Locomotion gait optimization for a quadruped robot

This article describes the development of a gait optimization system that allows a fast but stable robot quadruped crawl gait. We focus in the development of a quadruped robot walking gait locomotion that combine bio-inspired Central Patterns Generators (CPGs) and Genetic Algorithms (GA). The CPGs are modelled as autonomous differential equations, that generate the necessary limb movement to perform the walking gait, and the Genetic Algorithm perform the search of the CPGs parameters. This approach allows to explicitly specify parameters such as amplitude, offset and frequency of movement and to smoothly modulate the generated trajectories according to changes in these parameters. It is therefore easy to combine the CPG with an optimization method. A genetic algorithm determines the best set of parameters that generates the limbs movements. We intend to obtain a walking gait locomotion that minimizes the vibration and maximizes the wide stability margin and the forward velocity. The experimental results, performed on a simulated Aibo robot, demonstrated that our approach allows low vibration with a high velocity and wide stability margin for a quadruped walking gait locomotion

Head motion stabilization during quadruped robot locomotion: combining CPGs and stochastic optimization methods

In this work, the authors propose a combined approach based on a controller architecture that is able to generate locomotion for a quadruped robot and a global optimization algorithm to generate head movement stabilization. The movement controllers are biologically inspired in the concept of Central Pattern Generators (CPGs) that are modelled based on nonlinear dynamical systems, coupled Hopf oscillators. This approach allows for explicitly specified parameters such as amplitude, offset and frequency of movement and to smoothly modulate the generated oscillations according to changes in these parameters. The overall idea is to generate head movement opposed to the one induced by locomotion, such that the head remains stabilized. Thus, in order to achieve this desired head movement, it is necessary to appropriately tune the CPG parameters. Three different global optimization algorithms search for this best set of parameters. In order to evaluate the resulting head movement, a fitness function based on the Euclidean norm is investigated. Moreover, a constraint-handling technique based on tournament selection was implemented

Development of dioctadecyldimethylammonium bromide/monoolein liposomes for gene delivery

The artificial introduction of nucleic acids (NA) into mammalian cells (transfection) has become, in recent years, a well-established procedure in basic and applied research, which allowed the study of gene function and regulation. The advances in this area have made possible the use of these methods for gene-based medicines, which constitute alternative therapeutic approaches. One of the most prominent methods is lipofection that uses cationic liposome/NA complexes (a.k.a. lipoplexes) for the complexation, transport and release of therapeutic sequences into target cells. Although yielding lower transfection efficiencies compared with viral gene delivery, lipofection vectors are much safer for medical applications because no significant mutational or toxicological risk exist. Dioctadecyldimethylammonium Bromide (DODAB)/Monoolein (MO) liposomes have recently been described as a new promising alternative to common transfection reagents, due to the pioneering application of MO as helper lipid in lipoplex formulations. In this chapter, we will review the effect of MO on the physicochemical properties of DODAB/MO liposomes and pDNA/DODAB/MO lipoplexes. How lipoplex properties may affect the interaction with different extracellular components and their cell uptake and trafficking will be discussed. The importance of lipoplex biocompatibility towards efficient gene therapy will also be approached presenting pDNA/DODAB/MO system as a lipoplex model, supporting the use of MO as new helper lipid in lipofection.FCTCOMPETEThis work was supported by FCT research project PTDC/QUI/69795/2006, which is cofunded by the program COMPETE from QREN with co-participation from the European Community fund FEDER; CFUM [PEst-C/FIS/UI0607/2011]; CBMA [Pest C/BIA/UI4050/2011]; J.P.N. Silva holds a PhD Grant (SFRH/BD/46968/2008); A. C.N. Oliveira holds a PhD grant (SFRH/BD/68588/2010)

A Global optimization stochastic algorithm for head motion stabilization during quadruped robot locomotion

Visually-guided locomotion is important for autonomous robotics. However, there are several di culties, for instance, the robot locomotion induces head shaking that constraints stable image acquisition and the possibility to rely on that information to act accordingly. In this work, we propose a combined approach based on a controller architecture that is able to generate locomotion for a quadruped robot and a genetic algorithm to generate head movement stabilization. The movement controllers are biologically inspired in the concept of Central Pattern Generators (CPGs) that are modelled based on nonlinear dynamical systems, coupled Hopf oscillators. This approach allows to explicitly specify parameters such as ampli- tude, o set and frequency of movement and to smoothly modulate the generated oscillations according to changes in these parameters. Thus, in order to achieve the desired head movement, opposed to the one induced by locomotion, it is necessary to appropriately tune the CPG parameters. Since this is a non-linear and non-convex optimization problem, the tuning of CPG parameters is achieved by using a global optimization method. The genetic algorithm searches for the best set of parameters that generates the head movement in order to reduce the head shaking caused by locomotion. Optimization is done o ine according to the head movement induced by the locomotion when no stabilization procedure was performed. In order to evaluate the resulting head movement, a tness function based on the Euclidian norm is investigated. Moreover, a constraint handling technique based on tournament selection was im- plemented. Experimental results on a simulated AIBO robot demonstrate that the proposed approach generates head movement that reduces signi cantly the one induced by locomotion

Biological treatment of solid wastes from the tobacco industry for enzyme production

