Structure and electronic properties of molybdenum monoatomic wires encapsulated in carbon nanotubes

Monoatomic chains of molybdenum encapsulated in single walled carbon nanotubes of different chiralities are investigated using density functional theory. We determine the optimal size of the carbon nanotube for encapsulating a single atomic wire, as well as the most stable atomic arrangement adopted by the wire. We also study the transport properties in the ballistic regime by computing the transmission coefficients and tracing them back to electronic conduction channels of the wire and the host. We predict that carbon nanotubes of appropriate radii encapsulating a Mo wire have metallic behavior, even if both the nanotube and the wire are insulators. Therefore, encapsulating Mo wires in CNT is a way to create conductive quasi one-dimensional hybrid nanostructures.Comment: 8 pages, 10 figure

Impact of dimerization and stretching on the transport properties of molybdenum atomic wires

We study the electrical and transport properties of monoatomic Mo wires with different structural characteristics. We consider first periodic wires with inter-atomic distances ranging between the dimerized wire to that formed by equidistant atoms. We find that the dimerized case has a gap in the electronic structure which makes it insulating, as opposed to the equidistant or near-equidistant cases which are metallic. We also simulate two conducting one-dimensional Mo electrodes separated by a scattering region which contains a number of dimers between 1 and 6. The $I-V$ characteristics strongly depend on the number of dimers and vary from ohmic to tunneling, with the presence of different gaps. We also find that stretched chains are ferromagnetic.Comment: 8 pages, 7 figure

Derivation of the physical parameters of the jet in S5 0836+710 from stability analysis

A number of extragalactic jets show periodic structures at different scales that can be associated with growing instabilities. The wavelengths of the developing instability modes and their ratios depend on the flow parameters, so the study of those structures can shed light on jet physics at the scales involved. In this work, we use the fits to the jet ridgeline obtained from different observations of S5 B0836$+$710 and apply stability analysis of relativistic, sheared flows to derive an estimate of the physical parameters of the jet. Based on the assumption that the observed structures are generated by growing Kelvin-Helmholtz (KH) instability modes, we have run numerical calculations of stability of a relativistic, sheared jet over a range of different jet parameters. We have spanned several orders of magnitude in jet-to-ambient medium density ratio, and jet internal energy, and checked different values of the Lorentz factor and shear layer width. This represents an independent method to obtain estimates of the physical parameters of a jet. By comparing the fastest growing wavelengths of each relevant mode given by the calculations with the observed wavelengths reported in the literature, we have derived independent estimates of the jet Lorentz factor, specific internal energy, jet-to-ambient medium density ratio and Mach number. We obtain a jet Lorentz factor $\gamma \simeq 12$, specific internal energy of $\varepsilon \simeq 10^{-2}\,c^2$, jet-to-ambient medium density ratio of $\eta\approx 10^{-3}$, and an internal (classical) jet Mach number of $M_\mathrm{j}\approx 12$. We also find that the wavelength ratios are better recovered by a transversal structure with a width of $\simeq 10\,\%$ of the jet radius. This method represents a powerful tool to derive the jet parameters in all jets showing helical patterns with different wavelengths.Comment: Accepted for publication in A&A, 15 pages, 12 figure

Star polymers rupture induced by constant forces

In this work, we study the breakage process of an unknotted three-arm star-shaped polymer when it is pulled from its free ends by a constant force. The star polymer configuration is described through an array of monomers coupled by anharmonic bonds, while the rupture process is tracked in three-dimensional space by means of Langevin Molecular Dynamics simulations. The interaction between monomers is described by a Morse potential, while a Weeks-Chandler-Anderson energetic contribution accounts for the excluded volume interaction. We explore the effect of the molecular architecture on the distributions of rupture times over a broad interval of pulling forces and star configurations. It was found that the rupture time distribution of the individual star arms is strongly affected by the star configuration imposed by the pulling forces and the length of the arms. We also observed that for large pulling forces the rupture time distributions resemble the dominant features observed for linear polymer chains. The model introduced here provides the basic ingredients to describe the effects of tensile forces on stress-induced degradation of branched macromolecules and polymer networks.Fil: García, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Febbo, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Vega, Daniel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Milchev, A.. Bulgarian Academy of Sciences; Bulgari

