Efficiency characterization of a large neuronal network: a causal information approach

When inhibitory neurons constitute about 40% of neurons they could have an important antinociceptive role, as they would easily regulate the level of activity of other neurons. We consider a simple network of cortical spiking neurons with axonal conduction delays and spike timing dependent plasticity, representative of a cortical column or hypercolumn with large proportion of inhibitory neurons. Each neuron fires following a Hodgkin-Huxley like dynamics and it is interconnected randomly to other neurons. The network dynamics is investigated estimating Bandt and Pompe probability distribution function associated to the interspike intervals and taking different degrees of inter-connectivity across neurons. More specifically we take into account the fine temporal ``structures'' of the complex neuronal signals not just by using the probability distributions associated to the inter spike intervals, but instead considering much more subtle measures accounting for their causal information: the Shannon permutation entropy, Fisher permutation information and permutation statistical complexity. This allows us to investigate how the information of the system might saturate to a finite value as the degree of inter-connectivity across neurons grows, inferring the emergent dynamical properties of the system.Comment: 26 pages, 3 Figures; Physica A, in pres

The (in)visible hand in the Libor market: an Information Theory approach

This paper analyzes several interest rates time series from the United Kingdom during the period 1999 to 2014. The analysis is carried out using a pioneering statistical tool in the financial literature: the complexity-entropy causality plane. This representation is able to classify different stochastic and chaotic regimes in time series. We use sliding temporal windows to assess changes in the intrinsic stochastic dynamics of the time series. Anomalous behavior in the Libor is detected, especially around the time of the last financial crisis, that could be consistent with data manipulation.Comment: PACS 89.65.Gh Econophysics; 74.40.De noise and chao

Libor at crossroads: stochastic switching detection using information theory quantifiers

This paper studies the 28 time series of Libor rates, classified in seven maturities and four currencies), during the last 14 years. The analysis was performed using a novel technique in financial economics: the Complexity-Entropy Causality Plane. This planar representation allows the discrimination of different stochastic and chaotic regimes. Using a temporal analysis based on moving windows, this paper unveals an abnormal movement of Libor time series arround the period of the 2007 financial crisis. This alteration in the stochastic dynamics of Libor is contemporary of what press called "Libor scandal", i.e. the manipulation of interest rates carried out by several prime banks. We argue that our methodology is suitable as a market watch mechanism, as it makes visible the temporal redution in informational efficiency of the market.Comment: 17 pages, 9 figures. arXiv admin note: text overlap with arXiv:1508.04748, arXiv:1509.0021

A permutation Information Theory tour through different interest rate maturities: the Libor case

This paper analyzes Libor interest rates for seven different maturities and referred to operations in British Pounds, Euro, Swiss Francs and Japanese Yen, during the period years 2001 to 2015. The analysis is performed by means of two quantifiers derived from Information Theory: the permutation Shannon entropy and the permutation Fisher information measure. An anomalous behavior in the Libor is detected in all currencies except Euro during the years 2006--2012. The stochastic switch is more severe in 1, 2 and 3 months maturities. Given the special mechanism of Libor setting, we conjecture that the behavior could have been produced by the manipulation that was uncovered by financial authorities. We argue that our methodology is pertinent as a market overseeing instrument.Comment: arXiv admin note: text overlap with arXiv:1304.039

A conceptual model for integrating non-material components in sustainability assessment

A adoção do conceito de desenvolvimento sustentável (DS) originou inúmeros sistemas de avaliação da sustentabilidade, para os quais diversos autores têm sugerido a incorporação de componentes não materiais. O presente trabalho teve como objetivo principal o desenvolvimento de um modelo conceitual para a futura integração desses componentes em sistemas de avaliação da sustentabilidade. A revisão da literatura possibilitou construir um modelo conceitual para os componentes não materiais da sustentabilidade e identificar temas associados. Essa proposta foi analisada em escala local-regional, através de entrevistas semiestruturadas dirigidas a atores-chave no estado de Alagoas e na cidade de Maceió, Brasil. A proposta foi considerada pelos atores envolvidos como genericamente adequada, e foram apresentadas propostas de melhoria e ajuste, para facilitar compreensão e aplicação prática. A análise da percepção dos entrevistados permitiu identificar o vínculo preferencial do termo sustentabilidade com a dimensão ambiental e a restrita referência ao compromisso intergeracional.Researchers have adopted a concept for sustainable development (SD) that has given rise to different systems of sustainability assessment, systems to which several authors have suggested non-material components should be incorporated. This work aims at developing a conceptual model to integrate these components into systems of sustainability assessment. A review of the literature made it possible to design a conceptual model for the non-material components of sustainability and to identify associated themes. This proposal was analyzed at both regional and local levels through semi-structured interviews addressed to stakeholders from Alagoas and Maceió, Brazil. The proposal was considered by the actors involved (interviewees) to be generally adequate, and suggestions for improvement and adjustment were put forward by them, to facilitate both the understanding and practical application of the model. The analysis of the respondents’ perceptions allowed us to identify the preferred link between the term sustainability and the environmental dimension, as well as their restricted reference to intergenerational commitment.info:eu-repo/semantics/publishedVersio

Interactions among resource partitioning, sampling effect, and facilitation on the biodiversity effect: A modeling approach

