Trapping of Spin-0 fields on tube-like topological defects

We have considered the localization of resonant bosonic states described by a scalar field $\Phi$ trapped in tube-like topological defects. The tubes are formed by radial symmetric defects in $(2,1)$ dimensions, constructed with two scalar fields $\phi$ and $\chi$, and embedded in the $(3,1)-$dimensional Minkowski spacetime. The general coupling between the topological defect and the scalar field $\Phi$ is given by the potential $\eta F(\phi,\chi)\Phi^2$. After a convenient decomposition of the field $\Phi$, we find that the amplitudes of the radial modes satisfy Schr\"odinger-like equations whose eigenvalues are the masses of the bosonic resonances. Specifically, we have analyzed two simple couplings: the first one is $F(\phi,\chi)=\chi^2$ for a fourth-order potential and, the second one is a sixth-order interaction characterized by $F(\phi,\chi)=(\phi\chi)^2$% . In both cases the Schr\"odinger-like equations are numerically solved with appropriated boundary conditions. Several resonance peaks for both models are obtained and the numerical analysis showed that the fourth-order potential generates more resonances than the sixth-order one.Comment: 7 pages, 10 figures, matches version published in Physics Letters

Suppression of two-bounce windows in kink-antikink collisions

We consider a class of topological defects in $(1,1)$-dimensions with a deformed $\phi^4$ kink structure whose stability analysis leads to a Schr\"odinger-like equation with a zero-mode and at least one vibrational (shape) mode. We are interested in the dynamics of kink-antikink collisions, focusing on the structure of two-bounce windows. For small deformation and for one or two vibrational modes, the observed two-bounce windows are explained by the standard mechanism of a resonant effect between the first vibrational and the translational modes. With the increasing of the deformation, the effect of the appearance of more than one vibrational mode is the gradual disappearance of the initial two-bounce windows. The total suppression of two-bounce windows even with the presence of a vibrational mode offers a counterexample from what expected from the standard mechanism. For even larger deformation, some two-bounce windows reappear, but with a non-standard structure.Comment: 13 pages, 6 figure

Structural properties of crumpled cream layers

The cream layer is a complex heterogeneous material of biological origin which forms spontaneously at the air-milk interface. Here, it is studied the crumpling of a single cream layer packing under its own weight at room temperature in three-dimensional space. The structure obtained in these circumstances has low volume fraction and anomalous fractal dimensions. Direct means and noninvasive NMR imaging technique are used to investigate the internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy

Frutas de clima temperado e subtropical: algumas propriedades medicinais.

bitstream/CPACT-2010/13217/1/folder-frutas2009.pdfProjeto Quintais Orgânicos de Frutas

Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10(17) m(-2). We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching. (C) 2015 Author(s).Dutch Polymer Institute (DPI), BISTABLE [704]; Fundacao para Ciencia e Tecnologia (FCT) through the research Instituto de Telecommunicacoes (IT-Lx); project Memristor based Adaptive Neuronal Networks (MemBrAiNN) [PTDC/CTM-NAN/122868/2010]; European Community Seventh Framework Programme FP7', ONE-P [212311]; Dutch Ministry of Education, Culture and Science (Gravity Program) [024.001.035]info:eu-repo/semantics/publishedVersio

Baseline information on prokaryotic and microeukaryotic plankton communities inside and outside of Indonesian marine lakes

Marine lakes represent a unique and globally rare aquatic environment characterised by lower salinities and pH and higher temperatures than the surrounding open water environment. Here we provide baseline data on planktonic communities of Archaea, Bacteria and microeukaryotes inside and outside (open water habitat) of three marine lakes (Kakaban, Haji Buang and Tanah Bamban) in the Berau region of Indonesia. Compositional variation was highly congruent with the major axis of variation separating open water from marine lake samples for all three domains. Planktonic Archaea mainly consisted of OTUs assigned to Euryarchaeota that were closely related to organisms in Genbank previously obtained from seawater samples. The majority of archaeal OTUs were most abundant in open water habitat with a few OTUs abundant in all habitats. Most bacterial sequences were assigned to Proteobacteria, Cyanobacteria and Bacteroidetes with the percentage of Cyanobacteria highest in two of the marine lakes and lowest in the remaining lake (Tanah Bamban). In contrast to Archaea, there were a number of bacterial OTUs that were markedly more abundant in marine lake habitat. Most microeukaryote sequences were assigned to the Alveolata, Stramenopiles, Opisthokonta, Archaeplastida and Hacrobia. As was the case with Bacteria, a number of abundant microeukaryote OTUs were more abundant in marine lake habitat. Our results thus indicate similar compositional responses to the environmental conditions in marine lake habitat across the major domains of life and point to marine lakes harbouring distinct microbial communities.publishe