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
  • Quantum theory needs complex numbers (2021)

    Acín Dal Maschio, Antonio (ICFO)

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    Quantum theory needs complex numbers

    Complex numbers are essential in mathematics, but are they necessary for physics? Without further qualifications, this question must be answered in the negative: physics experiments are described by the statistics they generate, that is, by probabilities, and hence real numbers. There is therefore no need for complex numbers. Physics however aims to explain, rather than describe, experiments through theories. Whether complex numbers are needed within a physical theory to correctly explain experiments, or whether real numbers only are sufficient, is not straightforward. Complex numbers are sometimes introduced in electromagnetism to simplify calculations: one might, for instance, regard the electric and magnetic fields as complex vector fields in order to describe electromagnetic waves. However, this is just a computational trick. Quantum theory radically challenged this state of affairs because its building postulates were phrased in terms of complex  numbers. This has puzzled countless physicists, including the fathers of the theory, for whom a real version of quantum theory seemed much more natural. For instance, Erwing Schrödinger, one of the founders of quantum theory, wrote: “What is unpleasant here, and indeed directly to be objected to, is the use of complex numbers. The quantum wave function is surely fundamentally a real function”. Previous works confirmed this intuition by showing that such “real quantum theory” can reproduce the outcomes of any multipartite experiment, as long as the parts share arbitrary real quantum states. Thus, are complex numbers really needed in the quantum formalism? In our work, we showed this to be case by proving that real and complex quantum theory make different predictions in network scenarios comprising independent quantum states and measurements. This allows us to devise a Bell-like experiment whose successful realization disproves real quantum theory, in the same way as standard Bell experiments disproved local physics. Our results demonstrate how quantum networks, beyond their practical relevance, open radically new perspectives to solve open questions in the foundations of quantum theory.

  • Unveiling the hidden genes (2021)

    Albà Soler, M. Mar (IMIM)

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    Unveiling the hidden genes

    De novo gene birth is emerging as an important mechanism for the formation of new genes, but how de novo genes evolve and which is their impact in the functional proteome, are still poorly understood questions. In contrast to genes formed by duplication and subsequent divergence, de novo genes arise from non-genic parts of the genome, which become transcribed and translated. We have used comparative transcriptomics data from 11 different yeast species, together with ribosome profiling data from Saccharomyces cerevisiae, to obtain a comprehensive view of the genes that have recently been born de novo in the species.

    The study has identified 213 transcripts that have emerged de novo in the past few Million years, nearly half of which encode proteins. We have discovered that these transcripts often overlap other genes in the opposite orientation, unveiling novel ways in which the coding capacity of a compact genome can be increased during evolution. We have also obtained evidence that a subset of de novo proteins are likely to represent recent adaptations to stress conditions. The work advances our understanding on de novo genes and helps establish S. cerevisiae and closely related species as a model system to study this intriguing evolutionary process.

  • The same drug has opposite effects in memory when comparing males and females. (2021)

    Andero Galí, Raül (UAB)

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    The same drug has opposite effects in memory when comparing males and females.

    A drug of the Tac2 neuronal circuit, involved in the formation of the memory of fear, has opposite effects on the ability to remember aversive events in mice according to sex: it is reduced in male mice and increased in female mice.

    This is the first time that a drug has been shown to produce this opposite effect on the memory of male and female mice. The study also evidences that opposing molecular mechanisms and behaviours can occur in memory formation depending on sex. The study has been published in Nature Communications.

    The research group on Translational Mechanisms of Fear Memory, led by Raül Andero, has been studying the functioning of fear memory for years to find treatments for pathologies associated with traumatic experiences, such as post-traumatic stress and phobias.

    The research team had identified that the Tac2 circuit, located in the amygdala, could be temporarily blocked by the effect of a drug they are studying. This drug, called Osanetant, was able to reduce the capacity to recall traumatic events in male mice. In the study, they discovered that this same drug produces the opposite effect in female mice, increasing their fear memory.

    This opposite effect is explained by the fact that, in blocking the Tac2 pathway, the drug interacts with the neuronal receptors of two sex hormones: testosterone in males and estrogen in females. In addition, it has been observed that hormonal fluctuations during the oestrous cycle in female mice, equivalent to the menstrual cycle in women, vary the effects of the drug on the ability to remember aversive events.

    In the field of neurosciences, only one study in females is published for every 5.5 done in males. And research on Tac2 pathway has also been done mostly in males so far.

    The drug studied is not new, but it is safe for use in humans. However, at the moment it is not being used to treat any disease. Prof. Andero's group is now investigating its potential use in treating fear disorders differently by sex.

  • The health impacts and pathways of gentrification in European and American cities.  (2021)

    Anguelovski, Isabelle (UAB)

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    The health impacts and pathways of gentrification in European and American cities. 