The Internationalisation of R&D and the Knowledge Production Function

This paper considers the effect of acquisition FDI on the knowledge production function. We distinguish between acquisitions by MNEs from technologically leading countries and those behind the technological frontier. We show that both acquire similarly R&D intensive domestic firms, but there are important differences post-acquisition. Acquisitions from technologically intensive countries reduce domestic R&D effort, in favour of an increase in foreign technology transfers, which suggests complementarities in the knowledge assets of the MNE and the target firm as a reason for FDI. In contrast, consistent with technology sourcing FDI, acquisitions from non-leading countries increase internal R&D efforts.MNE, knowledge production function, acquisition FDI, knowledge complementarities, technology sourcing

EL PRINCIPIO CONSTITUCIONAL DE SOLIDARIDAD INTERTERRITORIAL EN ESPAÑA Y EN ALEMANIA: APLICACIÓN Y LÍMITES

El present estudi analitza l’aplicació del principi constitucional de solidaritat interterritorial a Espanya i a Alemanya centrant-se en la qüestió dels seus límits. Inicialment es presenta el cas d’Espanya, incloent tant les comunitats autònomes de règim comú com les forals i prestant especial atenció als límits a la solidaritat que va introduir l’Estatut d’autonomia de Catalunya, i que en part van ser declarats inconstitucionals pel seu caràcter unilateral. Aquestes previsions estatutàries s’havien inspirat en gran mesura en els principis seguits a Alemanya, com el de prohibició d’anivellament total o el d’ "ordinalitat”, motiu pel qual la segona part de l’article analitza la normativa d’aquest país i la seva interpretació per la jurisprudència constitucional. En general, la situació existent actualment a tots dos estats no és tan dispar, ja que, malgrat la sentència del Tribunal Constitucional sobre l’Estatut, el sistema de finançament aprovat el 2009 continua aplicant aquests principis. Tanmateix, a diferència del que succeeix a Alemanya, a Espanya destaca l’asimetria provocada per l’escassa contribució dels territoris forals a la solidaritat, aspecte que resulta injustificat i que per tant s’hauria de corregir.This article analyses the application of the constitutional principle of fiscal equalization in Spain and Germany focusing on the issue of its limits. To begin with, the Spanish case is presented, including both the autonomous communities under the common system and the Basque Country and Navarre, and paying particular attention to the limits to solidarity which had been foreseen by the Statute of Autonomy of Catalonia and which have been partly declared unconstitutional due to their unilateral character. Given that these statutory provisions had been inspired to a large extent by the principles followed in Germany, such as the prohibition of a complete fiscal equalization, the second part of the article analyses the legal framework of this country and its interpretation in the constitutional case law. In general, the current situation in both States is not so different, given that, despite the decision of the Spanish Constitutional Court on the Statute of Autonomy of Catalonia, the general financing system of 2009 still applies these principles. Catalonia, the general financing system of 2009 still applies these principles. However, in contrast to the situation in Germany, a notable difference is the asymmetry which exists in Spain due to the limited contribution of the Basque Country and Navarre to fiscal equalization transfers, which is unjustified and therefore should be corrected.El presente estudio analiza la aplicación del principio constitucional de solidaridad interterritorial en España y en Alemania centrándose en la cuestión de sus límites. Inicialmente se presenta el caso de España, incluyendo tanto las comunidades autónomas de régimen común como las forales y prestando especial atención a los límites a la solidaridad que introdujo el Estatuto de Autonomía de Cataluña y que en parte fueron declarados inconstitucionales por su carácter unilateral. Tales previsiones estatutarias se habían inspirado en gran medida en los principios seguidos en Alemania, como el de prohibición de nivelación total o el de “ordinalidad”, por lo que la segunda parte del artículo analiza la normativa de este país y su interpretación por la jurisprudencia constitucional. En general, la situación existente actualmente en ambos Estados no es tan dispar, ya que, a pesar de la sentencia del Tribunal Constitucional sobre el Estatuto, el sistema de financiación aprobado en 2009 continúa aplicando estos principios. Sin embargo, a diferencia de lo que sucede en Alemania, en España destaca la asimetría provocada por la escasa contribución de los territorios forales a la solidaridad, aspecto que resulta injustificado y que por lo tanto debería corregirse