Does Warfare Matter? Severity, Duration, and Outcomes of Civil Wars

Importa si una guerra civil es combat com un conflicte irregular, convencional o simètric no convencional? En altres paraules, tenen les “tecnologies de la rebel·lió” un impacte sobre la gravetat d’una guerra, la seva durada o el seu resultat? Aquest treball mostra que els conflictes irregulars duren més que els altres tipus de conflicte, mentre els convencionals tendeixen a ser més greus en termes de letalitat al camp de batalla. D’altra banda, els conflictes irregulars tendeixen a ser guanyats pels governs, mentre els altres són més propensos a acabar en empat. Substancialment, aquests resultats ens ajuden a donar sentit a l’evolució de les guerres civils, les quals tendeixen a ser més curtes, més intenses i més difícils per als governs. Teòricament, aquests resultats donen suport a la importància de la tecnologia de rebel·lió a l’estudiar la gravetat, la durada i els resultats de les guerres civils; a més, contribueixen a una millor comprensió de la contribució històrica de la guerra irregular a la construcció de l’Estat i al canvi social.

N-dimensional dynamical systems exploiting instabilities in full

We report experimental and numerical results showing how certain N-dimensional dynamical systems are able to exhibit complex time evolutions based on the nonlinear combination of N-1 oscillation modes. The experiments have been done with a family of thermo-optical systems of effective dynamical dimension varying from 1 to 6. The corresponding mathematical model is an N-dimensional vector field based on a scalar-valued nonlinear function of a single variable that is a linear combination of all the dynamic variables. We show how the complex evolutions appear associated with the occurrence of successive Hopf bifurcations in a saddle-node pair of fixed points up to exhaust their instability capabilities in N dimensions. For this reason the observed phenomenon is denoted as the full instability behavior of the dynamical system. The process through which the attractor responsible for the observed time evolution is formed may be rather complex and difficult to characterize. Nevertheless, the well-organized structure of the time signals suggests some generic mechanism of nonlinear mode mixing that we associate with the cluster of invariant sets emerging from the pair of fixed points and with the influence of the neighboring saddle sets on the flow nearby the attractor. The generation of invariant tori is likely during the full instability development and the global process may be considered as a generalized Landau scenario for the emergence of irregular and complex behavior through the nonlinear superposition of oscillatory motions

Outage thresholds of LDPC codes over nonergodic block-fading channels

This paper derives approximations allowing the estimation of outage probability for standard irregular LDPC codes and full-diversity Root-LDPC codes used over nonergodic block-fading channels. Two separate approaches are discussed: a numerical approximation, obtained by curve fitting, for both code ensembles, and an analytical approximation for Root-LDPC codes, obtained under the assumption that the slope of the iterative threshold curve of a given code ensemble matches the slope of the outage capacity curve in the high-SNR regime.

A generalization of histogram type estimators

We introduce simple nonparametric density estimators that generalize theclassical histogram and frequency polygon. The new estimators are expressed as linear combination of density functions that are piecewisepolynomials, where the coefficients are optimally chosen in order to minimize the integrated square error of the estimator. We establish the asymptotic behaviour of the proposed estimators, and study theirperformance in a simulation study.

Audit risk and rent extraction: Evidence from a randomized evaluation in Brazil

We report results from a randomized policy experiment designed to test whether increasedaudit risk deters rent extraction in local public procurement and service delivery in Brazil. Ourestimates suggest that temporarily increasing annual audit risk by about 20 percentage pointsreduced the proportion of irregular local procurement processes by about 17 percentage points.This reduction was driven entirely by irregularities involving mismanagement or corruption. Incontrast, we find no evidence that increased audit risk affected the quality of publicly providedpreventive and primary health care services -measured based on user satisfaction surveys- orcompliance with national regulations of the conditional cash transfer program "Bolsa Família".

