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

A generalized mechanistic codon model.

Models of codon evolution have attracted particular interest because of their unique capabilities to detect selection forces and their high fit when applied to sequence evolution. We described here a novel approach for modeling codon evolution, which is based on Kronecker product of matrices. The 61 × 61 codon substitution rate matrix is created using Kronecker product of three 4 × 4 nucleotide substitution matrices, the equilibrium frequency of codons, and the selection rate parameter. The entities of the nucleotide substitution matrices and selection rate are considered as parameters of the model, which are optimized by maximum likelihood. Our fully mechanistic model allows the instantaneous substitution matrix between codons to be fully estimated with only 19 parameters instead of 3,721, by using the biological interdependence existing between positions within codons. We illustrate the properties of our models using computer simulations and assessed its relevance by comparing the AICc measures of our model and other models of codon evolution on simulations and a large range of empirical data sets. We show that our model fits most biological data better compared with the current codon models. Furthermore, the parameters in our model can be interpreted in a similar way as the exchangeability rates found in empirical codon models.

Millora en la creació i configuració automatitzada de dispositius a la xarxa lliure Guifi.net

Guifi.net es una red libre de telecomunicaciones construida a iniciativa de los propios participantes que, mediante un acuerdo entre iguales, se interconectan para compartir servicios y recursos. Del vínculo filosófico con el software libre deriva que toda la información sea pública, mientras que del agnosticismo tecnológico, la utilización de cualquier dispositivo del mercado. Por esto existe el 'unsolclic', una secuencia de órdenes de confi guración genérica de dispositivos y verdadero factor de éxito. El objetivo del proyecto es mejorar el proceso de incorporación de nuevos dispositivos a la aplicación actual. Mediante una nueva gestión web y un sistema de plantillas estándar, los usuarios avanzados podran crear los confi guradores 'unsolclic' para los nuevos dispositivos del mercado y mantener los existentes con más facilidad y eficiencia.

Marcatge estructural i morfosintàctic del Corpus Tècnic amb l'estàndard SGML

L'edició de textos fent ús de mitjans informàtics ha comportat avantatges i inconvenients. Mentre que ha fet molt accessible l'edició acurada de textos també ha provocat tot un seguit de problemes, un del quals és la dificultat de compartir recursos.Per altra banda, la lingüística necessita emprar corpus voluminosos per conèixer amb més precisió i fonament el comportament real del llenguatge. És evident que l'obtenció i consegüent preparació d'un corpus per a la seva explotació esdevé un procés costós en temps i recursos, motiu pel qual és força atractiu i gairebé necessari compartir aquest material de recerca amb altres organitzacions. En aquest treball s'examinen les diferents propostes d'aplicació de l'estàndard SGML (Standard Generalized Markup Language) en la constitució de corpus textuals per a la recerca lingüística, amb èmfasi especial en les solucions proposades a l'Institut Universitari de Lingüística Aplicada de la Universitat Pompeu Fabra.

Arte y desacuerdo: un estudio del proyecto Megafone.net de Antoni Abad a partir de las tesis estético-políticas de Jacques Rancière

Este trabajo tiene por objeto el estudio de las relaciones entre arte y política en el contexto del capitalismo neoliberal. Propone una lectura e interpretación de las tesis estético-políticas de Jacques Rancière incidiendo en dos ejes fundamentales de las mismas. De un lado, la elaboración de su concepto de política, planteado como un desacuerdo respecto a la hegemonía contemporánea del pensamiento neoliberal. Del otro, el modo en que su razonamiento se sostiene sobre una original reflexión estética, la cual desemboca en unaredefinición de las prácticas artísticas como medios eficaces de intervención política en la realidad. Es importante subrayar que esta investigación no se limita a una simple paráfrasis del pensamiento del filósofo francés. Así, sus ideas serán puestas en diálogo con lasaportaciones de otros autores y disciplinas y, sobre todo, se ensayará su pertinencia en el análisis de un caso concreto de estudio: el proyecto Megafone.net del artista catalán Antoni Abad, tomado como un ejemplo terminado del concepto de “arte político” elaborado por Rancière.

