2,266 research outputs found
Spin-orbit coupling, minimal model and potential Cooper-pairing from repulsion in BiS-superconductors
We develop the realistic minimal electronic model for recently discovered
BiS superconductors including the spin-orbit coupling based on a
first-principles band structure calculations. Due to strong spin-orbit
coupling, characteristic for the Bi-based systems, the tight-binding low-energy
model necessarily includes , , and orbitals. We analyze a
potential Cooper-pairing instability from purely repulsive interaction for the
moderate electronic correlations using the so-called leading angular harmonics
approximation (LAHA). For small and intermediate doping concentrations we find
the dominant instabilities to be -wave, and -wave
symmetries, respectively. At the same time, in the absence of the sizable spin
fluctuations the intra and interband Coulomb repulsion are of the same
strength, which yields the strongly anisotropic behaviour of the
superconducting gaps on the Fermi surface in agreement with recent ARPES
findings. In addition, we find that the Fermi surface topology for BiS
layered systems at large electron doping can resembles the doped iron-based
pnictide superconductors with electron and hole Fermi surfaces with sufficient
nesting between them. This could provide further boost to increase in
these systems.Comment: 10 pages, 3 figure
Variación de las características mecánicas de armaduras de alta ductilidad B500SD en función de su grado de corrosión / Mechanical properties variation of B500SD high ductility reinforcement regarding its corrosion degree
Los efectos de la corrosión sobre las armaduras se manifiestan por la pérdida de sección y la variación de las propiedades mecánicas relacionadas con la ductilidad. En este trabajo se han ensayado a tracción 96 barras de acero B500SD que previamente se han sometido a niveles variables de corrosión. Los resultados muestran que los alargamientos de las barras disminuyen y el cociente entre la tensión máxima y el límite elástico aumenta conforme el nivel de corrosión avanza. A partir del estudio del efecto de entalla y de la distinta constitución metalográfica del acero a nivel de sección debido a su procedimiento de fabricación se pueden explicar los fenómenos anteriores
Detection of emission in the Si i 1082.7 nm line core in sunspot umbrae
We analyze spectropolarimetric sunspot umbra observations taken in the
near-infrared Si i 1082.7 nm line taking NLTE effects into account. The data
were obtained with the GRIS instrument installed at the German GREGOR
telescope. A point spread function (PSF) was constructed using prior Mercury
observations with GRIS and the information provided by the adaptive optics
system of the GREGOR telescope. The data were then deconvolved from the PSF
using a principal component analysis deconvolution method and were analyzed via
the NICOLE inversion code. The Si i 1082.7 nm line seems to be in emission in
the umbra of the observed sunspot after the effects of scattered light are
removed. We show how the spectral line shape of umbral profiles changes
dramatically with the amount of scattered light. Indeed, the continuum levels
range, on average, from 44% of the quiet Sun continuum intensity to about 20%.
The inferred levels are in line with current model predictions and empirical
umbral models. Current umbral empirical models are not able to reproduce the
emission in the deconvolved umbral Stokes profiles. The results of the NLTE
inversions suggests that to obtain the emission in the Si i 1082.7 nm line, the
temperature stratification should first have a hump located at about log tau -2
and start rising at lower heights when moving into the transition region. This
is, to our knowledge, the first time the Si i 1082.7 nm line is seen in
emission in sunspot umbrae. The results show that the temperature
stratification of current umbral models may be more complex than expected with
the transition region located at lower heights above sunspot umbrae. Our
finding might provide insights into understanding why the sunspot umbra
emission in the millimeter spectral range is less than that predicted by
current empirical umbral models
Stress-strain response and microstructural evolution of a FeMnCAl TWIP steel during tension-compression tests
© 2016.
