Dynamical complexity of discrete time regulatory networks

Genetic regulatory networks are usually modeled by systems of coupled differential equations and by finite state models, better known as logical networks, are also used. In this paper we consider a class of models of regulatory networks which present both discrete and continuous aspects. Our models consist of a network of units, whose states are quantified by a continuous real variable. The state of each unit in the network evolves according to a contractive transformation chosen from a finite collection of possible transformations, according to a rule which depends on the state of the neighboring units. As a first approximation to the complete description of the dynamics of this networks we focus on a global characteristic, the dynamical complexity, related to the proliferation of distinguishable temporal behaviors. In this work we give explicit conditions under which explicit relations between the topological structure of the regulatory network, and the growth rate of the dynamical complexity can be established. We illustrate our results by means of some biologically motivated examples.Comment: 28 pages, 4 figure

Sliding Blocks Revisited: A simulational Study

A computational study of sliding blocks on inclined surfaces is presented. Assuming that the friction coefficient $\mu$ is a function of position, the probability $P(\lambda)$ for the block to slide down over a length $\lambda$ is numerically calculated. Our results are consistent with recent experimental data suggesting a power-law distribution of events over a wide range of displacements when the chute angle is close to the critical one, and suggest that the variation of $\mu$ along the surface is responsible for this.Comment: 6 pages, 4 figures. submitted to Int. J. Mod. Phys. (Proc. Brazilian Wokshop on Simulational Physics

Efeito do pH e do desengorduramento na qualidade do néctar misto de açaí e cupuaçu.

A utilização da polpa de açaí em néctares representa uma boa alternativa para agregar valor ao fruto, e a associação com a polpa de cupuaçu, que apresenta elevada acidez, permite reduzir o pH do produto final sem o uso de aditivos. Os objetivo do trabalho foram avaliar o efeito do pH na qualidade do néctar misto de açaí e cupuaçu e avaliar a vida de prateleira de um néctar misto com baixo teor de gordura. Na primeira etapa, foram elaborados néctares com polpas de cupuaçu de diferentes pHs (A=3,2, B=3,0, C=2,8, D=2,6). Na segunda etapa, foram elaborados néctares com polpa de açaí previamente desengordurada por centrifugação em escala piloto. Foi estudada a vida de prateleira por um período de 4 meses. Os produtos finais foram analisados quanto a composição química, pH, acidez titulável, cor instrumental, sólidos solúveis, microbiologia (coliformes totais e salmonella) e aceitação sensorial. Todos os néctares obtidos estavam em conformidade com os requisitos microbiológicos legais. Os néctares com menor pH final (C e D) apresentaram maior intensidade de cor vermelha, mas o néctar com o maior pH (A) foi melhor avaliado sensorialmente em relação ao sabor e impressão global. Em relação à vida de prateleira do néctar com baixo teor de gordura, verificou-se que o teor de antocianinas e a intensidade da cor vermelha diminuíram com o tempo, não havendo diferença em relação às demais características. As amostras apresentaram boa aceitação sensorial durante o período estudado, com notas superiores a 6 para todos os atributos testados. Apesar disso, ocorreu degradação das antocianinas, o que prejudicou o valor nutricional e a cor do produto

Estresse por déficit hídrico em plantas forrageiras.

bitstream/CNPC-2010/23051/1/doc89.pd

Numerical Simulation of Magnetic Interactions in Polycrystalline YFeO3

The magnetic behavior of polycrystalline yttrium orthoferrite was studied from the experimental and theoretical points of view. Magnetization measurements up to 170 kOe were carried out on a single-phase YFeO3 sample synthesized from heterobimetallic alkoxides. The complex interplay between weak-ferromagnetic and antiferromagnetic interactions, observed in the experimental M(H) curves, was successfully simulated by locally minimizing the magnetic energy of two interacting Fe sublattices. The resulting values of exchange field (H_E = 5590 kOe), anisotropy field (H_A = 0.5 kOe) and Dzyaloshinsky-Moriya antisymmetric field (H_D = 149 kOe) are in good agreement with previous reports on this system.Comment: 26 pages, 9 figure

Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3

We have grown high-quality single crystals of the colossal-magnetoresistance (CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG) method. Samples were grown as fibers of different diameters, and with lengths of the order of centimeters. Their composition and structure were verified through X-ray diffraction, scanning electron microcopy with EDX (Energy Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter Diffraction) patterns. Rocking curves performed along the fiber axis revealed a half-height width of 0.073 degrees. The CMR behavior was confirmed by electrical resistivity and magnetization measurements as a function of temperature.Comment: 11 pages (including 3 figures); to appear in Appl. Phys. Let

Novos registros de hospedeiros de Anastrepha striata Schiner (Diptera: Tephritidae) no estado do Amapa, Brasil.

Resumo 109

GAS TURBINE PERFORMANCE ANALYSIS OPERATING WITH LOWHEATING VALUE FUELS

Usually, power plants work with gas turbine designed to fire natural gas; however, there are possibilities to use other types of gaseous fuels with different calorific values that may be available close to the power plant site. These fuels can be gases obtained from steel (from blast furnaces and coking plants), from gasification processes of coal or biomass, among others. In this work, a gas turbine performance was evaluated at different operational conditions in order to verify the technical feasibility of burning low calorific value fuels. A gas turbine designed to operate with natural gas was used as a reference, the model was built and the performance evaluated at design and off-design conditions using a commercial computer program, GasTurb 11®. A good agreement was obtained between the model operating with natural gas and the available data from open literature, at design and off-design conditions. The model was simulated using low heating value fuels under the same conditions established for natural gas. A reduction in compressor’s surge margin was identified when using low heating value fuels as well as an increase in power output. Therefore, for safe operation a strategy for recovering the surge margin was adopted. In this study the control strategy adopted was bleed air at the compressor discharge. This control strategy presents a technical viability and ensures that the gas turbine operates with the same surge margin level as when using natural gas

Determinação do grau crítico de umidade em sementes de Cenostigma tocantinum Ducke e Dipteryx odorata Willd.

Este trabalho teve como objetivo avaliar o comportamento das sementes desta espécie quanto a sensibilidade à desidratação