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 subsampling approach to estimating the distribution of diversing statistics with application to assessing financial market risks

In this paper we propose a subsampling estimator for the distribution ofstatistics diverging at either known rates when the underlying timeseries in strictly stationary abd strong mixing. Based on our results weprovide a detailed discussion how to estimate extreme order statisticswith dependent data and present two applications to assessing financialmarket risk. Our method performs well in estimating Value at Risk andprovides a superior alternative to Hill's estimator in operationalizingSafety First portofolio selection.

Geometric and long run aspects of Granger causality

This paper extends multivariate Granger causality to take into account the subspacesalong which Granger causality occurs as well as long run Granger causality. The propertiesof these new notions of Granger causality, along with the requisite restrictions, are derivedand extensively studied for a wide variety of time series processes including linear invertibleprocess and VARMA. Using the proposed extensions, the paper demonstrates that: (i) meanreversion in L2 is an instance of long run Granger non-causality, (ii) cointegration is a specialcase of long run Granger non-causality along a subspace, (iii) controllability is a special caseof Granger causality, and finally (iv) linear rational expectations entail (possibly testable)Granger causality restriction along subspaces.

Determinación de sistemas de flujo regionales y locales en las depresiones tectónicas del Baix Empordà y La Selva (NE de España) en base a datos hidroquímicos e isotópicos

The Baix Empordà-Selva-Gavarres aquifer system is related to the fault set that created the tectonic basins of Empordà and Selva areas (NE Spain) during the Neogene. In this work, we describe groundwater hydrogeological, hydrochemical and isotopical (3H, δD, δ18O, and the 87Sr/86Sr ratio) characteristics of this system in order to illustrate the relevance of fault zones in groundwater flow-paths and the recharge. In that way, we identify two flow systems, with distinct hydrochemistry and isotopes. A local flow system originates at the Gavarres Range, and it flows towards the basins of the Baix Empordà and Selva, with an approximate residence time of 20 years. Additionally, a regional flow system has only been identified in the Selva basin. This one is related to the main fault zones, as preferential flow paths. Its recharge is located in mountain ranges with higher altitudes, namely the Transversal and Guilleries Ranges, with residence times larger than 50 years. Isotopical data has also shown mixing processes between both flow systems and rainfall recharge while multivariate statistical analysis of principal components has shown the main processes that control hydrochemistry of each flow systems

Obtenció d'estruvita a partir de la fracció líquida digerida de purins de vaca

Actualment a Catalunya existeixen zones amb importants limitacions per l’aplicació de purins al sòl, pel que és imprescindible trobar alternatives de gestió i tractament que permetin l’aprofitament adequat dels recursos continguts a les dejeccions ramaderes sense afectar el medi. La digestió anaeròbia és una de les tècniques utilitzades en el tractament de les dejeccions ramaderes. L’efluent líquid que s’obté d’aquest tractament no modifica el contingut de nitrogen i fòsfor i per tant ha de ser gestionat correctament. L’objectiu general d’aquest projecte és avaluar la precipitació d’estruvita (sal de magnesi, amoni i fosfat) com una alternativa de gestió de l’efluent líquid d’una planta de digestió anaeròbia i compostatge que tracta dejeccions ramaderes conjuntament amb altres residus orgànics. S’han avaluat els efectes dels diferents paràmetres operacionals en la formació d’estruvita (pH, temperatura, velocitat d’agitació, alcalinitat), mitjançant assaigs en discontinu amb solució sintètica. A continuació s’ha procedit a obtenir estruvita a partir de la fracció líquida digerida de purí (FLD), en assaigs en discontinu per estudiar l’efecte del contingut de matèria orgànica i sòlids Totals (ST), així com el contingut en fosfats i el pH de reacció. Finalment, s’han optimitzat els paràmetres de procés en continu, mitjançant la posada en marxa d’un reactor a escala de laboratori i estudi de l’efecte de la velocitat d’agitació i de la introducció del stripping de CO2, tant amb solució sintètica com amb la fracció líquida digerida del purí. Dels resultats obtinguts es pot concloure que els factors que tenen una major influència en el procés d’obtenció d’estruvita són el pH (el pH òptim es situa al voltant de 9), i la presència de matèria orgànica i sòlids ens suspensió, que interfereix de forma quantitativa i qualitativa en la formació de l’estruvita. En el procés en continu s’ha aconseguit reduccions d’un 84% i 98% d’amoni i fòsfor respectivament, obtenintse estruvita que pot ser utilitzada com a fertilitzant d’alliberació lenta. Es pot concloure que la precipitació d’estruvita és una bona alternativa per millorar la gestió de les dejeccions ramaderes alhora que permet recuperar nutrients i tancar cicles. La combinació amb un tractament previ que elimini la matèria orgànica, com podria ser la digestió anaeròbia, i una separació de fases, per eliminar els sòlids en suspensió, es presenta com una configuració amb molts avantatges.

