Layer Features of the Lattice Gas Model for Self-Organized Criticality

A layer-by-layer description of the asymmetric lattice gas model for 1/f-noise suggested by Jensen [Phys. Rev. Lett. 64, 3103 (1990)] is presented. The power spectra of the lattice layers in the direction perpendicular to the particle flux is studied in order to understand how the white noise at the input boundary evolves, on the average, into 1/f-noise for the system. The effects of high boundary drive and uniform driving force on the power spectrum of the total number of diffusing particles are considered. In the case of nearest-neighbor particle interactions, high statistics simulation results show that the power spectra of single lattice layers are characterized by different $\beta_x$ exponents such that $\beta_x \to 1.9$ as one approaches the outer boundary.Comment: LaTeX, figures upon reques

A Portable Bio-Inspired Architecture for Efficient Robotic Vergence Control

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Spontaneous circadian rhythms in a cold-Adapted natural isolate of Aureobasidium pullulans

Indexación: Scopus.Circadian systems enable organisms to synchronize their physiology to daily and seasonal environmental changes relying on endogenous pacemakers that oscillate with a period close to 24 h even in the absence of external timing cues. The oscillations are achieved by intracellular transcriptional/translational feedback loops thoroughly characterized for many organisms, but still little is known about the presence and characteristics of circadian clocks in fungi other than Neurospora crassa. We sought to characterize the circadian system of a natural isolate of Aureobasidium pullulans, a cold-Adapted yeast bearing great biotechnological potential. A. pullulans formed daily concentric rings that were synchronized by light/dark cycles and were also formed in constant darkness with a period of 24.5 h. Moreover, these rhythms were temperature compensated, as evidenced by experiments conducted at temperatures as low as 10 °C. Finally, the expression of clock-essential genes, frequency, white collar-1, white collar-2 and vivid was confirmed. In summary, our results indicate the existence of a functional circadian clock in A. pullulans, capable of sustaining rhythms at very low temperatures and, based on the presence of conserved clock-gene homologues, suggest a molecular and functional relationship to well-described circadian systems.https://www.nature.com/articles/s41598-017-14085-

Multifractal Properties of Price Fluctuations of Stocks and Commodities

We analyze daily prices of 29 commodities and 2449 stocks, each over a period of $\approx 15$ years. We find that the price fluctuations for commodities have a significantly broader multifractal spectrum than for stocks. We also propose that multifractal properties of both stocks and commodities can be attributed mainly to the broad probability distribution of price fluctuations and secondarily to their temporal organization. Furthermore, we propose that, for commodities, stronger higher order correlations in price fluctuations result in broader multifractal spectra.Comment: Published in Euro Physics Letters (14 pages, 5 figures

A cortical model for binocular vergence control without explicit calculation of disparity

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Biharmonic pattern selection

A new model to describe fractal growth is discussed which includes effects due to long-range coupling between displacements $u$. The model is based on the biharmonic equation $\nabla^{4}u =0$ in two-dimensional isotropic defect-free media as follows from the Kuramoto-Sivashinsky equation for pattern formation -or, alternatively, from the theory of elasticity. As a difference with Laplacian and Poisson growth models, in the new model the Laplacian of $u$ is neither zero nor proportional to $u$. Its discretization allows to reproduce a transition from dense to multibranched growth at a point in which the growth velocity exhibits a minimum similarly to what occurs within Poisson growth in planar geometry. Furthermore, in circular geometry the transition point is estimated for the simplest case from the relation $r_{\ell}\approx L/e^{1/2}$ such that the trajectories become stable at the growing surfaces in a continuous limit. Hence, within the biharmonic growth model, this transition depends only on the system size $L$ and occurs approximately at a distance $60 \%$ far from a central seed particle. The influence of biharmonic patterns on the growth probability for each lattice site is also analysed.Comment: To appear in Phys. Rev. E. Copies upon request to [email protected]

