62,130 research outputs found

    A unified projection formalism for the Al-Pd-Mn quasicrystal Xi-approximants and their metadislocations

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    The approximants xi, xi' and xi'_n of the quasicrystal Al-Mn-Pd display most interesting plastic properties as for example phason-induced deformation processes (Klein, H., Audier, M., Boudard, M., de Boissieu, M., Beraha, L., and Duneau, M., 1996, Phil. Mag. A, 73, 309.) or metadislocations (Klein, H., Feuerbacher, M., Schall, P., and Urban, K., 1999, Phys. Rev. Lett., 82, 3468.). Here we demonstrate that the phases and their deformed or defected states can be described by a simple projection formalism in three-dimensional space - not as usual in four to six dimensions. With the method we can interpret microstructures observed with electron microscopy as phasonic phase boundaries. Furthermore we determine the metadislocations of lowest energy and relate them uniquely to experimentally observed ones. Since moving metadislocations in the xi'-phase can create new phason-planes, we suggest a dislocation induced phase transition from xi' to xi'_n. The methods developed in this paper can as well be used for various other complex metallic alloys.Comment: 25 pages, 12 figure

    A psychoanalytic concept illustrated: Will, must, may, can ā€” revisiting the survival function of primitive omnipotence

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    The author explores the linear thread connecting the theory of Freud and Klein, in terms of the central significance of the duality of the life and death instinct and the capacity of the ego to tolerate contact with internal and external reality. Theoretical questions raised by later authors, informed by clinical work with children who have suffered deprivation and trauma in infancy, are then considered. Theoretical ideas are illustrated with reference to observational material of a little boy who suffered deprivation and trauma in infancy. He was first observed in the middle of his first year of life while he was living in foster care, and then later at the age of two years and three months, when he had been living with his adoptive parents for more than a year

    Infrared light emission from atomic point contacts

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    Gold atomic point contacts are prototype systems to evidence ballistic electron transport. The typical dimension of the nanojunction being smaller than the electron-phonon interaction length, even at room temperature, electrons transfer their excess energy to the lattice only far from the contact. At the contact however, favored by huge current densities, electron-electron interactions result in a nano hot electron gas acting as a source of photons. Using a home built Mechanically Controlled Break Junction, it is reported here, for the first time, that this hot electron gas also radiates in the infrared range (0.2eV to 1.2eV). Moreover, in agreement with the pioneering work of Tomchuk, we show that this radiation is compatible with a blackbody like spectrum emitted from an electron gas at temperatures of several thousands of Kelvin given by (kB.Te)2=Ī±.I.V(kB.Te)^2 = \alpha. I.V where Ī±\alpha, II and VV are respectively a fitting parameter, the current flowing and the applied bias.Comment: 13 pages, 5 figure

    Large-Scale Radio Structure in the Universe: Giant Radio Galaxies

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    Giant radio galaxies (GRGs), with linear sizes larger than 1 Mpc (H0=50 km/s/Mpc), represent the biggest single objects in the Universe. GRGs are rare among the entire population of radio galaxies (RGs) and their physical evolution is not well understood though for many years they have been of special interest for several reasons. The lobes of radio sources can compress cold gas clumps and trigger star or even dwarf galaxy formation, they can also transport gas from a host galaxy to large distances and seed the IGM with magnetic fields. Since GRGs have about 10 to 100 times larger sizes than normal RGs, their influence on the ambient medium is correspondingly wider and is pronounced on scales comparable to those of clusters of galaxies or larger. Therefore `giants' could play an important role in the process of large-scale structure formation in the Universe. Recently, thanks to the new all sky radio surveys, significant progress in searching for new GRGs has been made.Comment: To appear in Multiwavelength AGN Surveys, ed. R. Maiolino and R. Mujica, Singapore: World Scientific, 2004, 2 page

    Electrolytically regenerative hydrogen-oxygen fuel cell Patent

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    Electrolytically regenerative hydrogen-oxygen fuel cell

    Estimating single molecule conductance from spontaneous evolution of a molecular contact

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    We present an original method to estimate the conductivity of a single molecule anchored to nanometric-sized metallic electrodes, using a Mechanically Controlled Break Junction (MCBJ) operated at room temperature in liquid. We record the conductance through the metal / molecules / metal nanocontact while keeping the metallic electrodes at a fixed distance. Taking advantage of thermal diffusion and electromigration, we let the contact naturally explore the more stable configurations around a chosen conductance value. The conductance of a single molecule is estimated from a statistical analysis of raw conductance and conductance standard deviation data for molecular contacts containing up to 14 molecules. The single molecule conductance values are interpreted as time-averaged conductance of an ensemble of conformers at thermal equilibrium.Comment: 25 pages, 6 figure

    Multi-Frequency Study of the B3-VLA Sample II. The Database

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    We present total flux densities of 1049 radio sources in the frequency range from 151 MHz to 10.6 GHz. These sources belong to the B3-VLA sample, which is complete down to 100 mJy at 408 MHz. The data constitute a homogeneous spectral database for a large sample of radio sources, 50 times fainter than the 3C catalogue, and will be used to perform a spectral ageing analysis, which is one of the critical points in understanding the physics and evolution of extragalactic radio sources.Comment: 14 pages, 3 figures, accepted for publication in Astronomy & Astrophysics Supplement Series, gzipped postscript file also available at http://multivac.jb.man.ac.uk:8000/ceres/papers/papers.html or http://gladia.astro.rug.nl:8000/ceres/papers/papers.htm
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