Cada año, un comité de expertos debe acometer una ardua tarea: de entre todas las publicaciones de ICREA, debe escoger unas cuantas que destaquen del resto. Es todo un reto: a veces los debates se acaloran, y siempre son difíciles, pero acaba saliendo una lista de 24 publicaciones. No se concede ningún premio, y el único reconocimiento adicional es el honor de ser resaltado en la web de ICREA. Cada publicación tiene algo especial, ya sea una solución especialmente elegante, un éxito espectacular en los medios de comunicación o la simple fascinación por una idea del todo nueva. Independientemente de la razón, se trata de los mejores de los mejores y, como tales, nos complace compartirlos aquí.


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  • European seasonal mortality and influenza incidence due to winter temperature variability (2016)

    Rodó i López, Xavier (IC3)

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    European seasonal mortality and influenza incidence due to winter temperature variability

    Adaptation measures taken by different countries to adapt to climate change have resulted in different levels of vulnerability of their population to air temperatures. This is one of the new results of a study led by scientists at the Catalan Institute of Climate Sciences (IC3), and the Universities of Monpetller and Geneva.

    The study also shows that extreme winters are not directly related to seasonal mortality increases nor to flu rises, in countries like the United Kingdom, Belgium and the Netherlands. Conversely, all other countries show different levels of response as a function of the season’s severity. Another interesting result describes the role of low temperatures on mortality rates in the European population, with other factors influencing winter mortality, like hypothermia, hypertension, thrombosis, pneumonia and flu. Not surprisingly, Mediterranean countries are those more vulnerable to low temperatures, with Portugal, Spain and Italy being 7, 4 and 3 times more sensitive to winter temperatures than central Europe countries.

    The study was performed on more than 160 regions, belonging to 16 countries in western Europe, representing more than 400 million people. These new results therefore highlight the key role played by adaptation measures to environmental temperatures. Similarly the variety in the degree of vulnerability to low temperatures can serve to better identify which measures would be more effective to counterbalance the effects exerted by climate change and help mitigate the associate burden in terms of morbidity and mortality.

  • Neurons find order in the noise (2016)

    Sánchez-Vives, María Victoria (IDIBAPS)

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    Neurons find order in the noise


    High temporal precision sometimes emerges from noisy systems. This is often the case in recurrent networks of dynamic elements (from ionic channels to genes or lasers) that can exhibit emergent collective oscillations of substantial regularity even when the individual elements are considerably noisy. This phenomenon is called stochastic coherence and it can be observed in a large number of systems, for example, in dynamics of global climate. However, how noise-induced dynamics at the local level coexists with regular oscillations at the global level is still unclear. Here we studied the slow oscillation regime exhibited by the cerebral cortex network. Slow oscillations constitute a cortical state consisting of periods of activity or neuronal firing that are interspersed with periods of neuronal silence that alternate at a frequency of around 1 Hz (see Figure). Slow oscillations emerge from the recurrent interaction between cortical neurons, making them a network phenomenon.

    In a model of the cortical network, we observed that a combination of stochastic recurrence-based initiation with deterministic refractoriness lead to maximum collective coherence for an intermediate noise level, such that noise-induced dynamics at the local level coexisted with regular oscillations at the global level. Computational analysis of a biologically realistic network model revealed that an intermediate level of background noise lead to quasi-regular dynamics. We verified this prediction experimentally in cortical slices subject to varying amounts of extracellular potassium, which modulates neuronal excitability and thus synaptic noise (see Figure insets). For intermediate noise (or extracellular potassium) levels, the regularity of the slow oscillation was maximum. Furthermore, there was not only a maximum temporal but also spatial regularity. Taken together, these results allow us to construe the high regularity observed experimentally in the brain as an instance of collective stochastic coherence.




  • The hidden geometry of international trade (2016)

    Serrano, M. Ángeles (UB)

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    The hidden geometry of international trade

    International trade moves billions of euros annually and is one of the key mechanisms in the process of globalization. Its representation as a network of nodes and connections, where nodes are countries and the connections between them correspond to import and export relationships, reveals a complex architecture characterized by typical features of complex networks in different domains. Although the famous gravity model of trade reproduces flows well, it is unable to predict the existence of connections and, therefore, to explain the complex structure of the international trade network

    In our work, we combine economic size and the different dimensions that affect distance in international trade beyond mere geography to produce the World Trade Atlas 1870-2013 (, a collection of annual world trade maps. Trade distances in these maps, based on a gravity model predicting the existence of significant trade channels, are such that the closer countries are in the hyperbolic trade space, the greater their chance of becoming connected. The atlas provides us with information regarding the long-term evolution of the international trade system and demonstrates that, in terms of trade, the world is not flat but hyperbolic, as a reflection of its complex architecture. The departure from flatness has been increasing since World War I, meaning that differences in trade distances are growing and trade networks are becoming more hierarchical. Smaller-scale economies are moving away from other countries except for the largest economies; meanwhile those large economies are increasing their chances of becoming connected worldwide. At the same time, Preferential Trade Agreements do not fit in perfectly with natural communities within the trade space and have not necessarily reduced internal trade barriers. We discuss an interpretation in terms of globalization, hierarchization, and localization; three simultaneous forces that shape the international trade system.

