Complex order van der Pol oscillator

In this paper a complex-order van der Pol oscillator is considered. The complex derivative Dα±ȷβ , with α,β∈R + is a generalization of the concept of integer derivative, where α=1, β=0. By applying the concept of complex derivative, we obtain a high-dimensional parameter space. Amplitude and period values of the periodic solutions of the two versions of the complex-order van der Pol oscillator are studied for variation of these parameters. Fourier transforms of the periodic solutions of the two oscillators are also analyzed

Fractional central pattern generators for bipedal locomotion

Locomotion has been a major research issue in the last few years. Many models for the locomotion rhythms of quadrupeds, hexapods, bipeds and other animals have been proposed. This study has also been extended to the control of rhythmic movements of adaptive legged robots. In this paper, we consider a fractional version of a central pattern generator (CPG) model for locomotion in bipeds. A fractional derivative D α f(x), with α non-integer, is a generalization of the concept of an integer derivative, where α=1. The integer CPG model has been proposed by Golubitsky, Stewart, Buono and Collins, and studied later by Pinto and Golubitsky. It is a network of four coupled identical oscillators which has dihedral symmetry. We study parameter regions where periodic solutions, identified with legs’ rhythms in bipeds, occur, for 0<α≤1. We find that the amplitude and the period of the periodic solutions, identified with biped rhythms, increase as α varies from near 0 to values close to unity

Systèmes B

Assurer cohérence et efficacité par l\u27intégration, le partage et la mise en réseau, c\u27est à quoi travaillent les Systèmes des bibliothèques à l\u27échelle nationale, fédérale et municipale, tant pour les bibliothèques publiques que pour les établissements universitaires. Un enjeu stratégique dans un pays aux contrastes extrêmes à tous niveaux

Bipedal Locomotion: A Fractional CPG for Generating Patterns

Proceedings of the 10th Conference on Dynamical Systems Theory and ApplicationsThere has been an increase interest in the study of animal locomotion. Many models for the generation of locomotion patterns of different animals, such as centipedes, millipedes, quadrupeds, hexapods, bipeds, have been proposed. The main goal is the understanding of the neural bases that are behind animal locomotion. In vertebrates, goal-directed locomotion is a complex task, involving the central pattern generators located somewhere in the spinal cord, the brainstem command systems for locomotion, the control systems for steering and control of body orientation, and the neural structures responsible for the selection of motor primitives. In this paper, we focus in the neural networks that send signals to the muscle groups in each joint, the so-called central pattern generators (CPGs). We consider a fractional version of a CPG model for locomotion in bipeds. A fractional derivative) Dα f (x), with α non-integer, is a generalization of the concept of an integer derivative, where α = 1 The integer CPG model has been proposed by Golubitsky, Stewart, Buono and Collins, and studied later by Pinto and Golubitsky. It is a four cells model, where each cell is modelled by a system of ordinary differential equations. The coupling between the cells allows two independent permutations, and, as so, the system has D2 symmetry. We consider 0 < α ≤ 1 and we compute, for each value of α, the amplitude and the period of the periodic solutions identified with two legs' patterns in bipeds. We find the amplitude and the period increase as α varies from zero up to one

Studies On The Reduction Of β-enamino Ketones

Reduction of β-enamino ketones 1 with NaBH(OAc)3 in glacial acetic acid gave β-amino ketones 3 in 65% to 67% yield. These data and others observed in the reduction of β-enamino ketones 1 to preferentially syn γ-amino alcohols 2 with NaBH4/HOAc suggest that in this last reaction we have firstly the reduction of the β-enamino ketones 1 to produce the β-amino ketones 3, and then this compound is reduced to the γ-amino alcohols 2. We can say from this results that the diastereosselectivity of the reduction of β-enamino ketones 1 to mainly syn γ-amino álcohols 2, can be analysed as a competition between a chair-like transition state and a boat-like transition state, obtained from the β-amino ketones 3. © 2006 Sociedade Brasileira de Química.17714401442Harris, M.I.N.C., Braga, A.C.H., (2004) J. Braz. Chem. Soc., 15, p. 971Harris, M.I.N.C., (1993), Ph.D. Thesis, Universidade Estadual de Campinas, BrazilBraga, A. C. H.Harris, M. I. N. C.Br PI 9.502.467-0, 1995. (CA 128:243740)Gribble, G.W., Nutaitis, C.F., (1985) Org. Prep. Proced. Int., 17, p. 317Gribble, G.W., (1998) Chem. Soc. Rev., 27, p. 395For a better understanding of this reactivity, theoretical studies are in progressnoteMarchini, P., Liso, G., Reho, A., (1975) J. Org. Chem., 40, p. 3453Evans, D.A., Chapman, K.T., Carreira, E.M., (1988) J. Am. Chem. Soc., 110, p. 3560Palmieri, G., Cimarelli, C., (2006) Arkivoc, p. 10

