Turing patterns formation on surfaces under deformation: A total lagrangian method approach

En este artículo se desarrollan varios ejemplos numéricos sobre ecuaciones de reacción-difusión con dominio creciente. Para este fin se utiliza el modelo de reacción de Schnakenberg, con parámetros en el espacio de Turing. Por tanto se realizan ensayos numéricos sobre la aparición de los patrones de Turing en superficies que tienen alta tasa de deformación. Para la solución de las ecuaciones de reacción difusión se presenta un método de solución en superficies en 3 dimensiones mediante el método de los elementos finitos bajo el uso de la formulación lagrangiana total. Los resultados muestran que la formación de los patrones de Turing depende de las funciones de deformación de la superficie y la tasa a la cual se presenta el cambio de posición de cada punto del dominio donde se lleva a cabo la solución numérica. Estos resultados pueden esclarecer algunos fenómenos de cambio de patrón en la superficie de la piel de aquellos animales que exhiben manchas características.In this work we have developed several numerical examples of reaction-diffusion equations with growing domain. For this purpose we have used the Schnakenberg reaction model with parameters in space Turing. Therefore numerical tests are performed on the appearance of Turing patterns on surfaces that have high deformation rate. For the solution of reaction diffusion equations is presented a solution method on surfaces in three dimensions using the finite element method under the use of the total Lagrangian formulation. The results show that the formation of Turing patterns depends on the features of surface deformation and the rate at which change in position of each point of the domain. These results can explain some phenomena of change of pattern on the surface of the skin of animals that exhibit characteristic spots.Peer Reviewe

Effects Of Crossed Electric And Magnetic Fields On The Electronic And Excitonic States In Bulk Gaas And Gaas Ga1-x Alx As Quantum Wells

The variational procedure in the effective-mass and parabolic-band approximations is used in order to investigate the effects of crossed electric and in-plane magnetic fields on the electronic and exciton properties in semiconductor heterostructures. Calculations are performed for bulk GaAs and GaAs Ga1-x Alx As quantum wells, for applied magnetic fields parallel to the layers and electric fields in the growth direction, and it is shown that the combined effects on the heterostructure properties of the applied crossed electric and magnetic fields and the direct coupling between the center-of-mass and internal exciton motions may be dealt with via a simple parameter representing the spatial distance between the centers of the electron and hole magnetic parabolas. Exciton properties are analyzed by using a simple hydrogenlike envelope excitonic wave function and present theoretical results are found in fair agreement with available experimental measurements on the diamagnetic shift of the photoluminescence peak position of GaAs Ga1-x Alx As quantum wells under in-plane magnetic fields. © 2007 The American Physical Society.753Whittaker, D.M., Fisher, T.A., Simmonds, P.E., Skolnick, M.S., Smith, R.S., (1991) Phys. Rev. Lett., 67, p. 887. , PRLTAO 0031-9007 10.1103/PhysRevLett.67.887Fritze, M., Perakis, I.E., Getter, A., Knox, W., Goossen, K.W., Cunningham, J.E., Jackson, S.A., (1996) Phys. Rev. Lett., 76, p. 106. , PRLTAO 0031-9007 10.1103/PhysRevLett.76.106Butov, L.V., Mintsev, A.V., Lozovik, Y.E., Campman, K.L., Gossard, A.C., (2000) Phys. Rev. B, 62, p. 1548. , PRBMDO 0163-1829 10.1103/PhysRevB.62.1548Parlangeli, A., Christianen, P.C.M., Maan, J.C., Soerensen, C.B., Lindelof, P.E., (2000) Phys. 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Solution on square domains of reaction-convection-diffusion equations using spectral stochastic finite element and streamline upwind Galerkin Petrov

Se desarrolla la solución numérica de 2 problemas de difusión-convección (DC), mediante el empleo del método de elementos finitos de Petrov-Galerkin en contracorriente (SUPG). Los parámetros que definen el comportamiento de las ecuaciones se modelan como campos estocásticos, y son los siguientes: la velocidad convectiva, la difusión y la capacidad calorífica como valores de tipo aleatorio. Por tanto, se combina el método SUPG para ecuaciones de DC, con convección dominante, con el método de los elementos finitos estocásticos espectrales. Los parámetros de cada ecuación se han descrito mediante la expansión de Karhunen-Loève, mientras que la incógnita se representa mediante la expansión de los polinomios de caos. Los objetivos del artículo son: en primer lugar, estudiar la influencia de los campos estocásticos en la solución de problemas de DC con SUPG, y en segundo lugar obtener los patrones de cada coeficiente de la expansión en polinomios de caos. Los resultados muestran la versatilidad del método para solucionar diferentes problemas físicos gracias a la generalidad en la descripción estadística de la solución, y la riqueza en la representación de las zonas donde se halla la mayor variabilidad en la respuesta. Los patrones muestran la incertidumbre en la incógnita que depende de la dinámica de la difusión, la velocidad convectiva y el tipo de solución utilizado.In this paper we have developed the numerical solution of two problems of diffusion-convection (DC), using the finite element method of Streamline Upwind Petrov-Galerkin (SUPG). The parameters that define the behavior of the equations are modeled as stochastic fields, specifically, are used: the convective velocity, diffusion and heat capacity as values of random type. Therefore, we have included SUPG method to DC, with dominant convection, with the stochastic spectral finite element method. Each parameter was described by Karhunen-Loève expansion, while the unknown is represented by the polynomial expansion of the chaos. The objectives of the paper are: 1. To study the influence of stochastic fields in solving problems with SUPG DC and 2. Get the solution of each expansion unknown variable. The results show the versatility of the method for solving different physical problems due to the generality of the statistical description of the solution and the richness in the representation of the areas where there is the greater variability in response. The patterns shown in the unknown uncertainty depends on the dynamics of diffusion, convective velocity and the type of solution used.Peer Reviewe