  • Magneto-electric effect in the simplest copper oxide revealed (2016)

    Skumryev, Vassil (UAB)

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    Magneto-electric effect in the simplest copper oxide revealed

    Magnetism and ferroelectricity are essential to many areas of technology and the quest for multiferroic materials, where these two phenomena coexist, is of immense industrial and fundamental importance. Magnetically-induced ferroelectrics (i.e., multiferroics) constitute an exciting new paradigm in the design of functional materials by intimately coupling magnetic and polar orders. Apart from being so far the only known binary multiferroic compound, the cupric oxide CuO has a much higher transition temperature into the multiferroic state, 230 K, than any other known material in which the electric polarization is induced by spontaneous magnetic order. However, until now no magneto-electric effect has been observed as direct crosstalk between bulk magnetization and electric polarization counterparts, prompting to label CuO as “material with persistent multiferroicity without magneto-electric effects”.

    We have demonstrated that sufficiently high magnetic fields of up to 50 tesla are able to suppress the helical modulation of the magnetic moments in the multiferroic phase and dramatically affect the electric polarization. Furthermore, just below the spontaneous magnetic transition from commensurate (paraelectric) to incommensurate (ferroelectric) magnetic structures at 213 K, even modest magnetic fields can induce a transition into magnetic structure compatible with ferroelectricity and then suppress it at higher fields, thus causing remarkable polarization changes. The synergic use of number of experimental techniques at large scale European facilities (the Eur. Magnetic Field Laboratory; Laue Langevin Inst.) allowed tracing the magnetoelectric phase diagram of CuO, identifying new phase transitions and magnetic structures.

    This study, conceived and coordinated by ICREA researcher Vassil Skumryev, was carried out in collaboration with scientists from Russia, France, Germany, Brazil and Bulgaria. It adds substantial new knowledge, unveiling important new features of this prominent simple oxide with distinct position among the multiferroic materials and of general interest for material scientists and physicists.


    Sotomayor Torres, Clivia Marfa (ICN2)

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    Phonons are lattice vibration arising from collective atomic motion and one of the questions popping up is whether the associated physical properties can be explained by the particle picture or by the wave nature of these excitations. Why does this matter? It matters since it is intimately related to energy dissipation, rendering inadequate attempts to transmit useful signals, from few GHz to 100s of THz impacting, e.g., information processing.

    We investigated propagating phonons in two-dimensional silicon crystals with various positional disorder of otherwise periodically positioned holes, to ascertain to what degree disorder matters in their propagation, since they carry most of the heat in semiconductors materials, underpinning today’s (opto)electronics and nanoelectronics. We used a state-of-the-art pump-and-probe spectroscopy (see fig. 1) and a home-built two-laser Raman thermometry (2LRT) set up to extract the thermal conductivity. We measure at room temperature and simulate by finite element methods. We found that disorder lowers phonon energies and facilitates their in-plane propagation becoming impervious to disorder.  Surprisingly, disorder was found to be unaffected by disorder. We thus propose a practical criterion for predicting phonon coherence as a function of roughness and disorder: (i) phonon coherence is unaffected if the roughness R is smaller than 1/25 of the phonon wavelength and (ii) phonon coherence is destroyed if R is greater than 1/10 of the phonon wavelength.

    Our results have repercussions well beyond our own research in nano-scale thermal transport and thermoelectricity. They provide a hint to the factors affecting vibrational energy transport in condensed matter with variations in the nm-scale, the length scale of acoustic phonons relevant to electronics but also to biology.

  • Increase of protein abundance induces formation of cytotoxic assemblies (2016)

    Tartaglia, Gian Gaetano (CRG)
    Lehner, Ben (CRG)

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    Increase of protein abundance induces formation of cytotoxic assemblies

    From birth to degradation, RNA is bound to proteins. When the abundance of specific proteins increases, RNA is sequestered in large assemblies or granules. We investigated the physico-chemical principles promoting formation of granules and observed toxicity when the assemblies are formed in non-physiologial conditions.  Indeed, trapping molecules in granules prevents RNA from translation, which perturbes cell functions and impairs general homeostasis. Our work sheds light on the molecular mechanisms behind  processes that lead to devastating human diseases.