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

Identifiability of large nonlinear biochemical networks

Dynamic models formulated as a set of ordinary differential equations provide a detailed description of the time-evolution of a system. Such models of (bio)chemical reaction networks have contributed to important advances in biotechnology and biomedical applications, and their impact is foreseen to increase in the near future. Hence, the task of dynamic model building has attracted much attention from scientists working at the intersection of biochemistry, systems theory, mathematics, and computer science, among other disciplines-an area sometimes called systems biology. Before a model can be effectively used, the values of its unknown parameters have to be estimated from experimental data. A necessary condition for parameter estimation is identifiability, the property that, for a certain output, there exists a unique (or finite) set of parameter values that produces it. Identifiability can be analysed from two complementary points of view: structural (which searches for symmetries in the model equations that may prevent parameters from being uniquely determined) or practical (which focuses on the limitations introduced by the quantity and quality of the data available for parameter estimation). Both types of analyses are often difficult for nonlinear models, and their complexity increases rapidly with the problem size. Hence, assessing the identifiability of realistic dynamic models of biochemical networks remains a challenging task. Despite the fact that many methods have been developed for this purpose, it is still an open problem and an active area of research. Here we review the theory and tools available for the study of identifiability, and discuss some closely related concepts such as sensitivity to parameter perturbations, observability, distinguishability, and optimal experimental design, among others.This work was funded by the Galician government (Xunta de Galiza) through the I2C postdoctoral program (fellowship ED481B2014/133-0), and by the Spanish Ministry of Economy and Competitiveness (grant DPI2013-47100-C2-2-P)

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

The cyclical trend of local public service governance: evidence from urban water management in Spain

The level of public and private involvement in economic activity in societies has changed over time. One may talk about the existence of a cyclical trend in which the most important periods of public governance are replaced by periods in which private management dominates the situation. This phenomenon may also be observed in local areas. Some authors have pointed out the existence of an alternation in the provision of municipal services, resulting in periods dominated by governance compared to other stages dominated by private management. In order to illustrate this cyclical trend at local level, this paper intends to analyze the evolution of the governance of the Spanish water supply since the mid-nineteenth century to the present day. Recent evidence from the industry suggests the possibility that we may currently be witnessing a further change in the trend.: Local Government, urban water supply, privatization, municipalization

Supply-Side Policies and the Zero Lower Bound

This paper examines how supply-side policies may play a role in fighting a low aggregate demand that traps an economy at the zero lower bound (ZLB) of nominal interest rates. Future increases in productivity or reductions in mark-ups triggered by supply-side policies generate a wealth effect that pulls current consumption and output up. Since the economy is at the ZLB, increases in the interest rates do not undo this wealth effect, as we will have in the case outside the ZLB. We illustrate this mechanism with a simple two-period New Keynesian model. We discuss possible objections to this set of policies and the relation of supply-side policies with more conventional monetary and fiscal policies.

Structural Identifiability Analysis via Extended Observability and Decomposition

7 páginasStructural identifiability analysis of nonlinear dynamic models requires symbolic manipulations, whose computational cost rises very fast with problem size. This hampers the application of these techniques to the large models which are increasingly common in systems biology. Here we present a method to assess parametric identifiability based on the framework of nonlinear observability. Essentially, our method considers model parameters as particular cases of state variables with zero dynamics, and evaluates structural identifiability by calculating the rank of a generalized observability-identifiability matrix. If a model is unidentifiable as a whole, the method determines the identifiability of its individual parameters. For models whose size or complexity prevents the direct application of this procedure, an optimization approach is used to decompose them into tractable subsystems. We demonstrate the feasibility of this approach by applying it to three well-known case studiesPeer reviewe

Parameter identifiability analysis and visualization in large-scale kinetic models of biosystems

[Background] Kinetic models of biochemical systems usually consist of ordinary differential equations that have many unknown parameters. Some of these parameters are often practically unidentifiable, that is, their values cannot be uniquely determined from the available data. Possible causes are lack of influence on the measured outputs, interdependence among parameters, and poor data quality. Uncorrelated parameters can be seen as the key tuning knobs of a predictive model. Therefore, before attempting to perform parameter estimation (model calibration) it is important to characterize the subset(s) of identifiable parameters and their interplay. Once this is achieved, it is still necessary to perform parameter estimation, which poses additional challenges.[Methods] We present a methodology that (i) detects high-order relationships among parameters, and (ii) visualizes the results to facilitate further analysis. We use a collinearity index to quantify the correlation between parameters in a group in a computationally efficient way. Then we apply integer optimization to find the largest groups of uncorrelated parameters. We also use the collinearity index to identify small groups of highly correlated parameters. The results files can be visualized using Cytoscape, showing the identifiable and non-identifiable groups of parameters together with the model structure in the same graph.[Results] Our contributions alleviate the difficulties that appear at different stages of the identifiability analysis and parameter estimation process. We show how to combine global optimization and regularization techniques for calibrating medium and large scale biological models with moderate computation times. Then we evaluate the practical identifiability of the estimated parameters using the proposed methodology. The identifiability analysis techniques are implemented as a MATLAB toolbox called VisId, which is freely available as open source from GitHub ( https://github.com/gabora/visid ).[Conclusions] Our approach is geared towards scalability. It enables the practical identifiability analysis of dynamic models of large size, and accelerates their calibration. The visualization tool allows modellers to detect parts that are problematic and need refinement or reformulation, and provides experimentalists with information that can be helpful in the design of new experiments.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 686282 (“CANPATHPRO”), from the EU FP7 project "NICHE" (ITN Grant number 289384), and from the Spanish MINECO project "SYNBIOFACTORY" (grant number DPI2014-55276-C5-2-R).Peer reviewe