Aiming at the production of enzymes using solid wastes from the tobacco industry, the solid fermentation kinetics of Aspergillus niger and Aspergillus terreus using waste of dark tobacco and Virginia tobacco as substrate were characterized. The efficiency of the fermentation process was evaluated by determining the enzymatic activity of the three enzymes that constitute the cellulose enzymatic system (CMCase, PFase and Xylanase). The results obtained led to the establishment of the best initial conditions of fermentation and the selection of the most efficient microorganism for enzyme production. The best results were obtained with Aspergillus terreus for both tobacco residues. In the case of black tobacco, the best incubation temperature was 31 ºC for the enzymes CMCase and Xylanase and 36 ºC for the PFase and initial pH 5.5 for the three enzymes. For the Virginia tobacco, the best incubation temperature and initial pH are the same for the three enzymes, 36 ºC and 5.5 respectively. The biological activity of the fermented tobacco residues was evaluated being the highest rate of inhibition of microbial growth – 72% - obtained with the residue of Virginia tobacco treated with Aspergillus niger

Multiobjective optimization of a quadruped robot locomotion using a genetic algorithm

In this work, it is described a gait multiobjective optimization system that allows to obtain fast but stable robot quadruped crawl gaits. We combine bioinspired Central Patterns Generators (CPGs) and Genetic Algorithms (GA). A motion architecture based on CPGs oscillators is used to model the locomotion of the robot dog and a GA is used to search parameterizations of the CPGs parameters which minimize the body vibration, maximize the velocity and maximize the wide stability margin. In this problem, there are several conflicting objectives that leads to a multiobjective formulation that is solved using the Weighted Tchebycheff scalarization method. Several experimental results show the effectiveness of this proposed approach.Fundação para a Ciência e a Tecnologia (FCT

Antioxidant Activity and Cytotoxicity of Taraxacum hispanicum Aqueous and Ethanolic Extracts on HepG2 Cells

Plants belonging to the genus Taraxacum have been used in traditional medicine. Nowadays, extracts of these plants have been reported for the treatment of diseases, including liver disorders. Increasing interest and research on these plants also revealed its potential for treating cancer. This study aims to evaluate the antioxidant activity and cytotoxic properties of crude extracts from aerial parts of Taraxacum hispanicum H.Lindb, against human hepatocarcinoma (HepG2). Material and methods: Evaluation of the antioxidant properties was performed using DPPH in vitro test, superoxide scavenging assay and Fe2+ chelating activity. MTT assay was used to determine metabolic activity, for 24 and 48 hours.info:eu-repo/semantics/publishedVersio

Evaluation of antioxidant activity of selected Brazilian plants extracts

Numerous diseases are induced by free radicals and it has long been recognized that naturally occurring substances in higher plants have antioxidant activityinfo:eu-repo/semantics/publishedVersio

A novel approach for the production of DODAB:MO lipoplexes : the influence of temperature on the physicochemical characteristics and cell transfection efficiency

Cationic liposomes/ DNA complexes (lipoplexes) have been widely used as nano-carriers for animal cell transfection, with the neutral lipid (helper) playing a determinant role for the efficiency of this process due to the formation of non-lammellar intermediates that are akin to membrane fusion process [1]. We have developed a novel formulation containing the cationic agent dioctadecyldimethylammonium bromide (DODAB) and 1-monooleoyl-rac-glycerol (MO) as helper lipid [2]. In previous studies, we have demonstrated a strong dependence of the DNA complexation rate with several structural parameters such as the monoolein content or the DNA/cationic lipid charge ratio (+/-) [3]. The preparation method itself influences the structural properties of the lipoplexes formed as well as their lipofection capacity. This study addressed the effect of preparation temperature (25ºC or 50ºC) on DODAB:MO lipoplexes (molar ratios 4:1 and 2:1) physicochemical properties, as well as on their cell transfection efficiency (TE).Fundação para a Ciência e a Tecnologia (FCT) - PTDC/QUI/69795/2006, SFRH/BD/46968/200

Are endolysins promising agents in controlling E. coli associated post-weaning diarrhea in piglets?

Enterotoxigenic Escherichia coli (ETEC) associated infections are the major cause of piglets mortality in weaning and post-weaning period, resulting in significant economic losses to the swine industry. Furthermore, the increase of multidrug resistant ETECs have been recognized a public health danger due to the potential transfer of resistance into the food chain. Bacterio(phages) endolysins are enzymes produced in the end of phage lytic cycle that are responsible for cell lysis. So far, no resistance has been reported, which make endolysins an attractive alternative to antibiotics. In the present work, endolysins were exploited to tackle ETECs in piglets. Two enzymes previously cloned were tested against ETEC SP23 strain exponential cells. First, Lys68 (used herein as proof of concept) was tested alone or in combination with 5 different organics acids (already implemented in the piglets diet) citric, malic, formic, lactic and sorbic acids in 20 mM HEPES, 149 mM PBS and 140.33 mM simulated intestinal fluid (SIF). Later, PlyF307 endolysin was also tested with malic and citric acids in SIF. Results demonstrated that both enzymes reduced ETEC concentration in more than 4 orders of magnitude in HEPES. Lys68 together with malic acid displayed the best antibacterial activity in PBS, being able to reduce approximately 1 order of magnitude. However, enzymes efficacy was drastically reduced when tested in buffers that mimicked physiological conditions. In SIF, Lys68 and PlyF307 did not display antibacterial activity. In summary, phage endolysins revealed to be ineffective to treat ETEC bacterial load in more complex environments.info:eu-repo/semantics/publishedVersio