The frequency spectrum of finite samples from the intermittent silence process

It has been argued that the actual distribution of word frequencies could be reproduced or explained by generating a random sequence of letters and spaces according to the so-called intermittent silence process. The same kind of process could reproduce or explain the counts of other kinds of units from a wide range of disciplines. Taking the linguistic metaphor, we focus on the frequency spectrum, i.e., the number of words with a certain frequency, and the vocabulary size, i.e., the number of different words of text generated by an intermittent silence process. We derive and explain how to calculate accurately and efficiently the expected frequency spectrum and the expected vocabulary size as a function of the text size.Peer ReviewedPostprint (author's final draft

Patterns in syntactic dependency networks

Many languages are spoken on Earth. Despite their diversity, many robust language universals are known to exist. All languages share syntax, i.e., the ability of combining words for forming sentences. The origin of such traits is an issue of open debate. By using recent developments from the statistical physics of complex networks, we show that different syntactic dependency networks (from Czech, German, and Romanian) share many nontrivial statistical patterns such as the small world phenomenon, scaling in the distribution of degrees, and disassortative mixing. Such previously unreported features of syntax organization are not a trivial consequence of the structure of sentences, but an emergent trait at the global scale.Peer ReviewedPostprint (published version

Optimization in complex networks

Many complex systems can be described in terms of networks of interacting units. Recent studies have shown that a wide class of both natural and artificial nets display a surprisingly widespread feature: the presence of highly heterogeneous distributions of links, providing an extraordinary source of robustness against perturbations. Although most theories concerning the origin of these topologies use growing graphs, here we show that a simple optimization process can also account for the observed regularities displayed by most complex nets. Using an evolutionary algorithm involving minimization of link density and average distance, four major types of networks are encountered: (a) sparse exponential-like networks, (b) sparse scale-free networks, (c) star networks and (d) highly dense networks, apparently defining three major phases. These constraints provide a new explanation for scaling of exponent about -3. The evolutionary consequences of these results are outlined.Peer ReviewedPostprint (author's final draft

Selection, tinkering and emergence in complex networks: crossing the land of tinkering

Complex biological networks have very different origins than technologic ones. The latter involve extensive design and, as engineered structures, include a high level of optimization. The former involve (in principle) contingency and structural constraints, with new structures being incorporated through tinkering with previously evolved modules or units. However, the observation of the topological features of different biological nets suggests that nature can have a limited repertoire of ”attractors” that essentially optimize communication under some basic constraints of cost and architecture or that allow the biological nets to reach a high degree of homeostasis. Conversely, the topological features exhibited by some technology graphs indicate that tinkering and internal constraints play a key role, in spite of the ”designed” nature of these structures. Previous scenarios suggested to explain the overall trends of evolution are re-analyzed in light of topological patterns.Peer ReviewedPostprint (author's final draft

Trinocular ystem for 3D motion and dense structure estimation

The relief of the seafloor is an important source of data for many scientists. In this paper we present an optical system to deal with underwater 3D reconstruction. This system is formed by three cameras that take images synchronously in a constant frame rate scheme. We use the images taken by these cameras to compute dense 3D reconstructions. We use Bundle Adjustment to estimate the motion of the trinocular rig. Given the path followed by the system, we get a dense map of the observed scene by registering the different dense local reconstructions in a unique and bigger one.Peer Reviewe

An Alternative Approach to Analyze Ipsative Data. Revisiting Experiential Learning Theory

The ritualistic use of statistical models regardless of the type of data actually available is a common practice across disciplines. Statistical models involve a series of assumptions whose existence is often neglected altogether, thus making the mentioned common practice even more pervasive. This paper illustrates the consequences of this ritualistic practice within Kolb’s Experiential Learning Theory (ELT) operationalized through its Learning Style Inventory (KLSI). We show how using a well-known methodology in other disciplines -compositional data analysis (CODA)- KLSI data can be properly analyzed. In addition, a third dimension of the KLSI is unveiled providing room for future research. This third dimension describes an individual’s relative preference for learning by prehension rather than by transformation. Using a sample of European MBA students, we relate this dimension with another self-assessment instrument, the Philosophical Orientation Questionnaire (POQ), and with an observer-assessed instrument, the Emotional and Social Inventory (ESCI-U). Both show plausible statistical relationships. An intellectual operating philosophy is linked to a preference for prehension, whereas a pragmatic operating philosophy is linked to transformation. Self-management and social awareness competencies are linked to a learning preference for transforming knowledge, whereas relationship management and cognitive competencies are more related to approaching learning by prehension

Diez años de tratamiento sustitutivo renal en paciente crítico : evolución en el tiempo y factores pronósticos

El diagnóstic de insuficiència renal aguda (IRA) és complicat, encara i això els estudis mostren incidències elevades de IRA en els pacientes ingressats en UCI respecte a la resta de hospitalitzats. Així mateix la mortalitat del pacient amb IRA en UCI és molt més elevada respecte a la resta de pacients. La gran majoria dels que sobrevisquin presentaran curació complerta de la IRA. L'objectiu del treball és descriure les característiques dels pacients ingressats a la UCI amb IRA que van precisan teràpia reemplaçament renal, analitzar els canvis evolutius dels pacients i el tractament rebut durant els anys passats i determinar els factors de risc associats a mortalitat i recuperació de la funció renal.A pesar de las dificultades para el diagnóstico de insuficiencia renal aguda (IRA) los estudios muestran incidencias elevadas de IRA en los pacientes ingresados en UCI respecto al resto de hospitalizados. Así mismo la mortalidad del paciente con IRA en UCI es mucho mayor respecto al resto de pacientes. Entre los supervivientes la mayoría presentarán curación de la IRA. El objetivo del trabajo es describir las características de los pacientes ingresados en la unidad con IRA que precisaron terapia reemplazo renal, analizar los cambios evolutivos de los pacientes y del tratamiento recibido a través de los años y determinar los factores de riesgo asociados a mortalidad y recuperación de la función renal

Interaction analysis in islanded power systems with HVDC interconnections

Postprint (published version

Sarcoidosis or primary Sjögren's syndrome?

Correspondence: SIR, We were interested to read the case report by Melsom and coworkers.' We have been followinl up a patient who presented a similar difficult diagnosis