The oscillatory bioelectrical signal from plants explained by a simulated electrical model and tested using Lempel-Ziv complexity

This paper demonstrates the oscillatory characteristics of electrical signals acquired from two ornamental plant types (Epipremnum pinnatum and Philodendron scandens - Family Araceae), using a noninvasive acquisition system. The electrical signal was recorded using Ag/AgCl superficial electrodes inside a Faraday cage. The presence of the oscillatory electric generator was shown using a classical power spectral density. The Lempel and Ziv complexity measurement showed that the plant signal was not noise despite its nonlinear behavior. The oscillatory characteristics of the signal were explained using a simulated electrical model that establishes that for a frequency range from 5 to 15 Hz, the oscillatory characteristic is higher than for other frequency ranges. All results show that non-invasive electrical plant signals can be acquired with improvement of signal-to-noise ratio using a Faraday cage, and a simple electrical model is able to explain the electrical signal being generated. (C) 2010 Elsevier B.V. All rights reserved.

Selecting salient objects in real scenes: An oscillatory correlation model

Attention is a critical mechanism for visual scene analysis. By means of attention, it is possible to break down the analysis of a complex scene to the analysis of its parts through a selection process. Empirical studies demonstrate that attentional selection is conducted on visual objects as a whole. We present a neurocomputational model of object-based selection in the framework of oscillatory correlation. By segmenting an input scene and integrating the segments with their conspicuity obtained from a saliency map, the model selects salient objects rather than salient locations. The proposed system is composed of three modules: a saliency map providing saliency values of image locations, image segmentation for breaking the input scene into a set of objects, and object selection which allows one of the objects of the scene to be selected at a time. This object selection system has been applied to real gray-level and color images and the simulation results show the effectiveness of the system. (C) 2010 Elsevier Ltd. All rights reserved.

Semilinear parabolic problems in thin domains with a highly oscillatory boundary

In this paper, we study the behavior of the solutions of nonlinear parabolic problems posed in a domain that degenerates into a line segment (thin domain) which has an oscillating boundary. We combine methods from linear homogenization theory for reticulated structures and from the theory on nonlinear dynamics of dissipative systems to obtain the limit problem for the elliptic and parabolic problems and analyze the convergence properties of the solutions and attractors of the evolutionary equations. (C) 2011 Elsevier Ltd. All rights reserved.

Temperature (over) compensation in an oscillatory surface reaction

Biological rhythms are regulated by homeostatic mechanisms that assure that physiological clocks function reliably independent of temperature changes in the environment. Temperature compensation, the independence of the oscillatory period on temperature, is known to play a central role in many biological rhythms, but it is rather rare in chemical oscillators. We study the influence of temperature on the oscillatory dynamics during the catalytic oxidation of formic acid on a polycrystalline platinum electrode. The experiments are performed at five temperatures from 5 to 25 degrees C, and the oscillations are studied under galvanostatic control. Under oscillatory conditions, only non-Arrhenius behavior is observed. Overcompensation with temperature coefficient (q(10), defined as the ratio between the rate constants at temperature T + 10 degrees C and at T) < I is found in most cases, except that temperature compensation with q(10) approximate to I predominates at high applied currents. The behavior of the period and the amplitude result from a complex interplay between temperature and applied current or, equivalently, the distance from thermodynamic equilibrium. High, positive apparent activation energies were obtained under voltammetric, nonoscillatory conditions, which implies that the non-Arrhenius behavior observed under oscillatory conditions results from the interplay among reaction steps rather than, from a weak temperature dependence of the individual steps.

Spatiotemporal Pattern Formation in the Oscillatory Electro-Oxidation of Sulfide on a Platinum Disk

Spatiotemporal pattern formation in the electrocatalytic oxidation of sulfide on a platinum disk is investigated using electrochemical methods and a charge-coupled device (CCD) camera simultaneously. The system is characterized by different oscillatory regions spread over a wide potential range. An additional series resistor and a large electrode area facilitate observation of multiple regions of kinetic instabilities along the current/potential curve. Spatiotemporal patterns on the working electrode, such as fronts, pulses, spirals, twinkling eyes, labyrinthine stripes, and alternating synchronized deposition and dissolution, are observed at different operating conditions of series resistance and sweep rate.

