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Brain-Circulation Network: The Global Mobility of the Life Scientists
Full text linkGlobal mobility and migration of scientists is an important modern phenomenon with economic and
political implications. As scientists become ever more footloose it is important to identify general patterns
and regularities at a global scale. At the same time cities, and especially global cities, have become impor-
tant loci of economic and scientific activity. Limiting research to international migration, would disregard
the importance of local innovation systems. The analysis of the mobility and brain circulation patterns at
global scale remains challenging, due to difficulties in obtaining individual level mobility data. In this work
we propose a methodology to trace intercity and international mobility through bibliographic records. We
reconstruct the intercity and international mobility network of 3.7 Million Life Scientists moving between
9,745 cities. We present several features of the extracted network, offer evidence that the international
innovation system is marked by national borders and linguistic similarity and show that international mo-
bility largely contributes to the scientific output of national research systems. Moreover we find evidence to
suggest that global cities attract highly productive scientist early in their careers
Uncertainty-aware demand management of water distribution networks in deregulated energy markets
No full textWe present an open-source solution for the operational control of drinking water distribution networks which accounts for the inherent uncertainty in water demand and electricity prices in the day-ahead market of a volatile deregulated economy. As increasingly more energy markets adopt this trading scheme, the operation of drinking water networks requires uncertainty-aware control approaches that mitigate the effect of volatility and result in an economic and safe operation of the network that meets the consumers’ need for uninterrupted water supply. We propose the use of scenario-based stochastic model predictive control: an advanced control methodology which comes at a considerable computation cost which is overcome by harnessing the parallelization capabilities of graphics processing units (GPUs) and using a massively parallelizable algorithm based on the accelerated proximal gradient method
Tax Morale, Fiscal Capacity, and Wars
Full text linkThis paper studies how mobilization for war motivates citizens to contribute to their
own community and therefore help forming tax morale in a constituency. We derive a
theoretical model to investigate government's decision to expand tax revenues from alternative
sources, namely changing the country's culture of tax compliance or expanding
fiscal capacity. Despite the two are initially substitute, we show how in equilibrium dynamic
complementarity arises. Our mechanism exploits exogenous variation in the cost of
tax morale formation, induced by an expected war (either internal or external) that makes
easier for the government to mobilize the constituency. We motivate our theory through a
novel cross-country analysis that uses information on war frequency, tax morale, and fiscal
capacity. We additionally discuss some historical cases consistent with our mechanism
The Political Economy of Collective Memories: Evidence from Russian Politics
Full text linkHow do political elites exploit salient historical events to reactivate collective memories and entrench their power? We study this question using data from the Russian Federation under Putin. We document a substantial recollection campaign of the traumatic transition the Russian population experienced during the 1990s, starting with the year 2003. We combine this time discontinuity in the recollection of negative collective memories with regional-level information about
traumatic experiences of the 1990s. Our results show that Russians vote more for the government, and less for the liberal political opposition, in regions that suffered more during the transition period, once memories from the period are recalled on state-controlled media. We then provide additional evidence on the mechanism and find, using a text analysis of local newspapers, that in those regions where local newspapers more intensively recall the chaotic 1990s, electoral support for the government is higher. Finally, we show that in regions in which the media is less independent from the state, this recollection campaign is more effective
Fracture of solar-grade anisotropic polycrystalline Silicon: A combined phase field–cohesive zone model approach
No full textThis work presents a novel computational framework to simulate fracture events in brittle anisotropic polycrystalline materials at the microscopical level, with application to solar-grade polycrystalline Silicon. Quasi-static failure is modeled by combining the phase field approach of brittle fracture (for transgranular fracture) with the cohesive zone model for the grain boundaries (for intergranular fracture) through the generalization of the recent FE-based technique published in M. Paggi, J. Reinoso, Comput. Methods Appl. Mech. Engrg., 31 (2017) 145–172 to deal with anisotropic polycrystalline microstructures. The proposed model, which accounts for any anisotropic constitutive tensor for the grains depending on their preferential orientation, as well as an orientation-dependent fracture toughness, allows to simulate intergranular and transgranular crack growths in an efficient manner, with or without initial defects. One of the advantages of the current variational method is the fact that complex crack patterns in such materials are triggered without any user-intervention, being possible to account for the competition between both dissipative phenomena. In addition, further aspects with regard to the model parameters identification are discussed in reference to solar cells images obtained from transmitted light source. A series of representative numerical simulations is carried out to highlight the interplay between the different types of fracture occurring in solar-grade polycrystalline Silicon, and to assess the role of anisotropy on the crack path and on the apparent tensile strength of the material
Motion processing after sight restoration: No competition between visual recovery and auditory compensation
