Electoral competition through issue selection

Politics must tackle multiple issues at once. In a first-best world, political competition constrains parties to prioritize issues according to the voters' true concerns. In the real world, the opposite also happens: parties manipulate voter priorities by emphasizing issues selectively during the political campaign. This phenomenon, known as priming, should allow parties to pay less attention to the issues that they intend to mute. We develop a model of endogenous issue ownership in which two vote-seeking parties (i) invest to attract voters with "better" policy proposals and (ii) choose a communication campaign to focus voter attention on specific issues. We identify novel feedbacks between communication and investment. In particular, we find that stronger priming effects can backfire by constraining parties to invest more resources in all issues, including the ones they would otherwise intend to mute. We also identify under which conditions parties prefer to focus on their "historical issues" or to engage in issue stealing. Typically, the latter happens when priming effects are strong, and historical reputations differentiates parties less.

Comprehensive evaluation of the IEEE 802.15.4 MAC layer performance with retransmissions

Supported by IEEE 802.15.4 standardization activities, embedded networks have been gaining popularity in recent years. The focus of this paper is to quantify the behavior of key networking metrics of IEEE 802.15.4 beacon-enabled nodes under typical operating conditions, with the inclusion of packet retransmissions. We corrected and extended previous analyses by scrutinizing the assumptions on which the prevalent Markovian modeling is generally based. By means of a comparative study, we singled out which of the assumptions impact each of the performance metrics (throughput, delay, power consumption, collision probability, and packet-discard probability). In particular, we showed that - unlike what is usually assumed - the probability that a node senses the channel busy is not constant for all the stages of the backoff procedure and that these differences have a noticeable impact on backoff delay, packet-discard probability, and power consumption. Similarly, we showed that - again contrary to common assumption - the probability of obtaining transmission access to the channel depends on the number of nodes that is simultaneously sensing it. We evidenced that ignoring this dependence has a significant impact on the calculated values of throughput and collision probability. Circumventing these and other assumptions, we rigorously characterize, through a semianalytical approach, the key metrics in a beacon-enabled IEEE 802.15.4 system with retransmissions.

Sequential estimation of multipath MIMO-OFDM channels

Wireless “MIMO” systems, employing multiple transmit and receive antennas, promise a significant increase of channel capacity, while orthogonal frequency-division multiplexing (OFDM) is attracting a good deal of attention due to its robustness to multipath fading. Thus, the combination of both techniques is an attractive proposition for radio transmission. The goal of this paper is the description and analysis of a new and novel pilot-aided estimator of multipath block-fading channels. Typical models leading to estimation algorithms assume the number of multipath components and delays to be constant (and often known), while their amplitudes are allowed to vary with time. Our estimator is focused instead on the more realistic assumption that the number of channel taps is also unknown and varies with time following a known probabilistic model. The estimation problem arising from these assumptions is solved using Random-Set Theory (RST), whereby one regards the multipath-channel response as a single set-valued random entity.Within this framework, Bayesian recursive equations determine the evolution with time of the channel estimator. Due to the lack of a closed form for the solution of Bayesian equations, a (Rao–Blackwellized) particle filter (RBPF) implementation ofthe channel estimator is advocated. Since the resulting estimator exhibits a complexity which grows exponentially with the number of multipath components, a simplified version is also introduced. Simulation results describing the performance of our channel estimator demonstrate its effectiveness.

Assessing the Political Viability of Labour Market Reform: The Case of Employment Protection

We analyze the political support for employment protection legislation. Unlike my previous work on the same topic, this paper pays a lot of attention to the role of obsolescence in the growth process. In voting in favour of employment protection, incumbent employees trade off lower living standards (because employment protection maintains workers in less productive activities) against longer job duration. The support for employment protection will then depend on the value of the latter relative to the cost of the former. We highlight two key deeterminants of this trade-off: first, the workers' bargaining power, second, the economy's growth rate-more precisely its rate of creative destruction.