Finite-Size Scaling in Two-dimensional Continuum Percolation Models

We test the universal finite-size scaling of the cluster mass order parameter in two-dimensional (2D) isotropic and directed continuum percolation models below the percolation threshold by computer simulations. We found that the simulation data in the 2D continuum models obey the same scaling expression of mass M to sample size L as generally accepted for isotropic lattice problems, but with a positive sign of the slope in the ln-ln plot of M versus L. Another interesting aspect of the finite-size 2D models is also suggested by plotting the normalized mass in 2D continuum and lattice bond percolation models, versus an effective percolation parameter, independently of the system structure (i.e. lattice or continuum) and of the possible directions allowed for percolation (i.e. isotropic or directed) in regions close to the percolation thresholds. Our study is the first attempt to map the scaling behaviour of the mass for both lattice and continuum model systems into one curve.Comment: 9 pages, Revtex, 2 PostScript figure

Effective Interactions and Volume Energies in Charge-Stabilized Colloidal Suspensions

Charge-stabilized colloidal suspensions can be conveniently described by formally reducing the macroion-microion mixture to an equivalent one-component system of pseudo-particles. Within this scheme, the utility of a linear response approximation for deriving effective interparticle interactions has been demonstrated [M. J. Grimson and M. Silbert, Mol. Phys. 74, 397 (1991)]. Here the response approach is extended to suspensions of finite-sized macroions and used to derive explicit expressions for (1) an effective electrostatic pair interaction between pseudo-macroions and (2) an associated volume energy that contributes to the total free energy. The derivation recovers precisely the form of the DLVO screened-Coulomb effective pair interaction for spherical macroions and makes manifest the important influence of the volume energy on thermodynamic properties of deionized suspensions. Excluded volume corrections are implicitly incorporated through a natural modification of the inverse screening length. By including nonlinear response of counterions to macroions, the theory may be generalized to systematically investigate effective many-body interactions.Comment: 13 pages (J. Phys.: Condensed Matter, in press

Multifractality in Time Series

We apply the concepts of multifractal physics to financial time series in order to characterize the onset of crash for the Standard & Poor's 500 stock index x(t). It is found that within the framework of multifractality, the "analogous" specific heat of the S&P500 discrete price index displays a shoulder to the right of the main peak for low values of time lags. On decreasing T, the presence of the shoulder is a consequence of the peaked, temporal x(t+T)-x(t) fluctuations in this regime. For large time lags (T>80), we have found that C_{q} displays typical features of a classical phase transition at a critical point. An example of such dynamic phase transition in a simple economic model system, based on a mapping with multifractality phenomena in random multiplicative processes, is also presented by applying former results obtained with a continuous probability theory for describing scaling measures.Comment: 22 pages, Revtex, 4 ps figures - To appear J. Phys. A (2000

Utilidad de las redes conceptuales en una asignatura propedéutica contable de la Facultad de Ciencias Económicas de la Universidad Nacional de La Plata

