasnian-Famennian boundary. The genus Pammegetherhynchus seems to be particularly suited to stressed deep-water shelf environments in the European part of the Laurussian shelf, widely distributed in this crisis time

Proposition for Simplified Calculation of a Roll Motion of Ship in Waves with Partially Flooded Compartments

This paper contains a description of a numerical model for calculating behaviour of ships in waves. There are many models available, but the one described here can be characterised with a set of parameters that have a decisive impact on the final values of roll motion amplitude and frequency. In this paper, it is shown how a fitting of a standard-shape hull characterised by certain readily available parameters affects the final roll and frequency of the motion. In addition, calculations for a flooded tank were made, and a range of results for the maximum dynamic heeling forces from this tank is shown. This calculation can further be verified for a range of hull dimensions and geometries to present a viable method to the industry

The role of sea-level change and marine anoxia in the Frasnian-Famennian (Late Devonian) mass extinction

Johnson et al. (Johnson, J.G., Klapper, G., Sandberg, C.A., 1985. Devonian eustatic fluctuations in Euramerica. Geological Society of America Bulletin 96, 567–587) proposed one of the first explicit links between marine anoxia, transgression and mass extinction for the Frasnian–Famennian (F–F, Late Devonian) mass extinction. This cause-and-effect nexus has been accepted by many but others prefer sea-level fall and cooling as an extinction mechanism. New facies analysis of sections in the USA and Europe (France, Germany, Poland), and comparison with sections known from the literature in Canada, Australia and China reveal several high-frequency relative sea-level changes in the late Frasnian to earliest Famennian extinction interval. A clear signal of major transgression is seen within the Early rhenana Zone (e.g. drowning of the carbonate platform in the western United States). This is the base of transgressive–regressive Cycle IId of the Johnson et al. (Johnson, J.G., Klapper, G., Sandberg, C.A., 1985. Devonian eustatic fluctuations in Euramerica. Geological Society of America Bulletin 96, 567–587) eustatic curve. This was curtailed by regression and sequence boundary generation within the early linguiformis Zone, recorded by hardground and karstification surfaces in sections from Canada to Australia. This major eustatic fall probably terminated platform carbonate deposition over wide areas, especially in western North America. The subsequent transgression in the later linguiformis Zone, recorded by the widespread development of organic-rich shale facies, is also significant because it is associated with the expansion of anoxic deposition, known as the Upper Kellwasser Event. Johnson et al.'s (Johnson, J.G., Klapper, G., Sandberg, C.A., 1985. Devonian eustatic fluctuations in Euramerica. Geological Society of America Bulletin 96, 567–587) original transgression-anoxia–extinction link is thus supported, although some extinction losses of platform carbonate biota during the preceeding regression cannot be ruled out. Conodont faunas suffered major losses during the Upper Kellwasser Event, with deep-water taxa notably affected. This renders unreliable any eustatic analyses utilising changes in conodont biofacies. Claims for a latest Frasnian regression are not supported, and probably reflect poor biostratigraphic dating of the early linguiformis Zone sequence boundary

Direct observation of a highly spin-polarized organic spinterface at room temperature

The design of large-scale electronic circuits that are entirely spintronics-driven requires a current source that is highly spin-polarised at and beyond room temperature, cheap to build, efficient at the nanoscale and straightforward to integrate with semiconductors. Yet despite research within several subfields spanning nearly two decades, this key building block is still lacking. We experimentally and theoretically show how the interface between Co and phthalocyanine molecules constitutes a promising candidate. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecules's nitrogen pi orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanims in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature

Proposition for Simplified Calculation of a Roll Motion of Ship in Waves with Partially Flooded Compartments

This paper contains a description of a numerical model for calculating behaviour of ships in waves. There are many models available, but the one described here can be characterised with a set of parameters that have a decisive impact on the final values of roll motion amplitude and frequency. In this paper, it is shown how a fitting of a standard-shape hull characterised by certain readily available parameters affects the final roll and frequency of the motion. In addition, calculations for a flooded tank were made, and a range of results for the maximum dynamic heeling forces from this tank is shown. This calculation can further be verified for a range of hull dimensions and geometries to present a viable method to the industry

Magnetoresistance through a single molecule

The use of single molecules to design electronic devices is an extremely challenging and fundamentally different approach to further downsizing electronic circuits. Two-terminal molecular devices such as diodes were first predicted [1] and, more recently, measured experimentally [2]. The addition of a gate then enabled the study of molecular transistors [3-5]. In general terms, in order to increase data processing capabilities, one may not only consider the electron's charge but also its spin [6,7]. This concept has been pioneered in giant magnetoresistance (GMR) junctions that consist of thin metallic films [8,9]. Spin transport across molecules, i.e. Molecular Spintronics remains, however, a challenging endeavor. As an important first step in this field, we have performed an experimental and theoretical study on spin transport across a molecular GMR junction consisting of two ferromagnetic electrodes bridged by a single hydrogen phthalocyanine (H2Pc) molecule. We observe that even though H2Pc in itself is nonmagnetic, incorporating it into a molecular junction can enhance the magnetoresistance by one order of magnitude to 52%.Comment: To appear in Nature Nanotechnology. Present version is the first submission to Nature Nanotechnology, from May 18th, 201