Generalized linear and generalized additive models in studies of species distributions: setting the scene

An important statistical development of the last 30 years has been the advance in regression analysis provided by generalized linear models (GLMs) and generalized additive models (GAMs). Here we introduce a series of papers prepared within the framework of an international workshop entitled: Advances in GLMs/GAMs modeling: from species distribution to environmental management, held in Riederalp, Switzerland, 6-11 August 2001.We first discuss some general uses of statistical models in ecology, as well as provide a short review of several key examples of the use of GLMs and GAMs in ecological modeling efforts. We next present an overview of GLMs and GAMs, and discuss some of their related statistics used for predictor selection, model diagnostics, and evaluation. Included is a discussion of several new approaches applicable to GLMs and GAMs, such as ridge regression, an alternative to stepwise selection of predictors, and methods for the identification of interactions by a combined use of regression trees and several other approaches. We close with an overview of the papers and how we feel they advance our understanding of their application to ecological modeling.

Ensimmäiset äänet : yhteissoittomateriaali klarinetinsoiton vasta-alkajille

Työ on kaksiosainen. Raporttiosassa esittelen tekemäni yhteissoittomateriaalin ja sen tekemisen vaiheita ja haasteita. Klarinetin rakennetta ja alkeisoppijaksoja koskeva alkuselvitykseni tekee työn ymmärrettäväksi myös niille, jotka eivät ole tekemisissä klarinetinsoiton kanssa. Työn toinen osa on erillinen vihko, joka sisältää sovituksia tutuista kappaleista sekä omia sävellyksiäni klarinettiryhmille. Kappaleista on sekä partituurit että erilliset stemmat soittajille. Kappaleissa on 3-4 b-klarinettia ja basso, lisäksi mahdolliselle c-klarinetille on oma stemmansa. Kappaleissa on erityisesti otettu huomioon vasta-alkajat ja heidän taitonsa. Omissa sävellyksissä on kantavana ajatuksena oleellisesti klarinetinsoittoon liittyviä asioita kuten yksittäinen sormitusyhdistelmä tai intervalli, jonka ympärille kappale on rakennettu. Työni on tarpeen, koska klarinetinsoiton alkeisoppilaille on vaikea löytää yhteissoittomateriaalia, varsinkin jos ryhmässä on hyvin eritasoisia oppilaita. Aivan vasta-alkajille mielekästä materiaalia ei juuri ole saatavilla. Opinnäytetyön tekemisen tuloksena on avautunut uusia näkökulmia sekä opetukseen että yhteismusiikkiin. Olen sovituksia tehdessäni joutunut miettimään esimerkiksi kaikki helpot ja vaikeat sormitusyhdistelmät ja äänen tuottamisen kannalta vaikeat hypyt. Tällaisten asioiden tunteminen auttaa itseäni ja muita klarinettipedagogeja paitsi itse tekemään yhteissoittomateriaalia myös valitsemaan muiden tekemästä materiaalista omiin tarkoituksiin sopivimmat kappaleet.

On Certain Greedoid Polyhedra, Partially Indexable Scheduling Problems, and Extended Restless Bandit Allocation Indices

We present a polyhedral framework for establishing general structural properties on optimal solutions of stochastic scheduling problems, where multiple job classes vie for service resources: the existence of an optimal priority policy in a given family, characterized by a greedoid (whose feasible class subsets may receive higher priority), where optimal priorities are determined by class-ranking indices, under restricted linear performance objectives (partial indexability). This framework extends that of Bertsimas and Niño-Mora (1996), which explained the optimality of priority-index policies under all linear objectives (general indexability). We show that, if performance measures satisfy partial conservation laws (with respect to the greedoid), which extend previous generalized conservation laws, then the problem admits a strong LP relaxation over a so-called extended greedoid polytope, which has strong structural and algorithmic properties. We present an adaptive-greedy algorithm (which extends Klimov's) taking as input the linear objective coefficients, which (1) determines whether the optimal LP solution is achievable by a policy in the given family; and (2) if so, computes a set of class-ranking indices that characterize optimal priority policies in the family. In the special case of project scheduling, we show that, under additional conditions, the optimal indices can be computed separately for each project (index decomposition). We further apply the framework to the important restless bandit model (two-action Markov decision chains), obtaining new index policies, that extend Whittle's (1988), and simple sufficient conditions for their validity. These results highlight the power of polyhedral methods (the so-called achievable region approach) in dynamic and stochastic optimization.