A surface-enhanced infrared absorption spectroscopic (SEIRAS) study of the oscillatory electro-oxidation of methanol on platinum

The oscillatory electro-oxidation of methanol was studied by means of in situ infrared (IR) spectroscopy in the attenuated total reflection (ATR) configuration using a platinum film on a Si prism as working electrode. The surface-enhanced infrared absorption (SEIRA) effect considerably improves the spectroscopic resolution, allowing at following the coverage of some adsorbing species during the galvanostatic oscillations. Carbon monoxide was the main adsorbed specie observed in the induction period and within the oscillatory regime. The system was investigated at two distinct time-scales and its dynamics characterized accordingly. During the induction period the main transformation observed as the system move through the phase space towards the oscillatory region was the decrease of the coverage of adsorbed carbon, coupled to the increase of the electrode potential. Similar transition characterizes the evolution within the oscillatory region, but at a considerably slower rate. Experiments with higher time resolution revealed that the electrode potential oscillates in-phase with the frequency of the linearly adsorbed CO vibration and that the amount of adsorbed CO oscillates with small amplitude. Adsorbed formate was found to play, if any, a very small role. Results are discussed and compared with other systems. (C) 2010 Elsevier B.V. All rights reserved.

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

The objective of this work was to study the theological and thermal properties of film forming solutions (FFS) based on blends of gelatin and poly(vinyl alcohol) (PVA). The effect of the PVA concentration and plasticizer presence on the flow behavior, and viscoelastic and thermal properties of FFS was studied by steady-shear flow and oscillatory experiments, and also, by microcalorimetry. The FB presented Newtonian behavior at 30 degrees C, and the viscosity was not affected neither by the PVA concentration nor by the plasticizer. All FFS presented a phase transition during tests applying temperature scanning. It was verified that the PVA affected the viscoelastic properties of FFS by dilution of gelatin. This behavior was confirmed by microcalorimetric analysis. The behaviors of the storage (G`) and loss (G ``) moduli as a function of frequency of FFS obtained at 5 degrees C were typical of physical gels; with the G` higher than the G ``. The strength of the gels was affected by the PVA concentration. (C) 2009 Elsevier Ltd. All rights reserved.

SIMULATIONS OF WINDS OF WEAK-LINED T TAURI STARS. II. THE EFFECTS OF A TILTED MAGNETOSPHERE AND PLANETARY INTERACTIONS

Based on our previous work, we investigate here the effects on the wind and magnetospheric structures of weak-lined T Tauri stars due to a misalignment between the axis of rotation of the star and its magnetic dipole moment vector. In such a configuration, the system loses the axisymmetry presented in the aligned case, requiring a fully three-dimensional (3D) approach. We perform 3D numerical magnetohydrodynamic simulations of stellar winds and study the effects caused by different model parameters, namely the misalignment angle theta(t), the stellar period of rotation, the plasma-beta, and the heating index.. Our simulations take into account the interplay between the wind and the stellar magnetic field during the time evolution. The system reaches a periodic behavior with the same rotational period of the star. We show that the magnetic field lines present an oscillatory pattern. Furthermore, we obtain that by increasing theta(t), the wind velocity increases, especially in the case of strong magnetic field and relatively rapid stellar rotation. Our 3D, time-dependent wind models allow us to study the interaction of a magnetized wind with a magnetized extrasolar planet. Such interaction gives rise to reconnection, generating electrons that propagate along the planet`s magnetic field lines and produce electron cyclotron radiation at radio wavelengths. The power released in the interaction depends on the planet`s magnetic field intensity, its orbital radius, and on the stellar wind local characteristics. We find that a close-in Jupiter-like planet orbiting at 0.05 AU presents a radio power that is similar to 5 orders of magnitude larger than the one observed in Jupiter, which suggests that the stellar wind from a young star has the potential to generate strong planetary radio emission that could be detected in the near future with LOFAR. This radio power varies according to the phase of rotation of the star. For three selected simulations, we find a variation of the radio power of a factor 1.3-3.7, depending on theta(t). Moreover, we extend the investigation done in Vidotto et al. and analyze whether winds from misaligned stellar magnetospheres could cause a significant effect on planetary migration. Compared to the aligned case, we show that the timescale tau(w) for an appreciable radial motion of the planet is shorter for larger misalignment angles. While for the aligned case tau(w) similar or equal to 100 Myr, for a stellar magnetosphere tilted by theta(t) = 30 degrees, tau(w) ranges from similar to 40 to 70 Myr for a planet located at a radius of 0.05 AU. Further reduction on tau(w) might occur for even larger misalignment angles and/or different wind parameters.

