Urban characteristics attributable to density-driven tie formation

Motivated by empirical evidence on the interplay between geography, population density and societal interaction, we propose a generative process for the evolution of social structure in cities. Our analytical and simulation results predict both super-linear scaling of social tie density and information flow as a function of the population. We demonstrate that our model provides a robust and accurate fit for the dependency of city characteristics with city size, ranging from individual-level dyadic interactions (number of acquaintances, volume of communication) to population-level variables (contagious disease rates, patenting activity, economic productivity and crime) without the need to appeal to modularity, specialization, or hierarchy.Comment: Early version of this paper was presented in NetSci 2012 as a contributed talk in June 2012. An improved version of this paper is published in Nature Communications in June 2013. It has 14 pages and 5 figure

Time Critical Social Mobilization: The DARPA Network Challenge Winning Strategy

It is now commonplace to see the Web as a platform that can harness the collective abilities of large numbers of people to accomplish tasks with unprecedented speed, accuracy and scale. To push this idea to its limit, DARPA launched its Network Challenge, which aimed to "explore the roles the Internet and social networking play in the timely communication, wide-area team-building, and urgent mobilization required to solve broad-scope, time-critical problems." The challenge required teams to provide coordinates of ten red weather balloons placed at different locations in the continental United States. This large-scale mobilization required the ability to spread information about the tasks widely and quickly, and to incentivize individuals to act. We report on the winning team's strategy, which utilized a novel recursive incentive mechanism to find all balloons in under nine hours. We analyze the theoretical properties of the mechanism, and present data about its performance in the challenge.Comment: 25 pages, 6 figure

Magnetoresistance in Thin Permalloy Film (10nm-thick and 30-200nm-wide) Nanocontacts Fabricated by e-Beam Lithography

In this paper we show spin dependent transport experiments in nanoconstrictions ranging from 30 to 200nm. These nanoconstrictions were fabricated combining electron beam lithography and thin film deposition techniques. Two types of geometries have been fabricated and investigated. We compare the experimental results with the theoretical estimation of the electrical resistance. Finally we show that the magnetoresistance for the different geometries does not scale with the resistance of the structure and obtain drops in voltage of 20mV at 20Oe.Comment: 15 pages, 4 figures. Accepted by AP

Scaling laws of solar and stellar flares

In this study we compile for the first time comprehensive data sets of solar and stellar flare parameters, including flare peak temperatures T_p, flare peak volume emission measures EM_p, and flare durations t_f from both solar and stellar data, as well as flare length scales L from solar data. Key results are that both the solar and stellar data are consistent with a common scaling law of EM_p ~ T_p^4.7, but the stellar flares exhibit ~250 times higher emission measures (at the same flare peak temperature). For solar flares we observe also systematic trends for the flare length scale L(T_p) ~ T_p^0.9 and the flare duration t_F(T_p) ~ T_p^0.9 as a function of the flare peak temperature. Using the theoretical RTV scaling law and the fractal volume scaling observed for solar flares, i.e., V(L) ~ L^2.4, we predict a scaling law of EM_p ~ T_p^4.3, which is consistent with observations, and a scaling law for electron densities in flare loops, n_p ~ T_p^2/L ~ T_p^1.1. The RTV-predicted electron densities were also found to be consistent with densities inferred from total emission measures, n_p=(EM_p/q_V*V)^1/2, using volume filling factors of q_V=0.03-0.08 constrained by fractal dimensions measured in solar flares. Our results affect also the determination of radiative and conductive cooling times, thermal energies, and frequency distributions of solar and stellar flare energies.Comment: 9 Figs., (paper in press, The Astrophsycial Journal

BNG local government in Carballo : long distance run or perfect storm? (2003 - 2016)

Traballo fin de Máster en Márketing, Consultoría e Comunicación Política. Facultade de Ciencias Políticas e Sociais. Curso 2014-2015Este traballo pretende realizar unha aproximación ás chaves da consolidación do goberno local do BNG no Concello de Carballo entre os anos 2003 e 2015. A través da análise dos principais acontecementos destes doce anos. Intentaremos achar os resortes políticos e comunicativos que contribuíron ao éxito deste proxecto político dentro dun contexto que, en principio, parecía bastante desfavorable

How redundant is it? : An empirical analysis on linked datasets

Publisher PD

Solea solea: landings data and LPUE standardization from official logbooks in Atlantic Iberian waters

Time series of abundance indices are the main source of information to calibrate stock assessment models. Standardized LPUEs (Landings per unit effort) derived from fishery-dependent data can be used as a proxy of the species abundance. In this study we present a first attempt of standardization of landings per unit of effort (LPUE) for soleid species. Soleid species, in particular the common sole (Solea solea), are important fisheries resources with high economic value, targeted by the Spanish fleet in Iberian Atlantic waters. Nevertheless, information on these resources is scarce. Time series data from 2009 to 2020 from the official logbooks of the Spanish fleet operating in the ICES subdivisions 8.c and 9.a. have been analysed in order to provide some insights into this fishery. Uncertainties in the accuracy of the identification of the species led to the aggregation of 6 taxa: Solea solea, Solea senegalensis, Solea elongata, Solea spp., Pegusa lascaris and Pegusa cadenati, as one single category, being the common sole, Solea solea, the most important taxon in terms of economic value and landings. Landings per unit of effort (LPUE) based on the estimated soleid species landed weight by fishing days (unit effort), for the most important métiers in terms of landings, were used as response variable. Generalised linear mixed models, fitted with a Gamma distribution, were employed, and several explanatory variables were tested to be included in the models: year, quarter, month, ICES division, statistical rectangle, landing port, vessel characteristics (LOA category, vessel power), depth, fishing time and number of fishing operations

Adaptive random quantum eigensolver

We propose an adaptive random quantum algorithm to obtain an optimized eigensolver. Specifically, we introduce a general method to parametrize and optimize the probability density function of a random number generator, which is the core of stochastic algorithms. We follow a bioinspired evolutionary mutation method to introduce changes in the involved matrices. Our optimization is based on two figures of merit: learning speed and learning accuracy. This method provides high fidelities for the searched eigenvectors and faster convergence on the way to quantum advantage with current noisy intermediate-scaled quantum computers.Junta de Andalucía (Grants No. P20-00617 and No. US-1380840)Science and Technology Commission of Shanghai Municipality (Grant No. 2019SHZDZX01-ZX04

The salting coefficient and size of alkylamines in saline media at different temperatures: estimation from Pitzer equations and the mean spherical approximation

The renewed theoretical interest in the proton transfer associated to the amino group together with the scarcity of acid-base studies of amines in moderate to concentrated saline media focussed our attention on the study of the basicities of some alkylamines, namely monomethyl, dimethyl and trimethylamine, in aqueous saline solutions of KCl at various temperatures. A non-conventional analysis of stoichiometric equilibrium constants versus ionic strength data is carried out. On one hand, Pitzer’s model is easily applied to calculate the salting coefficient and the thermodynamic equilibrium constant of the alkylamines. On the other hand, the mean spherical approximation has the advantage over the Debye–Hückel based theories that it can account for effects produced by species of different sizes. Here, it is applied to predict the dependence of the salting behavior on the size of the alkylamines.Xunta de Galicia; XUGA 10310B9