442 research outputs found

    Minor and major flaws of a widely used data set: the ICPSR 'German Weimar Republik data 1919-1933' under scrutiny

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    Die Deutsche Forschungsgemeinschaft und die Stiftung Volkswagenwerk finanzieren zwei getrennte, aber thematisch zusammenhängende Forschungsprojekte über Wahlen und das Wahlverhalten in der Weimarer Republik und Österreich. Beide Forschungsteams arbeiten unter der Leitung von J. Falter an der Hochschule der Bundeswehr in München. Der größte Teil ihrer Arbeit greift, neben anderen Quellen, auf die vielbenutzte Datensammlung 'German Weimar Republic Data 1919 - 1933' (ICPSR Nr. 0042) zurück, die in der BRD vom Kölner Zentralarchiv für europäische Sozialforschung betrieben wird. (KWübers.)'The Deutsche Forschungsgemeinschaft and the Stiftung Volkswagenwerk are funding two separate but thematically connected research projects on elections and voting behaviour in Weimar Germany and Austria. The two research teams, headed by J. Falter, are based at the Hochschule der Bundeswehr in Munich (German Military University, Munich). Much of their work is, among other sources, drawing on the widely used ICPSR data set 'German Weimar Republic Data 1919 - 1933' (ICPSR No. 0042) which is distributed in West Germany by the Cologne Zentralarchiv für empirische Sozialforschung.' (author's abstract

    Atomic Mass Dependence of Hadron Production in Deep Inelastic Scattering on Nuclei

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    Hadron production in lepton-nucleus deep inelastic scattering is studied in an absorption model. In the proposed model, the early stage of hadronization in the nuclear medium is dominated by prehadron formation and absorption, controlled by flavor-dependent formation lengths and absorption cross sections. Computations for hadron multiplicity ratios are presented and compared with the HERMES experimental data for pions, kaons, protons and antiprotons. The mass-number dependence of hadron attenuation is shown to be sensitive to the underlying hadronization dynamics. Contrary to common expectations for absorption models, a leading term proportional to A^{2/3} is found. Deviations from the leading behavior arise at large mass-numbers and large hadron fractional momenta.Comment: 30 pages, 10 figures, v2: minor changes (legend in figs 5 & 6 is added), v3: additional explanations are added, v4: Version combines v3 and the erratum hep-ph/050803

    Nuclear shadowing at low photon energies

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    We calculate the shadowing effect in nuclear photoabsorption at low photon energies (1-3 GeV) within a multiple scattering approach. We avoid some of the high energy approximations that are usually made in simple Glauber theory like the narrow width and the eikonal approximation. We find that the main contribution to nuclear shadowing at low energies stems from ρ0\rho^0 mesons with masses well below their pole mass. We also show that the possibility of scattering in non forward directions allows for a new contribution to shadowing at low energies: the production of neutral pions as intermediate hadronic states enhances the shadowing effect in the onset region. For light nuclei and small photon energies they give rise to about 30% of the total shadowing effect.Comment: RevTeX, 16 pages including 6 eps figures; new calculation of effective pion propagator, negligible effect on results; version to be published in Phys. Rev.

    Electron-phonon anomaly related to charge stripes: static stripe phase versus optimally-doped superconducting La1.85Sr0.15CuO4

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    Inelastic neutron scattering was used to study the Cu-O bond-stretching vibrations in optimally doped La1.85Sr0.15CuO4 (Tc = 35 K) and in two other cuprates showing static stripe order at low temperatures, i.e. La1.48Nd0.4Sr0.12CuO4 and La1.875Ba0.125CuO4. All three compounds exhibit a very similar phonon anomaly, which is not predicted by conventional band theory. It is argued that the phonon anomaly reflects a coupling to charge inhomogeneities in the form of stripes, which remain dynamic in superconducting La1.85Sr0.15CuO4 down to the lowest temperatures. These results show that the phonon effect indicating stripe formation is not restricted to a narrow region of the phase diagram around the so-called 1/8 anomaly but occurs in optimally doped samples as well.Comment: to appear in J. Low Temp. Phy