U.S. Universities’ Net Returns from Patenting and Licensing: A Quantile Regression Analysis, September 2006

In line with the rights and incentives provided by the Bayh-Dole Act of 1980, U.S. universities have increased their involvement in patenting and licensing activities through their own technology transfer offices. Only a few U.S. universities are obtaining large returns, however, whereas others are continuing with these activities despite negligible or negative returns. We assess the U.S. universities’ potential to generate returns from licensing activities by modeling and estimating quantiles of the distribution of net licensing returns conditional on some of their structural characteristics. We find limited prospects for public universities without a medical school everywhere in their distribution. Other groups of universities (private, and public with a medical school) can expect significant but still fairly modest returns only beyond the 0.9th quantile. These findings call into question the appropriateness of the revenue-generating motive for the aggressive rate of patenting and licensing by U.S. universities.

Aitchison Geometry for Probability and Likelihood as a new approach to mathematical statistics

The Aitchison vector space structure for the simplex is generalized to a Hilbert space structure A2(P) for distributions and likelihoods on arbitrary spaces. Centralnotations of statistics, such as Information or Likelihood, can be identified in the algebraical structure of A2(P) and their corresponding notions in compositional data analysis, such as Aitchison distance or centered log ratio transform.In this way very elaborated aspects of mathematical statistics can be understoodeasily in the light of a simple vector space structure and of compositional data analysis. E.g. combination of statistical information such as Bayesian updating,combination of likelihood and robust M-estimation functions are simple additions/perturbations in A2(Pprior). Weighting observations corresponds to a weightedaddition of the corresponding evidence.Likelihood based statistics for general exponential families turns out to have aparticularly easy interpretation in terms of A2(P). Regular exponential families formfinite dimensional linear subspaces of A2(P) and they correspond to finite dimensionalsubspaces formed by their posterior in the dual information space A2(Pprior).The Aitchison norm can identified with mean Fisher information. The closing constant itself is identified with a generalization of the cummulant function and shown to be Kullback Leiblers directed information. Fisher information is the local geometry of the manifold induced by the A2(P) derivative of the Kullback Leibler information and the space A2(P) can therefore be seen as the tangential geometry of statistical inference at the distribution P.The discussion of A2(P) valued random variables, such as estimation functionsor likelihoods, give a further interpretation of Fisher information as the expected squared norm of evidence and a scale free understanding of unbiased reasoning

Research joint ventures in an international economy

D'Aspremont and Jacquemin's (1988) model is extended to studyalternative configurations of research agreements in a two--country integratedworld economy. Under unambiguous conditions on spillovers we show that:1) Allowing national firms to cooperate in R\&D confers them an advantageover foreign rivals, an effect similar to R\&D subsidies. 2) In a policygame, each government would allow national cooperative agreements. 3) Contraryto other trade policies which lead to a ``prisoners' dilemma'' result,welfare in both countries increases when they both allow R\&D cooperation.4) Welfare is even higher if a generalized (international) coalition isformed.

Contagion and efficiency in gross and net interbank payment systems

The increased fragility of the banking industry has generatedgrowing concern about the risks associated with the paymentsystems. Although in most industrial countries differentinterbank payment systems coexist, little is really knownabout their propierties in terms of risk and efficiency. Wetackle this question by comparing the two main types ofpayment systems, gross and net, in a framework whereuncertainty arises from several sources: the time ofconsumption, the location of consumption and the return oninvestment. Payments across locations can be made either bydirectly transferrring liquidity or by transferring claimsagainst the bank in the other location. The two mechanism areinterpreted as the gross and net settlement systems ininterbank payments. We characterize the equilibria in the twosystems and identify the trade-off in terms of safety andefficiency.

On the term structure of Interbank interest rates: Jump-diffusion processes and option pricing

In this paper we study the dynamic behavior of the term structureof Interbank interest rates and the pricing of options on interest ratesensitive securities. We posit a generalized single factor model withjumps to take into account external influences in the market. Daily datais used to test for jump effects. Qualitative examination of the linkagebetween Monetary Authorities' interventions and jumps are studied. Pricingresults suggests a systematic underpricing in bonds and call options ifthe jumps component is not included. However, the pricing of put optionson bonds presents indeterminacies.