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7 páginas, 5 figuras.-- et al. ; We apply time-dependent density functional theory to study the valence electron excitations of molecules and generalize the typically used time-propagation scheme and Casida's method to calculate the full wavevector dependent response function. This allows the computational study of dipole-forbidden valence electron transitions and the dispersion of spectral weight as a function of the wavevector. The method provides a novel analysis tool for spectroscopic methods such as inelastic x-ray scattering and electron energy loss spectroscopy. We present results for benzene and CF3Cl and make a comparison with experimental results. ; Acknowledge HPCEuropa2 program, Academy of Finland (1127462, Centers of Excellence Program 2006–2011, and National Graduate School in Materials Physics) for financial support, and CSC-IT Center for Science Ltd for computational resources. A.R. acknowledges Spanish MEC (FIS2007-65702-C02-01), ACI-Promociona (ACI2009-1036), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT-319-07), the European Union through e-13 ETSF (Contract No. 211956), and THEMA (Contract No. 228539) projects, as well as the support by the Red Española de Supercomputación and ARINA. ; Peer reviewed

4 páginas, 3 figuras, 1 tabla.-- et al. ; The understanding and control of the magnetic properties of carbon-based materials is of fundamental relevance in applications in nano- and biosciences. Ring currents do play a basic role in those systems. In particular the inner cavities of nanotubes offer an ideal environment to investigate the magnetism of synthetic materials at the nanoscale. Here, by means of high resolution NMR of encapsulated molecules in peapod hybrid materials, we report the largest diamagnetic shifts (down to −68.3 ppm) ever observed in carbon allotropes, which is connected to the enhancement of the aromaticity of the nanotube envelope upon doping. This diamagnetic shift can be externally controlled by in situ modifications such as doping or electrostatic charging. Moreover, defects such as C-vacancies, pentagons, and chemical functionalization of the outer nanotube quench this diamagnetic effect and restore NMR signatures to slightly paramagnetic shifts compared to nonencapsulated molecules. The magnetic interactions reported here are robust phenomena independent of temperature and proportional to the applied magnetic field. The magnitude, tunability, and stability of the magnetic effects make the peapod nanomaterials potentially valuable for nanomagnetic shielding in nanoelectronics and nanobiomedical engineering. ; This work was supported by the Centre National de la Recherche Scientifique and the Region Languedoc-Roussillon, the Office of Basic Energy Sciences, Materials Sciences and Engineering Division, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, via the sp2-bonded nanostructures program and the Molecular Foundry, the Wenner-Gren Foundations, and Vetenskapsrådet, the Spanish MEC (Grant No. FIS2007-65702-C02-01), Grupos Consolidados UPV/EHU of the Basque Country Government (Grant No. IT-319-07), and European Community e-I3 ETSF project. ; Peer reviewed

"Examines introduction of palm oil production in agricultural cooperatives from 1970s onward in a region previously dominated by banana plantations controlled by foreign capital. Summarizes project-specific and national land reform policies, and analyzes resulting changes in the labor market and the organization of production and exchange"--Handbook of Latin American Studies, v. 57

PACS nrs.: 79.60.-i, 71.10.-w, 71.20.Tx, 71.55.Ak.p.-- et al. ; The full three-dimensional dispersion of the π bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials. ; A. G. acknowledges a Marie Curie Individual Fellowship (COMTRANS) from the European Union. T. P. acknowledges DFG Projects No. PI 440/3 and No. 440/4. C.A. and L.W. acknowledge support from the French national research agency. A. R. is supported by the EC Network of Excellence Nanoquanta (No. NMP4-CT-2004-500198), SANES project (No. NMP4-CT-2006-017310), Basque Country University (SGIker Arina), and MEC (No. FIS2007-65702-C02-01). ; Peer reviewed

This paper was presented in part at the Symposium of Microtechnologies for the New Millennium, Nanotechnology Conference, Gran-Canaria, Spain, May 2003. ; We present ab initio calculations of phonons in single-wall boron-nitride (BN) nanotubes. Raman and infrared (IR) active modes of isolated and infinitely long tubes are evaluated according to the nonsymmorphic rod groups of BN nanotubes. For tubes of finite length, the selection rules are less restrictive and give rise to additional modes, which may be observed in Raman and IR spectroscopy with an intensity depending on the tube length. Bundling of tubes is shown to have little effect on the phonon frequencies. However, arranging tubes in a large periodic array (larger than the wavelength of incoming light) gives rise to a strong frequency shift (longitudinal-optical-transverse-optical splitting) of certain modes due to the establishing of a macroscopic electric field. Modes of A1 symmetry experience a shift for laser light along the tube axis and E1 modes are split for light incidence in the perpendicular direction. ; This work was supported in part by the European Union under Grant HPRN-CT-2000-00 128, and in part by the Spanish Ministry of Science and Technology under Grant MAT2001-0946, and in part by the University of the Basque Country under Contract 00 206.215-13 639/2001. ; Peer reviewed

9 páginas, 2 figuras, 1 tabla. ; The delocalised nature of π-electrons in carbon-based compounds has opened a huge path for new fundamental and technological developments using carbon-based materials of different dimensionality (from clusters, to surfaces, nanotubes and graphene, among others). The success of this field has prompted the proposal that other inorganic structures based on B and N and more recently on Si and Ge could be formed with specific structural, mechanical, and electronic properties. In this paper we provide an analysis of the similarities of the two fields starting from the analysis of the Si6H6 molecule, the analogue of the benzene molecule but now being nonplanar. Then we move to the study of the two-dimensional (buckled) analogues of graphene but now formed by Si and Ge. Similarly, we look to nonplanar compounds based on boron and boron-carbon nitrogen composites. In particular, we focus on the mechanical properties of those new materials that exhibit a very high stiffness, resilience, and flexibility. Possible applications in the fields of catalysis, lubrication, electronic, and photonic devices now seem a likely by-product. We also address future directions triggered by the predicted superconducting properties of graphene, among other areas. ; This work has been supported also by the Spanish MEC (FIS2007-65702-C02-01), ACI-Promociona (ACI2009-1036), "Grupos Consolidados UPV/EHU del Gobierno Vasco" (IT-319-07), ETORTEK and the European Union through e-I3 ETSF (Contract: 211956), NANANODEVICES (IST-2006-029192), and THEMA (Contract: 228539) projects. ; Peer reviewed

