1,251 research outputs found

    New militarism, the media and the manufacture of warfare 1982-1991: the implications for peace journalism theory and practice

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    This article highlights the emergence of a distinctly new kind of militarism in the 1980s - in which the mainstream media played a crucial role

    Bifurcated polarization rotation in bismuth-based piezoelectrics

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    ABO3 perovskite-type solid solutions display a large variety of structural and physical properties, which can be tuned by chemical composition or external parameters such as temperature, pressure, strain, electric, or magnetic fields. Some solid solutions show remarkably enhanced physical properties including colossal magnetoresistance or giant piezoelectricity. It has been recognized that structural distortions, competing on the local level, are key to understanding and tuning these remarkable properties, yet, it remains a challenge to experimentally observe such local structural details. Here, from neutron pair-distribution analysis, a temperature-dependent 3D atomic-level model of the lead-free piezoelectric perovskite Na0.5Bi0.5TiO3 (NBT) is reported. The statistical analysis of this model shows how local distortions compete, how this competition develops with temperature, and, in particular, how different polar displacements of Bi3+ cations coexist as a bifurcated polarization, highlighting the interest of Bi-based materials in the search for new lead-free piezoelectrics

    Structural and Magnetic Investigations of Single-Crystals of the Neodymium Zirconate Pyrochlore, Nd2Zr2O7

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    We report structural and magnetic properties studies of large high quality single-crystals of the frustrated magnet, Nd2_2Zr2_2O7_7. Powder x-ray diffraction analysis confirms that Nd2_2Zr2_2O7_7 adopts the pyrochlore structure. Room-temperature x-ray diffraction and time-of-flight neutron scattering experiments show that the crystals are stoichiometric in composition with no measurable site disorder. The temperature dependence of the magnetic susceptibility shows no magnetic ordering at temperatures down to 0.5 K. Fits to the magnetic susceptibility data using a Curie-Weiss law reveal a ferromagnetic coupling between the Nd moments. Magnetization versus field measurements show a local Ising anisotropy along the axes of the Nd3+^{3+} ions in the ground state. Specific heat versus temperature measurements in zero applied magnetic field indicate the presence of a thermal anomaly below T7T\sim7 K, but no evidence of magnetic ordering is observed down to 0.5 K. The experimental temperature dependence of the single-crystal bulk dc susceptibility and isothermal magnetization are analyzed using crystal field theory and the crystal field parameters and exchange coupling constants determined.Comment: 10 pages, 6 figures, 4 tables. Accepted for publication in Physical Review

    Angular and radial correlation in doubly excited systems when 1 ≤ Z ≤ 4. The 2p2 3P state

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    The angular and radial components of electron correlation have each been examined in detail for the discrete 2p2 3P states of H-, He, Li+ and Be2+. These doubly excited systems were described by highly accurate explicitly correlated wavefunctions. The analysis involved the use of angular Coulomb holes, changes in the one- and two-particle radial density distributions and several angular and radial expectation values. Additionally, various statistical correlation coefficients were used which emphasized, in turn, angular and radial correlation properties in different regions of the two-particle density. The angular holes and related properties showed a clearly defined inverse-Z effect for He and the positive ions. This trend was not repeated for the radial curves. However, the radial densities did reveal a distinct \u27in-out\u27 correlation effect-similar in character to the split-shell behaviour for the ground state. By comparison with the findings for Z ≥ 2, the angular and radial correlation effects for H- were always exceedingly large, thus setting it apart from the other systems. For He, the angular hole for the comparatively slow moving 2p2 3P electrons was found to be over 50% deeper than that for the ground state and about six times the depth of a 1s2p 3P hole. The statistical correlation coefficients highlighted a steady growth, with Z, in the relative importance of angular correlation. Nevertheless, for each system, these coefficients indicated that the radial effect was the prevailing influence on the two-particle probability distribution

    The doubly-excited state 2p 2 3P for 1 ≤ Z ≤ 4: Coulomb holes derived from explicitly correlated wavefunctions

