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

  • Neutrinos: still skinny after all (2014)

    Verde, Licia (UB)

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    Neutrinos: still skinny after all

    Scientists have many tools for measuring the cosmic structures of the universe, which includes structures such as galaxies, galaxy clusters, and intergalactic gas. Cosmic structures can be observed directly, such as by observations of large-scale structure, or indirectly, such as with experiments that measure temperature fluctuations in the cosmic microwave background. Although having multiple ways to measure cosmic structure is beneficial, there is one problem: the measurements don't agree.Recently, several studies have suggested that this disagreement, or tension, in the data can be relieved by massive sterile neutrinos. Neutrinos were originally thought to be massless, but experiments later showed that they do have mass. Massive neutrinos suppress the growth of structures that lead to the formation of galaxy clusters. For this reason, it has been claimed that fairly massive neutrinos resolve the tension between the experimental data and bring the different measurements into better agreement.But in a new study  we show that this may not be so.  Massive neutrinos (as massive as has been proposed) do not bring about a new cosmological concordance between the measurements. Instead, the apparent concordance may result from systematic biases in the measurements. The results suggest that the tension between the measurements must be resolved either by considering systematics in one or more of the data sets, or—if further investigation shows that correcting systematic effects does not resolve the tension—then new physics other than the introduction of massive neutrinos must be considered.In terms of a larger framework for viewing cosmic structure, the results  strongly favor the cold dark matter model with a cosmological constant over more complex models that are extended with massive neutrinos. Yet, as the researchers explain, the questions surrounding cosmic structure are still far from being answered.There is no evidence for significantly massive neutrinos in cosmology. Therefore there is not yet the need for extending the standard cosmological model to include an extra parameter for neutrino mass. Instead, future investigations will likely focus on finding exactly what the neutrino mass is. Particle physics experiments give a firm lower limit to the neutrino mass, cosmology at present gives an upper limit. But there is not much wiggle room left. The next generation of cosmology surveys will have enough statistical power to really see neut

  • Full randomness from arbitrarily deterministic events (2013)

    Acín Dal Maschio, Antonio (ICFO)

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    Full randomness from arbitrarily deterministic events

    Do random events exist in nature? This question has attracted and keeps attracting the interest of many different communities, ranging from philosophers to physicists and mathematicians. Classical physics is deterministic and does not contain any form of randomness. Quantum physics, however, does contain some form of randomness as it is only able to make predictions in probabilistic terms. Yet, the fact that a theory is only able to make probabilistic predictions does not necessarily imply that nature is random, but may simply be a limitation of the predictability power of the theory.In 1964, Bell proved a theorem where he implied that quantum theory cannot be completed, suggesting the existence of an intrinsic form of randomness in the quantum world. Unfortunately Bell's theorem assumes in its derivation the existence of an initial source of perfect randomness, which introduces circularity in the argument: random processes are shown to exist by assuming an initial random source!The necessity of some form of randomness to run a Bell test implies that the strongest proof of randomness one can hope for using quantum physics is the following: does any amount of randomness, however small, suffice to run a Bell test that certifies perfect randomness? In other words, can randomness be amplified in the quantum regime?In our work published in Nature Communications, we provide a solution to this question and indicate that randomness is indeed unavoidable in our description of nature: given an arbitrarily small amount of initial randomness, we show how non-local quantum correlations certify the existence of fully random processes in nature.Beyond the clear implications this achievement has from a fundamental perspective, the obtained results are also relevant for quantum information processing. In fact the study provides the first quantum protocol for full randomness amplification. In randomness amplification, the goal is to extract perfect random bits from a source of arbitrarily imperfect randomness. In a seminal work, Santha and Vazirani proved that randomness amplification is impossible when relying only on classical systems. In our study, we prove that full randomness amplification becomes possible when using quantum resources.

  • Self-Assembled 0D, 1D and 2D Quantum Structures in-a-Nanowire: direct correlation between physical properties and structure at atomic scale (2013)

    Arbiol Cobos, Jordi (CSIC - ICMAB)

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    Self-Assembled 0D, 1D and 2D Quantum Structures in-a-Nanowire: direct correlation between physical properties and structure at atomic scale

    Inherent to the nanowire morphology is the exciting possibility of fabricating materials organized at the nanoscale in three dimensions. Composition and structure can be varied along and across the nanowire, as well as within coaxial shells. This opens up a manifold of possibilities in nanoscale materials science and engineering which is only possible with a nanowire as a starting structure. As the variation in composition and structure is accompanied by a change in the band structure, it is possible to confine carriers within the nanowire. Interestingly, this results in the formation of local two, one and zero-dimensional structures from the electronic point of view and this, within the nanowire. This novel palette of nano-structures paves the way towards novel applications in many engineering domains such as lasers, high-mobility transistors, quantum information and energy harvesting. The quantum structures obtained and analyzed have been grown by molecular beam epitaxy and correspond to different confinement approaches: quantum wells (2D), quantum wires (1D) and quantum dots (0D). The structure and morphology of these quantum structures integrated in single nanowires have been determined at atomic scale by means of aberration corrected STEM, 3D atomic models were obtained and the final enhanced optical properties cross-correlated.