On the throughput-WIP trade-off in queueing systems, diminishing returns and the threshold property: A linear programming approach

We present a new unifying framework for investigating throughput-WIP(Work-in-Process) optimal control problems in queueing systems,based on reformulating them as linear programming (LP) problems withspecial structure: We show that if a throughput-WIP performance pairin a stochastic system satisfies the Threshold Property we introducein this paper, then we can reformulate the problem of optimizing alinear objective of throughput-WIP performance as a (semi-infinite)LP problem over a polygon with special structure (a thresholdpolygon). The strong structural properties of such polygones explainthe optimality of threshold policies for optimizing linearperformance objectives: their vertices correspond to the performancepairs of threshold policies. We analyze in this framework theversatile input-output queueing intensity control model introduced byChen and Yao (1990), obtaining a variety of new results, including (a)an exact reformulation of the control problem as an LP problem over athreshold polygon; (b) an analytical characterization of the Min WIPfunction (giving the minimum WIP level required to attain a targetthroughput level); (c) an LP Value Decomposition Theorem that relatesthe objective value under an arbitrary policy with that of a giventhreshold policy (thus revealing the LP interpretation of Chen andYao's optimality conditions); (d) diminishing returns and invarianceproperties of throughput-WIP performance, which underlie thresholdoptimality; (e) a unified treatment of the time-discounted andtime-average cases.

Measuring the stability of histogram appearance when the anchor position is changed

Although the histogram is the most widely used density estimator, itis well--known that the appearance of a constructed histogram for a given binwidth can change markedly for different choices of anchor position. In thispaper we construct a stability index $G$ that assesses the potential changesin the appearance of histograms for a given data set and bin width as theanchor position changes. If a particular bin width choice leads to an unstableappearance, the arbitrary choice of any one anchor position is dangerous, anda different bin width should be considered. The index is based on the statisticalroughness of the histogram estimate. We show via Monte Carlo simulation thatdensities with more structure are more likely to lead to histograms withunstable appearance. In addition, ignoring the precision to which the datavalues are provided when choosing the bin width leads to instability. We provideseveral real data examples to illustrate the properties of $G$. Applicationsto other binned density estimators are also discussed.

Implementing interactive computing in an object-oriented environment

Statistical computing when input/output is driven by a Graphical User Interface is considered. A proposal is made for automatic control ofcomputational flow to ensure that only strictly required computationsare actually carried on. The computational flow is modeled by a directed graph for implementation in any object-oriented programming language with symbolic manipulation capabilities. A complete implementation example is presented to compute and display frequency based piecewise linear density estimators such as histograms or frequency polygons.

The Library: from classic to postmodern

In its long and irregular transition, from traditional library to the electronic book we have seen combining and alternating the hybrid, electronic and most recently the digital libraries. All these concepts which are combining and are conditioning each other, are referring to methods of organization and use of an informational content (which exists or not in an informational structure).

Los hábitats del proyecto CORINE en el ámbito territorial catalán: delimitación y cartografía.

nd items. Once maps are drawn up they are digitized and put into a GIS and finally subjected to quality control. Table 4 shows the most important habitats (according to polygon number and area covered) and the least represented habitats in the sheets drawn so far. Sheets can be obtained through internet (www.gencat.net/mediamb/pn.htm).

El mostratge fitocenològic a Catalunya

irregular. With reference to the 10 km UTM network, the number of relevés per cell ranges between 0 and 527, with a mean of 36, the most exhaustively prospected areas lying in the Pyrenean range. On the other hand, 44 cells spread ± regularly over the Catalan territory have not available relevés yet, the larger spot lying in the Lluçanés area (C Catalonia). As a general rule. communities seem to be rather adequately prospected and no great discordances between syntaxa have been observed. However. further studies may be required for several alliances such as Berberidion, Pruno-Rubion ulmifolii, Taeniathero-Aegilopion, Alkanno-Malcolmion, Thero-Suaedion, Posidonion or Rupion maritimae. Key words: Phytocoenology, Relevés Database, Geographical prospection, Syntaxonomical prospection, Catalonia.

Velar verbs and verbal classes in catalan

There is in Catalan a set of verbs, the so-called «velar verbs», whose differential characteristic consists in presenting a velar segment between the root and the inflectional suffixes in certain morphosyntactic contexts. This velar segment has traditionally been considered as being part of the root in the contexts where it occurs, and has been made responsible for the typical allomorphic character of velar verbs. Under the assumption that regular verbs are only one-root verbs, velar verbs have been treated as irregular verbs. Nevertheless, neither the phonic character of the velar segment nor the marginal character of velar verbs is clear. The aim of this paper is to present a different account of velar verbs on the basis of the inflectional morphological character of the velar segment. The work is split into two parts. The first one focuses on standard Catalan, and tries to show that in this variety velar verbs are better treated as regular verbs. The second one focuses on other Catalan varieties, and aims to exhibit the incoherence implied in the traditional treatment of velar verbs in the context of the Catalan language as a whole. The discussion is mainly developed on morphological grounds, halfway between theory and description.

