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 24 publications 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: 2017
  • Climate treaty: Pricing would limit carbon rebound (2015)

    van den Bergh, Jeroen (UAB)

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    This commentary was written as an advice to the negotations for a climate agreement at the COP21 climate summit in Paris (30 November - 13 December 2015). It raised attention for a neglected issue, namely carbon rebound of climate strategies in the absence of an adequate climate treaty. Energy rebound denotes that saving energy through technological improvements or behavioral changes triggers indirect, additional energy use. Various mechanisms contribute to this: e.g., improvements in energy efficiency make associated energy services cheaper which increases their consumption; saving energy means often saving money which is then spent on other energy-using goods or services; and more energy-efficient technologies diffuse easily to new types of uses or sectors.

    Unilateral national climate policies are not strict enough to control carbon rebound — a side effect of some energy conservation strategies that undercuts net carbon savings. I suggest that a global agreement on variable carbon pricing at the forthcoming climate summit in Paris would reap considerable rebound-related benefits.

    Economy-wide studies indicate that overall carbon rebound is at least 50%, depending on the country (J. Dimitropoulos Energy Policy 35, 6354–6363; 2007). Despite this, the effects of rebound have been largely ignored by the Intergovernmental Panel on Climate Change and at United Nations climate meetings.

    Technical standards do not control rebound effectively: they cover only a small subset of products. For example, when the European Union began phasing out incandescent light bulbs in 2009, light-emitting diodes became so widespread that any energy savings were reduced.

    The most effective way to discourage rebound is through carbon pricing, a policy that underpins all potential energy saving decisions. Any rebound tendency would elicit a higher carbon price under a cap-and-trade permit scheme. A carbon tax would require frequent adjustment to achieve the same outcome. This would be difficult politically, especially in the form of nationally distinct taxes.

  • Ultrafast Graphene (2015)

    van Hulst, Niek F. (ICFO)
    Koppens, Frank (ICFO)

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    The efficient conversion of light into electricity plays a crucial role in many technologies, ranging from cameras to solar cells. It also forms an essential step in data communication applications, since it allows for information carried by light to be converted into electrical information that can be processed in electrical circuits. Graphene is an excellent material for ultrafast conversion of light to electrical signals, but so far it is not known how fast graphene responds to ultrashort flashes of light.

    Researchers at ICFO, in collaboration with MIT & UC Riverside, have developed a graphene-based photodetector capable of converting absorbed light into an electrical voltage at ultrafast timescales. The new device combines the ICFO expertise in both ultrafast pulse shaping and graphene electronics. Finally, facilitated by graphene’s nonlinear photo-thermoelectric response, these elements enabled the observation of femtosecond photodetection response times.

    The ultrafast creation of a photovoltage in graphene is possible due to the extremely fast and efficient interaction between all conduction band carriers in graphene. This interaction leads to a rapid creation of an electron distribution with an elevated electron temperature. Thus, the energy absorbed from light is efficiently and rapidly converted into electron heat. Next, the electron heat is converted into a voltage at the interface of two graphene regions with different doping. This photo-thermoelectric effect turns out to occur almost instantaneously, thus enabling the ultrafast conversion of absorbed light into electrical signals and opening new pathways towards ultra-fast optoelectronic conversion. Clearly, graphene photodetectors show fascinating performances addressing a wide range of applications.

  • A transcription factor that promotes the formation of tumours in the colon (2014)

    Batlle Gómez, Eduard (IRB Barcelona)

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    Constitutive activation of WNT signalling in the intestinal epithelium by mutations in genes encoding pathway components such as APC or beta-catenin leads to the formation of adenomas. These precancerous lesions are prevalent in the population and represent the substrate from which colorectal cancer (CRC) develops. An alternative pathway leading to the formation of intestinal tumours is initiated by mutational inactivation of the bone morphogenetic protein (BMP) signalling pathway. Individuals with germline mutations in BMP pathway components such as BMPRI or SMAD4 develop hamartomatous polyps, benign outgrowths of the epithelium that confer high risk of CRC. In addition, genome wide association studies of CRC have identified about 30 common low-risk susceptibility variants, four of which map in genomic regions located near the locus encoding BMP pathway components SMAD7, GREM1, BMP4 and BMP7. In this work, we screen for genes required for maintaining the tumour stem cell phenotype and identify the zinc-finger transcription factor GATA6 as a key regulator of the WNT and BMP pathways in CRC. GATA6 directly drives the expression of bona-fide stem cell maker LGR5 in adenoma stem cells whereas it restricts BMP signaling to differentiated tumour cells. We show that the genetic deletion of Gata6 from mouse colon adenomas increases the levels of BMP factors, which signal to block self-renewal of tumour stem cells. In human tumours, GATA6 competes with beta-catenin/TCF4 for binding to a distal regulatory region of the BMP4 locus that has been linked to increased susceptibility to development of CRC. Therefore, GATA6 creates an environment permissive for CRC initiation by lowering the threshold of BMP signalling required for tumour stem cell expansion.

