Fluid-rock interactions in the Martian meteorite North West Africa 817

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The Vale of Pickering : an initial summary of the Quaternary/superficial geology and data holdings

The British Geological Survey (BGS), together with a number of partners is undertaking an independent environmental monitoring programme to characterise baseline conditions across the Vale of Pickering in North Yorkshire, in the vicinity of a site close to Kirby Misperton (Third Energy, KM8) proposed for shale-gas exploration and production. The monitoring will include measurement of: water quality (groundwater and surface water), seismicity, ground motion, air quality including radon, and soil gas. The programme aims to establish the environmental baseline before any shale-gas explorations begin. This report presents the results of a desk study to develop an initial summary of the Quaternary superficial geology across the Vale of Pickering. It is a component and specific deliverable of the environmental baseline project. The Quaternary deposits form a shallow aquifer that is used locally for drinking water supply and agriculture. A separate report considers the bedrock geology. The geological information in this report will be used to identify aquifer dimensions and configurations, groundwater flow paths and potential contaminant migration pathways, as well as determining optimum locations for sampling and monitoring. It will also provide information to support the locating of new borehole infrastructure (suitable for groundwater sampling and seismometers) and will underpin the interpretation of acquired hydrogeochemical data

Parity Problem With A Cellular Automaton Solution

The parity of a bit string of length $N$ is a global quantity that can be efficiently compute using a global counter in ${O} (N)$ time. But is it possible to find the parity using cellular automata with a set of local rule tables without using any global counter? Here, we report a way to solve this problem using a number of $r=1$ binary, uniform, parallel and deterministic cellular automata applied in succession for a total of ${O} (N^2)$ time.Comment: Revtex, 4 pages, final version accepted by Phys.Rev.

Nitrogen quadrupole coupling constants for HCN and H2CN +: Explanation of the absence of fine structure in the microwave spectrum of interstellar H2CN+

Nitrogen 14 quadrupole coupling constants for H2CN+ and HCN are predicted via ab initio self-consistent-field and configuration interaction theory. Effects of electron correlation, basis set completeness, and geometrical structure on the predicted electric field gradients are analyzed. The quadrupole coupling constant obtained for H2CN+ is one order of magnitude less than in HCN, providing an explanation for the experimental fact that the fine structure of the microwave spectrum of H 2CN+ has not been resolved. This research also allows a reliable prediction of the nuclear quadrupole moment of 14N, namely Q(14N)=2.00×10-26 cm2. © 1986 American Institute of Physics.Fil:Scuseria, G.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

A 3D geological model of the superficial deposits in the Selby area

The Selby 3D geological model, commissioned by the Environment Agency, covers an area of 1,300km2 and shows the distribution and thickness of superficial deposits between Thorne, just north of Doncaster, to Haxby, just north of York. Surfaces derived from this model will be used by the Environment Agency to construct a numerical, spatially distributed model of recharge to the underlying regionally important Sherwood Sandstone Group aquifer and to update their existing numerical regional groundwater model. This report describes the geological units modelled, the 3D modelling methodology used and the limitations of the model

Bound-free pair production in ultra-relativistic ion collisions at the LHC collider: Analytic approach to the total and differential cross sections

A theoretical investigation of the bound-free electron-positron pair production in relativistic heavy ion collisions is presented. Special attention is paid to the positrons emitted under large angles with respect to the beam direction. The measurement of these positrons in coincidence with the down--charged ions is in principle feasible by LHC experiments. In order to provide reliable estimates for such measurements, we employ the equivalent photon approximation together with the Sauter approach and derive simple analytic expressions for the differential pair--production cross section, which compare favorably to the results of available numerical calculations. Based on the analytic expressions, detailed calculations are performed for collisions of bare Pb$^{82+}$ ions, taking typical experimental conditions of the LHC experiments into account. We find that the expected count rate strongly depends on the experimental parameters and may be significantly enhanced by increasing the positron-detector acceptance cone.Comment: 10 pages, 4 figure

Quantum Maxwell-Bloch equations for spatially inhomogeneous semiconductor lasers

We present quantum Maxwell-Bloch equations (QMBE) for spatially inhomogeneous semiconductor laser devices. The QMBE are derived from fully quantum mechanical operator dynamics describing the interaction of the light field with the quantum states of the electrons and the holes near the band gap. By taking into account field-field correlations and field-dipole correlations, the QMBE include quantum noise effects which cause spontaneous emission and amplified spontaneous emission. In particular, the source of spontaneous emission is obtained by factorizing the dipole-dipole correlations into a product of electron and hole densities. The QMBE are formulated for general devices, for edge emitting lasers and for vertical cavity surface emitting lasers, providing a starting point for the detailed analysis of spatial coherence in the near field and far field patterns of such laser diodes. Analytical expressions are given for the spectra of gain and spontaneous emission described by the QMBE. These results are applied to the case of a broad area laser, for which the frequency and carrier density dependent spontaneous emission factor beta and the evolution of the far field pattern near threshold are derived.Comment: 22 pages RevTex and 7 figures, submitted to Phys.Rev.A, revisions in abstract and in the discussion of temporal coherenc

N\'eel transition, spin fluctuations, and pseudogap in underdoped cuprates by a Lorentz invariant four-fermion model in 2+1 dimensions

We show that the N\'eel transition and spin fluctuations near the N\'eel transition in planar cuprates can be described by an SU(2) invariant relativistic four-fermion model in 2+1 dimensions. Features of the pseudogap phenomenon are naturally described by the appearance of an anomalous dimension for the spinon propagator.Comment: 5 pages, 2 figures (revtex4). Final revised and corrected versio

Doping Dependence of the Magnetic Resonance Peak in YBa_2 Cu_3 O_{6+x}

We report inelastic neutron scattering experiments on the doping dependence of the energy and spectral weight of the sharp magnetic resonance peak in YBa_2 Cu_3 O_{6+x}. These measurements also shed light on the relationship between the magnetic excitations in the normal and superconducting states.Comment: (mostly corrections to figures and minor change to caption in Fig.5) 5 figures. It will be published in the proceedings of M2S-HTSC-V. It needs the elsevier style file (not included) to convert to postscrip

Enhancement of long-range magnetic order by magnetic field in superconducting La2CuO(4+y)

We report a detailed study, using neutron scattering, transport and magnetization measurements, of the interplay between superconducting (SC) and spin density wave (SDW) order in La2CuO(4+y). Both kinds of order set in below the same critical temperature. However, the SDW order grows with applied magnetic field, whereas SC order is suppressed. Most importantly, the field dependence of the SDW Bragg peak intensity has a cusp at zero field, as predicted by a recent theory of competing SDW and SC order. This leads us to conclude that there is a repulsive coupling between the two order parameters. The question of whether the two kinds of order coexist or microscopically phase separate is discussed.Comment: Version accepted for publication in Phys. Rev. B. Improved discussion in connection with the muSR result