    As global cities grapple with the increasing challenge of gentrification and displacement, research in public health and urban geography has presented growing evidence about the negative impacts of those unequal urban changes on the health of historically marginalized groups. Yet, to date comprehensive research about the variety of health impacts and their pathways beyond single case sites and through an international comparative approach of different gentrification drivers and manifestations remains scarce. Our paper analyzes qualitative data on the pathways by which gentrification impacts the health of historically marginalized residents in 14 cities in Europe and North America. We build on 77 interviews with key neighborhood stakeholders. Data analysis indicates four main concurrent processes: Threats to housing and financial security; Socio-cultural displacement; Loss of services and amenities through institutional gentrification; and Increased risks of criminal behavior and compromised public safety. Gentrification is experienced as a chain of physical and emotional community and individual traumas – an overall shock for historically marginalized groups – because of permanent pressures of insecurity, loss, state of displaceability, and the associated exacerbation of socio-environmental disadvantages.

  • Single-Atom Catalysts for Energy and Environmental Applications (2021)

    Arbiol Cobos, Jordi (ICN2)
    Cabot, Andreu (IREC)

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    Single-Atom Catalysts for Energy and Environmental Applications

    Single-atom catalysts (SACs), thanks to the higher density of exposed catalytic sites, can provide high selectivity and and efficiency as well as the suppression of the competing reactions. We have explored different SACs based on Fe,[1] Ni [2] and a combination of both [3].

    First of all, we proposed the use of a C2N framework (a carbon nitride-based 2D layered nanostructure) loaded with atomically and uniformly dispersed iron (Fe/C2N) as a host material for the sulfur in a lithium-sulfur battery cathode.[1] C2N shows excellent electrical conductivity and is a highly porous and high surface area framework. The iron atoms trapped in the pores improve the ability of the cathode material to immobilize the soluble polysulfides and promote the reaction kinetics between sulfur, polysulfides and lithium sulfide.

    Secondly, we tuned the electronic environment of atomically dispersed Ni-based 2D organic framework catalyst through the modification of their edge coordination toward alcohol electrooxidation.[2] We demonstrated that such nickel-based organic frameworks, combined with carbon nanotubes, exhibit outstanding catalytic activity and durability toward the oxidation of methanol, ethanol, and benzyl alcohol.  The work not only introduced a new atomically dispersed Ni-based catalyst, but also demonstrates a new strategy for designing and engineering high-performance catalysts through the tuning of their chemical environment.

    Finally, we designed a new double-metal catalyst, presenting nearby nickel and iron active sites, which improved both efficiency and selectivity of the carbon dioxide (CO2) reduction reaction.[3] This configuration, provides excellent selectivity to CO2 evolution, boosting absorption and desorption of intermediates in the reduction process, and guarantees a low overpotential, which leads to less energy consumption. In addition, undesired competing reactions are strongly limited. Furthermore, the combination of Ni and Fe active sites demonstrated to act as a nano-reactor, since multistep reactions take place simultaneously with an improved overall activity and selectivity.

  • Children are less efficient at trasmitting SARS-CoV-2 than adults (2021)

    Bassat Orellana, Quique (ISGlobal)

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    Children are less efficient at trasmitting SARS-CoV-2 than adults

    In this article, we analyzed contagions of coronavirus disease 2019 inside school bubble groups in Catalonia, Spain, in the presence of strong nonpharmaceutical interventions from September to December 2020. More than 1 million students were organized in bubble groups and monitored and analyzed by the Health and the Educational departments.
    We had access to 2 data sources, and both were employed for the analysis, one is the Catalan school surveillance system and the other of the educational department. As soon as a positive index case is detected by the health system, isolation is required for all members of the bubble group, in addition to a mandatory proactive systematic screening of each individual. All infected cases are reported. It permits the calculation of the average reproductive number (R*), corresponding to the average number of infected individuals per index case.
    We found that propagation inside of the bubble group was small. Among 75% index cases, there was no transmission to other members in the classroom, with an average R* across all ages inside the bubble of R* = 0.4.
    We found a significant age trend in the secondary attack rates, with the R* going from 0.2 in preschool to 0.6 in high school youth.
    We concluded that he secondary attack rate depends on the school level and therefore on the age. Super-spreading events (outbreaks of 5 cases or more) in childhood were rare, only occurring in 2.5% of all infections triggered from a pediatric index case.

    This work, together with other research conducted in children from Catalonia (KIDS-Corona project), had important implications in the recommendations that we were able to make to the Ministeries of Education and Health for a safe return to school by Spanish children.

    Indeed, Spain reopened their schools in September 2020, and has never closed them subsequently, something that not many other countries have been able to do. Transmission within schools has been kept to a minimum, and much of the merit was made on the design -evidence-based- of preventive recommendations tailored to children.

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