Exponential localization of singular vectors in spatiotemporal chaos

In a dynamical system the singular vector (SV) indicates which perturbation will exhibit maximal growth after a time interval $\tau$. We show that in systems with spatiotemporal chaos the SV exponentially localizes in space. Under a suitable transformation, the SV can be described in terms of the Kardar-Parisi-Zhang equation with periodic noise. A scaling argument allows us to deduce a universal power law $\tau^{-\gamma}$ for the localization of the SV. Moreover the same exponent $\gamma$ characterizes the finite-$\tau$ deviation of the Lyapunov exponent in excellent agreement with simulations. Our results may help improving existing forecasting techniques.Comment: 5 page

Subsampling inference in cube root asymptotics with an application to Manski's maximum score estimator

Kim and Pollard (Annals of Statistics, 18 (1990) 191?219) showed that a general class of M-estimators converge at rate n1/3 rather than at the standard rate n1/2. Many times, this situation arises when the objective function is non-smooth. The limiting distribution is the (almost surely unique) random vector that maximizes a certain Gaussian process and is difficult to analyze analytically. In this paper, we propose the use of the subsampling method for inferential purposes. The general method is then applied to Manski?s maximum score estimator and its small sample performance is highlighted via a simulation study.Publicad

ON THE (INTRADAILY) SEASONALITY AND DYNAMICS OF A FINANCIAL POINT PROCESS: A SEMIPARAMETRIC APPROACH.

A component model for the analysis of financial durations is proposed. The components are the long-run dynamics and the seasonality. The later is left unspecified and the former is assumed to fall within the class of certain family of parametric functions. The joint model is estimated by maximizing a (local) quasi-likelihood function, and the resulting nonparametric estimator of the seasonal curve has an explicit form that turns out to be a transformation of the Nadaraya-Watson estimator. The estimators of the parameters of interest are shown to be root-N consistent and asymptotically efficient. Furthermore, the seasonal curve is also estimated consistently. The methodology is applied to the trade duration process of Bankinter, a medium size Spanish bank traded in Bolsa de Madrid. We show that adjusting data by seasonality produces important misspecifications.

Continuous harmonic analysis and power quality measurements in three-phase systems

A virtual instrument, named Power Quality Meter, is presented for (a) measuring power consumption and harmonics in three-phase systems, under non-sinusoidal and imbalance conditions (b) detecting, classifying and organizes power disturbance events. Measurement of the power consumption follows the formulation proposed by the members of the IEEE Working Group on Nonsinusoidal Situations (1996). So, definitions are based on the analysis of functions in the frequency domain, separating the fundamental terms from the harmonic terms of the Fourier series. The virtual instrument has been developed too for monitoring and measuring power disturbances, which are automatically classified and organized in a database while they are being recorded. Software tools use the database structure to present summaries of power disturbances and locate an event by severity or time of occurrence. Records of actual measurements are included to demonstrate the versatility of the instrument

Logarithmic bred vectors in spatiotemporal chaos: structure and growth

Bred vectors are a type of finite perturbation used in prediction studies of atmospheric models that exhibit spatially extended chaos. We study the structure, spatial correlations, and the growth- rates of logarithmic bred vectors (which are constructed by using a given norm). We find that, after a suitable transformation, logarithmic bred vectors are roughly piecewise copies of the leading Lyapunov vector. This fact allows us to deduce a scaling law for the bred vector growth rate as a function of their amplitude. In addition, we relate growth rates with the spectrum of Lyapunov exponents corresponding to the most expanding directions. We illustrate our results with simulations of the Lorenz '96 model.Comment: 8 pages, 8 figure