A virtual exhibition of open source software for libraries

Frequently the choice of a library management program is conditioned by social, economic and/or political factors that result in the selection of a system that is not altogether suitable for the library’s needs, characteristics and functions. Open source software is quickly becoming a preferred solution, owing to the freedom to copy, modify and distribute it and the freedom from contracts, as well as for greater opportunities for interoperability with other applications. These new trends regarding open source software in libraries are also reflected in LIS studies, as evidenced by the different courses addressing automated programs, repositorymanagement, including the Linux/GNU operating system, among others. The combination of the needs of the centres and the new trends for open source software is the focus of a virtual laboratory for the use of open source software for library applications. It was the result of a project, whose aim was to make a useful contribution to the library community, that was carried out by a group of professors of the School of Library and Information Science of the University of Barcelona, together with a group of students, members of a Working Group on Open Source Software for Information Professionals, of the Professional Library Association of Catalonia.

Public infrastructure and the performance of manufacturing industries: short-and long-run

We present a theoretical framework for determining the short- and long-run effects of infrastructure. While the short-run effects have been the focus of most previous studies, here we derive long-run elasticities by taking into account the adjustment of quasi-fixed inputs to their optimum levels. By considering the impact of infrastructure on private investment decisions, we observe how, apart from the direct effect on costs in the short-run, infrastructure exerts an indirect source of influence in the long-run through their effect on private capital. The model is applied to manufacturing industries in the Spanish regions

Public infrastructure and the performance of manufacturing industries: short-and long-run

We present a theoretical framework for determining the short- and long-run effects of infrastructure. While the short-run effects have been the focus of most previous studies, here we derive long-run elasticities by taking into account the adjustment of quasi-fixed inputs to their optimum levels. By considering the impact of infrastructure on private investment decisions, we observe how, apart from the direct effect on costs in the short-run, infrastructure exerts an indirect source of influence in the long-run through their effect on private capital. The model is applied to manufacturing industries in the Spanish regions

Harmonic oscillators driven by colored noise: crossovers, resonances and spectra

We study second-order properties of linear oscillators driven by exponentially correlated noise. We focus our attention on dynamical exponents and crossovers and also on resonance phenomena that appear when the driving noise is dichotomous. We also obtain the power spectrum and show its different behaviors according to the color of the noise.

Extreme times in financial markets.

We apply the theory of continuous time random walks (CTRWs) to study some aspects involving extreme events in financial time series. We focus our attention on the mean exit time (MET). We derive a general equation for this average and compare it with empirical results coming from high-frequency data of the U.S. dollar and Deutsche mark futures market. The empirical MET follows a quadratic law in the return length interval which is consistent with the CTRW formalism.

Anàlisi de l'atenció a la diversitat a les tres escoles rurals de la Zer Tramuntana

L’objectiu d’aquest estudi, de caire interpretatiu - qualitatiu, consisteix en l’anàlisi de l’Atenció a la Diversitat a les tres escoles rurals de la ZER Tramuntana. Una recerca que pretén descriure, analitzar i interpretar els principals aspectes d’inclusió de l’alumnat en el grup - classe, la resposta educativa que donen els docents a la diversitat en les aules i els documents normatius que recullen aquests dos aspectes. Professors, alumnes i grup - classe són els actors que nosaltres hem estudiat detalladament, a partir d’entrevistes, tests sociomètrics i l’anàlisi dels documents vigents de les tres escoles de referència d’aquesta ZER que tenen present l’Atenció a la Diversitat. A partir de l’estudi dels tres casos reals, l’escola Puig Segalar de Viladamat, l’escola de Ventalló i l’escola Els Valentins de Vilamacolum, ens centrem en la perspectiva curricular i model inclusiu, per poder donar resposta a la nostra hipòtesi plantejada inicialment: El model d’escola rural afavoreix les estratègies d’Atenció a la Diversitat.