La Multi-metodología Autobiográfica Extendida (MAE). Una estrategia cualitativa para estudiar la identidad, los fondos de conocimiento y las formas de vida

La multi-metodología autobiográfica es una aproximación cualitativa que combina distintas técnicas para estudiar la construcción narrativa de la identidad. El objetivo de este artículo es ofrecer una revisión de dicho enfoque a partir de una expansión de los distintos instrumentos cualitativos utilizados. Más concretamente, la multi-metodología autobiográfica extendida (MAE) consta de cuatro grupos de técnicas: entrevistas en profundidad (historia de vida, entrevista de fondos de conocimiento y la entrevista de Durand), el retrato o dibujo identitario revisado (dibujo identitario, auto-definición, tarea identitaria de las diez definiciones), el análisis de los artefactos-rutinas-formas de vida (diario de una semana, detección de artefactos, rutinas a través de fotografías, rutinas educativas a través de fotografías ) y la utilización de distintos “mapas psicológicos o psicogeográficos” (cronograma, genograma, ecomapa, geomapa y mapa relacional). Después de definir la identidad, los fondos de conocimiento y las formas de vida como posibles objetos de estudio en ciencias sociales, el artículo describe e ilustra las distintas técnicas que componen la metodología propuesta. Se concluye recomendando la triangulación de técnicas cualitativas narrativas basadas en el lenguaje, el caso de las tradicionales entrevistas en profundidad, con determinados procedimientos visuales, a partir de la utilización de fotografías o representaciones gráficas

Quality coding by neural populations in the early olfactory pathway: analysis using information theory

In this article, we analyze the ability of the early olfactory system to detect and discriminate different odors by means of information theory measurements applied to olfactory bulb activity images. We have studied the role that the diversity and number of receptor neuron types play in encoding chemical information. Our results show that the olfactory receptors of the biological system are low correlated and present good coverage of the input space. The coding capacity of ensembles of olfactory receptors with the same receptive range is maximized when the receptors cover half of the odor input space - a configuration that corresponds to receptors that are not particularly selective. However, the ensemble's performance slightly increases when mixing uncorrelated receptors of different receptive ranges. Our results confirm that the low correlation between sensors could be more significant than the sensor selectivity for general purpose chemo-sensory systems, whether these are biological or biomimetic.

Local description of quantum inseparability

We show how to decompose any density matrix of the simplest binary composite systems, whether separable or not, in terms of only product vectors. We determine for all cases the minimal number of product vectors needed for such a decomposition. Separable states correspond to mixing from one to four pure product states. Inseparable states can be described as pseudomixtures of four or five pure product states, and can be made separable by mixing them with one or two pure product states.

Robustness of entanglement

In the quest to completely describe entanglement in the general case of a finite number of parties sharing a physical system of finite-dimensional Hilbert space an entanglement magnitude is introduced for its pure and mixed states: robustness. It corresponds to the minimal amount of mixing with locally prepared states which washes out all entanglement. It quantifies in a sense the endurance of entanglement against noise and jamming. Its properties are studied comprehensively. Analytical expressions for the robustness are given for pure states of two-party systems, and analytical bounds for mixed states of two-party systems. Specific results are obtained mainly for the qubit-qubit system (qubit denotes quantum bit). As by-products local pseudomixtures are generalized, a lower bound for the relative volume of separable states is deduced, and arguments for considering convexity a necessary condition of any entanglement measure are put forward.

Optimal estimation of two-qubit pure-state entanglement

We present optimal measuring strategies for an estimation of the entanglement of unknown two-qubit pure states and of the degree of mixing of unknown single-qubit mixed states, of which N identical copies are available. The most general measuring strategies are considered in both situations, to conclude in the first case that a local, although collective, measurement suffices to estimate entanglement, a nonlocal property, optimally.

Constraints on additional Z' gauge bosons from a precise measurement of the Z mass

We analyze the constraints on the mass and mixing of a superstring-inspired E6 Z' neutral gauge boson that follow from the recent precise Z mass measurements and show that they depend very sensitively on the assumed value of the W mass and also, to a lesser extent, on the top-quark mass.

Seasonal dependence in the solar neutrino flux

Mikheyev-Smirnov-Wolfenstein (MSW) solutions of the solar neutrino problem predict a seasonal dependence of the zenith angle distribution of the event rates, due to the nonzero latitude at the Super-Kamiokande site. We calculate this seasonal dependence and compare it with the expectations in the no-oscillation case as well as just-so scenario, in the light of the latest Super-Kamiokande 708-day data. The seasonal dependence can be sizable in the large mixing angle MSW solution and would be correlated with the day-night effect. This may be used to discriminate between MSW and just-so scenarios and should be taken into account in refined fits of the data.

New CP violation in neutrino oscillations

Measurements of CP-violating observables in neutrino oscillation experiments have been studied in the literature as a way to determine the CP-violating phase in the mixing matrix for leptons. Here we show that such observables also probe new neutrino interactions in the production or detection processes. Genuine CP violation and fake CP violation due to matter effects are sensitive to the imaginary and real parts of new couplings. The dependence of the CP asymmetry on the source-detector distance is different from the standard one and, in particular, enhanced at short distances. We estimate that future neutrino factories will be able to probe in this way new interactions that are up to four orders of magnitude weaker than the weak interactions. We discuss the possible implications for models of new physics.

Absence of epidemic threshold in scale free networks with degree correlations

Random scale-free networks have the peculiar property of being prone to the spreading of infections. Here we provide for the susceptible-infected-susceptible model an exact result showing that a scale-free degree distribution with diverging second moment is a sufficient condition to have null epidemic threshold in unstructured networks with either assortative or disassortative mixing. Degree correlations result therefore irrelevant for the epidemic spreading picture in these scale-free networks. The present result is related to the divergence of the average nearest neighbors degree, enforced by the degree detailed balance condition.