  • Crosstalk between Non-coding RNAs in Cancer Cells (2014)

    Esteller Badosa, Manel (IDIBELL)

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    When we talk about genetic material, we are usually referring to the DNA (deoxyribonucleic acid) that we inherit from our parents. This DNA is the factory where is built a similar molecule called RNA (ribonucleic acid) which produces our proteins, such as hemoglobin or insulin , allowing the lives of our cells. But there is a special group called non-coding RNA that has a more enigmatic function. The best known are microRNAs, tiny molecules that are responsible for turning on or off our genome like an electrical current switch. The article published in the prestigious journal Molecular Cell by Manel Esteller, Director of Epigenetics and Cancer Biology Program of the Bellvitge Biomedical Research Institute (IDIBELL), ICREA researcher and Professor of Genetics at the University of Barcelona, provides a twist over this mystery. Research shows that there is a second type of non-coding RNA, called ultra-conserved RNA that acts as switches switch, ie, controls the activity of microRNAs."Who watches the watchers? This was one of the issues that the researchers set at the beginning of the research. They found that special molecules called ultra-conserved RNA were not produced in human tumors and this contributed to their growth, but we knew nothing about this mechanism. It should be an important role because these molecules are highly conserved in evolution and there is no variation from chickens to humans. The researchers realized ultraconservated RNAs attached to the other family of non-coding RNAs, microRNAs, as a magnet and prevented its function. That is, they are the police internal affairs officers who supervise the battle soldiers in healthy cells. If a cell fails to produce the ultraconserved RNA, microRNA gets altered and hundreds of genes that should maintain cellular balance become disrupted, and thus contributes to the formation of human tumors.The results obtained by the group of Dr. Esteller in the Molecular Cell article are very important for understanding the function of the dark genome. Deciphering encrypted codes of cellular activity in these sequences of our DNA represents one of the most exciting challenges of modern biology. This cutting edge research is beginning to bear its first fruits in the field of medical research such as that described ultraconservated RNA is related with cancer development. 

  • The advantages of order in Biology: Cell membranes exploit hierarchical order to efficiently internalize pathogens (2014)

    García Parajo, Maria F. (ICFO)

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    Dendritic cells are the first line of fighters in our body against infections and foreign pathogens. These cells are equipped with a battery of receptors designed to recognize and uptake pathogens for further degradation. Amongst them, the pathogen recognition receptor DC-SIGN does this job with amazing efficiency and versatility. Previous work from our group found that organization of this receptor in small nanoclusters on the cell surface of dendritic cells was crucial for binding DC-SIGN to viruses, including HIV. Other molecules called glycans (sugars with different branching structures) which are ubiquitously present in the cell membrane, have the potential to interact with glycosylated proteins such as DC-SIGN, but until now their role on DC-SIGN was completely unknown. Using a combination of super-resolution imaging techniques and dual-color single-particle tracking, we visualized the organization of DC-SIGN on cells of the immune system at multiple spatial and temporal scales. Our study revealed that DC-SIGN organizes in a highly hierarchical fashion on cell the membrane (from the nano- to the meso-scale) exploring regions that are enriched with sites for endocytosis. Intriguingly, extracellular glycans micro-patterned the receptor in regions of around 1 μm in size. In turn, this micro-patterning corralled DC-SIGN into clathrin active regions (the primary internalization pathway in mammalian cells). This preferred organization increases the probability of internalizing virus pathogens for subsequent processing and degradation by dendritic cells. This work, carried out in collaboration with a team of scientists from the Radboud University Medical Center in Nijmegen, the Netherlands, has been published in PNAS this year and recommended by the Faculty of 1000 as an important paper that provides new findings in biology by means of technically advanced imaging instrumentation. Understanding how the cells of our immune system recognize and fight against pathogens is of key importance to human health. This work demonstrates that efficient pathogen binding and uptake crucially depends on how receptors organize on the cell membrane, providing clear guidelines for the design of new therapeutic drugs against infections. It is also a clear example on how Nature has devised strategies to optimize cellular function using concepts of compartmentalization and molecular modularity.

  • Prediction of tunable plasmons in atomically thin gold nanodisks (2014)

    Garcia de Abajo, Francisco Javier (ICFO)

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    The ability to modulate light at high speeds is of paramount importance for telecommunications, information processing and medical imaging technologies. This has stimulated intense efforts to master optoelectronic switching at visible and near-infrared frequencies, although coping with current computer speeds in integrated architectures still remains a major challenge. As a partial success, mid-infrared light modulation has been recently achieved through gating patterned graphene. Here we show that atomically thin noble metal nanoislands can extend optical modulation to the visible and near-infrared spectral range. We find plasmons in thin metal nanodisks to produce similar absorption cross-sections as spherical particles of the same diameter. Using realistic levels of electrical doping, plasmons are shifted by about half their width, thus leading to a factor-of-two change in light absorption. These results, which we substantiate on microscopic quantum theory of the optical response, hold great potential for the development of electrical visible and near-infrared light modulation in integrable, nanoscale devices. 

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