VHE Emission from Magnetic Reconnection in the RIAF of SgrA*

The cosmic-ray (CR) accelerator at the galactic centre (GC) is not yet established by current observations. Here we investigate the radiative-inefficient accretion flow (RIAF) of Sagittarius A* (SgrA*) as a CR accelerator assuming acceleration by turbulent magnetic reconnection, and derive possible emission fluxes of CRs interacting within the RIAF (the central $\sim10^{13}$cm). The target environment of the RIAF is modelled with numerical, general relativistic magneto-hydrodynamics (GRMHD) together with leptonic radiative transfer simulations. The acceleration of the CRs is not computed here. Instead, we inject CRs constrained by the magnetic reconnection power of the accretion flow and compute the emission/absorption of $\gamma$-rays due to these CRs interacting with the RIAF, through Monte Carlo simulations employing the {\tt CRPropa 3} code. The resulting very-high-energy (VHE) fluxes are not expected to reproduce the point source HESS J1745-290 as the emission of this source is most likely produced at pc scales. The emission profiles derived here intend to trace the VHE signatures of the RIAF as a CR accelerator and provide predictions for observations of the GC with improved angular resolution and differential flux sensitivity as those of the forthcoming Cherenkov Telescope Array (CTA). Within the scenario presented here, we find that for mass accretion rates $\gtrsim 10^{-7}$M$_\odot$yr$^{-1}$, the RIAF of SgrA* produces VHE fluxes which are consistent with the H.E.S.S. upper limits for the GC and potentially observable by the future CTA. The associated neutrino fluxes are negligible compared with the diffuse neutrino emission measured by the IceCube.Comment: Accepted for publication in the Ap

Experiencias caseras que muestran aspectos del funcionamiento de la vista, el gusto y el tacto

En el laboratorio de Biología explicamos el funcionamiento de algunos de nuestros órganos de los sentidos (vista, olfato, gusto y tacto) a través de una serie de experiencias que a lo largo de los años han evidenciado ser muy didácticas. Muestran parte del proceso físico en sí y, al exigir la participación activa del alumnado, permiten que éste aprenda divirtiéndose. Lo fácil y barato que resulta realizar estas experiencias, junto a su gran capacidad degenerar asombro, invitan a su difusión y ejecución a todos los niveles

Antioxidant activity of alkyl gallates and glycosyl alkyl gallates in fish oil in water emulsions: Relevance of their surface active properties and of the type of emulsifier

The antioxidant activity of gallic acid and a series of alkyl gallates (C4-C18) and glycosylated alkyl gallates (C4-C18) on fish oil-in-water emulsions was studied. Three types of emulsifiers, lecithin, Tween-20 and sodium dodecyl sulphate (SDS) were tested. A nonlinear behavior of the antioxidant activity of alkyl gallates when increasing alkyl chain length was observed for emulsions prepared with lecithin. Medium-size alkyl gallates (C6-C12) were the best antioxidants. In contrast, for emulsions prepared with Tween-20, the antioxidants seem to follow the polar paradox. Glucosyl alkyl gallates were shown previously to be better surfactants than alkyl gallates. Nevertheless, they exhibited a worse antioxidant capacity than their corresponding alkyl gallates, in emulsions prepared with lecithin or Tween-20, indicating the greater relevance of having three OH groups at the polar head in comparison with having improved surfactant properties but just a di-ortho phenolic structure in the antioxidant

Aproximación ás relacións literarias galego-catalanas. Noticias históricas e bibliográficas.

Sin resume

Regionalization and connectivity in the Gulf of Cádiz and Alborán Sea implication for marine spatial planning and coastal management

This work proposes a regionalization of marine waters south of the Iberian Peninsula based on empirical orthogonal functions and GIS analysis. The regions identified are consistent and correspond to hydrological mesoscale and macroscale structures well characterized from physical and biological viewpoints. Although it is difficult to determine the boundaries of a fluid continuously moving, the procedure used recognizes the most frequent patterns and can be used to reference geographically the most likely position of the limit among the regions. Once established the regions, the connectivity among them is addressed by means of geostrophic currents derived from altimetry data. The main geostrophic circulation pattern depict an elevate connectivity in the area that might facilitate the conservation and recovering of species, but also imply a higher vulnerability to negative externalities and highlight the need of models, marine spatial planning, and coastal management approaches that includes the pelagic ecosystem and connectivity of the seas. Furthermore, the results confirm that the cooperation between public authorities at different levels (local, regional, state) as well as among riparian countries is essential for marine spatial planning and prevention of potential risk derived from upcoming marine activities in the framework of the 2020 agenda and Blue Growth strategy.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec