Destacats

Cada any, un comitè d'experts s'ha d'enfrontar a la difícil tasca d'escolllir, d'entre totes les publicacions ICREA, unes poques que destaquin sobre la resta. És tot un repte: de vegades els debats s'acaloren, i sempre són difícils, però acaba sortint-ne una llista de 24 publicacions. No es concedeix cap premi, i l'únic reconeixement addicional és l'honor d'ésser presentat com a Highlight. Cada publicació té alguna cosa especial, sia una solució especialment elegant a un vell problema, un resó espectacular als mitjans de comunicació o simplement, la fascinació d'una idea revolucionària. Independentment del motiu, es tracta dels millors dels millors i, com a tals, ens plau compartir-los aquí.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: yyyy
  • The “DNA corrector” is more efficient in the most important regions of the genome (2017)

    López-Bigas, Núria (IRB Barcelona)

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    This work reveals that the mechanism that repairs errors in DNA is more efficient in the regions of genes that hold information for the production of proteins.

    The basic structure of genes is divided into exons and introns. The former holds the genetic sequences required to synthesize proteins, while most of the sequence of the latter hold less important information.

    When DNA is copied, the molecule called polymerase—responsible for replication—places one nucleotide after the other in the sister sequence following the original sequence, but from time to time the wrong nucleotide is incorporated, thus causing an error. These errors can be corrected by the DNA mismatch repair machinery.

    We showed that in tumors, with functional DNA mismatch repair machinery, exonic regions exhibit lower number of somatic mutations than expected. This decrease is not due to purifying selection. Instead, it can be explained by the enhanced activity of mismatch repair in exons compared to introns, a fact demonstrated by the lack of decrease in a type of paediatric brain cancer characterised by bialellic mismatch repair deficiency. The results of this work also suggest that the enhanced activity of mismatch repair in exons may be driven by the higher exonic levels of histone marks (H3K36me3).

    Mismatch repair system is conserved across evolution, which leads to the intriguing possibility that a combination of enhanced repair and purifying selection contributes to the observed lower exonic variation and divergence, both intra and inter-species. This has important implications for designing methods to study genic selection and for our understanding of the evolution of eukaryotic genes.

  • Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating (2017)

    Mantsinen, Mervi Johanna (BSC-CNS)

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    A new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas has been identified. These so-called ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. The potential of the method has been demonstrated on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen–deuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast 3He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, 3He-rich solar flares.

  • Towards quark matter from the fifth dimension (2017)

    Mateos, David (UB)

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    Quarks are the fundamental constituents of the protons and neutrons contained in the atoms that we and the things around us are made of. When quarks are compressed to the highest possible densities, even higher than those in atomic nuclei, the resulting form of matter is known as quark matter.

    Understanding the properties of quark matter is of great physical interest. A massive experimental effort is being devoted to this goal at particle colliders such as the Relativistic Heavy Ion Collider in Brookhaven (US) and at the Large Hadron Collider in Geneva (Switzerland). Moreover, quark matter may be naturally realized at the cores of neutron stars, the densest objects in the Universe, where gravity compresses quarks to densities that may be several times higher than those in atomic nuclei. The recent discovery of gravitational waves produced in neutron star collisions opens a new avenue for the study of the properties of quark matter.

    Despite its great physical interest, the theoretical study of quark matter by conventional, particle-physics methods is exceedingly difficult. For this reason, my group has resorted to a non-conventional method known as gauge/gravity duality.  The duality is a theoretical tool that maps the properties of quark matter in our four-dimensional world to those of … gravity in five dimensions! We have been able to build the first model in this context in which all the necessary ingredients are duly accounted for, and we have shown that it automatically incorporates several of the properties that quark matter is expected to have on general grounds. These results are hugely encouraging and open the door to a future understanding of quark matter from the fifth dimension.