Some Possible Dynamical Constraints for Life`s Origin

Oscillating biochemical reactions are common in cell dynamics and could be closely related to the emergence of the life phenomenon itself. In this work, we study the dynamical features of some classical chemical or biochemical oscillators where the effect of cell volume changes is explicitly considered. Such analysis enables us to find some general conditions about the cell membrane to preserve such oscillatory patterns, of possible relevance to hypothetical primitive cells in which these structures first appeared.

Dynamic portrait of the planetary 2/1 mean-motion resonance - II. Systems with a more massive inner planet

This paper presents the second part in our study of the global structure of the planar phase space of the planetary three-body problem, when both planets lie in the vicinity of a 2/1 mean-motion resonance. While Paper I was devoted to cases where the outer planet is the more massive body, the present work is devoted to the cases where the more massive body is the inner planet. As before, outside the well-known Apsidal Corotation Resonances (ACR), the phase space shows a complex picture marked by the presence of several distinct regimes of resonant and non-resonant motion, crossed by families of periodic orbits and separated by chaotic zones. When the chosen values of the integrals of motion lead to symmetric ACR, the global dynamics are generally similar to the structure presented in Paper I. However, for asymmetric ACR the resonant phase space is strikingly different and shows a galore of distinct dynamical states. This structure is shown with the help of dynamical maps constructed on two different representative planes, one centred on the unstable symmetric ACR and the other on the stable asymmetric equilibrium solution. Although the study described in the work may be applied to any mass ratio, we present a detailed analysis for mass values similar to the Jupiter-Saturn case. Results give a global view of the different dynamical states available to resonant planets with these characteristics. Some of these dynamical paths could have marked the evolution of the giant planets of our Solar system, assuming they suffered a temporary capture in the 2/1 resonance during the latest stages of the formation of our Solar system.

Melanopsin and Clock Genes: Regulation by Light and Endothelin in the Zebrafish ZEM-2S Cell Line

It is well known that clocks are present in brain regions other than the suprachiasmatic nucleus and in many peripheral tissues. In the teleost, Danio rerio, peripheral oscillators can be directly synchronized by light. Danio rerio ZEM-2S embryonic cells respond to light with differential growth: cells kept in constant light exhibited a strong inhibition of proliferation, whereas in cells kept in light:dark (LD) cycles (14L:10D and 10L:14D) or in constant darkness (DD), the doubling times were not statistically different. We demonstrated by RT-PCR followed by PCR that ZEM-2S cells express two melanopsins, Opn4x and Opn4m, and the six Cry genes. The presence of the protein OPN4x was demonstrated by immunocytochemistry. The pattern of temporal expression of the genes Opn4x, Per1, Cry1b, and Clock was studied in ZEM-2S cells kept for five days in 12L:12D or DD. In 12L:12D, the clock genes Per 1 and Cry1b exhibited robust circadian expression, while Opn4x and Clock expression seemed to vary in an ultradian pattern. Both Per1 and Cry1b genes had higher expression during the L phase; Clock gene had an increase in expression coincident with the D phase, and during the subjective night. In DD, the temporal variation of Per1 and Cry1b genes was greatly attenuated but not extinguished, and the higher expressions were shifted to the transition times between subjective day and night, demonstrating that Per and Cry1b were synchronized by the LD cycle. Clock and Opn4x kept the ultradian oscillation, but the rhythm was not statistically significant. As endothelins (ET) have been reported to be a potent stimulator of Per genes in rodents, we investigated the effect of endothelin on ZEM-2S cells, which express ETA receptors. Cells were kept in 12D:12L for five days, and then treated with 10-11 to 10-8M ET-1 for 24h. ET-1 exhibited a biphasic effect on Opn4x expression. At 10-11M, the hormone exerted a highly significant stimulation of Opn4x expression during the L phase and introduced a circadian oscillatory pattern. At 10-10M, a significant increase was seen at ZT21 and ZT0 (i.e., at the end of the D phase and beginning of the L phase), whereas 10-9 and 10-8M ET-1 inhibited the expression of Opn4x at most ZTs. Clock expression was unaffected by 10-8M ET-1; however, in the presence of lower concentrations, the expression was enhanced at some ZTs, strengthening the ultradian oscillation. ET-1 at 10-11 and 10-10M had no effect on Per1 circadian expression; however, 10-9 and 10-8M ET-1 reduced the amplitude of Per1 expression in the beginning of the L phase. ET-1 effects were less evident on Cry 1b. For both genes, the reduction in expression was not sufficient to abolish the circadian oscillatory pattern. Based on these results and data in the literature, a link between ET-1 stimulation of ETA receptors may be established by E4BP4 binding to the promoters and consequent inhibition of gene expression.

