741 research outputs found

    Mineral reconnaissance at the Highland boundary with special reference to the Loch Lomond and Aberfoyle areas

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    Serpentinite bodies at the Highland Boundary in the Loch Lomond and Aberfoyle areas are extensively altered to magnesite-quartz and ferroan-dolomite-quartz rocks. Silicification was probably initiated before conversion to carbonate. Relict textures indicate that the serpentinites were derived from peridotitic precursors, but one unaltered ultrabasic sample comprises mainly chromian diopside. Chromite geochemistry and hornblende-schist mineralogy rein force the ophiolitic character of the serpentinite-spilite-blackshale- chcrt assemblage of the Highland Border. Magnetic and VLF traverses across the Highland Boundary fracture-zone near Helensburgh identified several anomalous zones. One may be due to a concealed serpentinitic sheet. The most mineralised serpentinite body showed chromium values in the range 1000 to 3035 ppm. Such concentrations arc not encouraging for the small serpentinites at Loch Lomond and Aberfoyle, but may be significant regarding larger serpentinites elsewhere at the Highland Border

    Correlation of mechanical factors and gallbladder pain

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    Acalculous biliary pain occurs in patients with no gallstones, but is similar to that experienced by patients with gallstones. Surgical removal of the gallbladder (GB) in these patients is only successful in providing relief of symptoms to about half of those operated on, so a reliable pain-prediction model is needed. In this paper, a mechanical model is developed for the human biliary system during the emptying phase, based on a clinical test in which GB volume changes are measured in response to a standard stimulus and a recorded pain profile. The model can describe the bile emptying behaviour, the flow resistance in the biliary ducts, the peak total stress, including the passive and active stresses experienced by the GB during emptying. This model is used to explore the potential link between GB pain and mechanical factors. It is found that the peak total normal stress may be used as an effective pain indicator for GB pain. When this model is applied to clinical data of volume changes due to Cholecystokinin stimulation and pain from 37 patients, it shows a promising success rate of 88.2% in positive pain prediction

    Investigation of stratiform sulphide mineralisation at Meall Mor, South Knapdale, Argyll

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    A co-ordinated geochemical-geophysical-geological investigation of copper mineralisation in the Meal1 ?46r area, South Knapdale, Argyll was carried 0th in 1976 and followed by a drilling programme of 3 shallow holes in early 1977. The mineralisation occursin a zone of weak stratiform sulphide mineralisation (the pyrite zone) with a strike length of 1Okm in the Upper &ins Quartz&e of the Middle Dalradian. The geochemical drainage survey showed the existence of a strongly anomalous distribution of Cu and Sb in the Abhainn Srathain draining south from . Meal1 M&- and detailed soil sampling over the pyrite zone outlined a broad area enriched in copper. Deeper soil sampling confirmed the anomalously high copper values and a coincident IP anomaly was found stretching from Meal1 M& south to the old mine workings on Abhainn Srathain, and is probably caused by a local enrichment of pyrite and chalcopyrite within the pyrite zone. Three boreholes were drilled; two on coincident geochemical and geophysical anomalies, and the third beneath the old mines at Abhainn Srathain. Copper values in the first two holes range up to 0.24% Cu over 4.27m, but up to 1.06% Cu over 2.67m in the third and this enrichment may be related to a later remobilisation of the disseminated chalcopyrite. The results of subsequent drilling at two other sites are given in Appendix III

    New Insights into Uniformly Accelerated Detector in a Quantum Field

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    We obtained an exact solution for a uniformly accelerated Unruh-DeWitt detector interacting with a massless scalar field in (3+1) dimensions which enables us to study the entire evolution of the total system, from the initial transient to late-time steady state. We find that the Unruh effect as derived from time-dependent perturbation theory is valid only in the transient stage and is totally invalid for cases with proper acceleration smaller than the damping constant. We also found that, unlike in (1+1)D results, the (3+1)D uniformly accelerated Unruh-DeWitt detector in a steady state does emit a positive radiated power of quantum nature at late-times, but it is not connected to the thermal radiance experienced by the detector in the Unruh effect proper.Comment: 6 pages, invited talk given by SYL at the conference of International Association for Relativistic Dynamics (IARD), June 2006, Storrs, Connecticut, US

