Effect of rectified and modulated sine forces on chaos in Duffing oscillator

The effect of rectified and modulated sine forces on the onset of horseshoe chaos is studied both analytically and numerically in the Duffing oscillator. With single force analytical threshold condition for the onset of horseshoe chaos is obtained using the Melnikov method. The Melnikov threshold curve is drawn in a parameter space. For the rectified sine wave, onset of cross-well asymptotic chaos is observed just above the Melnikov threshold curve. For the modulus of sine wave long time transient motion followed by a periodic attractor is realized. The possibility of controlling of chaos by the addition of second modulated force is then analyzed. Parametric regimes where suppression of horseshoe chaos occurs are predicted analytically and verified numerically. Interestingly, suppression of chaos is found in the parametric regimes where the Melnikov function does not change sign.     

Production, Purification, and Characterization of a β-Glucosidase of Penicillium funiculosum NCL1

Penicillium funiculosum NCL1, a filamentous fungus, produced significantly higher levels of ??-glucosidase. The effect of initial pH, incubation temperature, and different carbon sources on extracellular ??-glucosidase production was studied in submerged fermentation. At 30?°C with initial pH 5.0, enzyme production was increased by 48-fold upon induction with paper mill waste, as compared to commercial cellulose powder. In zymogram analysis, four isoforms of ??-glucosidases were observed with wheat bran whereas a minimum of one isoform was observed with other carbon sources. A major ??-glucosidase (Bgl3A) with the apparent molecular weight of ~120?kDa, induced by paper mill waste, was purified 19-fold to homogeneity, with a specific activity of 1,796 U/mg. Bgl3A was a monomeric glycoprotein with 29% of neutral carbohydrate content. It showed optimum activity at pH 4.0 and 5.0, optimum temperature at 60?°C, and exhibited a half-life of 1?h at 60?°C. K _m of Bgl3A was found to be 0.057?mM with p-nitrophenyl ??-d-glucoside and V _max was 1,920 U/mg. The purified enzyme exhibited glucose tolerance with a K _i of 1.5?mM. Bgl3A readily hydrolyzed glucosides with ??-linkage. Bgl3A activity was enhanced (156%) by Zn²⁺ and was not affected by other metal cations and reagents. The supplementation of Bgl3A (5 U/mg) with Trichoderma reesei cellulase complex (5 FPU/mg) resulted in about 70% of enhanced glucose production, which emphasizes the industrial importance of Bgl3A.     

Crystal Structure Investigations and Thermal Behavior of the Five‐Leg Spin Ladder Compound La8Cu7O19

La₈Cu₇O₁₉ was synthesized by solid state reaction of the oxides La₂O₃ and CuO at 1288 K in air. The crystal structure was determined by a joint Rietveld refinement of X‐ray and neutron powder diffraction data. La₈Cu₇O₁₉ crystallizes in the monoclinic space group C2/c (No. 15) with the lattice parameters a = 13.8310(4)Å, b = 3.75827(9)Å, c = 34.5917(8)Å and β = 99.332(2)°. La₈Cu₇O₁₉ is the n = 3 member of the homologous series La_4+4nCu_8+2nO_14+8n. The Cu—O sub‐structure in La₈Cu₇O₁₉ contains infinite ribbons, which can be described as perovskite type layers with a width of n = 3 Jahn‐Teller‐elongated octahedra, and Cu—O planes of complex geometry. DSC/TG‐measurements in different gas atmospheres show peritectic decomposition of La₈Cu₇O₁₉. The anisotropic thermal expansion of the lattice parameters was investigated using synchrotron radiation. The Madelung part of lattice energy was calculated and compared with the corresponding values of other lanthanum cuprates.     

Microstructural characterization of next generation nuclear graphites

This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.     

Role of asymmetries in the chaotic dynamics of the double-well Duffing oscillator

Duffing oscillator driven by a periodic force with three different forms of asymmetrical double-well potentials is considered. Three forms of asymmetry are introduced by varying the depth of the left-well alone, location of the minimum of the left-well alone and above both the potentials. Applying the Melnikov method, the threshold condition for the occurrence of horseshoe chaos is obtained. The parameter space has regions where transverse intersections of stable and unstable parts of left-well homoclinic orbits alone and right-well orbits alone occur which are not found in the symmetrical system. The analytical predictions are verified by numerical simulation. For a certain range of values of the control parameters there is no attractor in the left-well or in the right-well.     

