974 research outputs found
Extending the CRESST-II commissioning run limits to lower masses
Motivated by the recent interest in light WIMPs of mass ~O(10 GeV), an
extension of the elastic, spin-independent WIMP-nucleon cross-section limits
resulting from the CRESST-II commissioning run (2007) are presented.
Previously, these data were used to set cross-section limits from 1000 GeV down
to ~17 GeV, using tungsten recoils, in 47.9 kg-days of exposure of calcium
tungstate. Here, the overlap of the oxygen and calcium bands with the
acceptance region of the commissioning run data set is reconstructed using
previously published quenching factors. The resulting elastic WIMP cross
section limits, accounting for the additional exposure of oxygen and calcium,
are presented down to 5 GeV.Comment: 4 pages, 4 figure
The multiplicity of massive stars in the Orion Nebula cluster as seen with long-baseline interferometry
The characterization of multiple stellar systems is an important ingredient
for testing current star formation models. Stars are more often found in
multiple systems, the more massive they are. A complete knowledge of the
multiplicity of high-mass stars over the full range of orbit separations is
thus essential to understand their still debated formation process.
Observations of the Orion Nebula Cluster can help to answer the question about
the origin and evolution of multiple stars. Earlier studies provide a good
knowledge about the multiplicity of the stars at very small (spectroscopic) and
large separations (AO, speckle) and thus make the ONC a good target for such a
project. We used the NIR interferometric instrument AMBER at VLTI to observe a
sample of bright stars in the ONC. We complement our data set by archival NACO
observations of \theta 1 Ori A to obtain more information about the orbit of
the close visual companion. Our observations resolve the known multiple systems
\theta 1 Ori C and \theta 1 Ori A and provide new orbit points, which confirm
the predicted orbit and the determined stellar parameters for \theta 1 Ori C.
Combining AMBER and NACO data for \theta 1 Ori A we were able to follow the
motion of the companion from 2003 to 2011. We furthermore find hints for a
companion around \theta 1 Ori D and a previously unknown companion to NU Ori.
With a probability of ~90% we can exclude further companions with masses of > 3
Msun around our sample stars for separations between ~2 mas and ~110 mas. We
conclude that the companion around \theta 1 Ori A is most likely physically
related to the primary star. The newly discovered possible companions further
increase the multiplicity in the ONC. For our sample of two O and three B-type
stars we find on average 2.5 known companions per primary, which is around five
times more than for low-mass stars.Comment: accepted by A&
Theoretical Study of Molecular Electronic and Rotational Coherences by High-Harmonic Generation
The detection of electron motion and electronic wavepacket dynamics is one of
the core goals of attosecond science. Recently, choosing the nitric oxide (NO)
molecule as an example, we have introduced and demonstrated a new experimental
approach to measure coupled valence electronic and rotational wavepackets using
high-harmonic generation (HHG) spectroscopy [Kraus et al., Phys. Rev. Lett.
111, 243005 (2013)]. A short outline of the theory to describe the combination
of the pump and HHG probe process was published together with an extensive
discussion of experimental results [Baykusheva et al., Faraday Discuss 171, 113
(2014)]. The comparison of theory and experiment showed good agreement on a
quantitative level. Here, we present the generalized theory in detail, which is
based on a generalized density matrix approach that describes the pump process
and the subsequent probing of the wavepackets by a semiclassical quantitative
rescattering approach. An in-depth analysis of the different Raman scattering
contributions to the creation of the coupled rotational and electronic
spin-orbit wavepackets is made. We present results for parallel and
perpendicular linear polarizations of the pump and probe laser pulses.
Furthermore, an analysis of the combined rotational-electronic density matrix
in terms of irreducible components is presented, that facilitates
interpretation of the results.Comment: 14 figure
Hearing It Again and Again: On-Line Subcortical Plasticity in Humans
Background: Human brainstem activity is sensitive to local sound statistics, as reflected in an enhanced response in repetitive compared to pseudo-random stimulus conditions [1]. Here we probed the short-term time course of this enhancement using a paradigm that assessed how the local sound statistics (i.e., repetition within a five-note melody) interact with more global statistics (i.e., repetition of the melody). Methodology/Principal Findings: To test the hypothesis that subcortical repetition enhancement builds over time, we recorded auditory brainstem responses in young adults to a five-note melody containing a repeated note, and monitored how the response changed over the course of 1.5 hrs. By comparing response amplitudes over time, we found a robust time-dependent enhancement to the locally repeating note that was superimposed on a weaker enhancement of the globally repeating pattern. Conclusions/Significance: We provide the first demonstration of on-line subcortical plasticity in humans. This complements previous findings that experience-dependent subcortical plasticity can occur on a number of time scales, including life-long experiences with music and language, and short-term auditory training. Our results suggest that the incoming stimulus stream is constantly being monitored, even when the stimulus is physically invariant and attention is directed elsewhere, to augment the neural response to the most statistically salient features of the ongoing stimulus stream. These real-tim
Research of the structure of gallstones by IR-spectroscopy method
The composition of gallstones was studied by IR spectroscopy. It is shown that it is possible to establish the presence in the gallstones of such compounds as bilirubin and its salts, calcium phosphates, calcium carbonate, which are present in them in small amounts and difficult to determine
Quantum interference and multielectron effects in high-harmonic spectra of polar molecules
ISSN:1094-1622ISSN:0556-2791ISSN:1050-294
Functional recovery after implantation of artificial nerve grafts in the rat- a systematic review
<p>Abstract</p> <p>Purpose</p> <p>The aim of this study was to compare functional data of different nerve-gap bridging materials evaluated in rat experiments by means of a systematic review.</p> <p>Materials and methods</p> <p>A systematic review was conducted, searching MEDLINE, HTS and CENTRAL to identify all trials evaluating functional recovery of artificial nerve conduits in the rat model.</p> <p>Results</p> <p>There was a trend towards a favourable outcome of conduits coated with Schwann-cells compared to the plain synthetics. Histomorphometry, electrophysiology and muscle-weight correlated poorly with functional outcome.</p> <p>Conclusion</p> <p>Schwann-cell coated conduits showed promising results concerning functional recovery. Further standardization in outcome reporting is encouraged.</p
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