INJECTABLE HYBRID SYSTEM FOR STRONTIUM LOCAL DELIVERY TO PROMOTE BONE REGENERATION

In bone tissue regeneration strategies, injectable bone substitutes are very attractive since they can be applied with minimally invasive surgical procedures and can perfectly fill irregular defects created in cases of trauma, infection or tumor resection. These materials must combine adequate mechanical properties with the ability to induce new bone formation. Incorporating strontium (Sr) in bone substitute biomaterials may be a strategy to achieve high Sr concentrations, not in a systemic but in a local environment, taking advantage of the osteoanabolic and anti-osteoclastic activity of Sr, for the enhancement of new bone formation. In this context, the aim of the present work was to evaluate the response of a Sr-hybrid injectable system for bone regeneration, designed by our group, consisting of hydroxyapatite microspheres doped with Sr and an alginate vehicle crosslinked in situ with Sr, in an in vivo scenario. Two different animal models were used, rat (Wistar) and sheep (Merino Branco) critical sized bone defect. Non Sr-doped similar materials (Ca-hybrid) or empty defects were used as control. Sr-hybrid system led to an increased bone formation in both center and periphery of a rat critical sized defect compared to a non Sr–doped similar system, where new bone formation was restricted to the periphery. Moreover newly formed bone was identified as early as one week after its implantation in a sheep model. After eight weeks, the bone surrounded the microspheres, both in the periphery and in the center of the defect. Most importantly, the hybrid system provided a scaffold for cell migration and tissue ingrowth and offered structural support, as observed in both models. The effective improvement of local bone formation suggests that this might be a promising approach for bone regeneration, especially in osteoporotic conditions

Substrate specificity and the effect of calcium on Trypanosomabrucei metacaspase 2

Metacaspases are cysteine peptidases found only in yeast, plants and lower eukaryotes, including the protozoa. To investigate the extended substrate specificity and effects of Ca&lt;sup&gt;2+&lt;/sup&gt; on the activation of these enzymes, detailed kinetic, biochemical and structural analyses were carried out on metacaspase 2 from Trypanosoma brucei (TbMCA2). These results reveal that TbMCA2 has an unambiguous preference for basic amino acids at the P&lt;sub&gt;1&lt;/sub&gt; position of peptide substrates and that this is most probably a result of hydrogen bonding from the P&lt;sub&gt;1&lt;/sub&gt; residue to Asp95 and Asp211 in TbMCA2. In addition, TbMCA2 also has a preference for charged residues at the P&lt;sub&gt;2&lt;/sub&gt; and P&lt;sub&gt;3&lt;/sub&gt;positions and for small residues at the prime side of a peptide substrate. Studies into the effects of Ca&lt;sup&gt;2+&lt;/sup&gt; on the enzyme revealed the presence of two Ca&lt;sup&gt;2+&lt;/sup&gt; binding sites and a reversible structural modification of the enzyme upon Ca&lt;sup&gt;2+&lt;/sup&gt; binding. In addition, the concentration of Ca&lt;sup&gt;2+&lt;/sup&gt; used for activation of TbMCA2 was found to produce a differential effect on the activity of TbMCA2, but only when a series of peptides that differed in P&lt;sub&gt;2&lt;/sub&gt; were examined, suggesting that Ca&lt;sup&gt;2+&lt;/sup&gt;activation of TbMCA2 has a structural effect on the enzyme in the vicinity of the S2 binding pocket. Collectively, these data give new insights into the substrate specificity and Ca&lt;sup&gt;2+&lt;/sup&gt; activation of TbMCA2. This provides important functional details and leads to a better understanding of metacaspases, which are known to play an important role in trypanosomes and make attractive drug targets due to their absence in humans

New Features to Look at Natural Phenomena

Proceeding of the 3rd International Conference on Fractional Systems and Signals, at Ghent, BelgiumThe paper focuses the patterns seen in the number of victims from natural catastrophic phenomena. We consider the number of victims of storms from 1900 up to 2013 in 11 countries and study the distributions of the events with more than 30 deadly victims. The similarities among events across the 11 countries are analysed using agglomerative hierarchical clustering. Countries belonging to the same cluster are similar with respect to fatalities. Power laws and hierarchical clustering provide comparable results for the data. Future work is needed in order to explore these numerical tools in more countries and in victims of other hazards

A review of power laws in real life phenomena

Power law distributions, also known as heavy tail distributions, model distinct real life phenomena in the areas of biology, demography, computer science, economics, information theory, language, and astronomy, amongst others. In this paper, it is presented a review of the literature having in mind applications and possible explanations for the use of power laws in real phenomena. We also unravel some controversies around power laws

Double power laws, fractals and self-similarity

Power law (PL) distributions have been largely reported in the modeling of distinct real phenomena and have been associated with fractal structures and self-similar systems. In this paper, we analyze real data that follows a PL and a double PL behavior and verify the relation between the PL coefficient and the capacity dimension of known fractals. It is to be proved a method that translates PLs coefficients into capacity dimension of fractals of any real data