The stress-strain response of a Fe-17.5Mn-0.7C-2Al TWIP steel during cyclic loading has been investigated by means of tension-compression tests within the strain limits of ±2%, ±5% and ±10%. In addition, the microstructural evolution during the ±5% cyclic test has also been studied. The difference between the forward and reverse stress for each pre-strain has been analyzed at 0.2% offset strain and at the strains in which forward and reverse curves were parallel in order to study the Bauschinger effect (BE) and permanent softening, respectively. The evolution of the BE with pre-strain for this steel is similar to other FeMnC TWIP steels, that is, increasing values of BE are obtained as the pre-strain increases. However, its absolute values are half those reported in the literature on other FeMnC steels. This diminution of the BE is related to the lower activity of mechanical twinning in FeMnCAl TWIP steels at the pre-strains herein investigated, which promotes less polarized stresses in the matrix due to the lower dislocation storage capacity.Regarding permanent softening, the evolution is similar to that of the BE and the same analysis can be applied. During reverse compression, a slight increase of twin thickness and twin spacing with respect to the first tensile stage took place. This fact might be linked to the lower flow stress observed in the permanent softening period during reverse straining.Peer ReviewedPostprint (author's final draft
Anisakis infection in allis shad, Alosa alosa (Linnaeus, 1758), and twaite shad, Alosa fallax (Lacépède, 1803), from Western Iberian Peninsula Rivers : zoonotic and ecological implications
Acknowledgments The authors would like to thank M. N. Cueto and J.M. Antonio (ECOBIOMAR) for their excellent technical support and also Rodrigo López for making the map of the study area. We also thank the personal of the Vigo IEO, for providing information about shad captures at sea collected on the basis of national program (AMDES) included in the European Data Collection Framework (DCF) project. We are also grateful to Comandancia Naval de Tui for providing fishing data. M. Bao is supported by a PhD grant from the University of Aberdeen and also by financial support of the contract from the EU Project PARASITE (grant number 312068). This study was partially supported by a PhD grant from the Portuguese Foundation for Science and Technology (FCT) SFRH/BD/44892/2008) and partially supported by the European Regional Development Fund (ERDF) through the COMPETE—Operational Competitiveness Programme and national funds through Foundation for Science and Technology (FCT), under the project BPEst-C/MAR/ LA0015/2013. The authors thank the staff of the Station of Hydrobiology of the USC BEncoro do Con^ due their participation in the surveys. This work has been partially supported by the project 10PXIB2111059PR of the Xunta de Galicia and the project MIGRANET of the Interreg IV BSUDOE (South-West Europe) Territorial Cooperation Programme (SOE2/P2/E288). D.J. Nachón is supported by a PhD grant from the Xunta de Galicia (PRE/2011/198)Peer reviewedPostprin
On the validity of the 630 nm Fe I nm lines for the magnetometry of the internetwork quiet Sun
The purpose of this work is to analyze the reliability of the magnetic field
strengths inferred from the 630 nm pair of Fe I lines at internetwork quiet Sun
regions. Some numerical experiments have been performed that demonstrate the
inability of these lines to recover the magnetic field strength in such low
flux solar regions. It is shown how different model atmospheres, with magnetic
field strengths ranging from few hundred Gauss to kiloGauss, give rise to
Stokes profiles that can not be distinguished. The reasons for this degeneracy
are discussed.Comment: Accepted for publication in A&
Low-lying magnetic loops in the solar internetwork
The aim of this work is to study the structure of the magnetic field vector
in the internetwork and search for the presence of small-scale loops. We invert
1.56 micron spectropolarimetric observations of internetwork regions at disc
centre by applying the SIR code. This allows us to recover the atmospheric
parameters that play a role in the formation of these spectral lines. We are
mainly interested in the structure of the magnetic field vector. We find that
many opposite polarity elements of the internetwork are connected by short
(2-6''), low-lying (photospheric) loops. These loops connect at least the 10-20
% of the internetwork flux visible in our data. Also we have some evidence that
points towards a dynamic scenario which can be produced by the emergence of
internetwork magnetic flux.Comment: Accepted for publication in A&A letter
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