Libia: prueba de fuego para la comunidad internacional

¿Qué posibilidades hay de que se lleve a cabo una intervención internacional, que incluya medios militares, para frenar la violencia que se está produciendo en Libia? En contra de lo inicialmente esperado, Muamar al Gadafi no ha sido barrido del escenario político por la oleada de revueltas impulsadas por diferentes actores libios que desean un cambio de régimen. Por el contrario, los datos más recientes apuntan a que, en el terreno militar, no solo ha logrado frenar el empuje de los grupos que se han rebelado contra él, sino que ha recuperado algunas posiciones que parecían ya sólidamente en manos de la oposición y hasta podría terminar por inclinar la balanza a su favor. La grave crisis humanitaria que se ha producido y los crímenes de guerra ya cometidos podrían ser argumentos suficientes para impulsar una intervención internacional que ponga fin a la violencia. Aunque se van acumulando declaraciones en ese sentido y se hacen visibles algunos preparativos militares, nada permite concluir que la comunidad internacional, más allá de la ya aprobada Resolución 1970 del Consejo de Seguridad de la ONU, esté en condiciones de implicarse directa y militarmente en la resolución del conflicto. El problema añadido es que, una vez que los más significados actores nacionales e internacionales se han declarado abiertamente en contra de Gadafi, nos encontramos ahora ante una situación que ofrece pocas salidas si finalmente el dictador libio no es derrotado por sus adversarios

España en el Mediterráneo: una agenda recuperada ¿a tiempo?

¿Cuál es el papel de España en el Mediterráneo en vísperas de asumir la Presidencia rotatoria de la UE? España trata de regresar a una zona que define como una de sus principales prioridades de política exterior, tras un largo paréntesis de bajo perfil. La reciente visita del jefe del gobierno español a Oriente Próximo debe interpretarse tanto en clave nacional como comunitaria, dado que en breve se hará cargo de la Presidencia de la UE. Las condiciones objetivas en el sur y este del Mediterráneo no son nada halagüeñas y esto hace más difícil aún –pero igualmente necesaria– cualquier iniciativa para cerrar conflictos tan enmarañados como el saharaui y el árabe-israelí y para promover un verdadero espacio euromediterráneo de paz y prosperidad compartida. España debe seguir apostando, tanto en el marco bilateral como en los foros internacionales de los que forma parte, por impulsar los esfuerzos que permitan una mejora de la estabilidad de una región a la que estamos indisolublemente unidos

La FINUL reforzada, un actor imperfecto en un conflicto inconcluso

Análisis de las motivaciones, condiciones y posible evolución de la Fuerza Interina de Naciones Unidas en Líbano (FINUL) reforzada que ahora inicia su despliegue en Líbano. En un contexto estructuralmente tan complejo como el de Oriente Próximo, agudizado por el reciente estallido violento entre Israel y Hezbolá en territorio libanés, la resolución 1701, aprobada por unanimidad en el Consejo de Seguridad de Naciones Unidas el pasado 11 de agosto, es vista por algunos como el inicio de una nueva etapa que conducirá invariablemente a la paz regional. Frente a esa visión emerge otra que toma en cuenta que ninguna de las partes renuncia definitivamente a reemprender la violencia, que el núcleo fundamental del conflicto (el palestino-israelí) queda al margen de esta iniciativa, mientras los Territorios Palestinos continúan sumidos en uno de sus más graves periodos de crisis, y que la comunidad internacional sigue sin manifestar una sólida voluntad por implicarse directamente en la resolución de este largo conflicto. Vista así la situación, la FINUL no puede ser más que un parche, o un punto de apoyo en el mejor de los casos, para modificar las tendencias destructivas que desde hace demasiado tiempo vienen caracterizando a la zona

Superconducting properties of the attractive Hubbard model

A self-consistent set of equations for the one-electron self-energy in the ladder approximation is derived for the attractive Hubbard model in the superconducting state. The equations provide an extension of a T-matrix formalism recently used to study the effect of electron correlations on normal-state properties. An approximation to the set of equations is solved numerically in the intermediate coupling regime, and the one-particle spectral functions are found to have four peaks. This feature is traced back to a peak in the self-energy, which is related to the formation of real-space bound states. For comparison we extend the moment approach to the superconducting state and discuss the crossover from the weak (BCS) to the intermediate coupling regime from the perspective of single-particle spectral densities.Comment: RevTeX format, 8 figures. Accepted for publication in Z.Phys.

