A gravity interpretation of the Central North Sea

A gravity investigation of the Central North Sea has been undertaken with the aim of supplementing a parallel seismic investigation (Arsenikos et al., 2015) by targeting those areas where the seismic information was sparse or of poor quality. By stripping the gravity effect of the Zechstein and younger sequence it was hoped that concealed Upper Palaeozoic basins could be identified in the residual gravity signatures and distinguished from anomalies associated with Late Caledonian granitic plutons. Density logs from a set of wells across the region were compiled and used to calibrate a density model for the cover sequence. This model employed a combination of compaction trends and burial anomalies in the post-Zechstein units and a relationship between overall thickness and average density in the Zechstein unit. It was used, together with a depth-converted structural model from the seismic interpretation, to calculate the gravity effect down to base Zechstein. This, along with a long-wavelength background field, was subtracted from the observations to leave a residual gravity anomaly that was inverted to produce a 3D model of variations in the thickness of a pre-Zechstein layer that incorporated the effects of both basins and granites. The modelling results were analysed in combination with magnetic imaging and available mapping of intra-Upper Palaeozoic seismic reflectors. Granites were often easy to identify on the basis of a low in the gravity inversion surface that coincided with a structural high defined seismically and, in some cases, a magnetic signature. There are, however, some more ambiguous features that cannot be confidently classified without further information. Relatively low density rocks within the Lower Palaeozoic basement and zones of high density basement or pervasive high density intrusive rocks introduce distortion into the model, and the identification and separation of these influences requires more detailed combined seismic, gravity and magnetic modelling. Potential targets (areas of pre-Zechstein sedimentary thickening) were identified in Quads 19-20, Quads 26-28, and just to the north of an 150 km offshore extrapolation of the line which forms the southern margin of the Tweed Basin in the onshore area (the Pressen-Flodden-Ford faults). Geophysical anomalies in the Q36-37 area suggest a complex interplay between sedimentary and igneous features and would also benefit from further investigation. A ‘ramp’ in the gravity inversion surface appears to be linked, at least in part, to lateral density variations associated with overcompaction along the Sole Pit axis. The geophysical feature extends beyond previous mapping of that axis and is overlain by the Breagh gas field, so is an appropriate target for more detailed study (which could address the possibility of a basement influence on the observed anomalies). The results obtained indicate that gravity/magnetic interpretation provides a useful supplement to seismic reflection surveys, even where the latter form the primary exploration method. There are, for example, features at the southern margin of the Forth Approaches Basin and possible intra-basinal structures within the North Dogger Basin that could add to our understanding of those areas. The new government-funded seismic/gravity/magnetic surveys over the Central North Sea, which were conducted in 2015 and will be released in 2016, will provide the ideal resource with which to follow up the results of this investigation

A gravity interpretation of the Orcadian Basin area

A gravity investigation of the Orcadian Basin area has been conducted which involved the following stages: - compilation, imaging and qualitative interpretation of BGS gravity and magnetic data from the region; - compilation of rock densities from geophysical well logs and modelling of density variations within the sedimentary sequence; - construction of a structural model of the cover sequence down to the top of the Permian, based on depth-converted seismic interpretation; - calculation of the gravity effect of the sequence to top Permian using the structural and density models; - removal of this calculated gravity effect and a regional background field from the observations to leave a residual stripped gravity anomaly; - analysis of the signatures within the residual stripped gravity anomaly map, integrated with seismic evidence of Upper Palaeozoic structure and magnetic imaging. The residual stripped gravity anomaly map reveals features that can be correlated with the West Bank Basin and the eastern end of the Caithness Graben of Arsenikos et al. (2016), and with the thickened Upper Palaeozoic sequence in the East Orkney Basin inferred by those authors. Gravity signatures indicative of a thickening of the Upper Palaeozoic sedimentary rocks are also identified in the Dutch Bank Basin and the South Buchan Basin, areas in which seismic interpretation of Palaeozoic structure was difficult because of problems with data quality and line spacing. The influence of granitic intrusions is seen in a belt that extends in a north-north-east direction from Quadrant 19 into Quadrant 13, although the magnetic characteristics of the bodies might indicate separate post-tectonic and late-tectonic suites of Caledonian intrusions. Further granites are inferred in the Inner Moray Firth, in Quadrants 12 and 17. A Caledonian age is possible for these but an alternative interpretation invokes Palaeoproterozoic calc-alkaline basement, at least for the more magnetic component. Gravity signatures in the Inner Moray Firth are also influenced by low density Dalradian (Grampian Group) basement and Devonian sedimentary rocks, making it difficult to partition the response accurately between the different sources. Positive gravity signatures are associated with the Buchan Block and its offshore extension, and with Jurassic intrusives beneath the Forties Volcanic Province. Dense/shallow basement extends in a west-north-west direction from the Forties area in a broad axis, and this is an important component of the long-lived structural configuration of the region that may be linked to an early transform offset in the Laurentian margin. Recommendations for further work include more detailed and extensive gravity modelling, quantitative magnetic modelling and a geochemical/isotopic study of the samples available from offshore granite well penetrations

