Role of Network Topology in the Synchronization of Power Systems

We study synchronization dynamics in networks of coupled oscillators with bimodal distribution of natural frequencies. This setup can be interpreted as a simple model of frequency synchronization dynamics among generators and loads working in a power network. We derive the minimum coupling strength required to ensure global frequency synchronization. This threshold value can be efficiently found by solving a binary optimization problem, even for large networks. In order to validate our procedure, we compare its results with numerical simulations on a realistic network describing the European interconnected high-voltage electricity system, finding a very good agreement. Our synchronization threshold can be used to test the stability of frequency synchronization to link removals. As the threshold value changes only in very few cases when aplied to the European realistic network, we conclude that network is resilient in this regard. Since the threshold calculation depends on the local connectivity, it can also be used to identify critical network partitions acting as synchronization bottlenecks. In our stability experiments we observe that when a link removal triggers a change in the critical partition, its limits tend to converge to national borders. This phenomenon, which can have important consequences to synchronization dynamics in case of cascading failure, signals the influence of the uncomplete topological integration of national power grids at the European scale.Comment: The final publication is available at http://www.epj.org (see http://www.springerlink.com/content/l22k574x25u6q61m/

La infraestructura verda en el sistema territorial metropolità. Anàlisi comparada de diferents àrees metropolitanes i elements estratègics per l'Àrea Metropolitana de Barcelona

En aquest document es vol contribuir al debat actual sobre quin ha de ser el paper dels espais naturals protegits, de les zones agrícoles i dels verds urbans, per tal d'articular una Infraestructura Verda funcional a l'Àrea Metropolitana de Barcelona (AMB). En tenir en compte els exemples de cinc metròpolis seleccionades (Randstad, Montpeller, Paris, Milà, Toronto) es pretenen definir les possibles variants en la gestió territorial de la Infraestructura Verda en diferents contexts, així com el caràcter canviant de la relació societat-naturalesa, tant en el propi espai urbà i com en el seu entorn proper. L'estudi de les experiències de cinc metròpolis de referència traça el camí per a descriure quins poden ser els elements estratègics per a una Infraestructura Verda a la metròpoli de Barcelona. És d'interès concretar amb quin pes s'aplica el concepte de la Infraestructura Verda en diverses polítiques metropolitanes. Noves bases conceptuals com ara el metabolisme social, l'economia social solidària o la sobirania alimentària, definiran una línia d'actuació i participació que acompanyaran al planejament com a eina per la defensa d'aquests nous paradigmes.With this document we want to contribute to the current debate about what has to be the role for natural spaces, protected spaces, agricultural spaces and urban green spaces, so as to articulate a working Green Infrastructure at the Àrea Metropolitana de Barcelona (AMB). Counting on the example of five selected metropolises (Randstad, Montpeller, Paris, Milà, Toronto) we try to define all possible variations in territorial management of the Green Infrastructure in different environments, and also the ever changing characteristics in society-nature relationship, be in the same urban space or its closest surroundings. The study about experiences in those five metropolises sets the way to describe whose can be the strategic elements for a Green Infrastructure in metropolitan Barcelona. It is of interest to set the importance of Green Infrastructure in various metropolitan policies. New concepts such as social metabolism, social and solidarity economy or food sovereignty will define a line of action and participation to go with planning as a tool to stand for these new models

Emergence of structural patterns out of synchronization in networks with competitive interactions

Synchronization is a collective phenomenon occurring in systems of interacting units, and is ubiquitous in nature, society and technology. Recent studies have enlightened the important role played by the interaction topology on the emergence of synchronized states. However, most of these studies neglect that real world systems change their interaction patterns in time. Here, we analyze synchronization features in networks in which structural and dynamical features co-evolve. The feedback of the node dynamics on the interaction pattern is ruled by the competition of two mechanisms: homophily (reinforcing those interactions with other correlated units in the graph) and homeostasis (preserving the value of the input strength received by each unit). The competition between these two adaptive principles leads to the emergence of key structural properties observed in real world networks, such as modular and scale–free structures, together with a striking enhancement of local synchronization in systems with no global order

La infraestructura verda en el sistema territorial metropolità. Anàlisi comparada de diferents àrees metropolitanes i elements estratègics per l'Àrea Metropolitana de Barcelona

En aquest document es vol contribuir al debat actual sobre quin ha de ser el paper dels espais naturals protegits, de les zones agrícoles i dels verds urbans, per tal d'articular una Infraestructura Verda funcional a l'Àrea Metropolitana de Barcelona (AMB). En tenir en compte els exemples de cinc metròpolis seleccionades (Randstad, Montpeller, Paris, Milà, Toronto) es pretenen definir les possibles variants en la gestió territorial de la Infraestructura Verda en diferents contexts, així com el caràcter canviant de la relació societat-naturalesa, tant en el propi espai urbà i com en el seu entorn proper. L'estudi de les experiències de cinc metròpolis de referència traça el camí per a descriure quins poden ser els elements estratègics per a una Infraestructura Verda a la metròpoli de Barcelona. És d'interès concretar amb quin pes s'aplica el concepte de la Infraestructura Verda en diverses polítiques metropolitanes. Noves bases conceptuals com ara el metabolisme social, l'economia social solidària o la sobirania alimentària, definiran una línia d'actuació i participació que acompanyaran al planejament com a eina per la defensa d'aquests nous paradigmes.With this document we want to contribute to the current debate about what has to be the role for natural spaces, protected spaces, agricultural spaces and urban green spaces, so as to articulate a working Green Infrastructure at the Àrea Metropolitana de Barcelona (AMB). Counting on the example of five selected metropolises (Randstad, Montpeller, Paris, Milà, Toronto) we try to define all possible variations in territorial management of the Green Infrastructure in different environments, and also the ever changing characteristics in society-nature relationship, be in the same urban space or its closest surroundings. The study about experiences in those five metropolises sets the way to describe whose can be the strategic elements for a Green Infrastructure in metropolitan Barcelona. It is of interest to set the importance of Green Infrastructure in various metropolitan policies. New concepts such as social metabolism, social and solidarity economy or food sovereignty will define a line of action and participation to go with planning as a tool to stand for these new models

Resultados en el tratamiento del ictus en hospitales con y sin Unidad de Ictus.

Organisational capacity in terms of resources and care circuits to shorten response times in new stroke cases is key to obtaining positive outcomes. This study compares therapeutic approaches and treatment outcomes between traditional care centres (with stroke teams and no stroke unit) and centres with stroke units. We conducted a prospective, quasi-experimental study (without randomisation of the units analysed) to draw comparisons between 2 centres with stroke units and 4 centres providing traditional care through the neurology department, analysing a selection of agreed indicators for monitoring quality of stroke care. A total of 225 patients participated in the study. In addition, self-administered questionnaires were used to collect patients' evaluations of the service and healthcare received. Centres with stroke units showed shorter response times after symptom onset, both in the time taken to arrive at the centre and in the time elapsed from patient's arrival at the hospital to diagnostic imaging. Hospitals with stroke units had greater capacity to respond through the application of intravenous thrombolysis than centres delivering traditional neurological care. Centres with stroke units showed a better fit to the reference standards for stroke response time, as calculated in the Quick study, than centres providing traditional care through the neurology department