Highlights

Every year, a committee of experts sits down with a tough job to do: from among all ICREA publications, they must find a handful that stand out from all the others. This is indeed a challenge. The debates are sometimes heated and always difficult but, in the end, a shortlist of  the most outstanding publications of the year is produced. No prize is awarded, and the only additional acknowledge is the honour of being chosen and highlighted by ICREA. Each piece has something unique about it, whether it be a particularly elegant solution, the huge impact it has in the media or the sheer fascination it generates as a truly new idea. For whatever the reason, these are the best of the best and, as such, we are proud to share them here.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: yyyy

  • Was it me who was speaking? Virtual body ownership can cause illusory agency (2014)

    Slater, Mel (UB)

    view details
    CLOSE

    Was it me who was speaking? Virtual body ownership can cause illusory agency

    Normally we trivially distinguish between acts that we execute ourselves from those carried out by other people, our sense of agency over our own actions. Neuroscientists have developed theories of agency based on the intention to act followed by observation of the sensory consequences of the act - if these match then this is one element of the attribution of self agency to the act. Cause should precede effect, in other words the act and its consequences should follow normal common sense rules of causality. There should be no other obvious explanation for the effect, and a strong temporal binding between execution of the act and observation of the consequences of the act itself. We carried out an experiment showing that it is possible to trick the brain into the illusion that the participants were speaking when they were not. Participants wore a head-tracked head-mounted display and a full body motion capture suit that placed them in an immersive virtual reality. When they looked down towards their own body they saw a virtual body instead, which was also reflected back to them in a virtual mirror. In one experimental condition their virtual body moved synchronously with their real body movements, as captured by the motion capture suit. In another condition the virtual body moved independently of real body movements. From previous results we expected that those in the synchronous condition would experience the illusion that the virtual body was their body. This is referred to in the literature as the illusion of body ownership. After a few minutes of moving around with synchronous or asynchronous virtual body movements, the virtual body spoke some words. We found that those in the synchronous condition had the illusion that it was they who had spoken the words (even though they had said nothing). Moreover, the voice of their virtual body had a higher fundamental frequency than the real voices of the participants. Those who had experienced the synchronous moving body also later spoke with a higher fundamental frequency after their experience compared with before. Our conclusion is that a strong illusion of ownership over a virtual body can lead to the illusory attribution of agency to acts carried out solely by that virtual body. As we become represented more and more by online characters or operate tele-present robots, we must understand agency scientifically, to avoid the profound legal and ethical problems associated with self-attribution of agency to acts that w

  • OPTOMECHANICAL CRYSTALS (2014)

    Sotomayor Torres, Clivia Marfa (ICN2)

    view details
    CLOSE

    OPTOMECHANICAL CRYSTALS

    Photon-phonon interactions occur in a plethora of physical systems and phenomena such as Brillouin scattering and Raman scattering. In systems supporting both optical and mechanical resonances, these types of interaction are called optomechanical coupling. There are optomechanical systems of sizes ranging from kilometere-long interferometers, intended for gravitational waves detection, to clouds of a few atoms. Whilst optomechanical coupling is inherently weak, it can be greatly enhanced by engineering the simultaneous confinement of light and sound in cavities with characteristic dimensions in the wavelength and sub-wavelength range. This approach, known as Cavity Optomechanics, enables efficient transfer of energy from an electromagnetic field to matter vibrations (and vice versa), thereby providing unprecedented coherent control of phonons. We have combined our expertise in photonic and phononic crystals to design, fabricate and characterise an optomechanical crystals based on a corrugated beam with holes that acts as a high-quality optical cavity for telecommunication-range light and a mechanical cavity for GHz phonons. The co-localization or spatial overlap of light and sound in the same micrometre cubic volume has enabled us to achieve a strong optomechanical coupling leading to novel findings at room temperature including the experimental verification of phonon-lasing. In fact, our contributions constitute two milestones in cavity optomechanics. Firstly, we have demonstrated for the first time optomechanically coupled phonons have been placed in a complete phonon bandgap, thus minimizing the limits otherwise experience by devices due to mechanical losses through clamping and improving the coherent lifetime of the confined phonons, both crucial for coherent manipulation of mechanical states and for the controlled generation of coherent phonons with light, also known as Optomechanically-Mediated Phonon Lasing. Moreover, we decoupled the design parameters of the optical and mechanical cavities, thus demonstrating a practical advantage that overcomes the historical limitations that kept optomechanical crystals designs limited to a few examples.  Our Nature Communications paper reporting these findings has been selected as a “Research Highlight” in Nature Photonics , Vol. 7, p. 746 (2014), DOI: 10.1038/nphoton.2014.229.

