A Chaotic Krill Herd Optimization Algorithm for Global Numerical Estimation of the Attraction Domain for Nonlinear Systems

Nowadays, solving constrained engineering problems related to optimization approaches is an attractive research topic. The chaotic krill herd approach is considered as one of most advanced optimization techniques. An advanced hybrid technique is exploited in this paper to solve the challenging problem of estimating the largest domain of attraction for nonlinear systems. Indeed, an intelligent methodology for the estimation of the largest stable equilibrium domain of attraction established on quadratic Lyapunov functions is developed. The designed technique aims at computing and characterizing a largest level set of a Lyapunov function that is included in a particular region, satisfying some hard and delicate algebraic constraints. The formulated optimization problem searches to solve a tangency constraint between the LF derivative sign and constraints on the level sets. Such formulation avoids possible dummy solutions for the nonlinear optimization solver. The analytical development of the solution exploits the Chebyshev chaotic map function that ensures high search space capabilities. The accuracy and efficiency of the chaotic krill herd technique has been evaluated by benchmark models of nonlinear systems. The optimization solution shows that the chaotic krill herd approach is effective in determining the largest estimate of the attraction domain. Moreover, since global optimality is needed for proper estimation, a bound type meta-heuristic optimization solver is implemented. In contrast to existing strategies, the synthesized technique can be exploited for both rational and polynomial Lyapunov functions. Moreover, it permits the exploitation of a chaotic operative optimization algorithm which guarantees converging to an expanded domain of attraction in an essentially restricted running time. The synthesized methodology is discussed, with several examples to illustrate the advantageous aspects of the designed approach

Chaotic Particle Swarm Optimisation for Enlarging the Domain of Attraction of Polynomial Nonlinear Systems

A novel technique for estimating the asymptotic stability region of nonlinear autonomous polynomial systems is established. The key idea consists of examining the optimal Lyapunov function (LF) level set that is fully included in a region satisfying the negative definiteness of its time derivative. The minor bound of the biggest achievable region, denoted as Largest Estimation Domain of Attraction (LEDA), can be calculated through a Generalised Eigenvalue Problem (GEVP) as a quasi-convex Linear Inequality Matrix (LMI) optimising approach. An iterative procedure is developed to attain the optimal volume or attraction region. Furthermore, a Chaotic Particular Swarm Optimisation (CPSO) efficient technique is suggested to compute the LF coefficients. The implementation of the established scheme was performed using the Matlab software environment. The synthesised methodology is evaluated throughout several benchmark examples and assessed with other results of peer technique in the literature

Asteraceae Artemisia campestris and Artemisia herba-alba Essential Oils Trigger Apoptosis and Cell Cycle Arrest in Leishmania infantum Promastigotes

International audienceWe report the chemical composition and anti-Leishmania and antioxidant activity of Artemisia campestris L. and Artemisia herba-alba Asso. essential oils (EOs). Our results showed that these extracts exhibit different antioxidant activities according to the used assay. The radical scavenging effects determined by DPPH assay were of IC 50 = 3.3 mg/mL and IC 50 = 9.1 mg/mL for Artemisia campestris and Artemisia herba-alba essential oils, respectively. However, antioxidant effects of both essential oils, determined by ferric-reducing antioxidant power (FRAP) assay, were in the same range (2.3 and 2.97 mg eq EDTA/g EO, resp.), while the Artemisia herba-alba essential oil showed highest chelating activity of Fe 2+ ions (27.48 mM Fe 2+). Interestingly, we showed that both EOs possess dose-dependent activity against Leishmania infantum promastigotes with IC 50 values of 68 í µí¼‡g/mL and 44 í µí¼‡g/mL for A. herba-alba and A. campestris, respectively. We reported, for the first time, that antileishmanial activity of both EOs was mediated by cell apoptosis induction and cell cycle arrest at the sub-G0/G1 phase. All our results showed that EOs from A. herba-alba and A. campestris plants are promising candidates as anti-Leishmania medicinal products

CVD Graphene Electrode for Direct Electrochemical Detection of Double-Stranded DNA

Understanding and regulating DNA interactions with solvents and redox-active centers opens up new possibilities for improving electrochemical signals and developing adequate biosensors. This work reports the development of a modified indium tin oxide (ITO) electrode by chemical vapor deposition (CVD) of graphene for the detection of double-stranded DNA. The modified electrode shows a better electrical conductivity than ITO, as confirmed by electrochemical impedance spectroscopy (EIS), where a drastic decrease in the charge–transfer resistance, Rct, from ~320 to ~60 Ω was observed. Sequences of double-stranded genomic DNA with a different number of base pairs are evaluated through differential pulse voltammetry (DPV), using ferri/ferrocyanide ([Fe(CN)6]3−/4−) as a mediator in the solution. Variations in the electrochemical response of the [Fe(CN)6]3−/4− probe are observed after introducing redox inactive double-stranded DNA ions. The redox-active [Fe(CN)6]3−/4− probe serves as a scaffold to bring DNA into the graphene-modified ITO electrode surface, provoking an increase in the current and a change in the potential when the number of base pairs increases. These results are confirmed by EIS, which shows a variation in the Rct. The calibration of DPV intensity and Rct vs. DNA base pairs (bps) number were linear in the 495–607 bps range. The proposed method could replace the nucleic acid gel electrophoresis technique to determine the presence of a DNA fragment and quantify its size