En el año 2017, en Argentina, el Ministerio de Educación aprueba los contenidos curriculares básicos de la carrera de Contador Público, incluyendo a la contabilidad social y ambiental, entre otros contenidos. En la Facultad de Ciencias Económicas de la Universidad Nacional de La Plata (UNLP), en el año 2018 comienza a regir un nuevo plan de estudios por medio del cual la asignatura Contabilidad Superior I cambia su denominación a Contabilidad I (Bases y Fundamentos) e incorpora el enfoque o perspectivas de la contabilidad social y ambiental. Como todas las asignaturas propedéuticas, Contabilidad I (Bases y Fundamentos) presenta particularidades que la distingue de otras asignaturas. En el año 2018 en la Cátedra C se propone contribuir a la apropiación por parte de los educandos de conocimientos de la disciplina contable con enfoque económico-financiero y social y ambiental adicionando redes conceptuales o redes semánticas, con apoyo del aula virtual. Durante el desarrollo áulico de la Comisión Nº 15, de dicha Cátedra, luego de la primera clase la docente a cargo elabora y comenta que es una red conceptual, como se realiza, cuales son sus ventajas y algunas diferencias que las distinguen de los mapas conceptuales, los cuales no han sido utilizados. Se sube al aula virtual la primera red. En dicha red conceptual se relacionan resumidamente a la contabilidad como disciplina científica, sus componentes teóricos (marco conceptual doctrinario y normativo) y a los entes económicos, donde se instrumentan sus conocimientos, diferenciando técnicas contables. Como resultado de dicha experiencia pedagógica surgen varios interrogantes, entre ellos: ¿Los contenidos de la primera red conceptual ha contribuido para que los educandos comprendan donde se aplican los conocimientos contables? ¿Qué sugerencias y comentarios pueden brindar los educandos a la primera red conceptual? Se interpreta que las redes conceptuales, o semánticas, constituyen un recurso didáctico que contribuye para que los educandos puedan apropiarse de conocimientos sólidos, básicos y fundamentales, permitiendo comprender los conocimientos contables y donde se aplican. Constituye el objetivo del presente estudio: conocer la opinión de los educandos de la Comisión Nº 15 de la Cátedra C de Contabilidad Superior I y Contabilidad I (Bases y Fundamentos) sobre el grado de utilidad de la primera red conceptual, realizada y explicada por la docente a cargo del curso, para comprender parte de los contenidos enunciados, así como conocer sus comentarios y sugerencias. De tener en cuenta que el proceso cognitivo es progresivo, se realiza una encuesta por medio de un formulario con preguntas genéricas. Se consulta si la primera red los ha ayudado a comprender donde se utilizan los conocimientos contables, si les ha servido para ubicar al proceso contable y si han desarrollado alguna red para contabilidad antes de la clase, solicitando comentarios y sugerencias para las dos primeras preguntas. Para el análisis de las respuestas, se interpreta para las respuestas a las preguntas 1) y 2) que el grado de utilidad de dicha red conceptual es: Alto cuando se encuentran respuestas positivas entre el 100% y el 70% de los casos, Medio entre menos del 70% y el 40% y Bajo en menos del 40%. Para determinar el grado en que los alumnos han desarrollado alguna red conceptual para contabilidad antes de la clase, según la pregunta 3), se entiende como Alto cuando se encuentran respuestas positivas entre el 100% y el 75% de los casos, Medio entre menos del 75% y el 40% de los casos y Bajo en menos del 40%. Se elabora y competa una grilla para la recolección y análisis de datos. Se obtienen resultados e infieren conclusiones. De recibir de los educandos veintitrés formularios con respuestas, se realiza la sistematización y análisis en conjunto, surgiendo: un Alto el grado de comprensión sobre donde se utilizan los conocimientos contables y para ubicar al proceso contable dentro del SIC de los entes, u organizaciones económicas; mientras que se observa un grado Bajo respecto al desarrollo de alguna red conceptual para contabilidad antes de la clase mencionada. De tener en cuenta que Contabilidad I (Bases y Fundamentos) es una asignatura propedéutica en la cual, por lo general, los educandos no tienen o es baja su “familiaridad” con la temática de la misma, y hasta pueden presentar confusión, del desarrollo realizado y los resultados obtenidos es posible inferir que las redes conceptuales o semánticas, así como la red seleccionada en particular, por constituir instrumentos basados en interconexiones, una vez explicadas por el profesor, han contribuido a incorporar conocimientos más sólidos y significativos y, con ello, al crecimiento cognitivo.Tema 5: El proceso de enseñanza-aprendizaje en contabilidad. Evaluación. Didáctica general y didáctica específica. Articulación con el sistema educativo. Inclusión y contención. Estrategias de apoyo y estímulo al egreso y la inserción laboral. La formación docente continuaFacultad de Ciencias Económica