  • Monograph "Analytic Capacity, the Cauchy Transform, and Non-homogeneous Calderón-Zygmund Theory" (2014)

    Tolsa Domènech, Xavier (UAB)

    view details
    CLOSE

    Monograph "Analytic Capacity, the Cauchy Transform, and Non-homogeneous Calderón-Zygmund Theory"

    The book "Analytic Capacity, the Cauchy Transform, and Non-homogeneous Calderón-Zygmund Theory", written by X. Tolsa, was published in 2014 by Birkhäuser in the series "Progress in mathematis". This text got the Ferran Sunyer i Balaguer Award in 2013.The book studies some of the groundbreaking advances in the field of geometric analysis that have been made regarding the notion of analytic capacity and its relationship to rectifiability in the decade 1995–2005. The Cauchy transform is an operator which plays a fundamental role in this area and is accordingly one of the main subjects covered. Another important topic, which may be of independent interest for many analysts, is the so-called non-homogeneous Calderón-Zygmund theory, the development of which has been largely motivated by the problems arising in connection with analytic capacity.The so called Painlevé problem was first posed around 1900 by the French mathematician and politician Paul Painlevé. This consists in finding a description of the removable singularities for bounded analytic functions in metric and geometric terms. One can think of removable singularities as invisible sets for this type of functions.Analytic capacity is a key tool in the study of the Painlevé problem. In the 1960s Anatoly Vitushkin conjectured that the removable sets which have finite length coincide with those which are purely unrectifiable. Moreover, because of the applications to the theory of uniform rational approximation, he posed the question as to whether analytic capacity is semiadditive. That is to say, is the analytic capacity of the union of two arbitrary sets in the plane smaller or equal than some universal constant times the sum of the analytic capacity of each set?This monograph presents full proofs of Vitushkin’s conjecture and of the semiadditivity of analytic capacity, both of which remained open problems until very recently. Other related questions are also discussed, such as the relationship between rectifiability and the existence of principal values for the Cauchy transforms and other singular integrals. The book is largely self-contained and should be accessible for graduate students in analysis, as well as a valuable resource for researchers.

  • SMUFIN, an innovative approach to find cancer associated mutations (2014)

    Torrents Arenales, David (BSC-CNS)

    view details
    CLOSE

    SMUFIN, an innovative approach to find cancer associated mutations

    Finding the relationship between genomic sequence variation and disease has been one of major focuses and challenges in biomedicine, as it allows the development of targeted diagnosis and therapy protocols. The possibility of easily decoding the sequence of genomes has recently pushed forward the understanding of disease at unprecedented levels, building the basis of personalized medicine, were each patient will be diagnosed and treated according to his particular genome context. In this sense, the identification of the genomic changes that lead to cancer is essential to understanding tumor variability and opens the door to more precise, personalized and efficient treatments, alternatives to the current unspecific and aggressive therapies. As the majority of tumors arise and evolve from changes (somatic mutations) in the genome of a single cell, current protocols for the identification of the genetic basis of oncogenesis consist of the sequencing and comparison of the genomes of cancer and healthy cells of the same individual. Despite the existence of protocols for finding these mutations and, although many cancer-driving mutations have been already found in tumor genomes, the analysis of cancer genomes still entails important challenges and limitations, leaving a significant number of cancer mutations undetected. In addition, existing protocols are computationally complex and expensive, restricting their use to a few centers with enough expertise and resources and leaving an important fraction of the community with no access to these kinds of protocols.   Our contribution to overcome these limitations consisted in developing SMUFIN, an innovative approach that compares tumor and normal genomes directly to identify nearly all types of somatic mutations potentially associated to cancer (from single nucleotide changes, to large chromosomal translocations) in a single execution. SMUFIN, compared to the other existing methods, is also much faster, as it is able to analyze multiple patients at a time and in less than 10 hours. The complete study, published in Nature Biotechnology, includes the positive evaluation of the performance of SMUFIN on different types of tumor genomes. SMUFIN was also able to identify types of complex chromosomal rearrangements, in Mantle Cell Lymphoma and Medulloblastoma samples that are invisible to the other methods and that had been related to aggressive tumors before.Taken together, SMUFIN constitutes the first realistic step forward in the analysis of gen

