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 amb les millors publicacions de l'any. 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 last meals of the extinct giant rhinoceros: Unexpected diet and cause of death (2020)

    Rivals, Florent (IPHES)

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    The last meals of the extinct giant rhinoceros: Unexpected diet and cause of death

    The now extinct giant rhinoceros, Elasmotherium sibiricum, also known as the ‘Siberian unicorn’, was one of the largest representatives of the formerly widely diverse family Rhinocerotidae. It survived in Eastern Europe and Central Asia until at least 39,000. This rhinoceros was the second largest among rhinoceroses. It weighed around 3500 kg and was over two meters high at the withers. The ecology of that extinct species is poorly known. According to its morphology (high crowned teeth), it should be expected to be a true grazer, exclusively feeding on grass. The objective of this research was to provide quantitative data to reconstruct the paleodiet of the elasmotheres. Two dietary proxies were used, tooth mesowear that indicate the ‘average’ diet over the last years of life of an individual, and microwear, a short-term signal, that reflects the diet over the last days or weeks before death. The fossil materials studied are coming from Irgiz 1, a site located in the Saratov region (Russia). The site is dated to the end of the Middle Pleistocene and the beginning of the Upper Pleistocene, about 120,000 years ago. Irgiz 1 is a paleontological site, and the elasmotheres there certainly died from natural causes.

    The long-term mesowear signal indicates that elasmotheres had a very abrasive diet i.e. it was grazing, as it could be expected from its dental morphology. The microwear pattern observed on the teeth revealed an unexpected browsing diet at the time of death (last days/weeks). This discrepancy between the two dietary proxies indicates it experienced a change in diet that occurred shortly before death. All the individuals recovered from Irgiz 1 shifted from a grazing to a browsing diet during the last days or weeks before they died. This sudden change in diet could be related to a catastrophic mortality event, perhaps related to the sudden accumulation of snow and ice coating (‘dzud’), limited the availability of grass and forced them to shift towards shrub /tree foliage that was still accessible. This first study of tooth meso- and microwear on elasmotheres provided unique data which allows us to broaden our knowledge about the diet of these animals.

  • Discovering a new dimension for spin control in topological materials (2020)

    Roche, Stephan (ICN2)

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    Discovering a new dimension for spin control in topological materials

    The ability to control and manipulate spin in materials is at the basis of spintronics, a field of research and branching sector of electronics that aims at using spin to carry and propagate information. Spin related phenomena are studied in order to take advantage of peculiar characteristics exhibited by some materials. Among them, transition metal dichalcogenide (TMDs) monolayers are particularly interesting. These two-dimensional materials exhibit an unusual spin-charge interconversion and topological characteristics, which are extremely relevant to their application.

    We recently predicted some unique features of a low-symmetry structural phase of the tungsten ditelluride (WTe2) monolayer which suggests alternative ways to manipulate spin information. Quantum transport simulations and modelling show that the structure of this material leads to an unprecedented canted quantum spin Hall (QSH) effect, which is stands as a new paradigm for topological physics.

    Typically, the strong symmetry in 2D materials’ structure compel the spins to align with one of the crystalline directions. In absence of such constrains, spins can assume arbitrary orientations. This is what happens in the so-called distorted octahedral phase (1T’) of the WTe2 monolayer, exhibiting a low-symmetry structure. While the traditional quantum spin Hall effect is usually associated with spin polarization pointing perpendicularly to the conducting plane, here a so-far-unique QSH effect defined by an oblique spin polarization axis is predicted. The orientation of this axis is prescribed by the spin-orbit coupling parameters, which are tuneable via a number of means: strain, electrostatic gates, substrates choice, or pressure.

    Remarkably, our predicted novel canted QSHE predictions has been confirmed experimentally by various groups just a couple of weeks ago. This research opens a new avenue for spintronics, in which spins can be controlled through the electronic environment, instead of by conventional magnetic means. 

  • A total lockdown needed to be enforced to contain COVID-19 first wave (2020)

    Rodó i López, Xavier (ISGlobal)

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    A total lockdown needed to be enforced to contain COVID-19 first wave

    At a time when the first wave of the COVID-19 pandemic was progressing out of control in Spain, we implemented a discrete-time epidemiological model specifically tailored to describe the transmission dynamics of SARS-COV-2, the etiological agent of COVID-19. We anticipated a collapse in the health care system in Spain in terms of its ICU capacity unless severe confinement restrictions were imposed. The model estimated the risk rate for each Spanish municipality, considering the following parameters: (1) the transmission dynamics of SARS-COV-2, (2) the usual movement patterns of the Spanish population, and (3) the demographics of the Spanish population. 

    This study was supplemented late in the year by a cautionary article in which we pointed that early studies of weather, seasonality, and environmental influences on COVID-19 have yielded inconsistent and confusing results. To provide policy-makers and the public with meaningful and actionable environmentally-informed COVID-19 risk estimates, the research community must meet robust methodological and communication standards.

