The Yang-Lee edge singularity in spin models on connected and non-connected rings

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Unusual Yang-Lee edge singularity in the one-dimensional axial-next-to-nearest-neighbor Ising model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Irregular satellites of Jupiter: capture configurations of binary-asteroids

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The Orbital Dynamics of Synchronous Satellites: Irregular Motions in the 2:1 Resonance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

ON THREE-PARAMETER FAMILIES of FILIPPOV SYSTEMS - THE FOLD-SADDLE SINGULARITY

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SINGULARITY THEORY and FORCED SYMMETRY BREAKING IN EQUATIONS

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Localization and irregular distribution of Na,K-ATPase in myelin sheath from rat sciatic nerve

Sodium, potassium adenosine triphosphatase (Na,K-ATPase) is a membrane-bound enzyme that maintains the Na+ and K+ gradients used in the nervous system for generation and transmission of bioelectricity. Recently, its activity has also been demonstrated during nerve regeneration. The present study was undertaken to investigate the ultrastructural localization and distribution of Na,K-ATPase in peripheral nerve fibers. Small blocks of the sciatic nerves of male Wistar rats weighing 250-300g were excised, divided into two groups, and incubated with and without substrate, the para-nitrophenyl phosphate (pNPP). The material was processed for transmission electron microscopy, and the ultra-thin sections were examined in a Philips CNI 100 (TM) electron microscope. The deposits of reaction product were localized mainly on the axolemma, on axoplasmic profiles, and irregularly dispersed on the myelin sheath, but not in the unmyelinated axons. In the axonal membrane, the precipitates were regularly distributed on the cytoplasmic side. These results together with published data warrant further studies for the diagnosis and treatment of neuropathies with compromised Na,K-ATPase activity. (c) 2007 Elsevier Ltd. All rights reserved.

Irregular Satellites of Jupiter: a study of the capture direction

The irregular satellites of Jupiter are believed to be captured asteroids or planetesimals. In the present work is studied the direction of capture of these objects as a function of their orbital inclination. We performed numerical simulations of the restricted three-body problem, Sun-Jupiter-particle, taking into account the growth of Jupiter. The integration was made backward in time. Initially, the particles have orbits as satellites of Jupiter, which has its present mass. Then, the system evolved with Jupiter losing mass and the satellites escaping from the planet. The reverse of the escape direction corresponds to the capture direction. The results show that the Lagrangian points L1 and L2 mainly guide the direction of capture. Prograde satellites are captured through these two gates with very narrow amplitude angles. In the case of retrograde satellites, these two gates are wider. The capture region increases as the orbital inclination increases. In the case of planar retrograde satellites the directions of capture cover the whole 360 degrees around Jupiter. We also verified that prograde satellites are captured earlier in actual time than retrograde ones.

Structural refinement and photoluminescence properties of irregular cube-like (Ca-1_Cu-x(x))TiO3 microcrystals synthesized by the microwave-hydrothermal method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Study of the potential of irregular shaped bodies and orbits around a non-spherical body

In the present work we show the expressions of the gravitational potential of homogeneous bodies with non-spherical three-dimensional shapes in order to study the trajectories around these bodies. The potentials of a prolate and an oblate ellipsoids with different values of semi-major axis are presented. Their results are validated with a test using a spherical body in order to guarantee the approximation of any body as a polyhedral model of the body. With these expressions we study trajectories of a point of mass around the three-dimensional bodies and the results indicated that there is a group of orbits around those bodies and the polyhedral form of the object does work very well. Copyright IAF/IAA. All rights reserved.

On a control design to an AFM microcantilever beam, operating in a tapping-mode, with irregular behavior

In last decades, control of nonlinear dynamic systems became an important and interesting problem studied by many authors, what results the appearance of lots of works about this subject in the scientific literature. In this paper, an Atomic Force Microscope micro cantilever operating in tapping mode was modeled, and its behavior was studied using bifurcation diagrams, phase portraits, time history, Poincare maps and Lyapunov exponents. Chaos was detected in an interval of time; those phenomena undermine the achievement of accurate images by the sample surface. In the mathematical model, periodic and chaotic motion was obtained by changing parameters. To control the chaotic behavior of the system were implemented two control techniques. The SDRE control (State Dependent Riccati Equation) and Time-delayed feedback control. Simulation results show the feasibility of the bothmethods, for chaos control of an AFM system. Copyright © 2011 by ASME.

Irregular satellites of Jupiter: Three-dimensional study of binary-asteroid captures

Among the hidden pieces of the giant puzzle, which is our Solar system, the origins of irregularsatellites of the giant planets stand to be explained, while the origins of regular satellites arewell explained by the in situ formation model through matter accretion. Once they are notlocally formed, the most acceptable theory predicts that they had been formed elsewhere andbecame captured later, most likely during the last stage of planet formation. However, underthe restricted three-body problem theory, captures are temporary and there is still no assistedcapture mechanism which is well established. In a previous work, we showed that the capturemechanism of a binary asteroid under the co-planar four-body scenario yielded permanentcaptured objects with an orbital shape which is very similar to those of the actual progradeirregular Jovian satellites. By extending our previous study to a 3D case, here we demonstratethat the capture mechanism of a binary asteroid can produce permanent captures of objects byitself which have very similar orbits to irregular Jovian satellites. Some of the captured objectswithout aid of gas drag or other mechanisms present a triplet: semi-major axis, eccentricityand inclination, which is comparable to the already known irregular Jovian objects. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.