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

  • Flexible quantum reference frames (2020)

    Winter, Andreas (UAB)

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    Flexible quantum reference frames

    A reference frame is commonly understood as a convention to give objective meaning to relative information such as time and distance. In modern physics, however, it is a concrete, rigid external structure to allow for the unambigous definition of such quantities as angles or lengths in terms of measurements. Thus, Einstein imagined a universe full of clocks and rods, but the role of a frame is not reducible to merely giving operational sense to observables through measurement. Indeed, in quantum mechanics, not all quantities can be measured simultaneously, yet frames exist for all sets of quantum numbers, regardless of whether they are jointly measureable or not (in mathematical terms: do or do not commute). In [1] we gave a simple and universal construction of frames for arbitrary quantum numbers. Previously, frames were known based on abstract representation-theoretic principles. Their crucial feature is that they enable arbitrary transformations on a system (including measurements), even ones that do not conserve the observables of interest, offsetting each change by an opposite change in the reference frame. The latter thus necessarily acts as a battery, a very useful point of view in thermodynamics. 

    It turns out that there is much freedom in constructing frames, and that this freedom can be exploited to impose additional desirable features. In thermodynamics the question had arisen whether there are frames with physically distinct parts serving as batteries for the different quantum numbers in question.

    We show that this is indeed the case in several interesting cases [2]. E.g. for angular momentum (Fig. 1), one needs a 3-dimensional coordinate system; a frame could be three large spins pointing in (roughly) orthogonal directions. Alternatively, each of the three directions can be given indirectly via the right-hand-rule based on tow large spins (Fig. 2). Whereas the first offsets any change of the principal spin components by an opposite change of declocalized internal degrees of freedom, the latter frame has three physically distinct parts for each of the principal spin components.

  • Last Interglacial Iberian Neandertals as Fisher-Hunter-Gatherers (2020)

    Zilhão, João (UB)

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    Last Interglacial Iberian Neandertals as Fisher-Hunter-Gatherers

    Marine food-reliant subsistence systems like those in the African Middle Stone Age (MSA) have not been known from Europe until the much later Mesolithic. Whether this difference reflects taphonomic biases or behavioral distinctions between archaic and modern humans remains much debated. Figueira Brava cave, in the Arrábida range (Portugal), provides a uniquely preserved record of Neandertal coastal resource exploitation on a comparable scale to the MSA and dated to ~86-106 thousand years ago. The breadth of the subsistence base — pine nuts, marine invertebrates, fish, marine birds and mammals, tortoise, waterfowl, hoofed game — exceeds that of regional early Holocene sites. The routine harvesting of shellfish implies knowledge of tidal regimes and, along the Portuguese littoral, awareness that, between late spring and autumn, the consumption of bivalves entails a significant risk of biotoxin poisoning. These cognitive aspects of the Figueira Brava subsistence data are consistent with the rapidly accumulating evidence for jewelry, cave art and other forms of symbolic material culture in the Middle Paleolithic of Europe. The major behavioral gap once thought to separate Neandertals from modern humans would thus seem to be just another example that “absence of evidence is not evidence of absence.” Another corollary of the Figueira Brava data is that the consumption of aquatic foods is not the differentia specifica that separated anatomically modern humans in Africa from coeval Eurasians, whose demise it would ultimately explain. Indeed, the possibility must now be entertained that the familiarity with marine resources and seascapes implied by the settlement of Southeast Asia, Sahul (Australia and New Guinea) and the Americas is deeply rooted in human history.

  • Ocean warming and acidification effects on calcareous phytoplankton communities (2020)

    Ziveri, Patrizia (UAB)

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    Ocean warming and acidification effects on calcareous phytoplankton communities

    Carbon dioxide (CO2) emissions by human activities have alarmingly increased in the past decades. A quarter of this anthropogenic CO2 has been absorbed by the ocean, changing the chemistry and ultimately lowering the pH of the seawater, a phenomenon known as ocean acidification. The extra heat trapped in the atmosphere due to greenhouse gases is also causing the seawater warming. The process hampers the supply of nutrients to the upper ocean layers, due to a sharp stratification of the surface water column. Atmospheric warming is expected to evolve in the Mediterranean area 20% faster than the global average, and marine heatwaves will occur with increasing frequency by the end of the 21st century, with serious consequences for marine biodiversity and production. Coccolithophores, a very abundant group of marine calcifying phytoplankton, play a major role in the biogeochemical cycles and in the regulation of the global climate. These tiny algae, which measure 1/1000 of a mm, are at the basis of the aquatic trophic chain, and interact with atmospheric and oceanic CO2 through calcification and photosynthesis. The study detailed the behaviour of these algae under conditions of water temperature ≥ 28°C and a pH of approximately 7.8 units. The results highlight a negative effect of thermal stress on coccolithophore cell production and calcification. Likewise, anomalous calcification in this group of phytoplankton was associated with ocean acidification.  This highlights the importance of looking at species-specific responses to climate change and addressing their specific adaptation mechanisms. Scientists believe that, due to the progressive increase of CO2 emissions in the atmosphere, the risks derived from ocean warming and acidification will become even more acute in the coming decades, thus changing the plankton communities of the Mediterranean. In the future, a clear understanding of the interactions between the different components of the plankton communities will be essential to better understand the future impact of environmental changes on their adaptation and productivity.