A 2d Honeycomb Photonic Crystal Under Applied Magnetic Fields

The band-structure properties of a photonic two-dimensional honeycomb lattice formed by cylindrical semiconductor shell rods with dielectric permitivities ε 1 and ε 2, and embedded in a background with permitivity ε 3, is studied by using an standard plane-wave expansion. The properties of bandgaps and density of states, considering dispersive dielectric responses, are investigated together with the possibility of fabricating systems with tunable photonic bandgaps, due to the Voigt magneto-optical effect, under the influence of an external magnetic field. © 2008 SPIE.7138J. D. Joannopoulos, R. D. Meade, J. N. Winn, Photonic Crystals: Molding the Flow of Light, Princeton University Press, Princeton, 1995E. Istrate and E. H. Sargent, Rev. Mod. Phys. 78, 455 (2006)Xu, C., Hu, X., Li, Y., Liu, X., Fu, R., Zi, J., (2003) Phys. Rev. B, 68, p. 193201Kee, C.-S., Kim, J.-E., Park, H.Y., Park, I., Lim, H., (2000) Phys. Rev. B, 61, p. 15523Anderson, C.M., Giapis, K.P., (1996) Phys. Rev. Lett, 77, p. 2949Rezaei, B., Kalafi, M., (2006) Optics Commun, 266, p. 159Busch, K., John, S., (1999) Phys. Rev. Lett, 83, p. 967S. B. Cavalcanti, M. de Dios-Leyva, E. Reyes-Gómez, and L. E. Oliveira, Phys. Rev. B 74, 153102 (2006)ibid., Phys. Rev. E 75, 026607 (2007)Ho, K.M., Chan, C.T., Soukoulis, C.M., (1990) Phys. Rev. Lett, 65, p. 315

A PLL-based multirate structure for time-varying power systems harmonic/interharmonic estimation

This paper describes a phase-locked-loop (PLL)-based power systems harmonic estimation algorithm, which uses an analysis filter bank and multirate processing. The filter bank is composed of bandpass filters. The initial center frequency of each filter is purposely chosen to be equal to harmonic frequencies. However, an adaptation strategy makes it possible to track time-varying frequencies as well as interharmonic components. A downsampler device follows the filtering stage, reducing the computational burden, especially because undersampling operations are performed. Finally, the last stage is composed of a PLL estimator which provides estimates for amplitude, phase, and frequency of the input signal. The proposed method improves the accuracy, computational effort, and convergence time of the previous harmonic estimator based on cascade PLL configuration

Tracking simultaneous time-varying power harmonic distortions using filter banks

Although it is well known that the Fourier analysis is only accurately applicable to steady-state waveforms, it is a widely used tool to study and monitor time-varying signals, such as are commonplace in electrical power systems. The disadvantages of the Fourier analysis, such as frequency spillover or problems due to sampling (data window) truncation can often be minimized by various windowing techniques, but they nevertheless exist. This paper demonstrates that it is possible to track and visualize amplitude and time-varying power systems harmonics, without frequency spillover caused by classical time-frequency techniques. This new tool allows for a clear visualization of time-varying harmonics, which can lead to better ways to track harmonic distortion and understand time-dependent power quality parameters. It has been applied to extract the harmonic contents of a rolling mill. It also has the potential to assist with control and protection applications

Synaptic Transmission: Looking for Clues to Autism Spectrum Disorders (ASD) Etiology in Copy Number Variants Containing Synaptic Genes

Copy Number Variants (CNVs) play an important role in susceptibility to ASD, often mediated by the deletion or duplication of genes involved in synaptic structure and function. Increasing evidence suggests a central role for defects in synaptic structure and function in the pathogenesis of non-syndromic ASD. In this study we tested the hypothesis of an enrichment in CNVs encompassing synaptic transmission genes in ASDThis work was supported by the fellowships SFRH/BD/79081/2011 to BO, SFRH/BPD/74739/2010 to ICC and SFRH/BPD/64281/2009 to CC from Fundação para a Ciência e a Tecnologia (FCT; Portugal)

Copy number variants involving components of the glutamatergic synaptic pathway in ASD patients

This work was supported by the fellowships SFRH/BD/79081/2011 to BO, SFRH/BPD/74739/2010 to ICC and SFRH/BPD/64281/2009 to CC from Fundação para a Ciência e a Tecnologia (FCT; Portugal).Copy Number Variants (CNVs) play an important role in susceptibility to Autism Spectrum Disorders (ASD), in particular when deleting or duplicating genes involved in synaptic structure and function such as glutamatergic synapse genes. Identifying CNVs of etiologic relevance for ASD that include glutamatergic genes may contribute to the understanding of glutamate-related pathogenic mechanisms in this disorder

Migration, TB control and elimination: Whom to screen and treat

Tuberculosis (TB) in migrants represents an important clinical and public health threat, particularly in low TB incidence countries. The current review is aimed to assess issues related to screening and treatment of migrants with latent TB infection or TB disease. Keywords: TB migrants, TB elimination, TB control screenin