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    Doubly-excited states (DES) of simple atoms involve, by comparison with the ground state, relatively slow moving electrons which should therefore be more responsive to electron correlation. Hence, for the 2p 23P state, correlation effects have been analyzed in detail in terms of Coulomb holes, partial Coulomb holes and (r n 12) when 1 ≤ Z ≤ 4. Comparisons are made with the 1s 2 1S ground state and with the singly-excited state 1s2p, 3P. As for the lower states, each DES was described by an accurate explicitly correlated wavefunction. For each Z, a similarity of characteristics, but not of scale, is found between the DES results and those for the ground state. The Coulomb holes for the 1s2p 3P states have a significantly different shape. The correlation effect for each DES system exceeds that for the corresponding lower states examined here. © 1992 IOP Pvblishing Ltd

    First-Order Reorientation of the Flux-Line Lattice in CaAlSi

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    The flux line lattice in CaAlSi has been studied by small angle neutron scattering. A well defined hexagonal flux line lattice is seen just above Hc1 in an applied field of only 54 Oe. A 30 degree reorientation of this vortex lattice has been observed in a very low field of 200 Oe. This reorientation transition appears to be of first-order and could be explained by non-local effects. The magnetic field dependence of the form factor is well described by a single penetration depth of 1496(1) angstroms and a single coherence length of 307(1) angstroms at 2 K. At 1.5 K the penetration depth anisotropy is 2.7(1) with the field applied perpendicular to the c axis and agrees with the coherence length anisotropy determined from critical field measurements.Comment: 5 pages including 6 figures, to appear in Physical Review Letter

    The Power Spectrum of the PSC Redshift Survey

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    We measure the redshift-space power spectrum P(k) for the recently completed IRAS Point Source Catalogue (PSC) redshift survey, which contains 14500 galaxies over 84% of the sky with 60 micron flux >= 0.6 Jansky. Comparison with simulations shows that our estimated errors on P(k) are realistic, and that systematic errors due to the finite survey volume are small for wavenumbers k >~ 0.03 h Mpc^-1. At large scales our power spectrum is intermediate between those of the earlier QDOT and 1.2 Jansky surveys, but with considerably smaller error bars; it falls slightly more steeply to smaller scales. We have fitted families of CDM-like models using the Peacock-Dodds formula for non-linear evolution; the results are somewhat sensitive to the assumed small-scale velocity dispersion \sigma_V. Assuming a realistic \sigma_V \approx 300 km/s yields a shape parameter \Gamma ~ 0.25 and normalisation b \sigma_8 ~ 0.75; if \sigma_V is as high as 600 km/s then \Gamma = 0.5 is only marginally excluded. There is little evidence for any `preferred scale' in the power spectrum or non-Gaussian behaviour in the distribution of large-scale power.Comment: Latex, uses mn.sty, 14 pages including 11 Postscript figures. Accepted by MNRA

    Operation Moshtarak and the manufacture of credible, “heroic” warfare

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    Richard Lance Keeble argues that Fleet Street’s coverage of the Afghan conflict has served largely to promote the interests of the military/industrial/media complex – and marginalise the views of the public who have consistently appealed in polls for the troops to be brought back hom

    Percutaneous balloon aortic valvuloplasty in the era of transcatheter aortic valve implantation: a narrative review

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    The role of percutaneous balloon aortic valvuloplasty (BAV) in the management of severe symptomatic aortic stenosis has come under the spotlight following the development of the transcatheter aortic valve implantation (TAVI) technique. Previous indications for BAV were limited to symptom palliation and as a bridge to definitive therapy for patients undergoing conventional surgical aortic valve replacement (AVR). In the TAVI era, BAV may also be undertaken to assess the ‘therapeutic response’ of a reduction in aortic gradient in borderline patients often with multiple comorbidities, to assess symptomatic improvement prior to consideration of definitive TAVI intervention. This narrative review aims to update the reader on the current indications and practical techniques involved in undertaking a BAV procedure. In addition, a summary of the haemodynamic and clinical outcomes, as well as the frequently encountered procedural complications is presented for BAV procedures conducted during both the pre-TAVI and post-TAVI era
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