7,718 research outputs found
Holographic Description of Finite Size Effects in Strongly Coupled Superconductors
Despite its fundamental and practical interest, the understanding of
mesoscopic effects in strongly coupled superconductors is still limited. Here
we address this problem by studying holographic superconductivity in a disk and
a strip of typical size . For , where depends on
the chemical potential and temperature, we have found that the order parameter
vanishes. The superconductor-metal transition at is controlled
by mean-field critical exponents which suggests that quantum and thermal
fluctuations induced by finite size effects are suppressed in holographic
superconductors. Intriguingly, the effective interactions that bind the order
parameter increases as decreases. Most of these results are consistent
with experimental observations in Pb nanograins at low temperature and
qualitatively different from the ones expected in a weakly coupled
superconductor.Comment: 4 pages, 3 figure
THROES: a caTalogue of HeRschel Observations of Evolved Stars. I. PACS range spectroscopy
This is the first of a series of papers presenting the THROES (A caTalogue of
HeRschel Observations of Evolved Stars) project, intended to provide a
comprehensive overview of the spectroscopic results obtained in the
far-infrared (55-670 microns) with the Her- schel space observatory on
low-to-intermediate mass evolved stars in our Galaxy. Here we introduce the
catalogue of interactively reprocessed PACS (Photoconductor Array Camera and
Spectrometer) spectra covering the 55-200 microns range for 114 stars in this
category for which PACS range spectroscopic data is available in the Herschel
Science Archive (HSA). Our sample includes objects spanning a range of
evolutionary stages, from the asymptotic giant branch to the planetary nebula
phase, displaying a wide variety of chemical and physical properties. The
THROES/PACS catalogue is accessible via a dedicated web-based inter- face
(https://throes.cab.inta-csic.es/) and includes not only the science-ready
Herschel spectroscopic data for each source, but also complementary photometric
and spectroscopic data from other infrared observatories, namely IRAS (Infrared
Astronomical Satellite), ISO (Infrared Space Observatory) or AKARI, at
overlapping wavelengths. Our goal is to create a legacy-value Herschel dataset
that can be used by the scientific community in the future to deepen our
knowledge and understanding of these latest stages of the evolution of
low-to-intermediate mass stars.Comment: 38 page
Light elements in stars with exoplanets
It is well known that stars orbited by giant planets have higher abundances
of heavy elements when compared with average field dwarfs. A number of studies
have also addressed the possibility that light element abundances are different
in these stars. In this paper we will review the present status of these
studies. The most significant trends will be discussed.Comment: 10 pages, 6 figures. Submitted to the proceedings of IAU symposium
268: Light elements in the universe
Link Invariants for Flows in Higher Dimensions
Linking numbers in higher dimensions and their generalization including gauge
fields are studied in the context of BF theories. The linking numbers
associated to -manifolds with smooth flows generated by divergence-free
p-vector fields, endowed with an invariant flow measure are computed in
different cases. They constitute invariants of smooth dynamical systems (for
non-singular flows) and generalizes previous results for the 3-dimensional
case. In particular, they generalizes to higher dimensions the Arnold's
asymptotic Hopf invariant for the three-dimensional case. This invariant is
generalized by a twisting with a non-abelian gauge connection. The computation
of the asymptotic Jones-Witten invariants for flows is naturally extended to
dimension n=2p+1. Finally we give a possible interpretation and implementation
of these issues in the context of string theory.Comment: 21+1 pages, LaTeX, no figure
A study of the Suess effect using a raised peat bog as historical archive
The radiocarbon content in a peat core from Gävle, Sweden, 61.0 oN, 17.0 oE, has been studied. This is a raised peat bog which only receives material from atmospheric deposition. There has been an increased use of fossil fuels by industries and also locally by transports and heating of domestic buildings. There has been fallout of 14C from nuclear tests during the 1950ies and 1960ies and also from the Chernobyl accident in 1986. There is also emission of 14C from nuclear facilities. The 14C/12C ratio from the Chernobyl accident is unclear since it was a graphite moderated reactor and the graphite was burning. The core was sampled in 2008 and was previously dated using the 210Pb method, giving a growth rate of 0.15 mm/yr. The top 21 cm have been analyzed to obtain radiocarbon content by Accelerator Mass Spectrometry (AMS) at the Centro Nacional de Aceleradores (CNA), Seville Spain. Using 0.5 cm samples, information about the last 140 years could be obtained with resolution better than 4 years. Results show a clear depletion of F14C levels in the area, the so called SUESS effect with maximum levels of only F14C=1.2333±0.0043, and the absence of a clear nuclear tests peak
