Avalanches in the Weakly Driven Frenkel-Kontorova Model

A damped chain of particles with harmonic nearest-neighbor interactions in a spatially periodic, piecewise harmonic potential (Frenkel-Kontorova model) is studied numerically. One end of the chain is pulled slowly which acts as a weak driving mechanism. The numerical study was performed in the limit of infinitely weak driving. The model exhibits avalanches starting at the pulled end of the chain. The dynamics of the avalanches and their size and strength distributions are studied in detail. The behavior depends on the value of the damping constant. For moderate values a erratic sequence of avalanches of all sizes occurs. The avalanche distributions are power-laws which is a key feature of self-organized criticality (SOC). It will be shown that the system selects a state where perturbations are just able to propagate through the whole system. For strong damping a regular behavior occurs where a sequence of states reappears periodically but shifted by an integer multiple of the period of the external potential. There is a broad transition regime between regular and irregular behavior, which is characterized by multistability between regular and irregular behavior. The avalanches are build up by sound waves and shock waves. Shock waves can turn their direction of propagation, or they can split into two pulses propagating in opposite directions leading to transient spatio-temporal chaos. PACS numbers: 05.70.Ln,05.50.+q,46.10.+zComment: 33 pages (RevTex), 15 Figures (available on request), appears in Phys. Rev.

Transboundary Impact Assessment in the north-western Iberian Peninsula

En el marco del proyecto SIMAtlantic, se ha llevado a cabo un caso de estudio entre España y Portugal. Este documento describe una metodología propuesta para la Evaluación de Efectos Acumulativos con el fin de evaluar los impactos/efectos acumulativos a escala transfronteriza. El trabajo se llevó a cabo en un caso de estudio específico en la región noroeste de la Península Ibérica, en una zona transfronteriza entre Portugal y España

The first genetic landscape of inherited retinal dystrophies in Portuguese patients identifies recurrent homozygous mutations as a frequent cause of pathogenesis.

Inherited retinal diseases (IRDs) are a group of ocular conditions characterized by an elevated genetic and clinical heterogeneity. They are transmitted almost invariantly as monogenic traits. However, with more than 280 disease genes identified so far, association of clinical phenotypes with genotypes can be very challenging, and molecular diagnosis is essential for genetic counseling and correct management of the disease. In addition, the prevalence and the assortment of IRD mutations are often population-specific. In this work, we examined 230 families from Portugal, with individuals suffering from a variety of IRD diagnostic classes (270 subjects in total). Overall, we identified 157 unique mutations (34 previously unreported) in 57 distinct genes, with a diagnostic rate of 76%. The IRD mutational landscape was, to some extent, different from those reported in other European populations, including Spanish cohorts. For instance, the EYS gene appeared to be the most frequently mutated, with a prevalence of 10% among all IRD cases. This was, in part, due to the presence of a recurrent and seemingly founder mutation involving the deletion of exons 13 and 14 of this gene. Moreover, our analysis highlighted that as many as 51% of our cases had mutations in a homozygous state. To our knowledge, this is the first study assessing a cross-sectional genotype-phenotype landscape of IRDs in Portugal. Our data reveal a rather unique distribution of mutations, possibly shaped by a small number of rare ancestral events that have now become prevalent alleles in patients

Electronic structure of nuclear-spin-polarization-induced quantum dots

We study a system in which electrons in a two-dimensional electron gas are confined by a nonhomogeneous nuclear spin polarization. The system consists of a heterostructure that has non-zero nuclei spins. We show that in this system electrons can be confined into a dot region through a local nuclear spin polarization. The nuclear-spin-polarization-induced quantum dot has interesting properties indicating that electron energy levels are time-dependent because of the nuclear spin relaxation and diffusion processes. Electron confining potential is a solution of diffusion equation with relaxation. Experimental investigations of the time-dependence of electron energy levels will result in more information about nuclear spin interactions in solids

Fock Representations of Quantum Fields with Generalized Statistic

We develop a rigorous framework for constructing Fock representations of quantum fields obeying generalized statistics associated with certain solutions of the spectral quantum Yang-Baxter equation. The main features of these representations are investigated. Various aspects of the underlying mathematical structure are illustrated by means of explicit examples.Comment: 26 pages, Te

Deviation From \Lambda CDM With Cosmic Strings Networks

In this work, we consider a network of cosmic strings to explain possible deviation from \Lambda CDM behaviour. We use different observational data to constrain the model and show that a small but non zero contribution from the string network is allowed by the observational data which can result in a reasonable departure from \Lambda CDM evolution. But by calculating the Bayesian Evidence, we show that the present data still strongly favour the concordance \Lambda CDM model irrespective of the choice of the prior.Comment: 15 Pages, Latex Style, 4 eps figures, Revised Version, Accepted for publication in European Physical Journal

Phenolic profile and antioxidant activity of different grape (Vitis vinifera L.) varieties

In the last years, the interest in non-alcoholic grape products has considerably increased. Table grapes are largely produced in the Mediterranean area and their consumption has raised worldwide. Beside the positive pattern of nutrients, table grapes could provide benefits on human health. Among the health-promoting substances contained in table grapes, flavonoids (mainly anthocyanins, flavan-3-ols and flavonols) seem to be the most interesting. The aim of this study was the characterization of the phenolic pattern of sixteen grape varieties, and the evaluation of the associated antioxidant activity. The methods were: 1) Folin-Cocalteau's assay for the quantification of total polyphenol content; 2) DPPH (1,1,-diphenil-2—picrylhydrazyl) assay and 3) ORAC (Oxygen Radical Absorbance Capacity) spectrophotometric assays for the assessment of radical scavenging activity; 4) High Performance Liquid Chromatography (HPLC) method, coupled with electrospray ionization mass spectrometer (ESI-MS) and DAD detector was developed in order to obtain the phenolic pattern of grape samples. Data obtained in this study underline that some table grape varieties can show interesting phenolic pattern independently from the presence or not of seeds. This observation suggests that selected varieties of seedless grapes could represent an interesting source of healthy compounds, satisfying consumers' preferences and reducing concerns versus alcoholic beverages

Stability and collapse of localized solutions of the controlled three-dimensional Gross-Pitaevskii equation

On the basis of recent investigations, a newly developed analytical procedure is used for constructing a wide class of localized solutions of the controlled three-dimensional (3D) Gross-Pitaevskii equation (GPE) that governs the dynamics of Bose-Einstein condensates (BECs). The controlled 3D GPE is decomposed into a two-dimensional (2D) linear Schr\"{o}dinger equation and a one-dimensional (1D) nonlinear Schr\"{o}dinger equation, constrained by a variational condition for the controlling potential. Then, the above class of localized solutions are constructed as the product of the solutions of the transverse and longitudinal equations. On the basis of these exact 3D analytical solutions, a stability analysis is carried out, focusing our attention on the physical conditions for having collapsing or non-collapsing solutions.Comment: 21 pages, 14 figure