No full textThe present study tested whether or not functional adaptations following congenital blindness are maintained in humans after sight-restoration and whether they interfere with visual recovery. In permanently congenital blind individuals both intramodal plasticity (e.g. changes in auditory cortex) as well as crossmodal plasticity (e.g. an activation of visual cortex by auditory stimuli) have been observed. Both phenomena were hypothesized to contribute to improved auditory functions. For example, it has been shown that early permanently blind individuals outperform sighted controls in auditory motion processing and that auditory motion stimuli elicit activity in typical visual motion areas. Yet it is unknown what happens to these behavioral adaptations and cortical reorganizations when sight is restored, that is, whether compensatory auditory changes are lost and to which degree visual motion processing is reinstalled. Here we employed a combined behavioral-electrophysiological approach in a group of sight-recovery individuals with a history of a transient phase of congenital blindness lasting for several months to several years. They, as well as two control groups, one with visual impairments, one normally sighted, were tested in a visual and an auditory motion discrimination experiment. Task difficulty was manipulated by varying the visual motion coherence and the signal to noise ratio, respectively. The congenital cataract-reversal individuals showed lower performance in the visual global motion task than both control groups. At the same time, they outperformed both control groups in auditory motion processing suggesting that at least some compensatory behavioral adaptation as a consequence of a complete blindness from birth was maintained. Alpha oscillatory activity during the visual task was significantly lower in congenital cataract reversal individuals and they did not show ERPs modulated by visual motion coherence as observed in both control groups. In contrast, beta oscillatory activity in the auditory task, which varied as a function of SNR in all groups, was overall enhanced in congenital cataract reversal individuals. These results suggest that intramodal plasticity elicited by a transient phase of blindness was maintained and might mediate the prevailing auditory processing advantages in congenital cataract reversal individuals. By contrast, auditory and visual motion processing do not seem to compete for the same neural resources. We speculate that incomplete visual recovery is due to impaired neural network turning which seems to depend on early visual input. The present results demonstrate a privilege of the first arriving input for shaping neural circuits mediating both auditory and visual functions
Cohesion Policy Meets Heterogeneous Firms
Full text linkIn this paper, we empirically test the effects of the EU ‘cohesion policy’ on the performance of
about 500,000 European manufacturing firms after combining regional policy data at NUTS-
2 level with firm-level data. In a framework of heterogeneous firms and different absorptive
capacity of regions, we show that financing of ‘cohesion policy’ by European Regional Development
Fund (ERDF) aimed at direct investments in R&D correlates with improvement of firms’
productivity in a region. Conversely, funding designed at overall Business Support correlates
with negative productivity growth rates. In both cases, we registered an asymmetric impact
along the firms’ productivity distribution, where a stronger impact can be detected in the first
quartile, i.e. less efficient firms in a region. We finally argue that considering the heterogeneity
of firms allows a better assessment of the impact of ‘cohesion policy’ measures
Evidence of a retinotopic organization of early visual cortex but impaired extrastriate processing in sight recovery individuals
Full text linkNumerous studies in visually deprived nonhuman animals have demonstrated sensitive periods for the functional development of the early visual cortex. However, in humans it is yet unknown which visual areas are shaped to which degree based on visual experience. The present study investigated the functional organization and processing capacities of early visual cortex in sight recovery individuals with either a history of congenital cataracts (CC) or late onset cataracts (developmental cataracts, DC). Visual event-related potentials (VERPs) were recorded to grating stimuli which were flashed in one of the four quadrants of the visual field. Participants had to detect rarely occurring grating orientations. The CC individuals showed the expected polarity reversal of the C1 wave between upper and lower visual field stimuli at the typical latency range. Since the C1 has been proposed to originate in the early retinotopic visual cortex, we concluded that one basic feature of the retinotopic organization, upper versus lower visual field organization, is spared in CC individuals. Group differences in the size and topography of the C1 effect, however, suggested a less precise functional tuning. The P1 wave, which has been associated with extrastriate visual cortex processing, was significantly attenuated in CC but not in DC individuals compared to typically sighted controls. The present study thus provides evidence for fundamental aspects of retinotopic processing in humans being independent of developmental vision. We suggest that visual impairments in sight recovery individuals may predominantly arise at higher cortical processing stages
Benefiting Colleagues but not the City: Localized Effects from the Relocation of Superstar Inventors
Full text linkIn this paper I examine episodes in which superstar inventors relocate to a new city. In particular,
in order to assess whether the beneficial effects of physical proximity to a superstar have a restricted
network dimension or a wider spatial breadth (spillovers), I estimate changes in patterns of patenting
activity following these events for two different groups of inventors: the superstar’s close collaborators,
and all the other inventors in a given urban area, for both the locality where the superstar moves
to and for the one that is left behind. In the case of collaborators, I restrict the attention to patents
realized independently from the superstar. The results from the event study register a large and persistent
positive effect on the collaborators in the city of destination, as well as a simultaneous negative
trend affecting those still residing in the previous location. In the long run, these effects translate
into an increased difference between the two groups of about 0.16 patents per inventor. Conversely,
no city-wide spillover effect can be attested, offering little support to place-based policies aimed at
inducing a positive influx of top innovators in urban areas
The Network of U.S. Mutual Fund Investments: Diversification, Similarity and Fragility throughout the Global Financial Crisis
Full text linkNetwork theory proved recently to be useful in the quantification of many properties of financial systems. The analysis of the structure of investment portfolios is a major application since their eventual correlation and overlap impact the actual risk diversification by individual investors. We
nvestigate the bipartite network of US mutual fund portfolios and their assets. We follow its evolution during the Global Financial Crisis and analyse the interplay between diversification, as understood in classical portfolio theory, and similarity of the investments of different funds. We show that, on average, portfolios have become more diversified and less similar during the crisis. However, we also find that large overlap is far more likely than expected from models of random allocation of investments. This indicates the existence of strong correlations between fund portfolio strategies. We introduce a simplified model of propagation of financial shocks, that we exploit to show that a systemic risk component origins from the similarity of portfolios. The network is still vulnerable after crisis because of this effect, despite the increase in the diversification of portfolios. Our results indicate that diversification may even increase systemic risk when funds diversify in the same way. Diversification and similarity can play antagonistic roles and the trade-off between the two should be taken into account to properly assess systemic risk