22 pp.-- PACS nrs.: 73.63.-b, 72.10.-d, 71.10.-w ; We give a detailed presentation of our recent scheme to include correlation effects in molecular transport calculations using the nonequilibrium Keldysh formalism. The scheme is general and can be used with any quasiparticle self-energy, but for practical reasons, we mainly specialize to the so-called GW self-energy, widely used to describe the quasiparticle band structures and spectroscopic properties of extended and low-dimensional systems. We restrict the GW self-energy to a finite, central region containing the molecule, and we describe the leads by density functional theory (DFT). A minimal basis of maximally localized Wannier functions is applied both in the central GW region and the leads. The importance of using a conserving, i.e., fully self-consistent, GW self-energy is demonstrated both analytically and numerically. We introduce an effective spin-dependent interaction which automatically reduces self-interaction errors to all orders in the interaction. The scheme is applied to the Anderson model in and out of equilibrium. In equilibrium at zero temperature, we find that GW describes the Kondo resonance fairly well for intermediate interaction strengths. Out of equilibrium, we demonstrate that the one-shot G0W0 approximation can produce severe errors, in particular, at high bias. Finally, we consider a benzene molecule between featureless leads. It is found that the molecule's highest occupied molecular orbital–lowest unoccupied molecular orbital gap as calculated in GW is significantly reduced as the coupling to the leads is increased, reflecting the more efficient screening in the strongly coupled junction. For the I-V characteristics of the junction, we find that Hartree–Fock (HF) and G0W0[G_HF] yield results closer to GW than does DFT and G0W0[G_DFT]. This is explained in terms of self-interaction effects and lifetime reduction due to electron-electron interactions. ; .S.T. acknowledges support from the Danish Natural Science Research Council and from the Danish Center for Scientific Computing through Grant No. HDW-1103-06. The Center for Atomic-scale Materials Design CAMD is sponsored by the Lundbeck Foundation. A.R. acknowledges support from the EC Network of Excellence NANOQUANTA Ref. No. NMP4-CT-2004-500198, the Spanish Ministry of Education Grant No. FIS2007-65702-C02-01, the SANES Ref. No. NMP4-CT-2006-017310 , the DNA-NANODEVICES Ref. No. IST-2006-029192, the NANO-ERA Chemistry projects, the University of the Basque Country EHU/UPV SGIker Arina, and the Basque Country Government, and the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center-Centro Nacional de Supercomputación. ; Peer reviewed

Se presenta un estudio bibliométrico de la Revista Española de Investigaciones Sociológicas, conmotivo de su 25.º aniversario. Los aspectos estudiados son producción, colaboración y materias.La reconocida importancia de esta revista en España convierte este estudio en altamente representativode la literatura sociológica de este país. Asimismo, el estudio se completa con un apartadodedicado a evaluar su calidad como revista científica.

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).-- et al. ; We characterize experimentally and theoretically the collective electronic excitations in two prototypical layered transition-metal dichalcogenides, NbSe2 and Cu0.2NbS2. The energy- and momentum-dependent dynamical structure factor was measured by inelastic x-ray scattering (IXS) spectroscopy and simulated by time-dependent density-functional theory. We find good agreement between theory and experiment, provided that Nb semicore states are taken into account together with crystal local-field effects. Both materials have very similar spectra, characterized by two main plasmons at 9 and 23 eV, which we show to both have π+σ character on the basis of a detailed analysis of the band structure. Finally, we discuss the role of the layer anisotropy in the dispersion of these plasmons. ; We acknowledge financial support from the European Research Council Advanced Grant DYNamo (ERC-2010-AdG-267374), Spanish grant (2010-21282-C02-01), Grupos Consolidados UPV/EHU del Gobierno Vasco (IT578-13), European Commission project CRONOS (Grant No. 280879-2). This research was also supported by a Marie Curie FP7 Integration Grant within the 7th European Union Framework Programme, and by Generalidad Valenciana (ISIC Nano program). S.H., K.O.R. and C.J.S. were supported by the Academy of Finland (projects 1256211, 1254065, 1259526) and University of Helsinki Research Funds (project 490076). ; Peer Reviewed

Transition-metal dichalcogenides (TMD) share the same global layered structure, but distinct polymorphs are characterized by different local coordinations of the transition-metal atoms. Here we compared the 1T and 2H families of metallic TMD, both in the bulk and in the two-dimensional forms. By means of first-principles time-dependent density functional calculations of the loss function, we established the direct connection between the low-energy plasmon properties and the crystal-structure symmetry. The different atomic environments affect the d−d electron-hole excitations, which are prominent at low energies, resulting in distinct in-plane plasmon dispersions in the two families. Conversely, the different periodicity of the plasmon reappearance along the c axis perpendicular to the layers can be used to distinguish the various crystal structures of TMD. ; We acknowledge financial support from the European Research Council Advanced grant DYNamo (Grant No. ERC- 2010-AdG-267374), Spanish grant (Grant No. 2010-21282-C02-01), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), and European Commission project CRONOS (Grant No. 280879-2). This research was also supported by a Marie Curie FP7 Integration Grant within the Seventh European Union Framework Programme. ; Peer Reviewed