Diradicals acting through diamagnetic phenylene vinylene bridges: Raman spectroscopy as a probe to characterize spin delocalization

We present a complete Raman spectroscopic study in two structurally well-defined diradical species of different lengths incorporating oligo p-phenylene vinylene bridges between two polychlorinated triphenylmethyl radical units, a disposition that allows sizeable conjugation between the two radicals through and with the bridge. The spectroscopic data are interpreted and supported by quantum chemical calculations. We focus the attention on the Raman frequency changes, interpretable in terms of: (i) bridge length (conjugation length); (ii) bridge conformational structure; and (iii) electronic coupling between the terminal radical units with the bridge and through the bridge, which could delineate through-bond spin polarization, or spin delocalization. These items are addressed by using the"oligomer approach" in conjunction with pressure and temperature dependent Raman spectroscopic data. In summary, we have attempted to translate the well-known strategy to study the electron (charge) structure of π−conjugated molecules by Raman spectroscopy to the case of electron (spin) interactions via the spin delocalization mechanism.

Monotonic continuous-time random walks with drift and stochastic reset events

In this paper we consider a stochastic process that may experience random reset events which suddenly bring the system to the starting value and analyze the relevant statistical magnitudes. We focus our attention on monotonic continuous-time random walks with a constant drift: The process increases between the reset events, either by the effect of the random jumps, or by the action of the deterministic drift. As a result of all these combined factors interesting properties emerge, like the existence (for any drift strength) of a stationary transition probability density function, or the faculty of the model to reproduce power-law-like behavior. General formulas for two extreme statistics, the survival probability, and the mean exit time, are also derived. To corroborate in an independent way the results of the paper, Monte Carlo methods were used. These numerical estimations are in full agreement with the analytical predictions.

Unidirectional quantum walks: Evolution and exit times

In this paper we focus our attention on a particle that follows a unidirectional quantum walk, an alternative version of the currently widespread discrete-time quantum walk on a line. Here the walker at each time step can either remain in place or move in a fixed direction, e.g., rightward or upward. While both formulations are essentially equivalent, the present approach leads us to consider discrete Fourier transforms, which eventually results in obtaining explicit expressions for the wave functions in terms of finite sums and allows the use of efficient algorithms based on the fast Fourier transform. The wave functions here obtained govern the probability of finding the particle at any given location but determine as well the exit-time probability of the walker from a fixed interval, which is also analyzed.

Com afronten els infants amb factors de risc de TDAH l'adquisició de la lectura: la consciència fonològica com a eina per millorar l'aprenentatge dels components bàsics de la lectura a educació infantil

L’adquisició de la lectura és un dels moments més importants i reconeguts socialment en la vida de l’infant, per això, amb aquesta recerca es pretén investigar les dificultats i mancances que tenen els infants davant d’aquest gran repte. Es centrarà l’atenció en aquells infants que mostren factors de risc de TDAH per tal de justificar i comprovar que aquests mostren més dificultats en l’adquisició de la lectura que els infants que no mostren aquest factor de risc. Per una altra banda, amb aquesta recerca també es pretén demostrar la importància del treball sistemàtic de la consciència fonològica en l’etapa d’educació infantil, per afavorir i garantir l’adquisició de la lectura de manera integra i significativa.

Efficiency and Equity in Learning Communities and schools

Traditionally, school efficiency has been measured as a function of educational production. In the last two decades, however, studies in the economics of education have indicated that more is required to improve school efficiency: researchers must explore how significant changes in school organization affect the performance of at-risk students. In this paper we introduce Henry Levin’s adoption of the X-efficiency approach to education and we describe the efficient and cost-effective characteristics of one Learning Communities Project School that significantly improved its student outcomes and enrollment numbersand reduced its absenteeism rate to zero. The organizational change that facilitatedthese improvements defined specific issues to address. Students’ school success became the focus of the school project, which also offered specific incentives, selected teachers, involved parents and community members in decisions, and used the most efficient technologies and methods. This case analysis reveals new two elements—family training and community involvement—that were not explicit parts of Levin’s adaptation. The case of the Antonio Machado Public School should attract the attention of both social scientists and policy makers