442 research outputs found
Minor and major flaws of a widely used data set: the ICPSR 'German Weimar Republik data 1919-1933' under scrutiny
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
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
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 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.
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Scarab III Remote Vehicle Deployment for Waste Retrieval and Tank Inspection
The Robotics Technology Development Program now known as the Robotics Crosscut Program, funded the development and deployment of a small remotely operated vehicle for inspection and cleanout of small horizontal waste storage tanks that have limited access. Besides the advantage of access through tank risers as small as 18-in. diameter, the small robotic system is also significantly less expensive to procure and to operate than larger remotely operated vehicle (ROV) systems. The vehicle specified to support this activity was the ROV Technologies, Inc., Scarab. The Scarab is a tracked vehicle with an independently actuated front and rear ''toe'' degree-of-freedom which allows the stand-off and angle of the vehicle platform with respect to the floor to be changed. The Scarab is a flexible remote tool that can be used for a variety of tasks with its primary uses targeted for inspection and small scale waste retrieval. The vehicle and any necessary process equipment are mounted in a deployment and containment enclosure to simplify deployment and movement of the system from tank to tank. This paper outlines the technical issues related to the Scarab vehicle and its deployment for use in tank inspection and waste retrieval operatio
Electron-phonon anomaly related to charge stripes: static stripe phase versus optimally-doped superconducting La1.85Sr0.15CuO4
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
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
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
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
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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