  • 'Human Epidermal Stem Cell Function Is Regulated by Circadian' (2013)

    Aznar Benitah, Salvador (IRB Barcelona)

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    'Human Epidermal Stem Cell Function Is Regulated by Circadian'

    Human skin copes with harmful environmental factors that are circadian in nature, yet how circadian rhythms modulate the function of human epidermal stem cells is mostly unknown. In this paper we show that in human epidermal stem cells and their differentiated counterparts, core clock genes peak in a successive and phased manner, establishing distinct temporal intervals during the 24hr day period. Each of these successive clock waves is associated with a peak in the expression of subsets of transcripts that temporally segregate the predisposition of epidermal stem cells to respond to cues that regulate their proliferation or differentiation, such as TGFβ and calcium. Accordingly, circadian arrhythmia profoundly affects stem cell function in culture and in vivo. We hypothesize that this intricate mechanism ensures homeostasis by providing epidermal stem cells with environmentally-relevant temporal functional cues during the course of the day, and that its perturbation may contribute to ageing and to carcinogenesis.

  • Is multiculturalism psychologically adaptive? (2013)

    Benet-Martínez, Verónica (UPF)

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    Is multiculturalism psychologically adaptive?

    Intercultural contact has a long history due to migration, transnationalism, or colonization, and more recently also due to cultural and economic globalization forces, and the speed of travel and communication. One result of this intercultural contact and mixing is the growing numbers of individuals who consider themselves bicultural or multicultural. Early sociological accounts of this phenomenon portrayed bicultural individuals as marginal and stumped between two worlds, and more recently, in the context of immigration, political discourse supportive of assimilation (i.e., abandoning the culture of origin in favor of the dominant culture) has become quite pervasive. But one question remains: What are the consequences of these intercultural and identity processes for individuals’ psychological, sociocultural, and health-related adjustment? To answer this question, we conducted a statistical meta-analysis that pooled data from 83 international studies, 322 effect sizes, and 23,197 acculturating participants (e.g., immigrants, ethnic and cultural minorities, international students). Results showed a strong and positive association between biculturalism –i.e., attachment to and competency in two cultures-- and both psychological (e.g., self-esteem, lack of depression) and sociocultural (e.g., career success, lack of delinquency) adjustment. This link between biculturalism and adjustment was stronger than the association between monoculturalism (exclusive orientation towards either the dominant or heritage/ethnic cultures) and adjustment. These results thus clearly invalidate both early sociological accounts of this phenomenon depicting bicultural individuals as “lost” between two worlds and also political discourse supportive of either assimilation or ethnic segregation. The positive relationship between biculturalism and adjustment may be due to a variety of factors internal and external to the acculturating individual. For instance, the cultural, linguistic, social, and cognitive competencies that bicultural individuals acquire in the process of learning and using two cultures may make these individuals more adept at adjusting to various life situations (i.e., have higher adjustment). Also, having social support networks in two cultures may buffer biculturals from the psychological and sociocultural challenges that sometimes result from acculturation experiences. Alternatively, perhaps better adjusted individuals find it easier to be bicultural. Lastly, societies supportive of multicultural

  • Investigating ancient wine residues in archaeological materials (2013)

    Cau Ontiveros, Miguel Ángel (UB)

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    Investigating ancient wine residues in archaeological materials

    Wine is one of the most important products produced, traded and consumed in the Mediterranean area in Antiquity. Consequently, its identification in archaeological materials provides valuable information in order to understand food production, trade and consumption. Investigation of organic residues in archaeological materials has been developed since the decade of 1970. Ceramics (Figure 1) and other porous materials such as plasters retain the substances in which they enter in contact with. Gas chromatography/mass spectrometry (GC/MS) is one of the methods most widely used for the identification of organic residues. Nevertheless, the identification of wine markers has always been difficult due to the problems of degradation. A new extraction method for the identification of tartaric acid and other markers of wine and its derivatives is proposed. Although tartaric acid is soluble in water, when it is identified, it can be considered a marker of wine or its derivatives. The results obtained with this extraction method and using gas chromatography/mass spectrometry (GC/MS), allowed for the identification of tartaric acid and other markers of wine. The method was tested on experimental, traditional materials used to store and/or produce wine, and finally applied to the study of archaeological materials (ceramics and plasters). The experiments also involved the degradation of wine through cooking, drastic heating and burial. The importance of the proposed methodology is that it allows the identification of traces of wine using the same facilities that are usually employed for the study of the organic residues preserved in archaeological samples (GC/MS), with no need for HPLC, LC/MS/MS or THM/GC/MS, thus allowing a larger number of laboratories to detect traces of wine. This will allow laboratories that only have a GC/MS to use a single instrument for the identification of lipids and wine markers, providing a deeper understanding of the residues preserved in the samples. This is particularly important in the case of archaeological samples, as they often come in contact with different substances. Amphorae as the most widely distributed container were often re-used. These results published in the Journal of Archaeological Science (Figure 2) are part of a larger project on production, trade and consumption of food in Late Antiquity that explores food practices in this period of deep transformation of the Mediterranean world between the Roman

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