Anti-arthritic activity of Tin oxide-Chitosan-Polyethylene glycol carvacrol nanoparticles against Freund’s adjuvant induced arthritic rat model via the inhibition of cyclooxygenase‑2 and prostaglandin E2

Rheumatoid arthritis (RA) results in increased rate of mortality in millions of people worldwide. Research utilizing Tin oxide – Chitosan- Polyethylene glycol Carvacrol (SCP-CAR) nanocomposites has gained increased attention because of its multipotent properties and application in diverse fields including medicinal preparations. The aim of the investigation was to synthesize and to examine the anti-arthritic ability of SCP-CAR nanocomposites against CFA -induced RA in rats. Arthritis induction was done by injecting 0.1 ml of Complete Freund’s adjuvant (CFA) intradermally. Body weight, weight of organs, hind paw volumes and arthritis score was assessed and the levels of inflammatory modulators such as IL-6, IL-1β, IL-10, TNF-α, PGE2 and COX-2 was examined using assay kits. Lipid peroxidation status, antioxidant enzyme activities and levels of liver function enzymes were evaluated using standard procedures. Histopathological changes observed in hind limb of experimental animals were viewed under microscope using H& E staining. The SCP-CAR nanocomposites treated arthritic animals showed increased bodyweight and reduced hind paw volume, organ weight and arthritis score together with elevated antioxidants status and depleted proinflammatory cytokines. Histopathological observation also showed reduction in bone destruction and penetration of inflammatory cells following treatment with SCP-CAR nanocomposites. Thus, together the findings depict the anti-arthritic and anti-inflammatory potential of SCP-CAR nanocomposites suggesting that it could be used as potent therapeutic agent to treat animals against arthritis induced by CFA.     

Statistical dynamics at critical bifurcations in Duffing-van der Pol oscillator

We study the characteristic features of certain statistical quantities near critical bifurcations such as onset of chaos, sudden widening and band-merging of chaotic attractor and intermittency in a periodically driven Duffing-van der Pol oscillator. At the onset of chaos the variance of local expansion rate is found to exhibit a self-similar pattern. For all chaotic attractors the variance Σ_n(q) of fluctuations of coarse-grained local expansion rates of nearby orbits has a single peak. However, multiple peaks are found just before and just after the critical bifurcations. On the other hand, Σ_n (q) associated with the coarse-grained state variable is zero far from the bifurcations. The height of the peak of Σ_n(q) is found to increase as the control parameter approached the bifurcation point. It is maximum at the bifurcation point. Power-law variation of maximal Lyapunov exponent and the mean value of the state variablex is observed near sudden widening and intermittency bifurcations while linear variation is seen near band-merging bifurcation. The standard deviation of local Lyapunov exponent λ(X,L) and the local mean valuex(L) of the coordinatex calculated after everyL time steps are found to approach zero in the limitL → ∞ asL ^-Β. Β is sensitive to the values of control parameters. Further weak and strong chaos are characterized using the probability distribution of ak-step difference quantity δx_k = x_i+k x _i.     

Synchronization of memristor‐based delayed BAM neural networks with fractional‐order derivatives

This article deals with the problem of synchronization of fractional‐order memristor‐based BAM neural networks (FMBNNs) with time‐delay. We investigate the sufficient conditions for adaptive synchronization of FMBNNs with fractional‐order 0 < α < 1. The analysis is based on suitable Lyapunov functional, differential inclusions theory, and master‐slave synchronization setup. We extend the analysis to provide some useful criteria to ensure the finite‐time synchronization of FMBNNs with fractional‐order 1 < α < 2, using Mittag‐Leffler functions, Laplace transform, and linear feedback control techniques. Numerical simulations with two numerical examples are given to validate our theoretical results. Presence of time‐delay and fractional‐order in the model shows interesting dynamics. © 2016 Wiley Periodicals, Inc. Complexity 21: 412–426, 2016