We say that a population is perfectly polarized when divided in two groups of the same size and opposite opinions. In this paper, we propose a methodology to study and measure the emergence of polarization from social interactions. We begin by proposing a model to estimate opinions in which a minority of influential individuals propagate their opinions through a social network. The result of the model is an opinion probability density function. Next, we propose an index to quantify the extent to which the resulting distribution is polarized. Finally, we apply the proposed methodology to a Twitter conversation about the late Venezuelan president, Hugo Chávez, finding a good agreement between our results and offline data. Hence, we show that our methodology can detect different degrees of polarization, depending on the structure of the network.

The complete sequencing of the genome of Saccharomyces cerevisiae indicated that this organism contains five genes encoding aldehyde dehydrogenases. YOR374w and YER073w correspond to the mitochondrial isoforms and we propose as gene names ALD4 and ALD5, respectively. YPL061w has been described as the cytoplasmic constitutive isoform and named ALD6. We characterize here the tandem‐repeated ORFs YMR170c and YMR169c as the cytoplasmic stress‐inducible isoforms, with gene names ALD2 and ALD3, respectively. The expression of ALD2 and ALD3 is dependent on the general‐stress transcription factors Msn2,4 but independent of the HOG MAP kinase pathway. ALD3 is induced by a variety of stresses, including osmotic shock, heat shock, glucose exhaustion, oxidative stress and drugs. ALD2 is only induced by osmotic stress and glucose exhaustion. A double null mutant, ald2 ald3, exhibited unchanged sensitivity to any of the above stresses. The only phenotype detected in this mutant was a reduced growth rate in ethanol medium as compared to the wild type. Copyright © 1999 John Wiley & Sons, Ltd.

The photocurrent-time dependence observed during experiments of water photo-oxidation at an n-TiO2 single crystal, as a function of the applied potential and illumination intensity, has been analyzed on the basis of a kinetic model previously proposed. In a basic medium, the model assumes as a first step the photogeneration of surface-bound OH~ radicals from Ti coordinated OH-ions of basic character. OH~ radicals further recombine on the TiO2 surface at a second step, leading to the formation of surface peroxo complexes (chemisorbed HO2-species). Finally, photogenerated hydrogen peroxide species become photo-oxidized and O2 evolves. At small bandbending the decay time constant, ~, characterizing the photocurrent transients is very sensitive to the applied potential, but does not depend on the illumination intensity. The photocurrent-time dependence is dominated by e--h § surface recombination, mainly via photogenerated OH~ radicals. _The pseudo first-order rate constant of this reaction shows a gaussian distribution around a main value k = k3nb exp (-q~JkT), with kz = 10 -1~ cm 3 s -1, nb and r representing the bulk electron density and the bandbending, respectively. This behavior indicates the existence of a heterogeneous distribution of Ti~OH-surface sites mediating the process. In the high bandbending region x is not sensitive to the applied external bias, but strongly depends on the light intensity. The transient is then due to the surface accumulation of positive charge at photogenerated OH~ radicals, which produces a slow bandbending decrease and a concomitant diminution of the photocurrent. These effects are controlled by the rate, ks, of hydrogen peroxide formation, which is a second-order reaction in the surface concentration of photogenerated OH~ radicals. A k2 ~ 1014 cm 2 s -1 can be estimated.Photostable oxides with large bandgaps, like n-TiO2, have been widely employed as photoelectrodes for water splitting in a photoelectrochemical cell (1). However, the mechanisms of charge transfer at the oxide-electrolyte interface involved in photo-oxidation of water are still obscure. Of special interest are the kinetics of the intermediate steps involved in the reaction and the nature of the photogenerated species.The technique of optically induced transients has proved to be an interesting tool for the kinetic research of photoreactions occurring at the semiconductor/electrolyte interface in photoelectrochemical cells (PEC) (2). In this type of time-resolved technique the transient can be induced by perturbing the system, either with a very short light pulse (laser flash), Ref. (2j-s), or with a continuous illumination source and a shutter, . In the first case time resolution is, in principle, limited by the width of the light pulse (from ps to ns) and kinetic information can be obtained about the ver~ fast processes following illumination of the system. In the second case time resolution is restricted to the range of ms because of the slow aperture speed of the shutter placed between the light source and the...

Transmitting messages in the most efficient way as possible has always been one of politicians main concerns during electoral processes. Due to the rapidly growing number of users, online social networks have become ideal platforms for politicians to interact with their potential voters. Exploiting the available potential of these tools to maximize their influence over voters is one of politicians actual challenges. To step in this direction, we have analyzed the user activity in the online social network Twitter, during the 2011 Spanish Presidential electoral process, and found that such activity is correlated with the election results. We introduce a new measure to study political support in Twitter, which we call the Relative Support. We have also characterized user behavior by analyzing the structural and dynamical patterns of the complex networks emergent from the mention and retweet networks. Our results suggest that the collective attention is driven by a very small fraction of users. Furthermore we have analyzed the interactions taking place among politicians, observing a lack of debate. Finally we develop a network growth model to reproduce the interactions taking place among politicians.