  • Building new biosensors using graphene (2017)

    Merkoçi, Arben (ICN2)

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    Graphene related materials are attracting scientists from both academia and industry for their various advantages with interest for several applications. Among graphene forms graphene oxide (GO) and graphene quantum dots (GQDs) display advantageous characteristics with interest for building innovative biosensing platforms. This is due to their excellent capabilities ranging from easy linking to (bio)chemical/synthetic receptors to unprecedented electronic and optical properties. Quenching of the fluorescence induced by GO or photoluminescence of GQDs can easily operate in synergy with various other nanomaterials and platforms opening the way to several unprecedented biosensing strategies. In our recent publications we have explained the rationale behind the use of GO and GQDs in several optical and electrochemical biosensing technologies. Taking advantage of graphene materials we have developed simple, sensitive, selective and rapid biosensing platforms for various diagnostics applications. Coupling of graphene with simple green materials such as nitrocellulose is further pushing paper-based sensors toward cost efficient sensing technologies opening the way to future industrialization of such point of care devices with interest for human health protection, safety and security beside other uses.

  • A new era in astronomy: the electromagnetic counterpart of the gravitational wave signal from a merger of two neutron stars (2017)

    Miquel Pascual, Ramon (IFAE)

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    In early 2016, the LIGO and Virgo Collaborations announced the first detection of gravitational waves, coming from a merger of two black holes, a discovery that led to the award of the 2017 Nobel Prize in Physics to three leading LIGO scientists. In 2017, LIGO and Virgo reported the first observation (GW170817) of gravitational waves coming from the merger of two neutron stars. The relevance lies in the fact that, contrary to a merger of two black holes, a merger of two neutron stars gives rise to electromagnetic waves, which can be detected on Earth. The combined observation of gravitational and electromagnetic waves from the same event enables a wide spectrum of astrophysical and cosmological studies, ranging from tests of quantum gravity models to a brand new method to determine the expansion rate of the Universe, and has been chosen as 2017 Breakthrough of the Year by the Science journal.

     

    The DECam camera of the Dark Energy Survey (DES) was one of the first optical instruments that reported the detection of an electromagnetic counterpart of GW170817, a few hours after the detection of the gravitational waves. The IFAE group led by Ramon Miquel was responsible for the design and production of most of the read-out electronics for the 74 CCDs in DECam. The electromagnetic signal observed by DECam and others pinpoint the host galaxy (NGC 4993) where the merger took place, together with its redshift and, hence, its recession velocity. On the other hand, the analysis of the detected gravitational wave signal provides the distance to the merger. Putting both things together, one can infer the current rate of expansion of the Universe, or Hubble constant, a parameter whose precise value has recently generated considerable controversy, to be H0 = (70 +12-8) km s-1 Mpc-1. While the precision achieved with this one event is rather limited, this kind of multi-messenger astronomy opens the possibility of an accurate and independent measurement of H0 in the near future.

  • Simultaneous tracking of spin angle and amplitude beyond classical limits (2017)

    Mitchell, Morgan W. (ICFO)

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    Measurement of spin precession is central to extreme sensing in physics, geophysics, chemistry, nanotechnology and neuroscience, and underlies the powerful spectroscopic technique of magnetic resonance. Because there is no spin-angle operator, any measurement of spin precession is necessarily indirect:  it can, for example, be inferred from projections of the spin at different times. Because the operators describing spin projections do not commute, quantum measurement back-action — the random change in one observable when a non-commuting observable is measured — necessarily enters the spin measurement record, introducing errors and limiting sensitivity. In [Colangelo et al. Nature 2017] we showed that this disturbance can be reduced by orders of magnitude, by directing the quantum measurement back-action almost entirely into an unmeasured spin component. This generates a planar squeezed state that enables simultaneous and precise knowledge of both spin angle and spin amplitude, i.e., all the variables of interest in spin precession. To prove the method in the lab, we used high-dynamic-range optical quantum non-demolition measurements applied to a precessing magnetic spin ensemble consisting of about 2 million laser-cooled atoms.  We observed spin tracking with steady-state angular sensitivity 2.9 decibels better than the "classical limit," defined as the best possible performance with independent particles, and amplitude sensitivity 7.0 decibels below the corresponding limit for spin amplitude. In sum, we identified a method to almost completely evade quantum uncertainty effects in the highest-performing technique for many important applications.

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