Symptom Check-List-90-R: fiabilidad, datos normativos y estructura factorial en estudiantes universitarios

El Symptom Checklist-90-R (SCL-90-R) es uno de los instrumentos más ampliamente utilizados en la medición de la sintomatología psicopatológica en población clínica y en población general. Ya que gran parte de la investigación en psicopatología se realiza con estudiantes universitarios, este estudio instrumental pretende proporcionar datos de referencia para esta población. Analizamos las propiedades psicométricas de esta escala en una muestra representativa de 1.277 estudiantes de la Universidad de Girona. Las dimensiones con puntuaciones más elevadas para el total de la muestra son Obsesividad-compulsividad, Depresión y Sensibilidad interpersonal. Los resultados muestran diferencias significativas entre hombres y mujeres. La fiabilidad de la escala resulta muy aceptable, con unos coeficientes de consistencia interna de las nueve dimensiones primarias y del GSI, que oscilan entre 0,69 y 0,97. El análisis de la estructura factorial y la fuerte interdependencia entre las escalas primarias cuestionan la multidimensionalidad del SCL-90-R y refuerzan la idea de que el instrumento proporciona una medida de distrés general, es decir, es un indicador unidimensional de malestar psicológico más que una medida de dimensiones psicopatológicas diferenciadas

Kinetic equations for difussion in the presence of entropic barriers

We use the mesoscopic nonequilibrium thermodynamics theory to derive the general kinetic equation of a system in the presence of potential barriers. The result is applied to a description of the evolution of systems whose dynamics is influenced by entropic barriers. We analyze in detail the case of diffusion in a domain of irregular geometry in which the presence of the boundaries induces an entropy barrier when approaching the exact dynamics by a coarsening of the description. The corresponding kinetic equation, named the Fick-Jacobs equation, is obtained, and its validity is generalized through the formulation of a scaling law for the diffusion coefficient which depends on the shape of the boundaries. The method we propose can be useful to analyze the dynamics of systems at the nanoscale where the presence of entropy barriers is a common feature.

Dissemination of periodic mammography and patterns of use, by birth cohort, in Catalonia (Spain)

Background: In Catalonia (Spain) breast cancer mortality has declined since the beginning of the 1990s. The dissemination of early detection by mammography and the introduction of adjuvant treatments are among the possible causes of this decrease, and both were almost coincident in time. Thus, understanding how these procedures were incorporated into use in the general population and in women diagnosed with breast cancer is very important for assessing their contribution to the reduction in breast cancer mortality. In this work we have modeled the dissemination of periodic mammography and described repeat mammography behavior in Catalonia from 1975 to 2006. Methods: Cross-sectional data from three Catalan Health Surveys for the calendar years 1994, 2002 and 2006 was used. The dissemination of mammography by birth cohort was modeled using a mixed effects model and repeat mammography behavior was described by age and survey year. Results: For women born from 1938 to 1952, mammography clearly had a period effect, meaning that they started to have periodic mammograms at the same calendar years but at different ages. The age at which approximately 50% of the women were receiving periodic mammograms went from 57.8 years of age for women born in 1938–1942 to 37.3 years of age for women born in 1963–1967. Women in all age groups experienced an increase in periodic mammography use over time, although women in the 50–69 age group have experienced the highest increase. Currently, the target population of the Catalan Breast Cancer Screening Program, 50–69 years of age, is the group that self-reports the highest utilization of periodic mammograms, followed by the 40–49 age group. A higher proportion of women of all age groups have annual mammograms rather than biennial or irregular ones. Conclusion: Mammography in Catalonia became more widely implemented during the 1990s. We estimated when cohorts initiated periodic mammograms and how frequently women are receiving them. These two pieces of information will be entered into a cost-effectiveness model of early detection in Catalonia.