Decomposition driven interface evolution for layers of binary mixtures: {II}. Influence of convective transport on linear stability

We study the linear stability with respect to lateral perturbations of free surface films of polymer mixtures on solid substrates. The study focuses on the stability properties of the stratified and homogeneous steady film states studied in Part I [U. Thiele, S. Madruga and L. Frastia, Phys. Fluids 19, 122106 (2007)]. To this aim, the linearized bulk equations and boundary equations are solved using continuation techniques for several different cases of energetic bias at the surfaces, corresponding to linear and quadratic solutal Marangoni effects. For purely diffusive transport, an increase in film thickness either exponentially decreases the lateral instability or entirely stabilizes the film. Including convective transport leads to a further destabilization as compared to the purely diffusive case. In some cases the inclusion of convective transport and the related widening of the range of available film configurations (it is then able to change its surface profile) change the stability behavior qualitatively. We furthermore present results regarding the dependence of the instability on several other parameters, namely, the Reynolds number, the Surface tension number and the ratio of the typical velocities of convective and diffusive transport.Comment: Published in Physics of Fluic

Many Attractors, Long Chaotic Transients, and Failure in Small-World Networks of Excitable Neurons

We study the dynamical states that emerge in a small-world network of recurrently coupled excitable neurons through both numerical and analytical methods. These dynamics depend in large part on the fraction of long-range connections or `short-cuts' and the delay in the neuronal interactions. Persistent activity arises for a small fraction of `short-cuts', while a transition to failure occurs at a critical value of the `short-cut' density. The persistent activity consists of multi-stable periodic attractors, the number of which is at least on the order of the number of neurons in the network. For long enough delays, network activity at high `short-cut' densities is shown to exhibit exceedingly long chaotic transients whose failure-times averaged over many network configurations follow a stretched exponential. We show how this functional form arises in the ensemble-averaged activity if each network realization has a characteristic failure-time which is exponentially distributed.Comment: 14 pages 23 figure

Homology and symmetry breaking in Rayleigh-Benard convection: Experiments and simulations

Algebraic topology (homology) is used to analyze the weakly turbulent state of spiral defect chaos in both laboratory experiments and numerical simulations of Rayleigh-Benard convection.The analysis reveals topological asymmetries that arise when non-Boussinesq effects are present.Comment: 21 pages with 6 figure

Análisis del tamaño de partículas en areniscas de las Catedrales de Salamanca. Independencia entre granulometría y deterioro

11 sandstone samples from the cathedrals of Salamanca were analysed granulometrically. The study was to establish whether there is a direct connection between the particle size of such stone and the surface deterioration of some of the ashlars in the facades. This was carried out with the help of diffraction spectrometry by laser beams. The results show that there is no connection between the nature of the stone texture and their degree of surface deterioration.Se analizan granulométricamente 11 muestras de arenisca de las Catedrales de Salamanca. El objetivo del estudio es establecer si existe relación directa entre el tamaño de las partículas de tales piedras y el deterioro superficial de alguno de los sillares de las fachadas. Esto se lleva a cabo con la ayuda de la espectrometría de difracción por rayos láser. Los resultados muestran que no hay conexión entre la finura textural de las piedras estudiadas y el grado de deterioro superficial que éstas presentan

Um método para determinar o volume comercial do Schizolobium amazonicum (Huber) ducke utilizando redes neurais artificiais.

Este trabalho apresenta um método para determinar o volume comercial do Schizolobium amazonicum (Huber) Ducke, com casca, utilizando Redes Neurais Artificiais (RNAs). Compara os resultados com estimativas obtidas pelo método de regressão linear e quadrática. O modelo neural artificial utiliza uma RNA multicamada direta com uma camada intermediária e, o algoritmo de treinamento supervisionado backpropagation. Os resultados obtidos pelo modelo neural foram mais próximos do real que os obtidos pelos métodos de regressão linear e quadrática. O erro médio absoluto obtido pela RNA foi aproximadamente 50% menor quando comparado com o obtido pelo modelo de regressão quadrática e o erro padrão da estimativa cerca de 30% menor do que os obtidos pelos modelos de regressão linear e quadrática. Com o uso do modelo neural, não foi necessário utilizar o fator de forma, já que este varia de acordo com a idade, diâmetro e altura das árvores

Desenvolvimento de uma prova de imunoadsorcao enzimática para detecção de anticorpos contra Trypanosoma vivax em bovinos: resultados preliminares.

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Caracterização físico-química de farinhas de mandioca (Manihot esculenta Crantz) dos povos indígenas Kaxinawá.

A produção de farinha na TI Kaxinawá de Nova Olinda é feita pelas famílias, cada qual produzindo o suficiente para seu próprio consumo sempre que considerem necessário e tenham matéria-prima adequada e suficiente para a produção de farinha. Não há produção para comercialização fora da TI. O processo de produção é bastante simples e pode ser de dois tipos: a partir da raiz ralada, prensada e torrada; ou a chamada farinha puba, que consiste em deixar as raízes de molho na água até amolecerem, seguido de prensagem e torração. Dessa forma, o objetivo deste trabalho foi caracterizar as farinhas de mandioca produzidas na TI Kaxinawá de Nova Olinda

Defect chaos and bursts: Hexagonal rotating convection and the complex Ginzburg-Landau equation

We employ numerical computations of the full Navier-Stokes equations to investigate non-Boussinesq convection in a rotating system using water as the working fluid. We identify two regimes. For weak non- Boussinesq effects the Hopf bifurcation from steady to oscillating (whirling) hexagons is supercritical and typical states exhibit defect chaos that is systematically described by the cubic complex Ginzburg-Landau equation. For stronger non-Boussinesq effects the Hopf bifurcation becomes subcritical and the oscil- lations exhibit localized chaotic bursting, which is modeled by a quintic complex Ginzburg-Landau equation