1,817 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
Fluxtube model atmospheres and Stokes V zero-crossing wavelengths
First results of the inversion of Stokes I and V profiles from plage regions
near disk center are presented. Both low and high spatial resolution spectra of
FeI 6301.5 and FeI 6302.5 A obtained with the Advanced Stokes Polarimeter (ASP)
have been considered for analysis. The thin flux tube approximation,
implemented in an LTE inversion code based on response functions, is used to
describe unresolved magnetic elements. The code allows the simultaneous and
consistent inference of all atmospheric quantities determining the radiative
transfer with the sole assumption of hydrostatic equilibrium. By considering
velocity gradients within the tubes we are able to match the full ASP Stokes
profiles. The magnetic atmospheres derived from the inversion are characterized
by the absence of significant motions in high layers and strong velocity
gradients in deeper layers. These are essential to reproduce the asymmetries of
the observed profiles. Our scenario predicts a shift of the Stokes V
zero-crossing wavelengths which is indeed present in observations made with the
Fourier Transform Spectrometer.Comment: To appear in ApJ Letters (1997) (in press
Endogenous Sanctioning Institutions and Migration Patterns: Experimental Evidence
We experimentally analyze the effect of the endogenous choice of sanctioning institutions on cooperation and migration patterns across societies. In our experiment, subjects are allocated to one of two groups, are endowed with group-specific preferences,and play a public goods game for 30 periods. Each period, subjects can move between groups and, at fixed intervals, can vote on whether to implement formal (centralized) sanctioning institutions in their group. We compare this environment to one in which only one group is exogenously endowed with sanctioning institutions. We find that subjects' ability to vote on institutions leads to (i) a more efficient partition of subjects between groups, (ii) a lower migration rate, (iii) an increase in overall payoffs, and (iv) a decrease in both inter- and intra-groups (payoff) inequality. Over time, subjects tend to vote for sanctioning institutions and contribute to the public good
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
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
Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals
The chain-polymer Cu(II) breathing crystals C21H19CuF12N4O6 were studied
using the x-ray diffraction and ab initio band structure calculations. We show
that the crystal structure modification at T=146 K, associated with the spin
crossover transition, induces the changes of the orbital order in half of the
Cu sites. This in turn results in the switch of the magnetic interaction sign
in accordance with the Goodenough-Kanamori-Andersen theory of the coupling
between the orbital and spin degrees of freedom.Comment: 6 pages, 7 figure
Museum libraries in Spain: A case study at state level
Special libraries are essential information and documentation centres for university teachers and researchers due to the quality and richness of their collections. In Spain, it is estimated that there are 2456 special libraries, although many are unknown either generally or among information professionals. These include museum libraries, which are important centres with valuable collections of bibliographic heritage for the area of Humanities and Social Sciences. The aim of this research is to gain an understanding of the real state of these information units and promote the social value of museum libraries in Spain. To do this, a survey was sent to the libraries of state-owned and -managed museums under the General Directorate of Fine Arts and Cultural Property (Ministry of Culture and Sports) of the Government of Spain. This general objective will be accompanied by a review of the scientific literature on various aspects of museum libraries at national and international level. After addressing the research methodology, the results obtained will be discussed and will include the following topics: collection management, library services and staff, economic and technological resources and finally, library management. Conclusions include recommendations for museum librarians and reveal that institutional cooperation is a strategic issue to improve both museum libraries visibility and their social recognition as cultural and research centre
The Molecular Basis of Radial Intercalation during Tissue Spreading in Early Development
Radial intercalation is a fundamental process responsible for the thinning of multilayered tissues during large-scale morphogenesis; however, its molecular mechanism has remained elusive. Using amphibian epiboly, the thinning and spreading of the animal hemisphere during gastrulation, here we provide evidence that radial intercalation is driven by chemotaxis of cells toward the external layer of the tissue. This role of chemotaxis in tissue spreading and thinning is unlike its typical role associated with large-distance directional movement of cells. We identify the chemoattractant as the complement component C3a, a factor normally linked with the immune system. The mechanism is explored by computational modeling and tested in vivo, ex vivo, and in vitro. This mechanism is robust against fluctuations of chemoattractant levels and expression patterns and explains expansion during epiboly. This study provides insight into the fundamental process of radial intercalation and could be applied to a wide range of morphogenetic events
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