Tight-binding study of the influence of the strain on the electronic properties of InAs/GaAs quantum dots

We present an atomistic investigation of the influence of strain on the electronic properties of quantum dots (QD's) within the empirical $s p^{3} s^{*}$ tight-binding (ETB) model with interactions up to 2nd nearest neighbors and spin-orbit coupling. Results for the model system of capped pyramid-shaped InAs QD's in GaAs, with supercells containing $10^{5}$ atoms are presented and compared with previous empirical pseudopotential results. The good agreement shows that ETB is a reliable alternative for an atomistic treatment. The strain is incorporated through the atomistic valence force field model. The ETB treatment allows for the effects of bond length and bond angle deviations from the ideal InAs and GaAs zincblende structure to be selectively removed from the electronic-structure calculation, giving quantitative information on the importance of strain effects on the bound state energies and on the physical origin of the spatial elongation of the wave functions. Effects of dot-dot coupling have also been examined to determine the relative weight of both strain field and wave function overlap.Comment: 22 pages, 7 figures, submitted to Phys. Rev. B (in press) In the latest version, added Figs. 3 and 4, modified Fig. 5, Tables I and II,.and added new reference

Generating Sustainable Value from Open Data in a Sharing Society

Part 1: Creating ValueInternational audienceOur societies are in the midst of a paradigm shift that transforms hierarchal markets into an open and networked economy based on digital technology and information. In that context, open data is widely presumed to have a positive effect on social, environmental and economic value; however the evidence to that effect has remained scarce. Subsequently, we address the question how the use of open data can stimulate the generation of sustainable value. We argue that open data sharing and reuse can empower new ways of generating value in the sharing society. Moreover, we propose a model that describes how different mechanisms that take part within an open system generate sustainable value. These mechanisms are enabled by a number of contextual factors that provide individuals with the motivation, opportunity and ability to generate sustainable value

Decoration of the enterococcal polysaccharide antigen EPA is essential for virulence, cell surface charge and interaction with effectors of the innate immune system

Enterococcus faecalis is an opportunistic pathogen with an intrinsically high resistance to lysozyme, a key effector of the innate immune system. This high level of resistance requires a complex network of transcriptional regulators and several genes (oatA, pgdA, dltA and sigV) acting synergistically to inhibit both the enzymatic and cationic antimicrobial peptide activities of lysozyme. We sought to identify novel genes modulating E. faecalis resistance to lysozyme. Random transposon mutagenesis carried out in the quadruple oatA/pgdA/dltA/sigV mutant led to the identification of several independent insertions clustered on the chromosome. These mutations were located in a locus referred to as the enterococcal polysaccharide antigen (EPA) variable region located downstream of the highly conserved epaA-epaR genes proposed to encode a core synthetic machinery. The epa variable region was previously proposed to be responsible for EPA decorations, but the role of this locus remains largely unknown. Here, we show that EPA decoration contributes to resistance towards charged antimicrobials and underpins virulence in the zebrafish model of infection by conferring resistance to phagocytosis. Collectively, our results indicate that the production of the EPA rhamnopolysaccharide backbone is not sufficient to promote E. faecalis infections and reveal an essential role of the modification of this surface polymer for enterococcal pathogenesis

Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He(e,e′) at Q2=0.3 to 0.6 (GeV/c)2

A high precision measurement of the transverse spin-dependent asymmetry AT′ in 3He(e,e′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q2, between 0.1 and 0.6 (GeV/c)2. AT′ is sensitive to the neutron magnetic form factor, GMn. Values of GMn at Q2=0.1 and 0.2 (GeV/c)2, extracted using Faddeev calculations, were reported previously. Here, we report the extraction of GMn for the remaining Q2 values in the range from 0.3 to 0.6 (GeV/c)2 using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target

Зміни в складі населення Донбасу в 1920-1926 рр.

У статті на основі вивчення літератури та джерел досліджуються зміни в складі населення Донбасу в 1920-1926 рр. Особливу увагу приділено аналізу даних переписів 1920, 1923, 1926 рр. Показано вплив політичних чинників на зміни чисельності населення, природний та механічний приріст.In article consider the Donbas population changes in 1920-1926 years, in his storage quantity and other. Shown changes dynamics quantity of population in 1920, 1923, 1926 years. The conclusions on the nature of influence of political factoris into changes quantity of population, natural and mechanical increase