Exact Search Directions for Optimization of Linear and Nonlinear Models Based on Generalized Orthonormal Functions

A novel technique for selecting the poles of orthonormal basis functions (OBF) in Volterra models of any order is presented. It is well-known that the usual large number of parameters required to describe the Volterra kernels can be significantly reduced by representing each kernel using an appropriate basis of orthonormal functions. Such a representation results in the so-called OBF Volterra model, which has a Wiener structure consisting of a linear dynamic generated by the orthonormal basis followed by a nonlinear static mapping given by the Volterra polynomial series. Aiming at optimizing the poles that fully parameterize the orthonormal bases, the exact gradients of the outputs of the orthonormal filters with respect to their poles are computed analytically by using a back-propagation-through-time technique. The expressions relative to the Kautz basis and to generalized orthonormal bases of functions (GOBF) are addressed; the ones related to the Laguerre basis follow straightforwardly as a particular case. The main innovation here is that the dynamic nature of the OBF filters is fully considered in the gradient computations. These gradients provide exact search directions for optimizing the poles of a given orthonormal basis. Such search directions can, in turn, be used as part of an optimization procedure to locate the minimum of a cost-function that takes into account the error of estimation of the system output. The Levenberg-Marquardt algorithm is adopted here as the optimization procedure. Unlike previous related work, the proposed approach relies solely on input-output data measured from the system to be modeled, i.e., no information about the Volterra kernels is required. Examples are presented to illustrate the application of this approach to the modeling of dynamic systems, including a real magnetic levitation system with nonlinear oscillatory behavior.

Oscillation for a second-order neutral differential equation with impulses

We consider a certain type of second-order neutral delay differential systems and we establish two results concerning the oscillation of solutions after the system undergoes controlled abrupt perturbations (called impulses). As a matter of fact, some particular non-impulsive cases of the system are oscillatory already. Thus, we are interested in finding adequate impulse controls under which our system remains oscillatory. (C) 2009 Elsevier Inc. All rights reserved.

A Mass-Conserving Algorithm for Dynamical Lubrication Problems With Cavitation

A numerical algorithm for fully dynamical lubrication problems based on the Elrod-Adams formulation of the Reynolds equation with mass-conserving boundary conditions is described. A simple but effective relaxation scheme is used to update the solution maintaining the complementarity conditions on the variables that represent the pressure and fluid fraction. The equations of motion are discretized in time using Newmark`s scheme, and the dynamical variables are updated within the same relaxation process just mentioned. The good behavior of the proposed algorithm is illustrated in two examples: an oscillatory squeeze flow (for which the exact solution is available) and a dynamically loaded journal bearing. This article is accompanied by the ready-to-compile source code with the implementation of the proposed algorithm. [DOI: 10.1115/1.3142903]

Chaotic synchronization in general network topology for scene segmentation

Chaotic synchronization has been discovered to be an important property of neural activities, which in turn has encouraged many researchers to develop chaotic neural networks for scene and data analysis. In this paper, we study the synchronization role of coupled chaotic oscillators in networks of general topology. Specifically, a rigorous proof is presented to show that a large number of oscillators with arbitrary geometrical connections can be synchronized by providing a sufficiently strong coupling strength. Moreover, the results presented in this paper not only are valid to a wide class of chaotic oscillators, but also cover the parameter mismatch case. Finally, we show how the obtained result can be applied to construct an oscillatory network for scene segmentation.