Pompeu Fabra University

About: Pompeu Fabra University is a education organization based out in Barcelona, Spain. It is known for research contribution in the topics: Population & Context (language use). The organization has 8093 authors who have published 23570 publications receiving 858431 citations. The organization is also known as: Universitat Pompeu Fabra & UPF.

Macroscopic description for networks of spiking neurons

Abstract: A major goal of neuroscience, statistical physics and nonlinear dynamics is to understand how brain function arises from the collective dynamics of networks of spiking neurons. This challenge has been chiefly addressed through large-scale numerical simulations. Alternatively, researchers have formulated mean-field theories to gain insight into macroscopic states of large neuronal networks in terms of the collective firing activity of the neurons, or the firing rate. However, these theories have not succeeded in establishing an exact correspondence between the firing rate of the network and the underlying microscopic state of the spiking neurons. This has largely constrained the range of applicability of such macroscopic descriptions, particularly when trying to describe neuronal synchronization. Here we provide the derivation of a set of exact macroscopic equations for a network of spiking neurons. Our results reveal that the spike generation mechanism of individual neurons introduces an effective coupling between two biophysically relevant macroscopic quantities, the firing rate and the mean membrane potential, which together govern the evolution of the neuronal network. The resulting equations exactly describe all possible macroscopic dynamical states of the network, including states of synchronous spiking activity. Finally we show that the firing rate description is related, via a conformal map, with a low-dimensional description in terms of the Kuramoto order parameter, called Ott-Antonsen theory. We anticipate our results will be an important tool in investigating how large networks of spiking neurons self-organize in time to process and encode information in the brain.

The Political Recrafting of Social Bases of Party Competition: Chile, 1973-95

Abstract: This article examines social cleavages and the impact of political legacies on Chile's post-authoritarian party system. In contrast to society-oriented approaches to party system formation, we argue that cleavage appearance in a party system depends on political agency, which can even (re)create social identities and social conflicts. The Chilean case illustrates this point; the structure of the party system is deeply influenced by distinctive political legacies of the authoritarian period. The cleavage between those who supported authoritarian rule and those who opposed it has powerfully shaped the party system during the new democratic period. In post-authoritarian Chile (1990-2001), a societal approach does not adequately explain the formation of cleavages or the contours of the party system. A class cleavage has appeared between the governing coalition and the conservative opposition, but this cleavage is politically constructed and maintained. The Chilean case also shows that it is important to examine the ways in which political elites craft party systems from above during the transition period. Political agency from the supply side played a decisive role in emphasizing or diminishing some of the political and cultural conflicts existing after the authoritarian experience and, therefore, an essential role in party system formation in post-authoritarian Chile. We have undertaken this enterprise of examining social cleavages and the impact of political legacies on Chile's post-authoritarian party system as a way of exploring how post-authoritarian party systems in general are structured. Because a party system is formed and/or re-established when democracy is restored, new democracies provide an ideal context in which to discuss theoretically important aspects of cleavages and the formation

Clusters of Entrepreneurship

Abstract: Employment growth is strongly predicted by smaller average establishment size, both across cities and across industries within cities, but there is little consensus on why this relationship exists. Traditional economic explanations emphasize factors that reduce entry costs or raise entrepreneurial returns, thereby increasing net returns and attracting entrepreneurs. A second class of theories hypothesizes that some places are endowed with a greater supply of entrepreneurship. Evidence on sales per worker does not support the higher returns for entrepreneurship rationale. Our evidence suggests that entrepreneurship is higher when fixed costs are lower and when there are more entrepreneurial people.

Association of Thyroid Function Test Abnormalities and Thyroid Autoimmunity with Preterm Birth: A Systematic Review and Meta-analysis

Abstract: Importance: Maternal hypothyroidism and hyperthyroidism are risk factors for preterm birth. Milder thyroid function test abnormalities and thyroid autoimmunity are more prevalent, but it remains controversial if these are associated with preterm birth. Objective: To study if maternal thyroid function test abnormalities and thyroid autoimmunity are risk factors for preterm birth. Data Sources and Study Selection: Studies were identified through a search of the Ovid MEDLINE, EMBASE, Web of Science, the Cochrane Central Register of Controlled Trials, and Google Scholar databases from inception to March 18, 2018, and by publishing open invitations in relevant journals. Data sets from published and unpublished prospective cohort studies with data on thyroid function tests (thyrotropin [often referred to as thyroid-stimulating hormone or TSH] and free thyroxine [FT4] concentrations) or thyroid peroxidase (TPO) antibody measurements and gestational age at birth were screened for eligibility by 2 independent reviewers. Studies in which participants received treatment based on abnormal thyroid function tests were excluded. Data Extraction and Synthesis: The primary authors provided individual participant data that were analyzed using mixed-effects models. Main Outcomes and Measures: The primary outcome was preterm birth (<37 weeks' gestational age). Results: From 2526 published reports, 35 cohorts were invited to participate. After the addition of 5 unpublished data sets, a total of 19 cohorts were included. The study population included 47045 pregnant women (mean age, 29 years; median gestational age at blood sampling, 12.9 weeks), of whom 1234 (3.1%) had subclinical hypothyroidism (increased thyrotropin concentration with normal FT4 concentration), 904 (2.2%) had isolated hypothyroxinemia (decreased FT4 concentration with normal thyrotropin concentration), and 3043 (7.5%) were TPO antibody positive; 2357 (5.0%) had a preterm birth. The risk of preterm birth was higher for women with subclinical hypothyroidism than euthyroid women (6.1% vs 5.0%, respectively; absolute risk difference, 1.4% [95% CI, 0%-3.2%]; odds ratio [OR], 1.29 [95% CI, 1.01-1.64]). Among women with isolated hypothyroxinemia, the risk of preterm birth was 7.1% vs 5.0% in euthyroid women (absolute risk difference, 2.3% [95% CI, 0.6%-4.5%]; OR, 1.46 [95% CI, 1.12-1.90]). In continuous analyses, each 1-SD higher maternal thyrotropin concentration was associated with a higher risk of preterm birth (absolute risk difference, 0.2% [95% CI, 0%-0.4%] per 1 SD; OR, 1.04 [95% CI, 1.00-1.09] per 1 SD). Thyroid peroxidase antibody-positive women had a higher risk of preterm birth vs TPO antibody-negative women (6.6% vs 4.9%, respectively; absolute risk difference, 1.6% [95% CI, 0.7%-2.8%]; OR, 1.33 [95% CI, 1.15-1.56]). Conclusions and Relevance: Among pregnant women without overt thyroid disease, subclinical hypothyroidism, isolated hypothyroxinemia, and TPO antibody positivity were significantly associated with higher risk of preterm birth. These results provide insights toward optimizing clinical decision-making strategies that should consider the potential harms and benefits of screening programs and levothyroxine treatment during pregnancy.

Responsibility and effort in an experimental labor market

Abstract: Previous indirect evidence suggests that impulses towards pro-social behavior are diminished when an external authority is responsible for an outcome. The responsibility-alleviation effect states that a shift of responsibility to an external authority dampens internal impulses toward honesty, loyalty, or generosity. In a gift-exchange experiment, we find that subjects respond with more generosity (higher effort) when wages are determined by a random process than when assigned by a third party, indicating that even a slight shift in perceived responsibility for the final payoffs can change behavior. Responsibility-alleviation can be a factor in economic environments featuring substantial personal interaction.