Possible liquid immiscibility textures in high-magnesia basalts from the Ventersdorp Supergroup, South Africa

The lowermost succession of lavas in the Proterozoic Ventersdorp Supergroup contains light weathering ocelli up to 15 cm in diameter which occur in layers of a darker weathering volcanic material. Some ocelli appear to merge, and discrete light weathering layers may be the ultimate end-stage of this coalescence. Alternatively, coexisting magmas in the neck of the volcano may have been erupted in varying proportions, and turbulence during flow caused spalling of large drops of the lighter weathering material into the other. Several lines of field evidence suggest that two distinct liquids coexisted and were rapidly quenched after eruption. Chemical data for ocelli and matrix are consistent with the hypothesis of liquid immiscibility. The differences in compositions between the coexisting pairs of liquids are small and it is suggested that the original magmas must have been close to the consulute composition

The influence of complex palaeobathymetry on development of deep-lacustrine fan systems

Pre-existing complex palaeobathymetry often plays a key role in the spatial-temporal distribution and character of deepwater sedimentary systems. Particularly in deep-marine fan systems where their spatial-temporal association with complex syn-depositional palaeobathymetry have been widely investigated. When present in deep-marine settings, complex palaeobathymetry is known to affect flow-type, flow direction, and resultant fan distribution, which ultimately leads to atypical reservoir rock distribution. By contrast, far fewer studies explore the influencing controls of palaeobathymetry on deep-lacustrine sedimentary systems. This is important to investigate as deep-lacustrine basins have quite different allogenic and autogenic controls on flow types and resultant fan systems and fan lobes, which varies through different stages of basin configuration. To address this knowledge gap, this study documents and characterises a suite of deep-lacustrine sedimentary systems imaged in high-quality 3D seismic data from the rift-sag transitional and early post-rift phases of the North Falkland Basin, Falkland Islands. A range of multi-scalar seismo-geomorphological features are identified, including super systems, fan systems, fan lobes, and channel elements. The influence of palaeobathymetry on flows and resultant sedimentary features is evidenced by frontal and lateral structural confinement at the super system scale, and lateral confinement plus fan/flow deflection at the fan system, fan, and lobe scale. Offset stacking and compensational lobe-scale stacking geometries are developed in response to the type and scale of confinement. Palaeobathymetry, created as depositional relief by preceding fan deposits, is shown to progressively influence flow types and resultant spatial distribution of ensuing sedimentary systems. During periods of basin-fill where encircling palaeobathymetry ultimately controlled super system scale distribution, the ponding of flows and resultant fan features against intra-basinal highs formed thick packages of potentially coarse-grained sediments. As the basin filled-up and encircling topography exerted less control on super system scale distribution, flows were able to surmount the intra-basinal highs, leading to flow stripping processes. The combination of ponding and flow stripping processes resulted in the deposition and preservation of coarse-grained sediments immediately behind or on top of intra-basin structures. The results of this study provide key insights into the interaction of deep-lacustrine sedimentary systems and complex palaeobathymetry, which ultimately influences reservoir distribution

Tectonostratigraphy and the petroleum systems in the Northern sector of the North Falkland Basin, South Atlantic

The North Falkland Basin represents one of the frontier areas for hydrocarbon exploration in the South Atlantic. This study presents the results of new subsurface mapping using 2D seismic data in the north of the Falkland Islands offshore area, which has delineated a series of discrete grabens northwards of the main North Falkland Basin, referred collectively to as the Northern sector of the North Falkland Basin (NNFB). Six regionally significant seismic reflectors are interpreted within this data, dividing the sedimentary fill into six tectonostratigraphic packages, including: early syn-rift; late syn-rift; transitional unit; early post-rift; middle to late post-rift; and a sag unit. Structural interpretation of the 2D seismic data has led to the definition of four north-south orientated depocentres, namely: (1) the Eastern Graben, largest of the depocentres; 20 km wide by 45 km long, reaching depths of 3 km; (2) the Eastern Graben Splay, a smaller depocentre; 10 km wide by 20 km long, reaching depths of 2–2.5 km; (3) the Western Graben Splay, the smallest depocentre; 5 km in width and 20 km long, with a basin depth of 2 km and (4) the newly defined Phyllis Graben, which is 13 km wide and 30 km long, with a basin depth of 3 km. A network of NW-SE and NE-SW trending faults controls the development of these grabens, separated by a Western, Eastern and Intra-Basin high. These grabens represent a northern continuation of the Northern Falkland Basin to the south. Hydrocarbon discoveries to the south of this study area (e.g. Sea Lion, Casper, Beverley, Zebedee, Isobel Deep, and Liz) confirm a working petroleum system adjacent to the Northern sector. This study has identified a number of seismic anomalies, including amplitude brightening events, which potentially correspond to an extension of this petroleum system, indicating active migration pathways. The main targets, in terms of hydrocarbon interest in the northern sector, are likely to be stratigraphically trapped hydrocarbon accumulations, contained within vertically-amalgamated turbidite fan sandstone reservoirs, deposited within the early post-rift. A second, yet to be tested, syn-rift play, in which the trapping geometries are structural and the reservoirs are fluvial sandstones is also identified