1,3-Propanediol production from glycerol with a novel biocatalyst Shimwellia blattae ATCC 33430: Operational conditions and kinetics in batch cultivations
Shimwellia blattae ATCC 33430 as biocatalyst in the conversion of 1,3-propanediol from glycerol is herein evaluated. Several operational conditions in batch cultivations, employing pure and raw glycerol as sole carbon source, were studied. Temperature was studied at shaken bottle scale, while pH control strategy, together with the influence of raw glycerol and its impurities during fermentation were studied employing a 2 L STBR. Thereafter, fluid dynamic conditions were considered by changing the stirring speed and the gas supply (air or nitrogen) in the same scale-up experiments. The best results were obtained at a termperature of 37ºC, an agitation rate of 200 rpm, with free pH evolution from 6.9 and subsequent control at 6.5 and no gas supply during the fermentation, employing an initial concentration of 30 g/L of raw glycerol. Under these conditions, the biocatalyst is competitive, leading to results in line with other previous works in the literature in batch conditions, reaching a final concentration of 1,3-propanediol of 13.84 g/L, with a yield of 0.45 g/g and a productivity of 1.19 g/(L·h) from
raw glycerol
Tunneling mechanism of light transmission through metallic films
A mechanism of light transmission through metallic films is proposed,
assisted by tunnelling between resonating buried dielectric inclusions. This is
illustrated by arrays of Si spheres embedded in Ag. Strong transmission peaks
are observed near the Mie resonances of the spheres. The interaction among
various planes of spheres and interference effects between these resonances and
the surface plasmons of Ag lead to mixing and splitting of the resonances.
Transmission is proved to be limited only by absorption. For small spheres, the
effective dielectric constant can be tuned to values close to unity and a
method is proposed to turn the resulting materials invisible.Comment: 4 papges, 5 figure
Analysis of pixel-mapping rounding on geometric distortion as a prediction for view synthesis distortion
We analyze the performance of the geometric distortion, incurred when coding depth maps in 3D Video, as an estimator of the distortion of synthesized views. Our analysis is motivated by the need of reducing the computational complexity required for the computation of synthesis distortion in 3D video encoders. We propose several geometric distortion models that capture (i) the geometric distortion caused by the depth coding error, and (ii) the pixel-mapping precision in view synthesis. Our analysis starts with the evaluation of the correlation of geometric distortion values obtained with these models and the actual distortion on synthesized views. Then, the different geometric distortion models are employed in the rate-distortion optimization cycle of depth map coding, in order to assess the results obtained by the correlation analysis. Results show that one of the geometric distortion models is performing consistently better than the other models in all tests. Therefore, it can be used as a reasonable estimator of the synthesis distortion in low complexity depth encoders
Unveiling the Dependence between Hydroxyl Radical Generation and Performance of Fenton Systems with Complexed Iron
[EN] Humiclike substances (HLS) have been demonstrated to be useful auxiliaries to drive the (photo)-Fenton process at mild pH, by avoiding iron inactivation via formation of active complexes. However, the actual performance of the process is affected by a manifold of opposite processes. In this work, the generation of hydroxyl radical-like reactive species in the Fentonlike process has been investigated using electron paramagnetic resonance, employing 5,5-dimethyl-1-pyrroline-N-oxide as a probe molecule. The signal obtained with the Fe(II)-HLS-H2O2 system at pH = was very intense but decreased with time, in line with the difficult reduction of the formed Fe(III) to Fe(II). On the contrary, the signal of the Fe(III)-HLS-H2O2 system was weak but stable. The most intense signal was observed at HLS concentration of ca. 30 mg/L. Interestingly, the performance of the Fenton system at pH = 5 to degrade caffeine followed the same trends, although caffeine removal was very low after 1 h of irradiation. The results were more evident in a solar simulated photo-Fenton process, where an increase in the abatement of caffeine was observed until an HLS concentration of 30 mg/L, where 98% removal was reached after 1 h.The authors want to acknowledge the financial support from Ministerio de Ciencia, Innovacion y Universidades (RTI2018-097997-B-C31) and European Union (645551-RISE-2014, MAT4TREAT). P.G.-N. would like to thank Spanish Ministerio de Economia y Competitividad for her fellowship (BES-2016-077962).GarcĂa-Negueroles, P.; GarcĂa-Ballesteros, S.; Amat Payá, AM.; Laurenti, E.; ArquĂ©s Sanz, A.; Santos-Juanes Jordá, L. (2019). Unveiling the Dependence between Hydroxyl Radical Generation and Performance of Fenton Systems with Complexed Iron. ACS Omega. 4(26):21698-21703. https://doi.org/10.1021/acsomega.9b02241S216982170342
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