Tweets on the road

The pervasiveness of mobile devices, which is increasing daily, is generating a vast amount of geo-located data allowing us to gain further insights into human behaviors. In particular, this new technology enables users to communicate through mobile social media applications, such as Twitter, anytime and anywhere. Thus, geo-located tweets offer the possibility to carry out in-depth studies on human mobility. In this paper, we study the use of Twitter in transportation by identifying tweets posted from roads and rails in Europe between September 2012 and November 2013. We compute the percentage of highway and railway segments covered by tweets in 39 countries. The coverages are very different from country to country and their variability can be partially explained by differences in Twitter penetration rates. Still, some of these differences might be related to cultural factors regarding mobility habits and interacting socially online. Analyzing particular road sectors, our results show a positive correlation between the number of tweets on the road and the Average Annual Daily Traffic on highways in France and in the UK. Transport modality can be studied with these data as well, for which we discover very heterogeneous usage patterns across the continent.Comment: 15 pages, 17 figure

Llenguatge jurídic i llenguatge poètic: les gosadies del comte-bisbe Miró Bonfill

En aquest treball s'estudia l'originalitat poètica del comte de Besalú i Bisbe de Girona, Miró Bonfill (segle X), en un dels documents que hom li atribueix: l'acta de confirmació de la dotació de l'església de Sant Pere de Besalú. L'anàlisi dels 27 versos identificats en aquest document posen en relleu una clara dependència de Miró Bonfill d'altres poetes com Paulí d'Aquileia o Venanci Fortunat, però també l'existència de relacions amb altres obres, anteriors, contemporànies i posteriors, circumstància que obre nous interrogants sobre les relacions literàries de Catalunya amb Europa al segle X

Quantifying the shadow economy: measurement with theory

We construct a dynamic, general equilibrium model of tax evasion where agents choose to report some of their income. Unreported income requires using a payment method that avoids recordkeeping – cash. Trade using cash to avoid taxes is the theoretical measure of the shadow economy from our model. We then calibrate our model using money, interest rate and GDP data to back out the size of the shadow economy for a sample of 30 countries and compare our estimates to traditional ad hoc estimates. Our results generate reasonably larger estimates for the size of the shadow economy than exist in previous literature.>Informal sector (Economics) ; Taxation ; Credit

Radiative capture on 242Pu for MOX fuel reactors

Proposal: Radiative capture on 242Pu for MOX fuel reactorsThe use of MOX fuel (mixed-oxide fuel made of UO2 and PuO2) in nuclear reactors allows substituting a large fraction of the enriched Uranium by Plutonium reprocessed from spent fuel. Indeed around 66% of the plutonium from spent fuel is made of 239Pu and 241Pu, which are fissile in thermal reactors. A typical reactor of this type uses a fuel with 7% reprocessed Pu and 93% depleted U, thus profiting from both the spent fuel and the remaining 238U following the 235U enrichment. With the use of such new fuel compositions rich in Pu the better knowledge of the capture and fission cross sections of the Pu isotopes becomes very important. This is clearly stated in the recent OECD NEA’s “High Priority Request List” and in the WPEC-26 “Uncertainty and target accuracy assessment for innovative systems using recent covariance data evaluations” report. In particular, a new series of cross section evaluations have been recently carried out jointly by the European (JEFF) and United States (ENDF) nuclear data agencies. As the new evaluations on 240Pu and 241Am have been already completed, 242Pu is the next to be reevaluated, and the scarceness of capture data (only two TOF measurements from 1973 and 1976 are available and disagree with each other) calls for a new time-of flight capture cross section measurement. This will be the first measurement in 40 years and, with the use of more advanced techniques, shall provide a more reliable and accurate result. We propose to measure the capture cross section of 242Pu in the region from thermal up to at least 60 keV, aiming for a high energy limit of 500 keV. The experiment would make use of an array of 4 low neutron sensitivity C6D6 detectors and be carried out at the n_TOF EAR-1 (185 m flight path) measuring station. Compared to the current uncertainty of 35%, this measurement aims at an improved accuracy between 7% and 12% depending on the energy region.Preprin