A topological charge selection rule for phase singularities

We present an study of the dynamics and decay pattern of phase singularities due to the action of a system with a discrete rotational symmetry of finite order. A topological charge conservation rule is identified. The role played by the underlying symmetry is emphasized. An effective model describing the short range dynamics of the vortex clusters has been designed. A method to engineer any desired configuration of clusters of phase singularities is proposed. Its flexibility to create and control clusters of vortices is discussed.Comment: 4 pages, 3 figure

On the classification of type D spacetimes

We give a classification of the type D spacetimes based on the invariant differential properties of the Weyl principal structure. Our classification is established using tensorial invariants of the Weyl tensor and, consequently, besides its intrinsic nature, it is valid for the whole set of the type D metrics and it applies on both, vacuum and non-vacuum solutions. We consider the Cotton-zero type D metrics and we study the classes that are compatible with this condition. The subfamily of spacetimes with constant argument of the Weyl eigenvalue is analyzed in more detail by offering a canonical expression for the metric tensor and by giving a generalization of some results about the non-existence of purely magnetic solutions. The usefulness of these results is illustrated in characterizing and classifying a family of Einstein-Maxwell solutions. Our approach permits us to give intrinsic and explicit conditions that label every metric, obtaining in this way an operational algorithm to detect them. In particular a characterization of the Reissner-Nordstr\"{o}m metric is accomplished.Comment: 29 pages, 0 figure

Fractura de Essex-Lopresti bilateral: caso clínico

El síndrome de Essex-Lopresti es una patología poco frecuente que en muchas ocasiones pasa des - apercibida en fase aguda. Su tratamiento se basa en estabilizar la cabeza del radio para evitar su migración proxi - mal, no existiendo protocolos claros acerca de la actuación a nivel distal, de la membrana interósea o el papel del acortamiento del cúbito. Presentamos un caso de afectación a nivel de ambos antebrazos, uno en forma aguda con un tratamiento mediante osteosíntesis y otro crónico en el que se ha realizado una artroplastia de la cabeza de radio, un acortamiento del cúbito y una técnica de Adams para la estabilización distal, ambos con excelente resultado. En nuestra opinión la estabilización de la articulación radio cubital distal debe ser parte del tratamiento del síndrome de Essex-Lopresti y la técnica de Adams constituye una alternativa en aquellos casos en los que la reconstrucción directa no es posible.Essex-Lopresti syndrome is an uncommon condition which in many occasions it goes unnoticed in acute phase. Its treatment is based on stabilize the head of the radius to prevent its proximal migration but there is no clear protocols on the performance at the distal radio-ulnar joint, the interosseous membrane or the role of the shortening of the ulna. We present a case report of effects at the levels of both forearms, one in acute form, with a treatment with osteosynthesis and another that has been treated with an arthroplasty of the radius head, a shor - tening of the ulna and an Adams ? technique for distal stabilization, both with excellent results. In our opinion, the stabilization of the distal radio-ulnar joint should be part of the treatment of Essex-Lopresti syndrome and the Adams ? technique is an alternative in those cases in which the direct reconstruction is not possible

Visual Spike-based Convolution Processing with a Cellular Automata Architecture

this paper presents a first approach for implementations which fuse the Address-Event-Representation (AER) processing with the Cellular Automata using FPGA and AER-tools. This new strategy applies spike-based convolution filters inspired by Cellular Automata for AER vision processing. Spike-based systems are neuro-inspired circuits implementations traditionally used for sensory systems or sensor signal processing. AER is a neuromorphic communication protocol for transferring asynchronous events between VLSI spike-based chips. These neuro-inspired implementations allow developing complex, multilayer, multichip neuromorphic systems and have been used to design sensor chips, such as retinas and cochlea, processing chips, e.g. filters, and learning chips. Furthermore, Cellular Automata is a bio-inspired processing model for problem solving. This approach divides the processing synchronous cells which change their states at the same time in order to get the solution.Ministerio de Educación y Ciencia TEC2006-11730-C03-02Ministerio de Ciencia e Innovación TEC2009-10639-C04-02Junta de Andalucía P06-TIC-0141

Graded-index optical fiber emulator of an interacting three-atom system: illumination control of particle statistics and classical non-separability

We show that a system of three trapped ultracold and strongly interacting atoms in one-dimension can be emulated using an optical fiber with a graded-index profile and thin metallic slabs. While the wave-nature of single quantum particles leads to direct and well known analogies with classical optics, for interacting many-particle systems with unrestricted statistics such analoga are not straightforward. Here we study the symmetries present in the fiber eigenstates by using discrete group theory and show that, by spatially modulating the incident field, one can select the atomic statistics, i.e., emulate a system of three bosons, fermions or two bosons or fermions plus an additional distinguishable particle. We also show that the optical system is able to produce classical non-separability resembling that found in the analogous atomic system.Comment: 14 pages, 5 figure

