O princípio de ação quântica de Schwinger: aspectos do tratamento de sistemas dependentes do tempo e interagentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vortex-antivortex annihilation in mesoscopic superconductors with a central pinning center

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Model updating of the non-linear vibrating structures through Volterra series and proper orthogonal decomposition

Classical procedures for model updating in non-linear mechanical systems based on vibration data can fail because the common linear metrics are not sensitive for non-linear behavior caused by gaps, backlash, bolts, joints, materials, etc. Several strategies were proposed in the literature in order to allow a correct representative model of non-linear structures. The present paper evaluates the performance of two approaches based on different objective functions. The first one is a time domain methodology based on the proper orthogonal decomposition constructed from the output time histories. The second approach uses objective functions with multiples convolutions described by the first and second order discrete-time Volterra kernels. In order to discuss the results, a benchmark of a clamped-clamped beam with an pre-applied static load is simulated and updated using proper orthogonal decomposition and Volterra Series. The comparisons and discussions of the results show the practical applicability and drawbacks of both approaches.

Controle robusto de sistemas não lineares e chaveado de sistemas lineares usando realimentação derivativa

Pós-graduação em Engenharia Elétrica - FEIS

Profile and crowding of currents in mesoscopic superconductors with an array of antidots

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

Influence of thermal gradient in vortex states of mesoscopic superconductors

In general, the studies of finite size effects in mesoscopic superconductors have been carried out in such a way that the temperature parameter is constant in the entire system. However, we could have situations where a real sample is near a heater source, as an example. In such situations, gradients of temperature are present. On the other hand, mesoscopic superconductors are interesting systems due to the fact that they present confinement effects which influence all the vortex dynamics. Thus, in this work we studied the influence of thermal gradients on the vortex dynamics in mesoscopic superconductors. For this purposes, we used the time dependent Ginzburg-Landau equations. The thermal gradients produce an asymmetric distribution of the currents around the system which, in turn, yield interesting vortex configurations and difficult the formation of giant vortices.

Time course of the meiotic arrest in sheep cumulus-oocyte complexes treated with roscovitine

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

A quantitative analysis of the polarization reversal in the 73 mol % vinylidene fluoride-27 mol % trifluorethylene copolymer

We show that a time-dependent, effective-medium approximation essentially explains the time behavior of the polarization reversals obtained in doped copolymers of vinylidene fluoride and trifluorethylene at 60°C by Ieda, Fukada, and Wada [J. Appl. Phys. 64, 2026 (1988)], who attributed the observed effects to charge accumulation at the boundaries of the permanently polarized crystallites. Moreover, the results seem to indicate that some hindrance (perhaps of mechanical origin) opposes the action of the switching electric field.

Propriedades estatísticas de bilhares abertos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação de técnicas para o acompanhamento do desgaste de um par engrenado utilizando tribologia e análise da resposta dinâmica processada via função densidade probabilidade Beta

Pós-graduação em Engenharia Mecânica - FEIS

Efeitos da timectomia neonatal sobre o dimorfismo sexual esquelético e concentração plasmática de leptina em ratos

Pós-graduação em Ciências Fisiológicas - FOA

Planning “Discrete” Movements Using a Continuous System: Insights from a Dynamic Field Theory of Movement Preparation

The timed-initiation paradigm developed by Ghez and colleagues (1997) has revealed two modes of motor planning: continuous and discrete. Continuous responding occurs when targets are separated by less than 60° of spatial angle, and discrete responding occurs when targets are separated by greater than 60°. Although these two modes are thought to reflect the operation of separable strategic planning systems, a new theory of movement preparation, the Dynamic Field Theory, suggests that two modes emerge flexibly from the same system. Experiment 1 replicated continuous and discrete performance using a task modified to allow for a critical test of the single system view. In Experiment 2, participants were allowed to correct their movements following movement initiation (the standard task does not allow corrections). Results showed continuous planning performance at large and small target separations. These results are consistent with the proposal that the two modes reflect the time-dependent “preshaping” of a single planning system.