Curvature effects on a simplified reaction-diffusion model of biodegradation

The biodegradation process of some types of polymers occurs due to many different factors including their morphology, structure and chemical composition. Although this is a complicated process, most of its important stages like the diffusion of monomers and the hydrolysis reactions have been modeled phenomenologically through reaction-diffusion equations, where the properties of the polymers were encompassed. Using a simplified reaction-diffusion model for the biodegradation of polymers, in this contribution we study the possible effects of the curvature of the system’s geometry in the degradation process, which is characterized by the interaction of the corresponding reaction rate and the diffusion coefficient. To illustrate the problem of diffusion on a curved surface we consider the surface of a cylinder and of the so-called Gaussian bump. We show how the degradation process is affected by the curvature of the system for the simplified model

Winding Strings in AdS_3

Correlation functions of one unit spectral flowed states in string theory on AdS_3 are considered. We present the modified Knizhnik-Zamolodchikov and null vector equations to be satisfied by amplitudes containing states in winding sector one and study their solution corresponding to the four point function including one w=1 field. We compute the three point function involving two one unit spectral flowed operators and find expressions for amplitudes of three w=1 states satisfying certain particular relations among the spins of the fields. Several consistency checks are performed.Comment: 35 pages. v2. Important additions: one more author, complete results for the 3-point function with two w=1 states and new section with computation of 4-point function with one w=1 state. Acknowledgments and references modifie

Fourier Method for Approximating Eigenvalues of Indefinite Stekloff Operator

We introduce an efficient method for computing the Stekloff eigenvalues associated with the Helmholtz equation. In general, this eigenvalue problem requires solving the Helmholtz equation with Dirichlet and/or Neumann boundary condition repeatedly. We propose solving the related constant coefficient Helmholtz equation with Fast Fourier Transform (FFT) based on carefully designed extensions and restrictions of the equation. The proposed Fourier method, combined with proper eigensolver, results in an efficient and clear approach for computing the Stekloff eigenvalues.Comment: 12 pages, 4 figure

Infrared spectra of one- and two-dimensional fullerene polymer structures: RbC60 and rhombohedral C-60

We compare the infrared spectra of two types of fullerene polymers: the linear-chain RbC60 and the two-dimensional pressure-polymerized rhombohedral C-60. Both the splitting of the F-1u modes and the structure of newly activated Lines are in agreement with fully ordered structures of molecular symmetry D-2h and D-3d, respectively

Vibrational spectra of C60C8H8 and C70C8H8 in the rotor-stator and polymer phases

C60-C8H8 and C70-C8H8 are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C60C8H8) and poly(C70C8H8) resulting from a solid state reaction occurring on heating. Based on the spectra we propose a connection pattern for the fullerene in poly(C60C8H8), where the symmetry of the C60 is D2h. On illuminating the C60-C8H8 cocrystal with green or blue light a photochemical reaction was observed leading to a similar product to that of the thermal polymerization.Comment: 26 pages, 8 figures, to appear in Journal of Physical Chemistry B 2nd version: minor changes in wording, accepted version by journa

Distortion of the QRS in elderly patients with myocardial infarction

Background: Distortion of the terminal portion of the QRS in the initial electrocardiogram (ECG) is a strong predictor of adverse outcome in myocardial infarction. Our purpose is to assess the relationship of distortion of QRS and other ECG characteristics with older age. Methods and results: We analysed 634 consecutive patients (age 62.6 &#177; 13.7, 77% male) admitted in the first 12 hours of ST-elevation myocardial infarction. Two groups of age were defined: < 75 years-old and &#8805; 75 years-old. Additionally, we defined two ECG groups according to the presence of ST segment elevation with distortion of the terminal portion of the QRS in two or more adjacent leads (QRS+) or the absence of this pattern (QRS&#8211;). Older people had more often QRS+ (30% vs. 20%, p = 0.023). The older group with QRS+ had an in-hospital mortality of 18%, vs. 7% with QRS&#8211; (p = 0.04), and an incidence of major adverse events of 40% vs. 14% (p = 0.002). In the multivariate analysis, age &#8805; 75 years was an independent predictor of distortion of the QRS (odds ratio 2.1, 1.2&#8211;4.9, p = 0.016). Conclusions: The distortion of the terminal portion of the QRS in myocardial infarction is more frequent in elderly people, and is significantly related to adverse prognosis. This ECG finding can be helpful to promptly stratify the risk in elderly patient