Resource partitioning, facilitation, and sampling effect are the three mechanisms behind the biodiversity effect, which is depicted usually as the effect of plant-species richness on aboveground net primary production. These mechanisms operate simultaneously but their relative importance and interactions are difficult to unravel experimentally. Thus, niche differentiation and facilitation have been lumped together and separated from the sampling effect. Here, we propose three hypotheses about interactions among the three mechanisms and test them using a simulation model. The model simulated water movement through soil and vegetation, and net primary production mimicking the Patagonian steppe. Using the model, we created grass and shrub monocultures and mixtures, controlled root overlap and grass water-use efficiency (WUE) to simulate gradients of biodiversity, resource partitioning and facilitation. The presence of shrubs facilitated grass growth by increasing its WUE and in turn increased the sampling effect whereas root overlap (resource partitioning) had, on average, no effect on sampling effect. Interestingly, resource partitioning and facilitation interacted so the effect of facilitation on sampling effect decreased as resource partitioning increased. Sampling effect was enhanced by the difference between the two functional groups in their efficiency in using resources. Morphological and physiological differences make one group outperform the other, once those differences were established further differences did not enhance the sampling effect. In addition, grass WUE and root overlap positively influence the biodiversity effect but showed no interactions.Fil: Flombaum, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Sala, Osvaldo Esteban. Arizona State University. School of Life Sciences and School of Sustainability; Estados UnidosFil: Rastetter, Edward B.. Marine Biological Laboratory. The Ecosystem Center; Estados Unido

Directional solidification of dilute Sn-Pb alloys

Microstructure evolution and pattern formation during directional solidification of dilute Sn-Pb system were analysed. Planar, cellular and dendritic morphologies were obtained by adequate thermal gradient and interface velocity control. The samples were obtained from pure elements in concentrations of 0·05, 1·0 and 4·0 wt-%Pb. Growth was carried out in a Bridgman device in the velocity range of 0·38-30 μm s -1 at thermal gradients from 1·3 to 2·6°C mm -1. The samples were examined using metallographic techniques to determine their morphology and dimensional characteristics. The system was analysed to describe the different stages of evolution of the morphology and transitions. It was observed that both primary cellular and dendritic spacing decreased with increasing velocity. However, in the cellular-dendritic transition zone, an important increase in spacing was detected and basically associated with convective effects during irregular cellular growth.Fil: Ochoa, H.. Universidad de Antofagasta (uantof);Fil: Fornaro, Osvaldo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Bustos, O.. Universidad de Santiago de Chile; ChileFil: Schulz, B.. Universidad de Santiago de Chile; Chil

Interpretation of the Flavor Dependence of Nucleon Form Factors in a Generalized Parton Distribution Model

We give an interpretation of the $u$ and $d$ quarks contributions to the nucleon electromagnetic form factors for values of the four-momentum transfer in the multi-GeV region where flavor separated data have been recently made available. The data show, in particular, a suppression of $d$ quarks with respect to $u$ quarks at large momentum transfer. %and constant ratios of the flavor dependent Pauli to Dirac form factors ratios. This trend can be explained using a reggeized diquark model calculation of generalized parton distributions, thus providing a correlation between momentum and coordinate spaces, both of which are necessary in order to interpret the partonic substructure of the form factors. We extend our discussion to the second moments of generalized parton distributions which are believed to contribute to partonic angular momentum.Comment: 22 pages, 19 figures; results and figures added and changed, tables added, formulae added, major rewriting of tex

Influencia de distintas citocininas en el cultivo in vitro de apices caulinares de Fragaria x ananassa y F. virginiana

p.65-70Se estudió la respuesta de Fragaria x ananassa (2n igual a 8x) cv. Brighton, de día netro (refloreciente) y cv. Douglas, de día corto, y de F. virginiana clon UC11 (2n igual 8x), de día corto, a distintas citocininas: 6- (4 - hidroxi - 3 metilbuí - 2 - txans - enilamino) purina (Z), 6 - (? -? - dimetil - alil - amimo) purina (2ip), 6 - bencilaminopurina (BAP) y 6 - furfurilaminopurina (Kin), mediante el cultivo in vitro de ápices caulinares. Se empleó el medio básico de Boxus (1974) suplementado con üamina-HCl; ácido nicotínico; piridozina-HCL glicina; mio-inositol; glucosa, agar; 0,5 x 10 6 m de ácido indolbutírico (IBA), 03 x 10 6 M de ácido giberélico (AG3) y 2 x 10 6 M de cada una de las citocinas citadas. Pudo comprobarse en las citocininas citadas ensayadas una actividad diferencial en el proceso de morfogénesis. Así, BAP fue el compuesto más efectivo en la inducción de nuevas yemas y el único que inhibió la formación de raíces en ambas especies. La mayor proliferación de callo basal se obtuvo con 2iP; Kin resultó la menos efectiva, y BAP y Z, efectos intermedios. Además se observó que el efecto de las citocininas puede ser diferencial entre especies y/o cultivares. Así el número de hojas expandidas por explanto original fue significativamente diferente entre especies cuando se utilizó Z en el medio de cultivo y menor en los cv. de F. x ananassa. También se observaron diferencias entre estos cv., en el número de yemas formadas en presencia de BAP y 2iP; su diferenciación fue mayor en el cv. refloreciente