    Low energy onset of nuclear shadowing in photoabsorption

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    The early onset of nuclear shadowing in photoabsorption at low photon energies has recently been interpreted as a possible signature of a decrease of the rho meson mass in nuclei. We show that one can understand this early onset within simple Glauber theory if one takes the negative real part of the rho N scattering amplitudes into account, corresponding to a higher effective mass of the rho meson in nuclear medium.Comment: REVTEX, 9 pages, including 4 eps figure

    Electronic Collective Modes and Superconductivity in Layered Conductors

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    A distinctive feature of layered conductors is the presence of low-energy electronic collective modes of the conduction electrons. This affects the dynamic screening properties of the Coulomb interaction in a layered material. We study the consequences of the existence of these collective modes for superconductivity. General equations for the superconducting order parameter are derived within the strong-coupling phonon-plasmon scheme that account for the screened Coulomb interaction. Specifically, we calculate the superconducting critical temperature Tc taking into account the full temperature, frequency and wave-vector dependence of the dielectric function. We show that low-energy plasmons may contribute constructively to superconductivity. Three classes of layered superconductors are discussed within our model: metal-intercalated halide nitrides, layered organic materials and high-Tc oxides. In particular, we demonstrate that the plasmon contribution (electronic mechanism) is dominant in the first class of layered materials. The theory shows that the description of so-called ``quasi-two-dimensional superconductors'' cannot be reduced to a purely 2D model, as commonly assumed. While the transport properties are strongly anisotropic, it remains essential to take into account the screened interlayer Coulomb interaction to describe the superconducting state of layered materials.Comment: Final version (minor changes) 14 pages, 6 figure

    Performance of multi-aperture grid extraction systems for an ITER-relevant RF-driven negative hydrogen ion source

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    The ITER neutral beam system requires a negative hydrogen ion beam of 48 A with an energy of 0.87 MeV, and a negative deuterium beam of 40 A with an energy of 1 MeV. The beam is extracted from a large ion source of dimension 1.9 × 0.9 m2 by an acceleration system consisting of seven grids with 1280 apertures each. Currently, apertures with a diameter of 14 mm in the first grid are foreseen. In 2007, the IPP RF source was chosen as the ITER reference source due to its reduced maintenance compared with arc-driven sources and the successful development at the BATMAN test facility of being equipped with the small IPP prototype RF source ( of the area of the ITER NBI source). These results, however, were obtained with an extraction system with 8 mm diameter apertures. This paper reports on the comparison of the source performance at BATMAN of an ITER-relevant extraction system equipped with chamfered apertures with a 14 mm diameter and 8 mm diameter aperture extraction system. The most important result is that there is almost no difference in the achieved current density—being consistent with ion trajectory calculations—and the amount of co-extracted electrons. Furthermore, some aspects of the beam optics of both extraction systems are discussed.</jats:p

    Technical Review of Retrieval and Closure Plans for the INEEL INTEC Tank Farm Facility

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    The purpose of this report is to document the conclusions of a technical review of retrieval and closure plans for the Idaho National Energy and Environmental Laboratory (INEEL) Idaho Nuclear Technology and Engineering Center (INTEC) Tank Farm Facility. In addition to reviewing retrieval and closure plans for these tanks, the review process served as an information exchange mechanism so that staff in the INEEL High Level Waste (HLW) Program could become more familiar with retrieval and closure approaches that have been completed or are planned for underground storage tanks at the Oak Ridge National Laboratory (ORNL) and Hanford sites. This review focused not only on evaluation of the technical feasibility and appropriateness of the approach selected by INEEL but also on technology gaps that could be addressed through utilization of technologies or performance data available at other DOE sites and in the private sector. The reviewers, Judith Bamberger of Pacific Northwest National Laboratory (PNNL) and Dr. Barry Burks of The Providence Group Applied Technology, have extensive experience in the development and application of tank waste retrieval technologies for nuclear waste remediation
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