Robust tori-like Lagrangian coherent structures

In general the term "Lagrangian coherent structure" (LCS) is used to make reference about structures whose properties are similar to a time-dependent analog of stable and unstable manifolds from a hyperbolic fixed point in Hamiltonian systems. Recently, the term LCS was used to describe a different type of structure, whose properties are similar to those of invariant tori in certain classes of two-dimensional incompressible flows. A new kind of LCS was obtained. It consists of barriers, called robust tori that block the trajectories in certain regions of the phase space. We used the Double-Gyre Flow system as the model. In this system, the robust tori play the role of a skeleton for the dynamics and block, horizontally, vortices that come from different parts of the phase space. (C) 2012 Elsevier B.V. All rights reserved.

Cost-effectiveness analysis of universal childhood hepatitis A vaccination in Brazil: Regional analyses according to the endemic context

Objective: To To conduct a cost-effectiveness analysis of a universal childhood hepatitis A vaccination program in Brazil. Methods: An age and time-dependent dynamic model was developed to estimate the incidence of hepatitis A for 24 years. The analysis was run separately according to the pattern of regional endemicity, one for South + Southeast (low endemicity) and one for the North + Northeast + Midwest (intermediate endemicity). The decision analysis model compared universal childhood vaccination with current program of vaccinating high risk individuals. Epidemiologic and cost estimates were based on data from a nationwide seroprevalence survey of viral hepatitis, primary data collection, National Health Information Systems and literature. The analysis was conducted from both the health system and societal perspectives. Costs are expressed in 2008 Brazilian currency (Real). Results: A universal immunization program would have a significant impact on disease epidemiology in all regions, resulting in 64% reduction in the number of cases of icteric hepatitis, 59% reduction in deaths for the disease and a 62% decrease of life years lost, in a national perspective. With a vaccine price of R$16.89 (US$7.23) per dose, vaccination against hepatitis A was a cost-saving strategy in the low and intermediate endemicity regions and in Brazil as a whole from both health system and society perspective. Results were most sensitive to the frequency of icteric hepatitis, ambulatory care and vaccine costs. Conclusions: Universal childhood vaccination program against hepatitis A could be a cost-saving strategy in all regions of Brazil. These results are useful for the Brazilian government for vaccine related decisions and for monitoring population impact if the vaccine is included in the National Immunization Program. (C) 2012 Elsevier Ltd. All rights reserved.

Plasma corticosterone levels in mouse models of pain

Background: Pain markedly activates the hypothalamic-pituitary-adrenal (HPA) axis and increases plasma corticosterone release interfering significantly with nociceptive behaviour as well as the mechanism of action of analgesic drugs. Aims/Methods: In the present study, we monitored the time course of circulating corticosterone in two mouse strains (C57Bl/6 and Balb/C) under different pain models. In addition, the stress response was investigated following animal handling, intrathecal (i.t.) manipulation and habituation to environmental conditions commonly used in nociceptive experimental assays. We also examined the influence of within-cage order of testing on plasma corticosterone. Results: Subcutaneous injection of capsaicin precipitated a prompt stress response whereas carrageenan and complete Freund's adjuvant induced an increased corticosterone release around the third hour post-injection. However, carrageenan induced a longer increased corticosterone in C57Bl/6 mice. In partial sciatic nerve ligation, neuropathic pain model corticosterone increased only in the first days whereas mechanical hypersensitivity remained much longer. Animal handling also represents an important stressor whereas the i.t. injection per se does not exacerbate the handling-induced stress response. Moreover, the order of testing animals from the same cage does not interfere with plasma corticosterone levels in the intrathecal procedure. Animal habituation to the testing apparatus also does not reduce the immediate corticosterone increase as compared with non-habituated mice. Conclusion: Our data indicate that HPA axis activation in acute and chronic pain models is time dependent and may be dissociated from evoked hyperalgesia. Therefore, HPA-axis activation represents an important variable to be considered when designing experimental assays of persistent pain as well as for interpretation of data.