  • Proteomeic investigation of ancient dental enamel resolves Early Pleistocene rhino evolution (2019)

    Agustí Ballester, Jordi (IPHES)
    Martínez Navarro, Bienvenido (IPHES)

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    Proteomeic investigation of ancient dental enamel resolves Early Pleistocene rhino evolution

    The sequencing of ancient DNA has enabled the reconstruction of speciation, migration and admixture events for extinct taxa. However, the irreversible post-mortem degradation of ancient DNA has so far limited its recovery—outside permafrost areas— to specimens that are not older than approximately 0.5 million years (Myr). By contrast, tandem mass spectrometry has enabled the sequencing of approximately 1.5-Myr-old collagen type I, and suggested the presence of protein residues in fossils of the Cretaceous period—although with limited phylogenetic use. In the absence of molecular evidence, the speciation of several extinct species of the Early and Middle Pleistocene epoch remains contentious. Here we address the phylogenetic relationships of the Eurasian Rhinocerotidae of the Pleistocene epoch, using the proteome of dental enamel from a Stephanorhinus tooth that is approximately 1.77-Myr old, recovered from the archaeological site of Dmanisi (South Caucasus, Georgia). Molecular phylogenetic analyses place this Stephanorhinus as a sister group to the clade formed by the woolly rhinoceros (Coelodonta antiquitatis) and Merck’s rhinoceros (Stephanorhinus kirchbergensis). We show that Coelodonta evolved from an early Stephanorhinus lineage, and that this latter genus includes at least two distinct evolutionary lines. The genus Stephanorhinus is therefore currently paraphyletic, and its systematic revision is needed. We demonstrate that sequencing the proteome of Early Pleistocene dental enamel overcomes the limitations of phylogenetic inference based on ancient collagen or DNA. Our approach also provides additional information about the sex and taxonomic assignment of other specimens from Dmanisi. Our findings reveal that proteomic investigation of ancient dental enamel—which is the hardest tissue in vertebrates, and is highly abundant in the fossil record—can push the reconstruction of molecular evolution further back into the Early Pleistocene epoch, beyond the currently known limits of ancient DNA preservation.

  • A new type of urban climate injustice: green climate gentrification  (2019)

    Anguelovski, Isabelle (ICTA-UAB)

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    A new type of urban climate injustice: green climate gentrification 

    My recent research led in collaboration with researchers from the BCNUEJ lab and colleagues from the United States highlights that urban climate resilience planning produces a new type of urban climate injustice: green climate gentrification. 

    Our studies find that low-income, working class, and minority residents are among the social groups most likely to experience residential and social displacement—in the short and mid-term—from green climate infrastructure. Although green roofs, resilient parks and greenways, rain gardens, or detention basins and canals are increasingly hailed as win-win infrastructure to protect cities against climate change impacts, we argue that such interventions overlook or minimize negative impacts for socially vulnerable groups. At the same time, those projects sell the image of a green and resilient 21st-century city to investors, real estate developers, and new sustainability-class residents who are those most benefiting from green interventions. 

    The research we conducted in Boston (on greening and resilience planning in East Boston) and Philadelphia (on green stormwater management infrastructure throughout the city) reveals that vulnerable populations—many of whom have already been exposed to hazardous conditions in their neighborhoods—now stand to benefit least from greening initiatives. For instance, in Philaldephia, we find a negative association between the siting of green infrastructure and increased minority population, and a strong positive association between green infrastructure siting, gentrification, and reduced minority and low-income population. In Boston, we find that the Boston real estate industry is building resilient properties for elites and displacing lower-income residents in East Boston, while advocating for the City of Boston to create new protection zones for future investments.

    In sum, improvement of marginalized neighborhoods through green infrastructure may cause these vulnerable populations to lose their neighborhoods altogether.

     

  • Tissues have independent clocks (2019)

    Aznar Benitah, Salvador (IRB Barcelona)

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    Tissues have independent clocks

    Circadian rhythms control organismal physiology throughout the day. At the cellular level, clock regulation is established by a self-sustained transcriptional oscillator network. However, it is still unclear how different tissues achieve a synchronized rhythmic physiology. That is, do they respond independently to environmental signals, or require interactions with each other to do so? These are important issues since deregulation of the clock is causative of accelerated aging and several diseases such as metabolic disorders and a higher predisposition to cancer. 

    In this work, we showed that unexpectedly, light synchronizes the circadian machinery in single tissues in the absence of clocks in all other tissues. Importantly, tissue-autonomous clocks partially sustain homeostasis in otherwise arrhythmic and prematurely aging animals. Our results therefore support a two-branched model for the daily synchronization of tissues: an autonomous clock that directly responds to light without any commitment of other tissue clocks, and a memory branch using other tissue clocks to "remember" time in the absence of external cues. This new model of the timed synchronization of our clocks nicely explains jetlag, while raising concerns regarding the ¨social jetlag¨ to which we are currently exposing our tissues on a daily basis due to the unnatural exposure to light at night.  In addition, our results indicate that tissues have a minimal functional independence which probably ensures a certain degree of tissue fitness even when the functionality of other tissues might be compromised. Overall this would extend organismal fitness even when some component (for instance a specific tissue or organ) is damaged. 

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