  • A new mechanism for wound healing (2014)

    Trepat, Xavier (IBEC)

    view details
    CLOSE

    A new mechanism for wound healing

    When we think of wound healing, we normally think of wounds to our skin. But wounds happen inside the body in all sorts of tissues and organs, and can have implications in many chronic diseases such as diabetes and asthma. Wounds also favour cancer progression by providing a physical and chemical environment that promotes the invasion of malignant cells.In this study, we designed a new way to decipher the mechanisms of wound healing, and by doing so we uncovered a new understanding of how cells move and work together to close a gap in a tissue.It had been known for a while that two different mechanisms contribute to wound healing. One is the ‘purse-string’ method, where a ring of contractile proteins forms at the edges of the wound and tightens like the strings of a purse. The other one is ‘cell crawling’, when cells themselves throw out ‘arms’ called lamellipodia to drag themselves along to close the gap. In some wounds, both mechanisms are thought to occur simultaneously, and in others, only one of the two is used.Here we pioneered a technique to measure the nano-scale forces behind wound healing. Using this technique, we discovered that the two currently accepted mechanisms are not sufficient to fully explain the phenomenon. Instead, we showed that a new mechanism applies in which cells assemble supracellular-contractile arcs that compress the tissue under the wound.By combining experiments and computational modeling, we showed that contractions arising from these arcs make the wound heal in a quicker and more robust way.Being able to optimize tissue repair is a major need for the treatment of acute and chronic diseases. The discovery of the basic mechanism reported in this study is a new step in the quest to achieve effective organ regeneration. 

  • Brightening up the photosynthetic complex (2014)

    van Hulst, Niek F. (ICFO)

    view details
    CLOSE

    Brightening up the photosynthetic complex

    Life on earth is essentially powered by the sun. Plants, bacteria and algae collect sunlight to store its energy and synthesize high energy molecular species: the process of photosynthesis. The photosynthetic complexes which harvest the sunlight transfer the light energy very effectively, with a remarkable transport efficiency, even above 90%. It is thought that nature exploits quantum concepts, such as coherence and delocalisation, to achieve the superior performance. Obviously the light-harvesting complexes are subject of intense study to learn these tricks of nature’s design. Yet, as such complexes did evolve for optimal light collection and transfer, they do not easily lose the light energy. Thus, they emit very little light, and it is hard to unveil their secrets.

    Fortunately artificial optical antennas can be designed to enhance the capture and emission of light. Particularly metal nanoantennas do confine light to the nanometer scale and do speed up the photocycle of light emission. Therefore metal nanoantennas seem ideal to address light-harvesting antenna complexes and prompt faster and brighter emission. This is exactly what we have done to brighten-up individual LH2-complexes of the purple bacteria.

    We have coupled single LH2-complexes resonantly to a gold nanoantenna. This way the fluorescence emission did speed up to 20 ps decay time and the quantum efficiency was enhanced from only a few percent to 50%. As a result almost 1000 times more emission was collected from a single complex.

    Using the bright photon emission of the bacterial complex we could look into its quantum properties at ambient conditions. To our surprise the bacterial complex revealed “anti-bunching” of photons: never two photons are emitted at the same time, the typical hallmark of a non-classical single-photon emitter. Finding quantum character in a room temperature bio-system is peculiar. Even more when one realizes that the LH2 complex contains 27 bacterio-chlorophylls coordinated in two rings with antenna molecules. The 27 molecules all cooperate to act jointly as one quantum system! Clearly the system is coupled and quantum transport plays a role in natural light-harvesting.

    Fascinating questions remain: do other biological processes exploit quantum effects; can we learn from nature in the development of more efficient solar cells?

Pages