    Fragility of a class of highly entangled states of many quantum-bits

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    We consider a Quantum Computer with n quantum-bits (`qubits'), where each qubit is coupled independently to an environment affecting the state in a dephasing or depolarizing way. For mixed states we suggest a quantification for the property of showing {\it quantum} uncertainty on the macroscopic level. We illustrate in which sense a large parameter can be seen as an indicator for large entanglement and give hypersurfaces enclosing the set of separable states. Using methods of the classical theory of maximum likelihood estimation we prove that this parameter is decreasing with 1/\sqrt{n} for all those states which have been exposed to the environment. Furthermore we consider a Quantum Computer with perfect 1-qubit gates and 2-qubit gates with depolarizing error and show that any state which can be obtained from a separable initial state lies inbetween a family of pairs of certain hypersurfaces parallel to those enclosing the separable ones.Comment: 9 Pages, RevTe

    Entangled Electronic States in Multiple Quantum-Dot Systems

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    We present an analytically solvable model of PP colinear, two-dimensional quantum dots, each containing two electrons. Inter-dot coupling via the electron-electron interaction gives rise to sets of entangled ground states. These ground states have crystal-like inter-plane correlations and arise discontinously with increasing magnetic field. Their ranges and stabilities are found to depend on dot size ratios, and to increase with PP.Comment: To appear in Physical Review B (in press). RevTeX file. Figures available from [email protected]

    Uniformly Accelerated Charge in a Quantum Field: From Radiation Reaction to Unruh Effect

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    We present a stochastic theory for the nonequilibrium dynamics of charges moving in a quantum scalar field based on the worldline influence functional and the close-time-path (CTP or in-in) coarse-grained effective action method. We summarize (1) the steps leading to a derivation of a modified Abraham-Lorentz-Dirac equation whose solutions describe a causal semiclassical theory free of runaway solutions and without pre-acceleration patholigies, and (2) the transformation to a stochastic effective action which generates Abraham-Lorentz-Dirac-Langevin equations depicting the fluctuations of a particle's worldline around its semiclassical trajectory. We point out the misconceptions in trying to directly relate radiation reaction to vacuum fluctuations, and discuss how, in the framework that we have developed, an array of phenomena, from classical radiation and radiation reaction to the Unruh effect, are interrelated to each other as manifestations at the classical, stochastic and quantum levels. Using this method we give a derivation of the Unruh effect for the spacetime worldline coordinates of an accelerating charge. Our stochastic particle-field model, which was inspired by earlier work in cosmological backreaction, can be used as an analog to the black hole backreaction problem describing the stochastic dynamics of a black hole event horizon.Comment: Invited talk given by BLH at the International Assembly on Relativistic Dynamics (IARD), June 2004, Saas Fee, Switzerland. 19 pages, 1 figur

    On Thermodynamical Properties of Some Coset CFT Backgrounds

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    We investigate the thermodynamical features of two Lorentzian signature backgrounds that arise in string theory as exact CFTs and possess more than two disconnected asymptotic regions: the 2-d charged black hole and the Nappi-Witten cosmological model. We find multiple smooth disconnected Euclidean versions of the charged black hole background. They are characterized by different temperatures and electro-chemical potentials. We show that there is no straightforward analog of the Hartle-Hawking state that would express these thermodynamical features. We also obtain multiple Euclidean versions of the Nappi-Witten cosmological model and study their singularity structure. It suggests to associate a non-isotropic temperature with this background.Comment: 1+39 pages, harvmac, 8 eps figure
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