414 research outputs found
Intrinsic and extrinsic x-ray absorption effects in soft x-ray diffraction from the superstructure in magnetite
We studied the (001/2) diffraction peak in the low-temperature phase of
magnetite (Fe3O4) using resonant soft x-ray diffraction (RSXD) at the Fe-L2,3
and O-K resonance. We studied both molecular-beam-epitaxy (MBE) grown thin
films and in-situ cleaved single crystals. From the comparison we have been
able to determine quantitatively the contribution of intrinsic absorption
effects, thereby arriving at a consistent result for the (001/2) diffraction
peak spectrum. Our data also allow for the identification of extrinsic effects,
e.g. for a detailed modeling of the spectra in case a "dead" surface layer is
present that is only absorbing photons but does not contribute to the
scattering signal.Comment: to appear in Phys. Rev.
Crystal-fields in YbInNi4 determined with magnetic form factor and inelastic neutron scattering
The magnetic form factor of YbInNi4 has been determined via the flipping
ratios R with polarized neutron diffraction and the scattering function S(Q,w)
was measured in an inelastic neutron scattering experiment. Both experiments
were performed with the aim to determine the crystal-field scheme. The magnetic
form factor clearly excludes the possibility of a \Gamma7 doublet as the ground
state. The inelastic neutron data exhibit two, almost equally strong peaks at
3.2 meV and 4.4 meV which points, in agreement with earlier neutron data,
towards a \Gamma8 quartet ground state. Further possibilities like a
quasi-quartet ground state are discussed.Comment: 7 pages, 5 figures, 2 tables, submitted to PR
Cryogenic silicon detectors with implanted contacts for the detection of visible photons using the Neganov-Luke Effect
There is a common need in astroparticle experiments such as direct dark
matter detection, 0{\nu}\b{eta}\b{eta} (double beta decay without emission of
neutrinos) and Coherent Neutrino Nucleus Scattering experiments for light
detectors with a very low energy threshold. By employing the Neganov-Luke
Effect, the thermal signal of particle interactions in a semiconductor absorber
operated at cryogenic temperatures, can be amplified by drifting the
photogenerated electrons and holes in an electric field. This technology is not
used in current experiments, in particular because of a reduction of the signal
amplitude with time which is due to trapping of the charges within the
absorber. We present here the first results of a novel type of Neganov-Luke
Effect detector with an electric field configuration designed to improve the
charge collection within the semiconductor.Comment: 6 pages, 5 figures, submitted to Journal of Low Temperature Physic
A database for on-line event analysis on a distributed memory machine
Parallel in-memory databases can enhance the structuring and parallelization of programs used in High Energy Physics (HEP). Efficient database access routines are used as communication primitives which hide the communication topology in contrast to the more explicit communications like PVM or MPI. A parallel in-memory database, called SPIDER, has been implemented on a 32 node Meiko CS-2 distributed memory machine. The spider primitives generate a lower overhead than the one generated by PVM or PMI. The event reconstruction program, CPREAD of the CPLEAR experiment, has been used as a test case. Performance measurerate generated by CPLEAR
CeRuSn: a strongly correlated material with nontrivial topology
Topological insulators form a novel state of matter that provides new
opportunities to create unique quantum phenomena. While the materials used so
far are based on semiconductors, recent theoretical studies predict that also
strongly correlated systems can show non-trivial topological properties,
thereby allowing even the emergence of surface phenomena that are not possible
with topological band insulators. From a practical point of view, it is also
expected that strong correlations will reduce the disturbing impact of defects
or impurities, and at the same increase the Fermi velocities of the topological
surface states. The challenge is now to discover such correlated materials.
Here, using advanced x-ray spectroscopies in combination with band structure
calculations, we infer that CeRuSn is a strongly correlated material
with non-trivial topology.Comment: 10 pages, 6 figures, submitted to Scientific Report
High resolution exposure modelling of heat and air pollution and the impact on mortality
Background Elevated temperature and air pollution have been associated with increased mortality. Exposure to heat and air pollution, as well as the density of vulnerable groups varies within cities. The objective was to investigate the extent of neighbourhood differences in mortality risk due to heat and air pollution in a city with a temperate maritime climate. Methods A case-crossover design was used to study associations between heat, air pollution and mortality. Different thermal indicators and air pollutants (PM10, NO2, O3) were reconstructed at high spatial resolution to improve exposure classification. Daily exposures were linked to individual mortality cases over a 15 year period. Results Significant interaction between maximum air temperature (Tamax) and PM10 was observed. During “summer smog” days (Tamax > 25 °C and PM10 > 50 μg/m3), the mortality risk at lag 2 was 7% higher compared to the reference (Tamax 15 °C and PM10 15 μg/m3). Persons above age 85 living alone were at highest risk. Conclusion We found significant synergistic effects of high temperatures and air pollution on mortality. Single living elderly were the most vulnerable group. Due to spatial differences in temperature and air pollution, mortality risks varied substantially between neighbourhoods, with a difference up to 7%
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