Vorticity cutoff in nonlinear photonic crystals

Using group theory arguments, we demonstrate that, unlike in homogeneous media, no symmetric vortices of arbitrary order can be generated in two-dimensional (2D) nonlinear systems possessing a discrete-point symmetry. The only condition needed is that the non-linearity term exclusively depends on the modulus of the field. In the particular case of 2D periodic systems, such as nonlinear photonic crystals or Bose-Einstein condensates in periodic potentials, it is shown that the realization of discrete symmetry forbids the existence of symmetric vortex solutions with vorticity higher than two.Comment: 4 pages, 5 figures; minor changes in address and reference

Geomorfología y paisaje en el ordenamiento territorial: valorizando el corredor inferior del río Mapocho

Considering the roles how biological corridor of the lower hydrological system of the Mapocho River, pointing to their integration in the urban planning of the respective communes from an ecologic, environmental and social perspective, is carried on a research about their geomorphological and landscape characteristics and the processes that are leading the evolution of the landscape. With this knowledge and from an ecosystemic perspective of the river territory, the limits of different homogeneous units were determined. Any geomorphological unit recognized, meaning also landscape systems, was characterized by its geology, sedimentology, soils and drainage, hydro-morphodynamic processes and human intervention, which allows through the determination of the quality and fragility of the geomorphic-landscape units, to establish land use proposals with their corresponding scopes on qualifications and restrictions. The resulting mapping contains implicit a proposal for land-use planning from the ecological planning point of view.    Considerando las funciones de corredor biológico del sistema hidrológico inferior del Río Mapocho, y apuntando a su integración a la planificación urbana de la intercomuna respectiva desde un punto de vista ecológico-ambiental y social, se reconocen sus características geomorfológicas y paisajísticas, y se establecen los procesos que lideran la evolución del modelado de las formas naturales. Con esta base se delimita el territorio fluvial desde una perspectiva ecosistémica y se determinan los límites de las diferentes unidades homogéneas resultantes. Cada unidad geomorfológica, en alta correspondencia con el sistema de paisajes, es caracterizada en función de su geología, sedimentología, suelos y drenaje, hidro-morfodinámica e intervención humana, lo cual permite mediante la determinación de la calidad y fragilidad de ellas, establecer propuestas de uso del suelo con sus correspondientes alcances sobre aptitudes y restricciones. La cartografía resultante contiene implícita una propuesta de ordenamiento del territorio desde el punto de vista de la planificación ecológica.  

Application of the level set method for the visual representation of continuous cellular automata oriented to anisotropic wet etching

[EN] Atomistic models are a very valuable simulation tool in the field of material science. Among them are the continuous cellular automata (CCA), which can simulate accurately the process of chemical etching used in micro-electro-mechanical-systems (MEMS) micromachining. Due to the CCA intrinsic atomistic nature, simulation results are obtained in the form of a cloud of points, so data visualization has been usually problematic. When using these models as a part of a computer aided design tool, good data visualization is very important. In this paper, a minimum energy model implemented with the level set (LS) method for improving the visual representation of simulated MEMS is presented. Additionally, the sparse field method has been applied to reduce the high computational cost of the original LS. Finally, some reconstructed surfaces with completely different topologies are presented, proving the effectiveness of our implementation and the fact that it is capable of producing any real surface, flat and smooth ones.We thank Miguel Angel Gosalvez for his collaboration in the early stages of this research. This work has been supported by the Spanish FPI-MICINN BES-2011-045940 grant. Also, we acknowledge support by the JAE-Doc grant form the Junta para la Ampliacion de Estudios program co-funded by FSE.Montoliu Álvaro, C.; Ferrando Jódar, N.; Cerdá Boluda, J.; Colom Palero, RJ. (2014). Application of the level set method for the visual representation of continuous cellular automata oriented to anisotropic wet etching. International Journal of Computer Mathematics. 91(1):124-134. https://doi.org/10.1080/00207160.2013.801464S12413491

Soliton topology versus discrete symmetry in optical lattices

We address the existence of vortex solitons supported by azimuthally modulated lattices and reveal how the global lattice discrete symmetry has fundamental implications on the possible topological charges of solitons. We set a general ``charge rule'' using group-theory techniques, which holds for all lattices belonging to a given symmetry group. Focusing in the case of Bessel lattices allows us to derive also a overall stability rule for the allowed vortex solitons.Comment: 4 pages, 3 figures. To appear in Phys. Rev. Let