Incoherent dynamics of vibrating single-molecule transistors

We study the tunneling conductance of nano-scale quantum ``shuttles'' in connection with a recent experiment (H. Park et al., Nature, 407, 57 (2000)) in which a vibrating C^60 molecule was apparently functioning as the island of a single electron transistor (SET). While our calculation starts from the same model of previous work (D. Boese and H. Schoeller, Europhys. Lett. 54, 66(2001)) we obtain quantitatively different dynamics. Calculated I-V curves exhibit most features present in experimental data with a physically reasonable parameter set, and point to a strong dependence of the oscillator's potential on the electrostatics of the island region. We propose that in a regime where the electric field due to the bias voltage itself affects island position, a "catastrophic" negative differential conductance (NDC) may be realized. This effect is directly attributable to the magnitude of overlap of final and initial quantum oscillator states, and as such represents experimental control over quantum transitions of the oscillator via the macroscopically controllable bias voltage.Comment: 6 pages, LaTex, 6 figure

Visions in monochrome: Families, marriage and the individualisation thesis

This paper takes issue with the way in which the individualisation thesis – in which it is assumed that close relationships have become tenuous and fragile - has become so dominant in ‘new’ sociological theorising about family life. Although others have criticised this thesis, in this paper the main criticism derives from empirical research findings carried out with members of transnational families living in Britain whose values and practices do not fit easily with ideas of individualisation. It is argued that we need a much more complex and less linear notion of how families change across generations and in time

The High Voltage Feedthroughs for the ATLAS Liquid Argon Calorimeters

The purpose, design specifications, construction techniques, and testing methods are described for the high voltage feedthrough ports and filters of the ATLAS Liquid Argon calorimeters. These feedthroughs carry about 5000 high voltage wires from a room-temperature environment (300 K) through the cryostat walls to the calorimeters cells (89 K) while maintaining the electrical and cryogenic integrity of the system. The feedthrough wiring and filters operate at a maximum high voltage of 2.5 kV without danger of degradation by corona discharges or radiation at the Large Hadron Collider

CO2 Sequestration in Unmineable Coal Seams: Potential Environmental Impacts

An initial investigation into the potential environmental impacts of CO2 sequestration in unmineable coal seams has been conducted, focusing on changes in the produced water during enhanced coalbed methane (ECBM) production using a CO2 injection process (CO2-ECBM). Two coals have been used in this study, the medium volatile bituminous Upper Freeport coal (APCS 1) of the Argonne Premium Coal Samples series, and an as-mined Pittsburgh #8 coal, which is a high volatile bituminous coal. Coal samples were reacted with either synthetic produced water or field collected produced water and gaseous carbon dioxide at 40 οC and 50 bar to evaluate the potential for mobilizing toxic metals during CO2-ECBM/sequestration. Microscopic and x-ray diffraction analysis of the post-reaction coal samples clearly show evidence of chemical reaction, and chemical analysis of the produced water shows substantial changes in composition. These results suggest that changes to the produced water chemistry and the potential for mobilizing toxic trace elements from coalbeds are important factors to be considered when evaluating deep, unmineable coal seams for CO2 sequestration

Physics, Topology, Logic and Computation: A Rosetta Stone

In physics, Feynman diagrams are used to reason about quantum processes. In the 1980s, it became clear that underlying these diagrams is a powerful analogy between quantum physics and topology: namely, a linear operator behaves very much like a "cobordism". Similar diagrams can be used to reason about logic, where they represent proofs, and computation, where they represent programs. With the rise of interest in quantum cryptography and quantum computation, it became clear that there is extensive network of analogies between physics, topology, logic and computation. In this expository paper, we make some of these analogies precise using the concept of "closed symmetric monoidal category". We assume no prior knowledge of category theory, proof theory or computer science.Comment: 73 pages, 8 encapsulated postscript figure

Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetry A2

We have measured the spin structure functions g2p and g2d and the virtual photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 1.0 < Q^2 < 30(GeV/c)^2 by scattering 38.8 GeV longitudinally polarized electrons from transversely polarized NH3 and 6LiD targets.The absolute value of A2 is significantly smaller than the sqrt{R} positivity limit over the measured range, while g2 is consistent with the twist-2 Wandzura-Wilczek calculation. We obtain results for the twist-3 reduced matrix elements d2p, d2d and d2n. The Burkhardt-Cottingham sum rule integral - int(g2(x)dx) is reported for the range 0.02 < x < 0.8.Comment: 12 pages, 4 figures, 1 tabl