     

  • Understanding singularities in mathematical equations (2020)

    Ros Oton, Xavier (UB)

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    Understanding singularities in mathematical equations

    Partial Differential Equations (PDE) are a type of mathematical equations that are used in essentially all sciences and engineering. They are the language in which most physical laws are written.

    From the mathematical point of view, the most fundamental question in this context is to understand whether solutions to a given PDE may (or may not) develop singularities. For example, in the case of the PDEs that describe fluid mechanics, this is one of the Millenium Prize Problems in mathematics.

    During the last decades, there has been an increasing interest in understanding PDE problems that involve unknown/moving interfaces, such as ice melting to water. In this context, it turns out that singularities do appear... sometimes. In a recent work with A. Figalli and J. Serra, we have proved for the first time that, while singularities may appear, they are actually extremely rare. Our precise theorem (whose proof is more than 100 pages long) completely solves a long-standing conjecture which had been open for almost half a century.

    Our work has been published in Publ. Math. IHÉS, an extremely selective journal which publishes only around 10 papers every year (in all areas of mathematics).

  • Three ways to break a sugar chain (2020)

    Rovira Virgili, Carme (UB)

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    Three ways to break a sugar chain

    One of the basic processes of nature is the decomposition of organic matter, which requires the degradation of complex carbohydrate structures. To do so, it is necessary to break the long chains of sugar molecules made up of smaller – ‘monosaccharide’ – units in order to transform them into  short chains. 

    The above process is performed by glycosidases, enzymes found in all life forms and are part of the machinery by which cells acquire their nutrients.

    In order to carry out these decomposition processes, only two catalytic mechanisms were known so far to help the acceleration of the corresponding chemical reactions. The most common mechanism is one in which the glycosidase enzyme uses two strategically located ‘amino acid residues’ to chemically cleave the bond. These molecules act like a pair of clippers that snip and cut the bond. This approach is used in a famous enzyme (lysozyme) found in egg-white that protects the chicken embryo from bacteria by cutting their cell walls.

    The second mechanism needs uses one amino acid residue, and instead uses another type of chemical unit, an ‘amide group’ on the glycoside (such as in crab chitin) as the second residue. This is used by glycosidases called chitinases to degrade crab exoskeletons allowing them to molt. These are now textbook mechanisms studied in undergraduate courses.

    We have recently discovered a special group of enzymes that instead use another type of chemical structure, a sugar hydroxyl and that forms a three membered ring (an epoxide) intermediate. This mechanism was found in a specific type of glycosidases: endo-α-mannosidases, necessary to modify the sugars linked to our proteins.

    The study has been carried out by an international team (UK, Canada, Australia and Spain), in which our group was in charge of modelling the enzyme mechanism of action using multiscale computational chemistry.

    The study provides the first convincing data to prove this particular mechanism from glycosidases, which will probably be used by other enzymes yet to be discovered. By learning how nature works, we can mimic its strategies to develop new enzymes for industrial applications.

  • Nanochemistry in motion: Two new chassis for nanomotors (2020)

    Sánchez Ordónez, Samuel (IBEC)
    Maspoch Comamala, Daniel (ICN2)

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    Nanochemistry in motion: Two new chassis for nanomotors

    Catalytic nanomotors are nanostructures that convert chemical energy into motion, showing great potential in biomedical and environmental applications. Once in a solution containing the “fuel”, nanomotors start to swim while performing tasks such as carrying drugs, sensing, penetrating cells and tissues and cleaning contaminated water. Using enzymes -organic molecules that accelerate the speed of biochemical reactions- as engines is an elegant and efficient way to generate energy for the propulsion of nanomotors. However, these enzyme-driven nanostructures may be exposed to adverse conditions, such as strong pH variations, harsh solvents, ionic species, and high temperatures, which could compromise both their movement and their functionalities. To overcome this issue, the groups from Prof. Samuel Sánchez (IBEC) and Prof. Daniel Maspoch (ICN2), have put together their expertise -nanomotors and nanochemistry- in two collaborative publications to provide nanomotors with new chassis, opening new avenues in this field enabling some applications never envisioned before.  

    The first one is called “Lipobots”, and comprises liposomes -spherical vesicles- containing urease enzyme in their interior. The researchers mimicked the journey of Lipobots towards the gastrointestinal track, where they would suffer from acidic conditions before reaching the bile salts. Surprisingly, the protective shell from the liposome maintains the enzymatic activity and the structure of the Lipobots at pH3. Thereafter, Lipobots were soaked in a solution containing a component of the bile salt present in the intestine, which opened the pores of the liposome leaving a thrust from the enzymatic reaction which in turn, provided the self-propulsion of Lipobots. In the second one, metal-organic frameworks (MOF) were synthesized so that two types of pores were generated, ones would incorporate catalase enzymes and the other one be available for the adsorption of contaminants like organic dyes while self-propelling (MOFtors). The high porosity, and dual functionality of the pores is of great importance for the creation of very active, multifunctional and mass-produced self-propelled microcleaners.

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